An Initial Evaluation of Potential 

Options for Managing Riparian 

Reserves of the Aquatic 

Conservation Strategy of the 

Northwest Forest Plan

Gordon H. Reeves, Brian R. Pickard, and K. Norman Johnson

United States Department of Agriculture

Forest 

Service

Pacific Northwest 

Research Station

General Technical Report

PNW-GTR-937

April 

2016
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Authors

Gordon H. Reeves is a research fish ecologist, U.S. Department of Agriculture, 

Forest Service, Pacific Northwest Research Station, Forestry Sciences Laboratory, 3200 SW Jefferson Way, Corvallis, OR 97331; Brian R. Pickard is a Ph.D. 

student, Center for Geospatial Analytics, College of Natural Resources, North 

Carolina State University, Raleigh, NC 27695; K. Norman Johnson is a university 

distinguished professor, Department of Forest Ecosystems and Society, College of 

Forestry, Oregon State University, Corvallis, OR 97331.

Cover: Smith River, Oregon. Photo by Loretta Ellenburg.
Abstract

Reeves, Gordon H.; Pickard, Brian R.; Johnson, K. Norman. 2016. An 

initial evaluation of potential options for managing riparian reserves of the 

Aquatic Conservation Strategy of the Northwest Forest Plan. Gen. Tech. Rep. 

PNW-GTR-937. Portland, OR: U.S. Department of Agriculture, Forest Service, 

Pacific Northwest Research Station. 97 p.

The Aquatic Conservation Strategy (ACS) of the Northwest Forest Plan guides 

management of riparian and aquatic ecosystems on federal lands in western 

Oregon, western Washington, and northern California. We applied new scientific 

findings and tools to evaluate two potential options, A and B, for refining interim 

riparian reserves to meet ACS goals and likely challenges of climate change while 

supporting other management goals, including timber production. Interim riparian 

reserves are retained in late-successional reserves and other special land designations in the options. In lands designated as matrix, the area for aquatic conservation 

extends upslope one site-potential tree-height along all streams, divided into an 

inner zone devoted solely to achieving ACS goals and an outer zone managed to 

achieve ACS and other goals. Option A uses a fixed-width approach and option B 

a context-dependent approach, with partitioning of zones based on the ecological 

sensitivity of stream reaches. Based on simulations of the area of interim riparian 

reserves in six watersheds in western Oregon with lands managed by the Bureau 

of Land Management (BLM): (1) about 76 percent under option A and 72 percent 

under option B remain solely devoted to ACS goals; (2) 15 percent under option A 

and 19 percent under option B should be able to meet ACS goals and also contribute 

toward matrix goals such as timber production; and (3) 9 percent would be returned 

to matrix. A large percentage of streams with high ecological sensitivity occurred 

on nonfederal lands, a circumstance that merits further analysis in the context of 

landscape-scale considerations for biodiversity and recovery of species listed under 

the Endangered Species Act. Information needs remain with regard to the application and effectiveness of these options, and an adaptive management context is 

critical for continued improvement.

Keywords: Aquatic Conservation Strategy, interim riparian reserves, riparian 

management, context-dependent buffers. 
Executive Summary 

The Aquatic Conservation Strategy (ACS) of the Northwest Forest Plan (NWFP) 

was designed to maintain and improve the ecological processes in aquatic ecosystems for Pacific salmon (Oncorhynchus spp.), other native fish, aquatic and ripariandependent organisms, and water quality. A key element of the ACS was a system of 

interim riparian reserves of two site-potential tree-heights on fish-bearing streams, 

and one site-potential tree-height on non-fish-bearing streams. These reserves were 

adopted in 1994 as part of the NWFP; it was expected that they would be revised 

during implementation based on scientifically sound reasoning but, in general, such 

revisions have not been made. 

We explore the application of new scientific findings and tools to do an initial 

ecological evaluation of two potential options for managing riparian and aquatic 

ecosystems in a way that could meet ACS goals, and the likely challenges of climate 

change, while also allowing the fulfillment of other management goals, including 

timber production. The options evaluated here were informed by new research, 

tools, and concepts, including: (1) the influence of the width of riparian area on 

microclimate; (2) movement of amphibians along non-fish-bearing streams; (3) the 

distance to and sources of wood for fish-bearing streams; (4) intrinsic potential 

(IP), a concept for assessing the capability of a given set of geomorphic conditions 

in a stream reach to provide habitat for selected species of Pacific salmon; (6) 

NetMap, a geo-spatial platform for watershed analysis that can, among other things, 

identify the location of key ecological processes that influence aquatic and riparian ecosystems on the landscape and in the stream network; and (7) concepts for 

managing riparian ecosystems and the activities that affect them, such as ecological 

forestry and tree-tipping.

Under both of the potential options for managing the riparian reserves of the 

ACS evaluated here, current interim riparian reserves of two site-potential treeheights along fish-bearing streams and one site-potential tree-height along non-fishbearing streams are retained in late-successional reserves and other special land 

designations. In lands allocated as matrix under the NWFP, the area of interest for 

aquatic conservation, which we refer to as the riparian conservation area, extends 

upslope from the stream for a distance equal to the height of one site-potential tree 

along fish-bearing and non-fish-bearing streams under both options. Riparian 

conservation areas are divided into an inner and an outer zone; the inner zone is 

devoted solely to achieving goals of the ACS, while the outer zone would be managed to achieve ACS and other management goals, which could include timber 

production. If timber production is implemented in the outer zone, ecological 
forestry prescriptions with significant amounts of retention would guide harvesting 

activities. The options differ in how the riparian conservation area is partitioned 

between inner and outer zones. Option A uses a fixed-width approach to partition 

the zones. Option B uses a context-dependent approach based on four important 

characteristics of each stream reach—susceptibility to surface erosion, debris flows, 

thermal loading, and habitat potential for target fish species—to determine the 

appropriate width of the inner zone. Both options are limited to stands ≤80 years of 

age, and “tree-tipping” is used throughout the riparian conservation area to ensure 

that harvest does not negatively affect wood recruitment to the stream.

We simulated and compared the two potential options to the existing interim 

riparian reserves across six watersheds that contain approximately 30 percent of 

matrix lands managed by the Bureau of Land Management (BLM) in western Oregon. Under option A, we found that an average of 54 percent of the interim riparian 

reserves on BLM matrix across the study watersheds would continue to be managed 

solely for ACS goals; under option B, an estimated average of 46 percent would be 

managed solely for those goals. Also, an estimated average of 29 percent of interim 

riparian reserves on BLM matrix under option A and 36 percent under option B 

would achieve ACS goals along with other potential goals, which could include 

timber production, and 18 percent could be returned to the terrestrial prescriptions 

of the NWFP. Interim riparian reserves in late-successional and other reserve 

allocations, which cover approximately half of the BLM lands in western Oregon, 

would remain unchanged under both options. Assuming that half of the interim 

riparian reserves on BLM lands in western Oregon would remain unchanged, and 

applying our study estimates of changes in matrix under the two modeled options 

to the entire BLM matrix in western Oregon, we estimate that about 76 percent of 

the interim riparian reserves under option A and 72 percent under option B would 

remain solely devoted to ACS goals. Under options A and B, respectively, an 

additional estimated 15 percent and 19 percent of the interim riparian reserves on 

BLM lands in western Oregon would likely meet ACS goals and may also provide 

opportunity for achievement of matrix goals including limited timber production. 

Under both options, reduction of the width of the riparian reserve along fish-bearing 

streams to one tree-height would return an estimated 9 percent of interim riparian 

reserves to matrix on these lands.

Because our analysis took a “whole-watershed” approach, we identified important stream segments for aquatic ecosystem conservation on all lands, federal and 

nonfederal. We found that federal lands contain some, but not all, streams with 

high ecological sensitivity, and determined that many ecologically sensitive streams 
occur on nonfederal lands. This finding merits further analysis in the context of 

landscape-scale considerations for biodiversity and the recovery of threatened or 

endangered species.

Our analysis is not intended to suggest or imply that the two potential options 

described here are the only alternatives for managing riparian ecosystems. And, 

just as with the interim riparian reserves, these or any other options should not be 

viewed as immutable. Our analysis provides a framework for understanding recent 

scientific information and how it might be used to develop options for managing 

interim riparian reserves other than as de facto reserves to meet the goals of the 

ACS, while allowing opportunities to achieve other goals such as timber production, and that also meet the challenges of climate change. Although new science 

has refined our understanding of the ecological processes that occur in the interim 

riparian reserves, uncertainties and information needs remain. Thus, an adaptive 

management context is critical for continual improvement and further evaluation.
Contents

1 Introduction

2 The Aquatic Conservation Strategy in the Northwest Forest Plan

2 Goals

4 Underlying Principles and Concepts

14 Potential Options for Managing Riparian Reserves on BLM Western 

Oregon Forests—Design and Scientific Rationale

18 Option A

27 Option B

33 Simulating the Potential Options for Managing Riparian Conservation 

Areas in Selected Watersheds

58 Division of the Interim Riparian Reserves Among Different Goals Under 

the Two Options

73 Rates and Intensities of Harvest in the Reclassified Interim Riparian Reserve

74 Distribution of Stream Classes Between Landowner Groups

74 Potential Impacts on Terrestrial Biodiversity

77 Research Implications

78 Conclusions

81 Acknowledgments

81 Metric Equivalents

81 Literature Cited

1

Potential Options for Managing Riparian Reserves of the Aquatic Conservation Strategy of the Northwest Forest Plan

Introduction

Across the area of the Northwest Forest Plan (NWFP) (USDA and USDI 1994), 

management of riparian and aquatic ecosystems is a major focus of and challenge 

to federal land-management agencies. These ecosystems occupy about 40 percent 

of the federal land base, and on federal forest lands within the range of the northern 

spotted owl (Strix occidentalis caurina), the Aquatic Conservation Strategy (ACS) 

guides federal agencies in their management. The goals of the ACS are to: (1) maintain and restore the ecological processes that create and maintain habitat for native 

aquatic and riparian-dependent organisms; and (2) provide sources of high-quality 

water, recreation, and other ecological benefits (USDA and USDI 1994). Recovery 

of species listed under the Endangered Species Act is tightly tied to successfully 

meeting these goals.

The riparian reserve network, a cornerstone of the ACS, defines the spatial 

extent of the riparian ecosystem based on the distance from the stream at which 

key ecological processes occur. Interim riparian reserves of two site-potential 

tree-heights on fish-bearing streams and one site-potential tree-height on nonfish-bearing streams were established when the NWFP was adopted. We focus on 

riparian reserves here because their interim boundaries could be adjusted based 

on “scientifically sound reasoning” and site-specific information resulting from 

watershed analysis (FEMAT 1993, p. V-35), thus enabling an improved reserve 

design to better meet ACS objectives (FEMAT 1993, p. V-44) and the broader goals 

of the NWFP. However, there have been only minor boundary adjustments, especially within one tree-height of streams (Reeves 2006), since adoption of the NWFP 

in 1994 (Baker et al. 2006, Reeves et al. 2006).

Everest and Reeves (2007) found no scientific evidence that the default prescriptions in the Northwest Forest Plan provided more protection than necessary to 

meet stated riparian management goals. However, they also stated that additional 

alternative riparian management strategies that meet ASC objectives, while providing opportunities for other management objectives, could be implemented and evaluated. We apply findings and results of scientific studies published since FEMAT 

(1993) in an evaluation of two potential options for management of the interim 

riparian reserves that meet ASC objectives while providing opportunities for other 

management objectives, then examine projected consequences in six watersheds 

in western Oregon that contain land managed by the Bureau of Land Management 

(BLM). Considering only lands allocated as matrix, where timber production is one 

of the goals of the NWFP, these options evaluate potential adjustments to riparian 

reserve boundaries and management strategies within the area currently designated 

as interim riparian reserves. In both options, the other components of the ACS (key 
2

GENERAL TECHNICAL REPORT PNW-GTR-937

watersheds, monitoring, and standards and guidelines) are maintained across all 

allocations, and existing interim riparian reserves are maintained in land allocations 

outside of matrix. 

Both potential options focus on the area within one site-potential tree-height 

of fish-bearing and non-fish-bearing streams in matrix and divide this area into an 

inner zone and outer zone with different management objectives and activities. The 

inner zone is devoted solely to achieving ACS goals; the outer zone is managed to 

achieve ACS goals as well as other management goals, which could include timber 

production. The first option uses a fixed-width approach to delineate the two zones, 

and the second uses a context-dependent approach based on the ecological characteristics of each stream reach. These options fall within the bounds of what was 

expected by the developers of the ACS (FEMAT 1993) and the Record of Decision 

(ROD) (USDA and USDI 1994).

Our analysis provides a means to understand recent scientific information in 

the context of possible management options, and suggests ways this information 

might be used to develop new approaches for managing interim riparian reserves 

other than as de facto reserves. These analyses are not intended to suggest or imply 

that the two options evaluated here are the only ones for managing interim riparian 

reserves. In common with the interim riparian reserves, these or any other options 

should not be viewed as immutable, and as with any new approach to management, 

implementation and evaluation in an adaptive management context (Stankey et al. 

2005) is imperative.

The Aquatic Conservation Strategy in the 

Northwest Forest Plan

Goals

The Aquatic Conservation Strategy is a regional strategy applied to aquatic and 

riparian ecosystems across the area covered by the NWFP. It seeks to prevent 

degradation of aquatic ecosystems and to restore and maintain water quality, 

habitat, and the ecological processes responsible for creating habitat for Pacific 

salmon (Oncorhynchus spp.) and other aquatic and riparian-dependent organisms, 

over broad landscapes of public lands administered by the U.S. Department of 

Agriculture Forest Service and the U.S. Department of the Interior Bureau of Land 

Management (USDA and USDI 1994). The ACS was developed during the analysis 

that led to the Northwest Forest Plan (FEMAT 1993), but its foundation was a 

refinement of earlier strategies: the Scientific Panel on Late-Successional Forest 

Ecosystems (“The Gang of Four”) (Johnson et al. 1991), PacFish (USDA 1992), and 

the Scientific Assessment Team (Thomas et al. 1993). In the short term (10 to 20 

As with any new 

approach to management, implementation 

and evaluation in an 

adaptive management 

context is imperative.
3

Potential Options for Managing Riparian Reserves of the Aquatic Conservation Strategy of the Northwest Forest Plan

years), the ACS was designed to halt further declines in watershed condition, and to 

protect watersheds that currently had good-quality habitat and strong fish populations (FEMAT 1993). The long-term goal (100+ years) was to develop a network 

of functioning watersheds that support populations of fish and other aquatic and 

riparian-dependent organisms across the NWFP area (USDA and USDI 1994). 

The ACS sets out five components to meet its goals and objectives: (1) watershed analysis; (2) riparian reserves; (3) key watersheds; (4) watershed restoration; 

and (5) standards and guidelines for management activities (USDA and USDI 

1994). Each component is essential for the success of the ACS (USDA and USDI 

1994), and any assessment must consider all five of these components in aggregate.

Riparian reserves were intended to define the outer boundaries of the riparian 

ecosystem, and encompass the portions of a watershed most tightly coupled with 

streams and rivers. Riparian areas provide the ecological functions and processes 

necessary to create and maintain habitat for aquatic and riparian-dependent organisms over time, dispersal corridors for a variety of terrestrial organisms, and 

connectivity of streams within watersheds (FEMAT 1993). The FEMAT scientists 

developed three riparian management scenarios (FEMAT 1993, p. V-37). Each scenario required a reserve width on fish-bearing streams equal to two times the height 

of a site-potential tree (minimum of 300 ft [91.4 m]), where a site-potential tree 

is defined as a tree that has attained the average maximum height possible given 

the conditions where it occurs (FEMAT 1993, p. V-32). The riparian management 

scenarios varied in their requirements for non-fish-bearing streams, ranging from 

a width equal to one-sixth of a site-potential tree-height (minimum of 25 ft [7.6 

m]) to that of one site-potential tree-height (FEMAT 1993, p. V37). One scenario 

was integrated into each of the 10 landscape alternatives developed by the FEMAT 

scientists (FEMAT 1993).

The Secretaries of Interior and Agriculture chose FEMAT’s option 9 as their 

preferred alternative, which called for a riparian reserve network that was two sitepotential tree-heights wide on fish-bearing streams and one half of a site-potential 

tree-height on most non-fish-bearing streams. Interim boundaries of riparian 

reserves were extended to a full site-potential tree-height on all non-fish-bearing 

streams between the draft and final environmental impact statements (USDA and 

USDI 1994) to increase the likelihood of success of the ACS, and to provide additional protections for non-fish organisms that use the area near streams as habitat or 

migratory corridors (FEMAT 1993). Thinning to advance aquatic ecosystem values 

is allowed within the riparian reserves, but timber production is not a management 

goal (USDA and USDI 1994).
4

GENERAL TECHNICAL REPORT PNW-GTR-937

Watershed condition since implementation of the ACS—

To date, the ACS has met the goal of improving the ecological condition of watersheds across federal lands to which it applies (Lanigan et al. 2012, Reeves et al. 

2006). After the first 10 years of implementation, the ecological condition of 65 

percent of watersheds improved, 28 percent declined, and 7 percent remained 

unchanged (Reeves 2006, Reeves et al. 2006). After 15 years, ecological conditions 

had improved in 69 percent of the watersheds, and declined in 18 percent (Lanigan 

et al. 2012). The primary factors responsible for improvement were an increase in 

the number of large trees (>20 inches [51 cm] in diameter) in riparian areas and a 

reduction in road densities in watersheds. Watersheds in which conditions declined 

have recently experienced wildfires. 

Underlying Principles and Concepts

We begin with a discussion of contemporary research findings that formed the 

foundation for designing both potential options in this report: (1) the dynamic 

nature of aquatic ecosystems in space and time, (2) the ecological importance of 

non-fish-bearing streams, and (3) the effects of timber harvest on microclimate and 

amphibians. Next, we discuss forest-management strategies that we incorporated 

into the options: (1) ecological forestry as described in Franklin and Johnson (2012) 

as a guide to silviculture, and (2) “tree-tipping” to compensate for potential loss in 

wood recruitment to streams.

Streams and associated aquatic ecosystems: dynamic in space and time—

Assessing potential ecological effects of management in riparian ecosystems is 

dependent on a number of factors. A critical though seldom explicitly recognized 

factor is the perspective on how streams and their associated aquatic ecosystems 

behave in space and time. One view holds that aquatic ecosystems tend to be in 

an equilibrium or steady state, and when disturbed they are expected to return 

to pre-disturbance conditions relatively quickly (Resh et al. 1988, Swanson et al. 

1988). Biological (Vannote et al. 1980) and physical conditions (Rosgen 1994) are 

presumed to be relatively constant through time and to be “good” (barring human 

interference) in all systems at the same time. Conditions in aquatic systems with 

little or no human influence, particularly those associated with old-growth forest, 

are understood to have the most favorable conditions for fish and other aquatic 

organisms, and are most frequently used as references against which the condition of managed streams (e.g., Index of Biotic Integrity) (Karr and Chu 1999) and 

impacts from management actions can be assessed.

In contrast, there is an emerging paradigm that views streams as being dynamic 

in space and time, exhibiting a range of potential conditions, as do the terrestrial 
5

Potential Options for Managing Riparian Reserves of the Aquatic Conservation Strategy of the Northwest Forest Plan

systems in which they are embedded. The condition of individual streams and 

watersheds is recognized as variable through time (Naiman et al. 1992) and 

dependent on landscape context, legacies of past disturbance, and time since past 

disturbance (Benda et al. 1998, Reeves et al. 1995, Rieman et al. 2006, Wondzell 

et al. 2007). Larger streams and rivers in the lower portion of the network are less 

variable through time; those in the upper and middle portions are more dynamic 

(Naiman et al. 1992). Pristine (i.e., unmanaged) and minimally disturbed aquatic 

systems may actually exhibit a wider range of conditions than more heavily managed systems (Lisle 2002, Lisle et al. 2007). The range of conditions that aquatic 

ecosystems in different areas likely experience through time will differ depending 

on the natural disturbance regime, topographic setting, and geology. See Reeves 

(2006) for a more detailed review.

Ecological importance of non-fish-bearing streams—

Riparian reserves are a cornerstone of the ACS, and include fish-bearing streams, 

which had been the focus of the management of aquatic ecosystems before FEMAT, 

as well as small, fishless headwater streams. Since the ACS was originally developed, the ecological importance of headwater streams, which generally make 

up 70 percent or more of the stream network (Gomi et al. 2002), has been firmly 

established. Headwaters are sources of sediment (Benda and Dunne 1997a, 1997b; 

MacDonald and Coe 2007; Zimmerman and Church 2001) and wood (Bigelow et 

al. 2007, May and Gresswell 2003, Reeves et al. 2003) for fish-bearing streams, 

provide habitat for several species of native amphibians (Kelsey and West 1998) 

and macroinvertebrates (Meyer and Wallace 2001), including recently discovered 

species (Dieterich and Anderson 2000), and may be important sources of food for 

fish (Wipfli and Gregovich 2002). Small streams are also storage and processing 

sites for nutrients and organic matter, forming the energy base for organisms used 

by fish as food (Kiffney et al. 2000, Wallace et al. 1997, Webster et al. 1999, Wipfli 

and Gregovich 2002).

Headwater streams are among the most dynamic portions of aquatic ecosystems 

(Naiman et al. 1992). Tributary junctions between headwater streams and larger 

channels are important nodes for regulating material flows in a watershed (Benda 

et al. 2004, Gomi et al. 2002) and are the locations where site-scale effects from 

management activities are often observed. These locations have unique hydrologic, 

geomorphic, and biological attributes. The movement of sediment, wood, and other 

materials through tributary junctions results in sites of high biodiversity (Johnson et 

al. 1995, Minshall et al. 1985). Habitat in these sites may also range from simple to 

complex, depending on time since disturbance (such as landslides and debris flows) 

and the types and amount of materials delivered to the channel.
6

GENERAL TECHNICAL REPORT PNW-GTR-937

Wood enters streams via chronic and episodic processes (Bisson et al. 1987). 

Chronic processes, such as tree mortality and bank undercutting (Bilby and Bisson 1998, Grette 1985, Murphy and Koski 1989), generally introduce single trees 

or relatively small numbers of trees at frequent intervals. Wood from headwater 

streams is delivered to fish-bearing streams by large, infrequent events, such as 

windthrow (Harmon et al. 1986), wildfire (Agee 1993), severe floods, landslides, 

and debris flows (Benda et al. 2003, Keller and Swanson 1979, May and Gresswell 

2003, Reeves et al. 2003). Geomorphic features of a watershed influence the potential contribution of upslope wood sources. Steeper, more highly dissected watersheds will likely have a greater proportion of wood coming from upslope sources 

than will watersheds with lower stream densities and gradients.

The presence of large wood from headwater streams influences the behavior of 

landslides and debris flows, and the response of the channel to such events. Large 

wood in debris flows and landslides influences the run-out length of these disturbance events (Lancaster et al. 2003). Debris flows without large wood move faster 

and for longer distances than those with wood, and they are less likely to stop high 

in the stream network. A debris flow without wood is likely to be a concentrated 

slurry of sediments of various sizes that can move at relatively high speeds over 

long distances, scouring substrate and wood from the affected channels. These 

types of debris flows are more likely to negatively affect fish-bearing channels, as 

compared to the potentially favorable effects that result from the presence of wood. 

Woodless debris flows can further delay or impede the development of favorable 

conditions for fish and other aquatic organisms. 

Over time, headwater depressions and channels are filled with material from 

the surrounding hillslopes, including large wood that falls into these channels, 

forming obstructions behind which sediments accumulate (Benda and Cundy 1990, 

May and Gresswell 2004). These filled areas are evacuated following a landslide 

or debris flow. This cycle of filling and emptying results in a punctuated movement 

of sediment and wood to larger, fish-bearing streams (Benda et al. 1998), which 

is—at least in part—responsible for the long-term productivity of many aquatic 

ecosystems (Benda et al. 2003, Hogan et al. 1998, Reeves et al. 1995). The absence 

of wood to replenish the refilling process may result in a chronic movement of sediment to larger channels, which could lead to those channels developing different 

characteristics than those that occurred before forest management. Such conditions 

could be outside the range of watershed conditions to which native biota are adapted 

(Beschta et al. 2004).
7

Potential Options for Managing Riparian Reserves of the Aquatic Conservation Strategy of the Northwest Forest Plan

Ecological forestry as a silvicultural guide— 

Ecological forestry applies current ecological understanding of forest ecosystems 

and how they work to achieve integrated environmental, economic, and cultural 

management outcomes (Franklin and Johnson 2012, Franklin et al. 2007). It contrasts with production forestry, which applies agronomic and economic models 

in the efficient production of wood products (Franklin and Johnson 2013). Key 

elements of ecological forestry (Franklin and Johnson 2012, Franklin et al. 2007) 

include: (1) retaining structural and compositional elements of the pre-harvest stand 

during variable-retention harvests; (2) using natural stand-development principles 

and processes to manipulate established stands in order to restore or maintain 

desired structure and composition; (3) using return intervals for silvicultural 

activities that are consistent with recovery of desired structures and processes; 

and (4) planning management activities at landscape scales, in accordance with 

knowledge of spatial pattern and ecological function in natural landscapes. 

Franklin and Johnson (2012) distinguish between “moist forests” and “dry 

forests” (fig. 1) in their recommendations on implementing ecological forestry 

(box 1), owing to the contrasting disturbance regimes and responses to management of these two types of forests. Historically, moist forests generally experienced 

large, infrequent wildfires (at intervals of one to several centuries) as their dominant 

disturbance agent, which produced extensive areas in which fire severity resulted 

in stand-replacement conditions (Agee 1993). Dry forest sites experienced predominantly low- and mixed-severity fire behaviors at frequent (e.g., 5- to 35-year) intervals (Agee 1993, Perry et al. 2011). Some plant associations currently straddle the 

boundary between moist and dry forest, but climate change is expected to increasingly shift these associations toward dry forest status, with projected increases in 

wildfire frequency (e.g., Dello and Mote 2010, Spies et al. 2010). 

The distinction between moist forests and dry forests is especially critical in 

developing policies and practices intended to protect old-growth forests and trees. 

Existing intact old-growth forests on moist forest sites have undergone limited 

changes as a result of >100 years of fire exclusion and suppression; active management to restore conditions within such stands is not only unnecessary, but could 

adversely affect them. Dry forest sites, on the other hand, have undergone dramatic 

changes from pre-European settlement conditions as a result of many human activities, including the elimination of fire. Consequently, dry forests have undergone 

significant changes and many are currently dense, fuel-loaded stands dominated by 

fire- and drought-intolerant species. Hence, policies may permit active management 

of such forests (including those with older trees) to create more resilient conditions 

(Franklin and Johnson 2012). 

Ecological forestry 

applies current ecological understanding 

of forest ecosystems 

and how they work 

to achieve integrated 

environmental, 

economic, and cultural 

management outcomes. 
8

GENERAL TECHNICAL REPORT PNW-GTR-937

Figure 1—Moist and dry forests (Franklin and Johnson 2012) on Bureau of Land Management and Forest Service lands outside of 

wilderness in western Oregon, with the six study watersheds highlighted.
9

Potential Options for Managing Riparian Reserves of the Aquatic Conservation Strategy of the Northwest Forest Plan

Box 1

Elements of Ecological Forestry Strategy (Franklin and Johnson 2012)

Moist forests—

• Retain existing older stands and individual older trees found within younger 

stands proposed for management, using a selected threshold age. 

• Accelerate development of structural complexity in younger stands, using diverse 

silvicultural approaches (Bailey and Tappeiner 1998, Carey 2003, Garman et al. 

2003, Wilson and Puettmann 2007).

• Implement variable-retention harvests (VRH) (Beese et al. 2003; Franklin et al. 

1997, 2007; Gustafsson et al. 2012) in younger moist forests, retaining such 

structures as individual trees, snags, logs, and intact forest patches. 

• Accommodate development of diverse early-seral ecosystems following harvest, 

by using less intense approaches to site preparation and tree regeneration. 

• Embed the preceding objectives in a silvicultural system that includes creation 

and management of multi-aged, mixed-species stands on long rotations (e.g., 

100 to 160 years). 

Dry forests—

• Retain and improve survivability of older conifers by reducing adjacent fuels 

and competing vegetation—old trees can respond positively (e.g., McDowell 

et al. 2003). 

• Retain and protect other important structures such as large hardwoods, snags, and 

logs; some protective cover may be needed for cavity-bearing structures that are 

currently being used (e.g., North et al. 2009).

• Reduce overall stand densities by thinning so as to: (1) reduce basal areas to 

desired levels; (2) increase mean stand diameter; (3) shift composition toward fireand drought-tolerant species; and (4) provide candidates for replacement old trees.

• Restore spatial heterogeneity by varying the treatment of the stand, such as by 

leaving untreated patches, creating openings, and providing for widely 

spaced single trees and tree clumps (Larson and Churchill 2012).

• Establish new tree cohorts of shade-intolerant species in openings.

• Treat management-related fuels and begin restoring historical levels of 

ground fuels and understory vegetation using prescribed fire.

• Plan and implement activities at landscape levels, incorporating spatial 

hetero-geneity (e.g., provision for denser forest patches) and restoration 

needs in non-
10

GENERAL TECHNICAL REPORT PNW-GTR-937

One specific objective of harvests in moist forests is the creation of diverse 

early-seral ecosystems as a part of a silvicultural system that includes management 

of mixed-age, mixed-species forests over long (e.g., 80- to 160-year) rotations. 

Early-seral ecosystems in moist forests in Oregon are highly diverse, trophic- and 

function-rich ecosystems that occur after a severe disturbance but before the 

re-establishment of a closed forest canopy (Swanson et al. 2011). In general, moist 

forest landscapes are currently lacking in high-quality early-seral ecosystems 

because of harvest, reforestation, and fire-suppression policies on both private and 

public lands (Spies et al. 2007, Swanson et al. 2011).

Functional early-seral habitat can be created using variable-retention harvest 

prescriptions that retain biological legacies and use less-intensive approaches to 

re-establishment of closed forest canopies (Franklin and Johnson 2012). Unlike 

conventional clearcuts, these variable-retention harvests retain significant elements 

of the pre-harvest stand through the following rotation, including undisturbed forest 

patches and individual live and dead trees that enrich the biodiversity, ecological 

processes, and structural diversity of the post-harvest stand (Gustafsson et al. 2012, 

Lindenmayer et al. 2012). 

Franklin and Johnson (2012) recommend moist forest variable-retention harvest 

that retains approximately one-third of the pre-harvest stand, inclusive of riparian 

buffers for small non-fish-bearing streams embedded in the harvest unit (fig. 2). 

Most of that retention is in patches, with some additional retention of individual 

trees scattered over the unit. 

With these biological legacies intermixed with openings created by harvest, 

variable-retention harvests can provide favorable conditions for the development 

of diverse early-seral ecosystems important for regional biodiversity (Swanson et 

al. 2011) and the establishment of new cohorts of desirable shade-intolerant tree 

species, while maintaining a flow of wood products (Franklin and Johnson 2012). 

Biological legacies, including retained tree patches, individual trees, snags, and 

down wood, provide structural and biological continuity across successional stages, 

and lead to multi-story stand structure and heterogeneous landscapes. See figure 

3 for an example of diverse early-seral ecosystems following a variable-retention 

harvest.

The ecological forestry strategy for dry forests (box 1) relies on a combination of stand-level treatments and retention of dense forest habitat patches at the 

landscape level; such an approach has recently been incorporated into projects on 

federal lands (e.g., Ager et al. 2007, Franklin et al. 2013, Gaines et al. 2010), and 

projects using this strategy are underway on BLM lands in southwestern Oregon 

(Reilly 2012). 
11

Potential Options for Managing Riparian Reserves of the Aquatic Conservation Strategy of the Northwest Forest Plan

Figure 2—Simulation of Franklin and Johnson’s variable-retention harvest scheme with retention patches, scattered retained trees, 

with retention focused along streams. Retention level across the harvest unit was approximately 35 percent. Simulation by Laura 

Hardin at the direction of K.N. Johnson, 2013. ACS = Aquatic Conservation Strategy.

Figure 3—Diverse early-seral ecosystem following a variable-retention harvest.

Norm Johnson
12

GENERAL TECHNICAL REPORT PNW-GTR-937

Retaining and nurturing older trees and other significant structural elements of 

dry forest stands is the starting point for this restoration strategy. Currently, these 

older trees and the forests in which they are embedded are at risk from intense 

wildfires, epidemics of defoliating insects, and competition, the latter resulting in 

accelerated mortality resulting from bark beetles (Franklin and Johnson 2012). The 

dry forest restoration strategy is designed to reduce these risks.

We focus the discussion of ecological forestry in this report on moist forests 

because they cover most of our study watersheds, and involve the most controversial harvest practice—variable-retention harvest to create openings. To achieve 

the goals of the ACS, activities in moist forests within riparian conservation areas 

(the area of interest for aquatic conservation) should generally be limited to stands 

currently less than or equal to 80 years of age.1 Watersheds with forests 80 to 

140 years old in the Oregon Coast Range are believed to be the most productive 

for salmon (Reeves et al. 1995). For example, reaches of streams with natural 

forests greater than 80 years old had the highest abundances of juvenile Chinook 

salmon (O. tshawytscha) in Elk River, Oregon (Burnett 2001). The joint riparian 

review group from the National Marine Fisheries Service, U.S. Forest Service, 

BLM, Environmental Protection Agency, U.S. Geological Survey, and U.S. Fish 

and Wildlife Service recommended that thinning be limited to stands less than or 

equal to 80 years of age (Spies et al. 2013). Also, Franklin and Johnson (2012) view 

younger, previously harvested acres (generally stands currently less than or equal to 

80 years of age) as prime candidates for variable-retention harvests, given that the 

area of older forests is far below historical levels (FEMAT 1993) and that scientific 

review (Forsman et al. 2011) and policy direction (USFWS 2011, 2012) increasingly 

call for retention of mature and old forest in matrix as northern spotted owl habitat. 

The silvicultural practices of ecological forestry for moist forests differ between 

the inner and outer zones of the riparian conservation area in the options evaluated 

here. The inner zone is managed solely to achieve the goals of the ACS; thinning 

could be allowed to further ACS goals. The outer zone is managed to achieve the 

goals of the ACS and for other goals, including timber production using ecological 

forestry. Both thinning and variable-retention harvest could be allowed in the outer 

zone. 

1 Most stands currently less than 80 years of age were previously clearcut and planted; 

many have since been precommercially thinned and some have been commercially thinned. 

Note that not all stands currently ≤80 years of age would be available. Some include a 

remnant overstory of older trees that could make them function as older stands from a 

biodiversity standpoint; their availability for long-term timber production may be limited 

under the guidance in the Northern Spotted Owl Recovery Plan (USFWS 2011) and the 

guidance in the Northwest Forest Plan for conservation of marbled murrelet sites as they 

are found (USDA and USDI 1994). 
13

Potential Options for Managing Riparian Reserves of the Aquatic Conservation Strategy of the Northwest Forest Plan

Tree-tipping to compensate for potential reduction in wood recruitment—

The lack of wood in streams in managed forests is a primary concern of management and regulatory agencies, and warrants consideration in any riparian management scheme. Thinning is a potential technique for increasing tree growth (Dodson 

et al. 2012, Garman et al. 2003), and the purposeful placement of some proportion 

of the harvested wood in the channel or on the forest floor could immediately 

reduce deficiencies in dead wood that exist in many streams and riparian areas 

(Benda et al. 2015; see also Olson and Burnett 2009 and Olson and Kluber 2014). 

Thinning would produce more dead wood in riparian areas and streams in the short 

term than a stand that is left unthinned, where dead trees accumulate slowly as a 

result of competition, disease, disturbance, and other factors. Given the right stand 

conditions, such actions could have the added benefit of accelerating future development of very large-diameter (>40 inches) trees (Spies et al. 2013). However, any 

thinning activity to increase wood recruitment in the near and long terms will also 

have to consider potential impacts on water temperature and water quality. 

Benda et al. (2015) explored tree-tipping by modeling the amount of instream 

wood that would result from thinning a stand from 400 trees per acre to 90 trees 

per acre, which is considered a moderate amount of thinning, then directionally 

falling or pulling over varying proportions of the trees scheduled for harvest (table 

1). This was compared to the amount of wood that would be expected to be found 

in the stream without thinning the stand. The amount of wood increased above 

the “no thin” level immediately after the entry in all of the options of wood additions. However, the cumulative total amount of wood expected in the stream over 

100 years relative to the unthinned stand varied depending on the amount of wood 

delivered. Adding ≤10 percent of the wood that would be removed during thinning 

produced less wood in the channel over time than the unthinned option. When 15 

to 20 percent of the volume of thinned trees was tipped from one side of the stream 

at each entry, the total amount of dead wood in the channel over time exceeded the 

unthinned scenario (table 1). 

While further modeling is being done to better understand the effects of treetipping, the initial modeling results and other published papers (Carah et al. 2014, 

Spies et al. 2013) suggest that adding wood to streams during management activities 

could provide benefits to fish and fish habitat. We therefore include tree-tipping in 

the two management options described below. We assume that this topic will be 

further explored and evaluated through time, and that appropriate modifications of 

its application could be made as new knowledge is generated.

Adding wood to 

streams during 

management activities 

could provide benefits 

to fish and fish habitat.
14

GENERAL TECHNICAL REPORT PNW-GTR-937

Potential Options for Managing Riparian Reserves 

on BLM Western Oregon Forests—Design and 

Scientific Rationale 

Based on recent scientific information, we design and compare two potential 

options for managing the interim riparian reserve on BLM lands in western Oregon 

(fig. 4) that meet ACS objectives and concerns related to ESA-listed fish (fig. 5), 

while also meeting other management objectives. In both options, the interim riparian reserves are retained in late-successional reserves (fig. 6), which were primarily 

areas with mature and old-growth forests and key habitats for the northern spotted 

owl and the marbled murrelet (Brachyramphus marmoratus) (Thomas et al. 2007), 

and in other reserves. Both options focus on the area within one site-potential 

tree-height of fish-bearing and non-fish-bearing streams, which we call the riparian 

conservation area. On matrix lands, where timber production with thinning and 

regeneration harvest is one of the goals (USDA and USDI 1994), and in adaptive 

management areas, where innovative adaptive management practices were to be 

tried, the riparian conservation area of one tree-height is divided into an inner zone 

and outer zone. The inner zone is solely devoted to achieving goals of the ACS; the 

outer zone is managed to achieve ACS goals as well as other potential goals, which 

could include timber production, achieved through ecological forestry practices. 

One option uses a fixed-width approach to divide the riparian conservation area 

between the two zones; the other uses a context-dependent approach based on the 

ecological characteristics of the stream reach. “Tree-tipping” is used throughout 

Table 1—Predicted cumulative wood storage (m3 ∙ 100 m-1) 

over the simulated century (includes decay), showing 

differences between the no-treatment alternative in 

comparison to various combinations of single- and 

double-entry thins, a 10-m buffer, and tree-tipping of 

between 5 percent and 20 percent

Scenario

Change from no treatment

Single-entry 

thin 

Double-entry 

thin 

Percent

No treatment (reference) 0 0

Thin -33 -42

Thin, buffer -7 -11

Thin, tip 5 percent -15 -15

Thin, tip 10 percent -6 +1

Thin, tip 15 percent +1 +16

Thin, tip 20 percent +6 +24
15

Potential Options for Managing Riparian Reserves of the Aquatic Conservation Strategy of the Northwest Forest Plan

Figure 4—Land ownership in western Oregon, with the six study watersheds highlighted.
16

GENERAL TECHNICAL REPORT PNW-GTR-937

Figure 5—Critical habitat for the Oregon Coast coho salmon, and Willamette River bull trout, spring Chinook salmon, and summer 

steelhead evolutionarily significant units (ESUs), with the six study watersheds highlighted. Critical habitat for the Southern Oregon/

Northern California ESU for coho salmon is not shown because spatial data were not available. 
17

Potential Options for Managing Riparian Reserves of the Aquatic Conservation Strategy of the Northwest Forest Plan

Figure 6— Northwest Forest Plan land allocations for western Oregon, with the six study watersheds highlighted.
18

GENERAL TECHNICAL REPORT PNW-GTR-937

the riparian conservation area to ensure that any harvest does not negatively affect 

wood recruitment to the stream. Both options limit harvest within one site-potential 

tree-height of streams to stands currently less than or equal to 80 years in age. Also, 

the recently developed recovery plan for the northern spotted owl and associated 

critical habitat (USFWS 2011) (fig. 7) will further limit harvest of mature and oldgrowth forest within two site-potential tree-heights of streams and throughout the 

matrix. 

We first discuss the logic behind the potential options and then simulate the 

application of these two options for BLM matrix in six watersheds, along with the 

interim riparian reserves for comparison.

Option A 

Under option A, all the components of the ACS are applied. Interim riparian 

reserves are retained in the late-successional reserves and other special land designations. In matrix, a riparian conservation area of one site-potential tree-height 

is recognized along all streams. For fish-bearing streams in matrix, the riparian 

conservation area would be managed solely to achieve goals of the ACS, as would 

an inner zone of one-half site-potential tree-height on non-fish-bearing streams 

(fig. 8). An outer zone of the riparian conservation area on non-fish-bearing streams 

equal to the remaining one-half of a site-potential tree-height could include timber 

production as an additional goal (see box 1 for prescriptions that could be considered in the outer zone). 

Scientific considerations for riparian conservation areas along 

fish-bearing streams—

A primary purpose of the riparian conservation areas is to maintain the key ecological processes that contribute to the long-term productivity of the aquatic ecosystem, 

similar to the purpose of the interim riparian reserves of the ACS. These processes 

occur almost exclusively within the first site-potential tree-height from the stream 

(USDA and USDI 1994), and include the beneficial effects of root strength for bank 

stability, litter fall, shading to moderate water temperatures, and delivery of coarse 

wood to streams (fig. 9a). In addition, the majority of moderating effects of sediment delivery to streams from overland erosion associated with upland activities 

generally occurs within a distance of one site-potential tree-height (Castelle et al. 

1994, Naylor et al. 2012). 

Options A and B retain 

all components of the 

Aquatic Conservation 

Strategy.
19

Potential Options for Managing Riparian Reserves of the Aquatic Conservation Strategy of the Northwest Forest Plan

Figure 7—Northern spotted owl critical habitat for Oregon, over Northwest Forest Plan land allocations, with the six study 

watersheds highlighted.
20

GENERAL TECHNICAL REPORT PNW-GTR-937

Figure 8—Comparison of the widths of riparian reserves under current federal policy, the inner and outer zones of riparian 

conservation areas under potential options A and B, with riparian management areas as they apply to private lands under the 

Oregon Forest Practices Rules as contrast.
21

Potential Options for Managing Riparian Reserves of the Aquatic Conservation Strategy of the Northwest Forest Plan

0 0.2 0.51

1000

Cumulative effectiveness (percent) Cumulative effectiveness (percent)

Shading

Coarse wood

debris to stream

Litter

fall

Root

strength

0 0.2 0.51

1000

Distance from channel (tree height)

Coarse wood

debris to stream

Original

Modified

AB

Figure 9—(A) Relation of distance from stream channel to cumulative effective-

ness of riparian ecological functions. From: FEMAT (1993, p. V-27); (B) Modified 

effectiveness curve for wood delivery to streams as a function of distance from the 

stream channel. The curve was changed based on scientific literature developed 

since the original curve was portrayed in FEMAT (1993).

One site-potential tree-height from the edge of a stream may not encompass the 

entire floodplain of some fish-bearing streams. Forests in floodplains can be important sources of large wood that provide a suite of ecological functions (Latterell 

and Naiman 2007). In such cases, it is critical to recognize and protect the entire 

floodplain. This was accomplished in the ACS by requiring the boundary of the 

riparian reserve to extend to the edge of the 100-year floodplain (USDA and USDI 

1994). That requirement would be retained under options A and B. In any case, 
22

GENERAL TECHNICAL REPORT PNW-GTR-937

most fish-bearing streams on BLM lands in western Oregon are small to medium in 

size, without extensive floodplains. As a result, one site-potential tree-height should 

be sufficient to retain the full suite of ecological processes in most situations.

A primary purpose for the extension of the boundary of the riparian reserve of 

the Northwest Forest Plan from one site-potential tree-height to two on fish-bearing 

streams was to protect and enhance the microclimate of the riparian ecosystem 

within the first tree-height (USDA and USDI 1994). Research on the effects of 

clearcutting on microclimatic conditions in adjacent upland forest stands (Chen 

et al. 1993) found that the influence (of the clearcut) extended from yards (e.g., 

soil moisture) to hundreds of yards (e.g., wind velocity) into adjacent unharvested 

stands. Based on the initial work of Chen et al. (1993), FEMAT (1993) hypothesized 

that a second tree-height could provide significant benefits to riparian reserves in 

terms of relative humidity and other microclimatic effects in the riparian reserve 

along fish-bearing streams (FEMAT 1993, fig. V-13, p. V-27). 

In the years since the ACS and associated ecological function curves were 

originally formulated, a number of research efforts have examined the effects of 

forest management on microclimate in riparian areas. The vast majority of this 

work has focused on small, headwater streams; few studies were conducted along 

larger streams (see review by Moore et al. 2005; Olson et al. 2007, 2014). The 

magnitude of harvest-related changes in microclimate in riparian areas is usually inversely related to the width of the riparian buffer and the type and extent 

of management activities on the outer edge. The extent varied from a distance of 

30 m (Anderson et al. 2007, Rykken et al. 2007) to 45 m (Brosofske et al. 1997) 

from the stream. A microclimate “stream effect” counteracts harvest edge effects, 

reducing the distance of climate effects in riparian zones (Rykken et al. 2007) from 

those projected by Chen et al. (1993) in uplands. Hence, the FEMAT microclimate 

curves are not necessarily accurate for riparian areas with a strong stream effect. 

As a result, a one tree-height buffer on fish-bearing streams has been suggested as 

a means to substantially reduce potential impacts of harvesting in areas on the edge 

of the riparian reserve on riparian microclimate and water temperature (Brosofske 

et al. 1997, Moore et al. 2005).

Uncertainties exist in reducing the size of the Northwest Forest Plan’s riparian reserves. One concern is the potential for increased warming of streams. The 

scientific evidence is mixed on this issue (see review by Moore et al. 2005); generally, the smaller the riparian area and the more extensive the activities, the greater 

the effect on stream temperature. Pollock et al. (2009) examined water temperatures 

in watersheds with varying extent of timber harvest. They found that watersheds 

with no harvest had statistically lower water temperatures than those with varying 

A one tree-height 

buffer on fish-bearing 

streams reduces 

potential impacts of 

harvesting in areas on 

the edge of the riparian 

reserve on riparian 

microclimate and 

water temperature.
23

Potential Options for Managing Riparian Reserves of the Aquatic Conservation Strategy of the Northwest Forest Plan

amounts (12.1 °C vs. 14.5 °C). Although the differences are statistically significant, 

the ecological consequences are less clear. The higher temperatures are still well 

within the range considered suitable for native fish (not mentioned by the authors) 

and below state standards in Oregon (ODEQ 2015). Additionally, Pollack et al. 

(2009) found that the amount of recently clearcut riparian forest (<20 years) within 

600 m upstream of their monitoring sites ranged from 0 to 100 percent and was not 

correlated with increased stream temperatures. However, the options we evaluated 

do not allow clearcutting in riparian areas. 

Other factors such as substrate (Janisch et al. 2012, Johnson 2004) and topographic shading can influence water temperatures as much as, and perhaps more 

than, shade from streamside forests. Although there is a potential for streams to 

warm as a result of silvicultural activities, the likelihood is very small when harvest 

takes place beyond one tree-height. This is especially applicable to small streams 

because temperature increases in headwater streams are unlikely to produce substantial changes in the temperatures of larger streams into which they flow, unless 

the total inflow of heated tributaries constitutes a significant proportion of the total 

flow in the receiving stream (Kibler et al. 2013, Moore et al. 2005). 

Scientific considerations for riparian conservation areas along 

non-fish-bearing streams— 

Effect on microclimate and water temperature—Anderson et al. (2007) conducted 

one of the more comprehensive studies on the effect of vegetation manipulation 

in riparian areas of varying sizes, in stands 30 to 70 years old. They monitored 

microclimatic conditions in riparian areas on fish- and non-fish-bearing headwater 

streams in western Oregon that had varying widths (<49 to 492 ft [14.9 to 150 m]) 

and moderate levels of thinning (reducing trees from 250–432 trees per acre to 100 

trees per acre), and measured changes in microclimate above the stream channel 

and in the adjacent riparian zone, relative to unthinned stands. With riparian management areas of 49 ft or greater width, daily maximum air temperature above the 

stream center was less than 1°C higher, and daily minimum relative humidity was 

less than 5 percent lower than for unthinned stands. If the area adjacent is clearcut, 

a 98.5-ft (30-m) riparian management area maintains microclimatic conditions 

(Rykken et al. 2007). 

Under option A, the inner zone of the resource conservation area along nonfish-bearing streams managed solely to achieve the goals of the ACS equals onehalf the height of a site-potential tree (minimum distance of 75 ft [22.9 m]). This 

width is greater than the 49-ft (15.9-m) threshold width reported by Anderson et al. 

(2007); at greater widths, post-treatment air temperature and humidity at stream 

center increased less than 1 °C and 5 percent, respectively. Strategic placement of 
24

GENERAL TECHNICAL REPORT PNW-GTR-937

aggregate or dispersed retention during variable-retention harvest (recommended as 

one-third of the preharvest stand) should help ameliorate potential negative impacts. 

As an example, retaining trees along the half-tree-height boundary would increase 

the effective width of the inner zone. Also, reduction in tree density in the outer 

zone could provide benefits, in the form of increased growth of trees, to trees in the 

inner zone, up to 49 ft (15 m) into an unthinned stand from the edge of a thinned 

stand (Ruzicka et al. 2014). Thus, although the area devoted solely to achieving 

the goals of the ACS is smaller than that of the interim riparian reserves, there is 

evidence to suggest that the suite of ecological benefits should be retained as part 

of a comprehensive approach that includes ecological forestry and tree-tipping (fig. 

10). 

Relative to temperature effects, non-fish-bearing streams tend to be narrow 

channels in steeper constrained valleys (Gomi et al. 2002, Moore et al. 2005). 

Near-stream vegetation and topographic features often shade the entire channel in 

such settings (Janisch et al. 2012), thus the application of the curve for shade in the 

FEMAT ecological curves graph (fig. 9a) is not necessarily appropriate. In addition, 

water temperatures in headwater streams are strongly influenced by in-channel 

substrate (Janisch et al. 2012, Johnson 2004). Neither of these factors would be 

affected by narrowing the riparian management areas, and adopting option A for 

non-fish-bearing streams is not anticipated to increase water temperatures in these 

streams. 

Effect on amphibians—Olson et al. (2007) reviewed studies of the effects of 

timber harvest activities, inside and outside of riparian reserves, on microclimatic 

conditions and amphibians. They concluded that relatively narrow buffers (compared to those of the Northwest Forest Plan) can be effective in maintaining microclimates 33 to 66 ft (10 to 20 m) from the stream center, although the type of 

upland harvest matters (Rykken et al. 2007). Potential concerns about microclimate 

can be further reduced by minimizing clearcutting along the outer boundary of 

riparian management areas (Anderson et al. 2007, Kluber et al. 2008, Moore et al. 

2005). As mentioned previously, clearcutting is not part of the silvicultural strategy 

under ecological forestry; strategically placing aggregated retention patches during 

harvest should help allay concerns. Instream and streambank amphibians were retained with a 49-ft (15-m) riparian management area through two rounds of upslope 

harvest in headwater streams in the Coast and Cascade ranges of western Oregon 

(Olson and Burton 2014). Management of the one-half of a site-potential tree-height 

(minimum distance of 75 ft [22.9 m]) along each side of non-fish-bearing streams 

(the inner zone) solely for ACS goals, and using ecological forestry and tree-tipping 
25

Potential Options for Managing Riparian Reserves of the Aquatic Conservation Strategy of the Northwest Forest Plan

Soil 

moisture

Soil

temperature Radiation

Air 

temperature

Wind speed

Relative

humidity

0 0.5 123

Relative

humidity,

from above

0 0.5 123

Relative

humidity,

adjusted

1000

Cumulative effectiveness (percent) Cumulative effectiveness (percent)

1000

Distance from stand edge into forest (tree-heights)

AB

Figure 10—(A) Relation of distance from stream channel to cumulative effectiveness 

of factors influencing microclimate in riparian ecosystems. From FEMAT (1993, p. 

V-27); (B) Modified effectiveness curve for relative humidity as a function of distance 

from the stream channel. The curve was changed based on scientific literature devel-

oped since the original curve was portrayed in FEMAT (1993).

on the distance equal to the other half of a site-potential tree-height (the outer zone) 

should be sufficient to maintain favorable conditions for many amphibians (Olson 

and Burton 2014). 

Headwater streams may also serve as connection corridors within and between 

watersheds (Olson and Burnett 2009). Most amphibians moved along the stream 

within 45 ft (13.6 m) of the channel (Olson and Kluber 2014). Maintaining a one 
26

GENERAL TECHNICAL REPORT PNW-GTR-937

tree-height riparian conservation area on non-fish-bearing streams, with the inner 

half (at least 75 ft [22.9 m] in width) solely devoted to the ACS goals of the NWFP 

and the outer half managed with ecological forestry, should provide movement 

corridors for amphibians and other organisms within and between watersheds. 

Retention of the interim riparian reserves in late-successional reserves and other 

areas also provides movement corridors. In addition, providing for down wood on 

the forest floor during harvest, by tree-tipping, will further reduce potential impacts 

on terrestrial salamanders (Olson and Kluber 2014, Rundio and Olson 2007). 

Effect on wood recruitment—Allowing ecological forestry in the outer zone of 

riparian conservation areas along non-fish-bearing streams with the requirement for 

tree-tipping is also unlikely to adversely affect wood recruitment. The graph of the 

relationship between the cumulative effectiveness of an ecological process and the 

distance (expressed as the height of a site-potential tree) for wood recruitment from 

the immediately adjacent riparian area, developed in FEMAT (1993), suggested that 

about 60 percent of wood recruitment function occurs within one-half of a treeheight (fig. 9a). This graph was based on a limited number of studies (McDade et 

al. 1990, Van Sickle and Gregory 1990) and the professional judgment of scientists 

involved with FEMAT. Since publication of the FEMAT (1993) report, new examinations of studies on the sources of wood (Spies et al. 2013) and information in 

Gregory et al. (2003) suggest that, in the Cascade Range of western Oregon, about 

95 percent of the total instream wood inputs from the adjacent riparian area came 

from distances that ranged between 82 to 148 ft (25 to 45 m) from the stream. Given 

that the height of a site-potential tree in the study area is approximately 180 ft,2

 this 

suggests that 95 percent of the wood comes from a distance equal to 0.46 to 0.82 of 

a site-potential tree-height (fig. 9b). This scientific finding compares to the hypotheses expressed in the FEMAT curve (fig. 9a), showing that 95 percent of the wood 

recruitment function occurs within a distance equal to about 0.95 of the height of a 

site-potential tree. Thus, more of the wood recruitment comes from the inner half 

of a site-potential tree-height than assumed in FEMAT; managing this inner half 

solely for the goals of the ACS and managing the outer half of the riparian conservation area using ecological forestry and requiring tree-tipping should maintain the 

wood recruitment process in non-fish-bearing streams.

Initial analyses (Benda et al. 2015) suggest that placing 15 to 20 percent of the 

total volume that would be harvested in the inner zone (thinning) and the outer zone 

(thinning and variable-retention harvest) in the channel would result in as much 

2 Personal communication. Cheryl Friesen, science liaison, Willamette National Forest, 

57600 McKenzie Highway, McKenzie Bridge, OR 97413.

Allowing ecological 

forestry in the outer 

zone of riparian 

conservation areas 

along non-fish-bearing 

streams with treetipping is unlikely to 

adversely affect wood 

recruitment.
27

Potential Options for Managing Riparian Reserves of the Aquatic Conservation Strategy of the Northwest Forest Plan

wood in the channel as would accumulate in unharvested stands (table 1). This 

amount is likely to be sufficient in most cases, but site-specific analyses can be used 

to estimate the amount needed for a given setting. Implementing directional felling 

and placement of wood in the channel can present operational challenges. Methods 

and procedures need to be developed to ensure that this can be done successfully so 

that the goal for wood loading is met. 

Option B 

Option B is based on the same scientific findings discussed for option A. However, 

rather than taking a “one-size-fits-all approach,” this potential option employs a 

context-dependent approach that recognizes natural variation in where ecological 

processes critical to aquatic habitats occur within a watershed, and the inherent 

capacity of streams to provide habitat for selected fish species. This concept was 

not well understood or recognized at the time of the development of the ACS in 

the NWFP. 

Rationale and concepts for a context-dependent approach to riparian 

conservation and management—

Management of riparian areas has almost exclusively used fixed-width buffers, with 

the prescribed width determined by the stream size (average flow) or type (presence 

or absence of fish) (Richardson et al. 2012). This approach is easy to administer 

and apply, and is less costly than developing site-specific recommendations, in part 

because of the analysis required for the latter approach. The combination of these 

factors and uncertainty about results has limited the development and application of 

a context-dependent approach to riparian management. 

A key component of the ACS is watershed analysis (FEMAT 1993), which is 

supposed to provide the context of a given location for adjusting the boundaries of, 

and allowing activities within, riparian reserves. However, the original intent of 

watershed analysis was never realized (Reeves et al. 2006), owing to a number of 

factors, including cost of analysis and the need to consider a multitude of species 

and their ecological requirements (USDA and USDI 1994). Neither FEMAT (1993) 

nor the Record of Decision (ROD) (USDA and USDI 1994) provided explicit criteria 

for changing the boundaries or demonstrating that proposed changes would meet or 

not prevent attainment of ACS objectives over the long term. Finally, there was also 

a lack of credible analytical tools to aid decisionmaking (Reeves 2006). As a result, 

adjustments proved difficult for the agencies to make, and interim boundaries of 

the riparian reserves remained intact in the vast majority of watersheds (Baker 

et al. 2006).

Option B employs a 

context-dependent 

approach.
28

GENERAL TECHNICAL REPORT PNW-GTR-937

There has been a call in the scientific literature to allow discretion in setting 

site-specific activities (Lee et al. 2004). This flexibility is directed toward the 

management of riparian areas, and depends on the “context” of (Kondolf et al. 

2003, Montgomery 2004) and primary management objective for the specific area 

(Burnett and Miller 2007). A mix of approaches could be undertaken that recognize 

ecological and other goals, such as timber harvest, especially if applied over larger 

spatial scales (Burnett and Miller 2007) and if consideration is given to the distribution of populations of concern and connectivity among them (Olson et al. 2007, 

2014). However, management options (Naiman et al. 2012), and many restoration 

efforts (Kondolf et al. 2003), are constrained by a reliance on “off-the-shelf” and 

one-size-fits-all concepts and designs, rather than on an understanding of specific 

features and capabilities of the location of interest.

There have been few attempts to design and implement a site-specific approach 

because available guidelines are vague (Naylor et al. 2012, Richardson et al. 2012). 

The best example is the Cissell et al. (1998, 1999) proposal for the Central Cascades Adaptive Management Area. Developed by many of the scientists involved 

in creation of the Northwest Forest Plan, the proposal was based on variation in 

the disturbance patterns (in this case, wildfire) in the target watershed, and called 

for harvest of some older trees and revision of the interim riparian reserves. Only 

limited parts of the proposal were ever implemented, however, and adjustments to 

riparian reserves were not made, in large part to avoid controversy and protest over 

the harvest of mature stands.

Under the context-dependent approach that we use for this potential option, the 

division of the riparian conservation area between the inner and outer zone could 

be tailored to the specific features and characteristics of individual stream reaches. 

Factors considered are: (1) the potential of streams and stream reaches to provide 

habitat for different fish species (Burnett et al. 2007); (2) the potential for erosion 

of stream-adjacent areas; (3) the potential of a stream to warm if streamside vegetation is modified; and (4) the potential of headwater streams to deliver wood to 

fish-bearing streams. 

Implementing a context-dependent approach— 

In option B, the division of the riparian management area between the inner and 

outer zones depends on the ecological context of the area. Site features include 

intrinsic potential (Burnett et al. 2007) for coho salmon and steelhead, thermal 

loading potential and erosion potential for fish-bearing streams, and potential of 

non-fish-bearing streams to deliver wood to the locations of interest. To map and 

analyze site features in our study watersheds, we employed NetMap (Benda et al. 
29

Potential Options for Managing Riparian Reserves of the Aquatic Conservation Strategy of the Northwest Forest Plan

2007), a geospatial platform that integrates a suite of models and analysis tools 

to provide insights about the landscape context of locations in a timely and costeffective manner, as watershed analysis was originally intended to do. NetMap uses 

models that are available in the published scientific literature to identify selected 

watershed features, such as channel gradient, valley configuration, channel orientation, and landslide susceptibility, which can be used to establish the context of a 

location of interest. We used NetMap to identify and help evaluate these key site 

features: 

Intrinsic potential of fish-bearing streams—

Intrinsic potential (IP) (Burnett et al. 2007) is an estimate of the capability of a 

given stream or stream segment to provide suitable habitat for a given species 

(table 2). We used IP to assess the potential of reaches in fish-bearing streams to 

provide productive habitat for coho salmon and steelhead, and considered stream 

reaches with IP > 0.5 as the “most ecologically sensitive.” Generally, an IP value 

of 0.5 to 0.7 represents a moderate capacity for production, and an IP > 0.7 is 

considered a high capacity (Burnett et al. 2007). Because of the heightened concern 

about fish and fish habitat on BLM and other lands, we recognize stream reaches 

with either high or moderate IP values as “most ecologically sensitive” to minimize 

potential adverse consequences.

Table 2—Parameters considered in assessing intrinsic potential (IP) 

(Burnett et al. 2007) for various fish species

Species

Stream size 

(mean 

annual flow) Gradient

Ratio of valley 

width/active 

channel width

m3

 ∙ s-1 Percent

Coho salmon (Oncorhynchus kisutch) 0.5–30 <1 8–10

Steelhead (anadromous O. mykiss) 0.5–75 2–5 1–5

Thermal loading potential of fish-bearing streams—

This variable was used as the best proxy to represent stream temperatures at the 

watershed scale. The susceptibility of a stream reach to warming is strongly influenced by topography and stream orientation, as well as riparian vegetation (Beschta 

et al. 1987, Sinokrot and Stefan 1993, Webb and Zhang 1997). Parameters used in 

the NetMap model of thermal loading for determining direct beam and diffuse solar 

radiation include: (1) topographic shading, (2) channel width, (3) aspect, (4) latitude, 

and (5) height and density of streamside vegetation. In concert with NetMap’s solar 

radiation model, incoming diffuse, direct, and total radiation for every vertex in a 
30

GENERAL TECHNICAL REPORT PNW-GTR-937

stream network was calculated based on hourly intervals on July 20th, on average 

the warmest day of the year. Thermal load to a stream reach (watt-hours ∙ m-2) 

was calculated as the hourly average of all vertices of the reach, summed over all 

daylight hours. To evaluate the effect of harvest within the outer zone of the riparian conservation area on thermal loading at the stream, we modeled two management scenarios on each fish-bearing stream reach of the subject watersheds. The 

first modeled scenario represented an undisturbed buffer of one tree-height on each 

side of the stream, and the second scenario represented a contracted buffer of 100 ft 

(30.5 m) on each side of the stream. Modeled vegetation conditions were 70-percent 

vegetation density and full tree-heights inside the buffers, and clearcut harvest outside of the buffers. The percent increase in thermal loading of the contracted-buffer 

model with respect to the thermal loading of the full-buffer model was calculated 

for each stream reach. Stream reaches with greater than 10 percent increase in 

thermal loading were assigned to the “most ecologically sensitive” category of our 

analysis (table 3). 

Table 3—Parameters used to determine riparian management classes of different 

stream types

Management category Stream type Site criteria

Most ecologically sensitive Fish-bearing Intrinsic potential > 0.5 for any species

OR

Changes in thermal loading > 10 percent

OR

High erosion potential

Non-fish-bearing High probability of delivering sediment 

 and wood to a fish-bearing stream

Other Fish-bearing All other fish-bearing streams

Non-fish-bearing All other non-fish-bearing streams

Erosion potential of fish-bearing streams and debris flows from 

non-fish-bearing streams— 

Hillslope gradient is a primary control when determining the type and magnitude 

of erosion processes occurring on a landscape (Dunne and Leopold 1978). NetMap 

provides estimates of potential erosion based on slope steepness and convergence, 

and topographic indicators derived from digital elevation models (Miller and 

Burnett 2007; Montgomery and Dietrich 1994). Erosion values from these models 

are a relative measure of the probability that sediment will reach a specific stream 

segment. 
31

Potential Options for Managing Riparian Reserves of the Aquatic Conservation Strategy of the Northwest Forest Plan

Debris flow potential is a quantitative measure of the potential for a landslide 

or debris flow to reach a specific stream reach. Burnett and Miller (2007) showed 

that a relatively small percentage of the landscape is needed to encapsulate the 

highest relative probabilities of debris-flow initiation and downstream traversal. 

Streams with high initiation probabilities are especially important as potential 

sources of wood for fish-bearing streams during landslides and debris flows 

(Benda and Dunne 1997a, 1997b; Reeves et al. 2003). 

We used the debris-flow susceptibility tools in NetMap (Benda et al. 2007) 

for all streams in each watershed to identify both the erosion potential of slopes 

adjacent to fish-bearing streams and the debris-flow potential of non-fish-bearing 

streams. The debris-flow susceptibility tool in NetMap is based on Miller and Burnett (2007, 2008), and considers four topographic attributes: (1) channel slope, (2) 

valley width or confinement, (3) angles of tributary junctions, and (4) cumulative 

length of scour and deposition. Values derived indicate the relative potential for 

debris-flow movement through a reach. This model lacks a temporal component; 

therefore, debris-flow probability values are relative to each individual watershed. 

We used the upper quartile of debris-flow probability for each watershed to identify stream reaches with a high level of either erosion potential (for fish-bearing) or 

high debris-flow susceptibility (for non-fish-bearing). Reaches so identified were 

considered “most ecologically sensitive.” 3

Identifying “most ecologically sensitive” stream reaches—

Fish-bearing stream reaches with an intrinsic potential ≥0.5 or with an increase in 

thermal loading potential ≥10 percent or adjacent to areas of high erosion potential 

were placed in the “most ecologically sensitive” category, as were non-fish-bearing 

reaches with a high potential to deliver sediment and wood to fish-bearing streams 

(table 3). Stream reaches that did not meet any one of these criteria were placed in 

the “other” category. 

Under option B, along the “most ecologically sensitive” reaches in fish-bearing 

and non-fish-bearing streams, the entire width of the one site-potential tree-height 

riparian conservation area would be managed solely for the goals of the ACS. 

Reaches classified as “other” could have an inner zone that varies in width, keyed 

to stream type: the inner zone is set at 100 ft (30.5 m) on fish-bearing streams and 

3 We approximated the high erosion-potential reaches for fish-bearing streams and the high 

debris-flow potential reaches in non-fish-bearing streams using the debris-flow potential 

algorithm of NetMap. More recent analysis of a subset of watersheds suggests that doing 

a separate analysis of each criterion would result in slightly more fish-bearing stream 

segments classified as “most ecologically sensitive” and slightly fewer non-fish-bearing 

streams placed in this category. These changes would largely balance out, having little or 

no effect on the acreage-weighted average percentages reported later in this report.
32

GENERAL TECHNICAL REPORT PNW-GTR-937

Table 4—Management in riparian conservation areas (RCAs) under option B

Management category Stream type Size of RCAs

Size of inner zone 

managed solely for 

ACS goals

Size of outer zone 

managed to achieve ACS 

goals and other goalsa

Most ecologically sensitive Fish-bearing 1 site-potential 

 tree-height

1 site-potential 

 tree-height 

N/A

Non-fish-bearing 1 site-potential 

 tree-height

1 site potential 

 tree-height

N/A

Other Fish-bearing 1 site-potential 

 tree-height 

Edge of stream to 

 100 ft (30.5 m)

Edge of inner zone to 

 a distance of 1 site-

 potential tree-height

Non-fish-bearing 1 site-potential 

 tree-height 

Edge of stream to 

 50 ft (15.2 m)

Edge of inner zone to 

 a distance of 1 site-

 potential tree-height

ACS = Aquatic Conservation Strategy; N/A = not applicable.

a

 Harvest can occur in stands currently less than or equal to 80 years of age using ecological forestry with tree-tipping. 

50 ft (15.2 m) on non-fish-bearing streams (table 4 and fig. 8). As a result, we expect 

to minimize potential adverse effects of management on the aquatic ecosystem 

and to contribute to achieving ACS goals. The width of the inner zone on nonfish-bearing streams is based, in part, on Anderson et al. (2007) and Anderson and 

Poage (2014), who found that this distance reduces potential effects of harvest on 

water temperatures in small streams, as discussed under option A, and maintains 

microclimatic conditions, which is particularly important for amphibians. A 50-ft 

(15.2-m) inner zone also provides a corridor for amphibian movement along the 

stream network (Olson and Kluber 2014). The size of the inner zone on fish-bearing 

streams and the requirement for tree-tipping in the outer zone should maintain the 

suite of ecological processes, meeting the goals of the ACS. 

Requiring variable-retention timber harvest under ecological forestry with 

tree-tipping in the outer zone on “other” streams, and limiting activity to stands 

currently less than or equal to 80 years of age, also increases the likelihood of 

achieving ACS goals. Additionally, strategic placement of aggregate retention 

patches in the outer zone during variable-retention harvest (fig. 2) could increase 

the effective width of the inner zone beyond what is estimated here.

Relative to maintaining wood delivery processes to fish-bearing streams, option 

B has two components: (1) a one tree-height riparian conservation area devoted 

solely to achieving ACS goals on fish-bearing streams with high erosion potential 

and on non-fish-bearing streams with a high probability of debris-flow delivery to 

fish-bearing streams; and (2) a one tree-height riparian conservation area composed 

Requiring variableretention timber 

harvest under 

ecological forestry 

with tree-tipping in the 

outer zone on “other” 

streams, and limiting 

activity to stands 

currently less than 

or equal to 80 years 

of age, increases the 

likelihood of achieving 

ACS goals. 
33

Potential Options for Managing Riparian Reserves of the Aquatic Conservation Strategy of the Northwest Forest Plan

Table 5—Size, land ownership, and distribution of fish-bearing and non-fish-bearing streams on federal and 

nonfederal land ownership for six case-study watersheds in western Oregon

Watershed

Myrtle 

Creek Applegate Coquille

North 

Umpqua McKenzie

SmithSiuslawWeighted 

average

Total acres 

 (total hectares)

76,207 

(30 863)

260,525 

(105 512)

381,629 

(154 560)

591,772 

(239 668)

608,072 

(246 269)

784,948 

(317 903)

450,526 

(182 463)

Percentage of forest lands 93 92.6 93.5 84.7 89.9 97.1 91.7

Percentage of federal land ownership 41.6 72.7 39.7 66 65.9 56.9 59.6

Percentage of federal matrix 38.9 57.2 20.9 26.1 49.8 12.0 30.0

Percentage of BLM matrix 38.9 37 20.9 8.7 8.2 9.4 14.1

Miles of streams 562 1,957 2,859 3,556 3,945 5,840 3,970

Stream density (mi/1,000 ac) 7.9 8.1 8.0 7.1 7.2 7.7 7.5

Percentage of fish-bearing streams 41.9 29.1 34.8 17.4 22.4 46.6 31.3

Federal fish-bearing streams 

 (mi/1,000 ac)

0.9 0.9 0.9 0.8 0.9 1.7 1.1

Nonfederal fish-bearing streams 

 (mi/1,000 ac)

2.4 1.4 1.8 0.4 0.8 1.9 1.3

Federal non-fish-bearing stream 

 (mi/1,000 ac)

2.1 4.6 2.1 4.6 3.5 2.5 3.3

Nonfederal non-fish-bearing stream 

 (mi/1,000 ac)

2.5 1.2 3.1 1.3 2.1 1.6 1.8

Note: All information other than total acres is for the forested portion of the watershed.

BLM = Bureau of Land Management.

of an inner zone managed solely for the goals of the ACS and an outer zone managed to achieve ACS goals as well as other potential goals, which could include 

timber production. Overall, this forestry approach is designed to ensure maintenance of processes that deliver wood to streams. 

Simulating the Potential Options for Managing Riparian 

Conservation Areas in Selected Watersheds

We chose six watersheds—Myrtle Creek, Applegate River, Coquille River, North 

Umpqua River, McKenzie River, and Smith/Siuslaw Rivers (fig. 4 and table 5)—to 

simulate the two options for managing riparian conservation areas. The Myrtle 

Creek and Coquille watersheds were chosen because they contain Secretarial 

Pilot Projects (see Johnson and Franklin 2012 for more discussion of these pilots). 

The Smith/Siuslaw was chosen because it had geologic features and soil stability 

different from the two pilot watersheds. The other three watersheds were chosen 

because they contain adaptive management areas designated under the NWFP. All 

watersheds are predominately forest lands (table 5). The Coquille, Smith/Siuslaw, 

and McKenzie support mostly moist forests, while the North Umpqua and Myrtle 

Creek have a mixture of moist and dry forests, and the Applegate is predominantly 
34

GENERAL TECHNICAL REPORT PNW-GTR-937

dry forest (fig. 1). All except the McKenzie watershed contain critical habitat for the 

ESA-listed coho salmon (Oregon Coast and Southern Oregon/Northern California 

Evolutionarily Significant Units) (fig. 5). The McKenzie has critical habitat for Willamette Chinook salmon, steelhead, and bull trout (Salvelinus confluentus) (fig. 5).

The proportion of federal ownership of forests ranges from 42 to 73 percent and 

proportion of federal matrix from 12 to 57 percent of the total forest area, depending on the watershed (table 5 and fig. 4). Most of the remaining forest is privately 

owned, with the forest industry being the predominant private owner except in the 

Myrtle Creek and Applegate watersheds, where substantial nonindustrial private 

(e.g., family forest) ownerships occur. Fish-bearing streams range from 17.4 to 47 

percent of the total stream network, depending on the watershed (table 5), with an 

acreage-weighted average of 31 percent. Federal forests averaged a lower density of 

fish-bearing streams than did nonfederal forests in most watersheds, and a higher 

density of non-fish-bearing streams in all but two of the watersheds (table 5). 

Lands allocated as BLM matrix, the focus of analysis, covered an average of 

14.1 percent (range 8.2–38.9 percent) of the watersheds or a total of 381,527 ac (table 

6a). Given a total BLM matrix area in western Oregon (including riparian reserves) 

of 1,219,548 ac (USDI BLM 2015, p. 29), our study watersheds cover approximately 

31 percent of BLM matrix in western Oregon.4

The analysis of each of our six study watersheds consisted of four steps: (1) 

delineate the fish-bearing and non-fish-bearing streams; (2) using the delineated 

stream networks, map current riparian policy on federal and private lands, for comparison; (3) map option A; (4) classify stream segments based on aquatic ecological 

sensitivity criteria for option B and assign the width of inner zones and outer zones 

in matrix based on the classification (fig. 11). 

Step 1: Delineate the stream network and categorize the streams into 

fish-bearing and non-fish-bearing— 

NetMap (Benda et al. 2007) delineates the streams in the watershed using a “catchment basin” approach. The initiation size for a stream varies with slope (steeper 

areas require less area and a shorter stream length than less-steep areas) and 

planform curvature (Clarke et al. 2008, Miller 2003). To validate the accuracy of 

NetMap-modeled stream networks, we compared our results to BLM and Oregon 

Department of Forestry (ODF) data sets of field-verified stream networks in the 

4 The Eastside Management Area shown on page 29 of the Western Oregon Draft 

RMP/EIS (USDI BLM 2015) is excluded from the analysis because it lies outside the 

area of the Northwest Forest Plan.
35

Watershed Total BLM matrix

Estimated total area in interim riparian reserves

Option A Option B

Fish Non-fish Fish

Non-fish Most ecologically 

 sensitive Other streams, fish Other st

Inner 

zone

Outer 

zone Fish Non-fish

Inner 

zone

Outer

zone

Inne

zon

 Acres

Myrtle Creek 29,655 4,413 4,624 2,236 2,522 2,624 1,376 1,089 525 334 1,1

Applegate 96,400 10,420 20,640 5,354 10,960 10,760 3,293 7,892 1,302 760 4,

Coquille 80,149 15,630 16,470 8,246 9,081 8,891 3,529 4,420 2,267 2,449 3,0North Umpqua 51,261 4,395 10,760 2,268 5,730 5,487 1,501 2,401 420 347 2,4

McKenzie 49,950 8,367 7,960 4,366 4,323 4,214 2,660 1,921 900 805 1,8Smith/Siuslaw 74,113 23,610 11,510 12,440 6,860 7,690 6,794 4,234 2,566 3,077 1,9 Total 381,527 66,835 71,964 34,910 476 39,666 19,153 21,957 7,980 7,772 14,7

Fish = fish-bearing streams. Non-fish = non-fish-bearing streams.

Current policy

Table 6a—Distribution of area in interim riparian reserves in matrix among different categories undercurrent policy and poA and B for six case-study watersheds on Bureau of Land Management lands in western OregonTable 6b—Proportion of matrix in interim riparian reserves under current policy and division of that proportion among different management objectives under potential options A and B for six case-study watersheds on Bureau of Land Management lands in western Oregon

Proportion of matrix under different management objectives

Current policy Option A Option B

Watershed ACS goals ACS goals Dual goals Matrix goals ACS goals Dual goals Matrix goalsMyrtle Creek 0.30 0.16 0.09 0.06 0.14 0.11 0.06

Applegate 0.32 0.17 0.11 0.04 0.17 0.11 0.04

Coquille 0.40 0.22 0.11 0.07 0.17 0.16 0.07

North Umpqua 0.30 0.16 0.11 0.03 0.13 0.13 0.03

McKenzie 0.33 0.17 0.08 0.07 0.15 0.11 0.07

Smith/Siuslaw 0.47 0.26 0.10 0.11 0.21 0.15 0.11

Weighted average 0.36 0.19 0.10 0.06 0.17 0.13 0.06ACS = Aquatic Conservation Strategy.
36

Figure 11—Example of the process of analysis for each study area. A small area of the Myrtle Creek watershed was used for these examples. The stream are not shown here.
37

Potential Options for Managing Riparian Reserves of the Aquatic Conservation Strategy of the Northwest Forest Plan

Smith/Siuslaw and Myrtle Creek watersheds. Based on our initial validation assessment, we found that we slightly underestimated the initiation points of headwater 

streams (they originate higher in the watershed than we determined using NetMap), 

which would cause us to slightly underestimate the extent of non-fish-bearing 

streams. 

We also compared the fish-bearing determinations between the NetMap analysis and the BLM and ODF data sets. We used a gradient of 10 percent to differentiate fish-bearing from non-fish-bearing streams. Stream reaches with a maximum 

downstream gradient of <10 percent are considered fish-bearing, hosting primarily 

anadromous and resident salmonids. Stream reaches with a maximum downstream 

gradient >10 percent are considered non-fish-bearing, although non-salmonid fishes 

such as sculpins (Cottus spp.) may be found there. There was approximately 90-

percent agreement between the NetMap-predicted fish distribution and agency data 

sets, with the main difference that the NetMap layer included reaches determined as 

fish-bearing that BLM and ODF designated as non-fish-bearing. A potential reason 

for this difference is that ODF field verifications assume that there are no fishbearing reaches above the first non-fish-bearing reach. In contrast, we identified the 

uppermost reach with <10-percent gradient and designated everything downstream 

as fish-bearing. Our NetMap analysis was based on the best available topographic 

data available at the time—10-m digital elevation models—which are not able to 

discern small, abrupt changes in stream gradient.

As should be expected, the criteria for delineating non-fish-bearing streams 

influenced our results (fig. 12). Had we used a higher gradient threshold to differentiate fish-bearing from non-fish-bearing streams, our analyses could have contained 

higher proportions of fish-bearing streams, which affects the proportion of the 

riparian conservation area managed strictly for ACS objectives. Given an increase 

in the gradient threshold for fish-bearing streams, the proportion of the landscape 

in which timber production could be one of the goals would decrease under option 

A, where fixed-width riparian conservation areas are uniformly applied to all 

fish-bearing streams. Under option B, where the width of the zone managed solely 

for ACS goals is a function of the ecological context of the stream reach, there 

would also be reduction in area available for timber production with an increase in 

stream-gradient threshold, but less so than under option A. The ability to modify 

parameters based on observed site conditions or new knowledge is a strength of the 

NetMap method; fundamental conclusions about the relative effectiveness of the 

options evaluated here remain sound even if the parameters for identifying fishbearing streams were to be modified.
38

Figure 12—Streams delineated as fish-bearing or non-fish-bearing in the six study watersheds. (A) Myrtle Creek; (B) Applegate; (C) Coquille; (D) North (F) Smith/Siuslaw.
39

Figure 12—Continued.
40

GENERAL TECHNICAL REPORT PNW-GTR-937

Figure 12—Continued.
41

Figure 12—Continued.
42

Figure 12—Continued.
43

Figure 12—Continued.
44

GENERAL TECHNICAL REPORT PNW-GTR-937

Step 2: Simulate current riparian management policy— 

The NWFP calls for interim riparian reserves of two site-potential tree-heights 

along each side of fish-bearing streams and one site-potential tree-height along 

each side of non-fish-bearing streams, with a minimum width of 300 ft (91.4 m) 

on each side of fish-bearing streams and 150 ft (45.7 m) on each side of non-fishbearing streams (fig. 13) (USDA and USDI 1994). On BLM forests in our study, a 

site-potential tree-height varies from 155 to 220 ft (47.2 to 67.1 m) (table 7). Thus, 

riparian reserve widths vary from 310 to 440 ft (94.4 to 134.2 m) on each side of 

a fish-bearing stream and 160 to 220 ft (48.7 to 67.1 m) on each side of a non-fishbearing stream (table 7), which results in interim riparian reserves covering an 

average of 36 percent of the acre-weighted area of BLM matrix lands in the six 

study watersheds (table 6b). For comparison, TNC/WSC (2012, p. 5) estimated that 

interim riparian reserves cover 37 percent of BLM western Oregon forests, and the 

BLM (2015, p. 28 and 32) estimated that interim riparian reserves cover 38 percent 

of its western Oregon forests and 43 percent of matrix lands in these forests under 

the No Action (Northwest Forest Plan) alternative.5

5 The Eastside Management Area shown on pages 28 and 32 of the Western Oregon Draft 

RMP/EIS (USDI BLM 2015) is excluded from the analysis because it lies outside the area 

of the Northwest Forest Plan.

For perspective, we simulated the designated widths of the riparian management areas for private lands under the Oregon Forest Practices rules (Adams and 

Storm 2011, ODF 2014). Those rules specify different maximum sizes of buffers 

based on rate of streamflow and whether or not the stream reach is a domestic water 

source or potentially contains fish (fig. 13; table 8). Within that maximum riparian 

Table 7—Modeled site-potential tree-heights and riparian reserve widths on federal lands 

under current implementation of the Aquatic Conservation Strategy of the Northwest 

Forest Plan

Watershed Ownership

Site-potential 

tree-height

Width of riparian reserve each side of stream

Fish-bearing Non-fish-bearing

 - - - - - - - - - - - - - - - - - - - - Feet - - - - - - - - - - - - - - - - - - - -

Myrtle Creek BLM 160 320 160

Applegate BLM/USFS 155 310 155

Coquille BLM 210 420 210

North Umpqua BLM/USFS 180/200 360/400 180/200

McKenzie BLM/USFS 180/200 360/400 180/200

Smith/Siuslaw BLM/FS 220/250 440/500 220/250

BLM = Bureau of Land Management; USFS = U.S. Forest Service.

Source: personal communications from federal managers on districts and national forests.
45

Figure 13— Northwest Forest Plan interim riparian reserves (current policy) mapped for the six study watersheds. (A) Myrtle Creek; (B) Applegate; (C) C(D) North Umpqua; (E) McKenzie; (F) Smith/Siuslaw. NWFP = Northwest Forest Plan; OFPA = Oregon Forest Practices Act.
46

Figure 13—Continued.
47

Potential Options for Managing Riparian Reserves of the Aquatic Conservation Strategy of the Northwest Forest Plan

Figure 13—Continued.
48

Figure 13—Continued.
49

Figure 13—Continued.
50

Figure 13—Continued.
51

Potential Options for Managing Riparian Reserves of the Aquatic Conservation Strategy of the Northwest Forest Plan

Table 8—Maximum size of riparian management areas in different types and sizes of 

streams under the Oregon State Forest Practices rules

Stream size

Stream type

Type F 

(used by fish) 

Type D 

(source of 

domestic water) Type N (all other streams)

Large 30.5 m (100 ft) 21.4 m (70 ft) 21.3 m (70 ft)

Medium 21.4 m (70 ft) 15.2 m (50 ft) 15.2 m (50 ft)

Small 15.2 m (50 ft) 6.1 m (20 ft) Coast and Cascades: 0 m (0 ft)a

Southwest Oregon: Retain understory vegetation 

and conifers ≤15.2 cm (6 in) dbh for 3 m (10 ft) 

on either side of the stream on portions of certain 

perennial non-fish-bearing streams.

a

 The value for the Coast and Cascades, 0 m (0 ft), was used in our modeling simulations. 

Sources: Adams and Storm (2011), ODF (2014). http://www.oregon.gov/odf/privateforests/docs/fparulebk.pdf.

management area width for a particular stream type, a specified level of tree basal 

area must be achieved before trees can be removed. If that target basal area can be 

achieved in less area than the maximum width, the buffer width can be reduced 

somewhat, but to no less than 20 ft (6.1 m) from the stream. For private lands in our 

study watersheds, we used the maximum widths specified in table 8 for our analyses. Our simulations suggest that about 6 percent of the forest area on private lands 

falls within the maximum riparian management area widths. This result is similar 

to that found in the Oregon Coast Range in other studies (Johnson et al. 2007). 

Step 3: Simulate Option A: a fixed-width division of the riparian conservation 

area between inner and outer zones—

As described previously, under option A, the full width of the one site-potential 

tree-height riparian conservation area along fish-bearing streams and the inner zone 

of one-half site-potential tree-height on non-fish-bearing streams could be managed 

solely for the goals of the ACS (fig. 14). An outer zone on non-fish-bearing streams 

equal to the additional one-half a site-potential tree-height could be managed to 

achieve the goals of the ACS as well as for timber production and other goals (fig. 

8). Ecological forestry with tree-tipping could be used in the outer zone. 

Step 4: Simulate option B: a context-dependent division of the riparian conservation area between inner and outer zones based on ecological sensitivity—

We classified each steam segment in our study watersheds into “most ecologically 

sensitive” and “other” based on our site criteria (table 3). The full one site-potential 

tree-height width of the riparian conservation area for the “most ecologically sensitive” reaches and the inner zone along “other” streams could be managed solely for 

the goals of the ACS. The outer zone for “other” streams could be managed with 
52

Figure 14—Simulation of option A riparian conservation area zones for the six study watersheds. (A) Myrtle Creek; (B) Applegate; (C) Coquille; (D) No(E) McKenzie; (F) Smith/Siuslaw. NWFP = Northwest Forest Plan; OFPA = Oregon Forest Practices Act.
53

Figure 14—Continued.
54

GENERAL TECHNICAL REPORT PNW-GTR-937

Figure 14—Continued.
55

Figure 14—Continued.
56

Figure 14—Continued.
57

Figure 14—Continued.
58

GENERAL TECHNICAL REPORT PNW-GTR-937

timber production as an additional goal, using ecological forestry with tree-tipping. 

Figure 15 demonstrates the stream segment delineation in the six study watersheds. 

We then applied the prescribed width of the different zones (table 4; fig. 8) to the 

classified streams (fig. 16) 

In our study, an average of 63 percent (range of 54–74 percent) of fish-bearing 

stream miles across all ownerships were classified as “most ecologically sensitive,” 

depending on watershed, as were an average of 28 percent (range 23–32 percent) 

of non-fish-bearing streams (table 9). In aggregate, an average of 38 percent (range 

37–40 percent) of the stream network across all ownerships was classified as “most 

ecologically sensitive.” 

Division of the Interim Riparian Reserves Among Different 

Goals Under the Two Options 

In matrix—

Compared to the NWFP, the two potential options evaluated here reduce the 

portion of the interim riparian reserves in the BLM matrix that has achievement 

of the goals of the ACS as a primary objective by approximately 18 percent (range 

11–23 percent) (table 10). This reduction results from changing the area of riparian reserves in matrix from two site-potential tree-heights to one site-potential 

tree-height on fish-bearing streams. Under both options, the forest in this second 

tree-height in BLM matrix would shift to the terrestrial prescription in the NWFP, 

which generally has timber production as one of the management objectives.6

The remainder of existing interim riparian reserves in BLM matrix—one 

tree-height on all streams—could be divided into two parts (table 10): 1) an average of 54 percent (range 53–55) and 46 percent (range 41–54) in options A and B, 

respectively, could continue to be managed solely for the goals of the ACS; 2) the 

remainder, an average of 29 percent in option A (range 22–36) and 36 percent in 

option B (range 33–44), could be managed jointly for ACS and timber production 

or other goals. Application of ecological forestry in conjunction with these options 

for riparian conservation areas could result in the retention of more forest within 

the outer zone of the riparian conservation area in matrix lands than estimated here. 

Retention aggregates, particularly the larger aggregates, could be located along fishbearing streams (fig. 2). As a result, a portion of the outer zone managed for timber 

and ecological values could be assigned to retention patches, increasing the number 

of trees in the outer zone. 

6 Matrix prescription of the Northwest Forest Plan uses variable-retention harvest, although 

at a somewhat lower retention rate than recommended for ecological forestry by Franklin 

and Johnson (2012).
59

Figure 15—Streams classified into ecologically sensitive and other, fish-bearing and non-fish-bearing categories in the six study watersheds. (A) Myrtle (B) Applegate; (C) Coquille; (D) North Umpqua; (E) McKenzie; (F) Smith/Siuslaw.
60

Figure 15—Continued.
61

Potential Options for Managing Riparian Reserves of the Aquatic Conservation Strategy of the Northwest Forest Plan

Figure 15—Continued.
62

Figure 15—Continued.
63

Figure 15—Continued.
64

Figure 15—Continued.
65

Figure 16—Simulation of option B riparian conservation area zones for the six study watersheds. (A) Myrtle Creek; (B) Applegate; (C) Coquille; (D) Nor(E) McKenzie; (F) Smith/Siuslaw.
66

Figure 16—Continued.
67

Potential Options for Managing Riparian Reserves of the Aquatic Conservation Strategy of the Northwest Forest Plan

Figure 15—Continued. Figure 16—Continued.
68

Figure 16—Continued.
69

Figure 16—Continued.
70

Figure 16—Continued.
71

Potential Options for Managing Riparian Reserves of the Aquatic Conservation Strategy of the Northwest Forest Plan

Table 9—Percentage of fish-bearing and non-fish-bearing streams, by land ownership group, designated as 

“most ecologically sensitive” under potential option B in the six case-study watersheds in western Oregon

Watershed

Percent of stream network in ownership in “most ecologically sensitive” category

Fish-bearing streams Non-fish-bearing streams Total stream network

Federal Nonfederal

Acreageweighted 

average Federal Nonfederal

Acreageweighted 

average Federal Nonfederal

Acreageweighted 

average

Myrtle Creek 56 61 60 24 21 23 31 41 37

Applegate 74 53 68 32 19 28 39 37 39

Coquille 58 58 58 30 27 28 39 39 39

North Umpqua 77 61 74 30 25 29 37 34 36

McKenzie 69 65 67 36 24 32 42 35 40

Smith/Siuslaw 53 55 54 27 28 27 37 43 40

Acreage-weighted 

 average

66 58 63 30 25 28 38 39 38

Across all BLM lands in western Oregon—

The change in the proportional area in interim riparian reserves when the entire 

BLM landscape in western Oregon is considered is less than what occurs in matrix. 

For the No Action Alternative (Northwest Forest Plan), the BLM estimates (USDI 

BLM 2015, p. 29) a total acreage in western Oregon of 2,331,989 ac, divided 

between matrix (including interim riparian reserves) of 1,219,548 ac (52 percent) 

and late-successional and other reserves of 1,112,441 ac (48 percent).7 A portion 

of matrix is also designated as critical habitat for the northern spotted owl, which 

7 The Eastside Management Area shown on page 29 of the Western Oregon Draft RMP/

EIS (USDI BLM 2015) is excluded from the analysis because it lies outside the area of the 

Northwest Forest Plan.

Table 10—Proportion of interim riparian reserves in matrix assigned to different management objectives 

in potential options A and B for six case-study watersheds on BLM lands in western Oregon

Proportion of interim riparian reserves allocated among management objectives

Option A Option B

Watershed ACS goals Dual goals Matrix goals ACS goals Dual goals Matrix goals

Myrtle Creek 0.53 0.29 0.18 0.46 0.35 0.18

Applegate 0.53 0.35 0.13 0.54 0.34 0.13

Coquille 0.54 0.28 0.18 0.41 0.40 0.18

North Umpqua 0.53 0.36 0.11 0.45 0.44 0.11

McKenzie 0.53 0.26 0.21 0.45 0.34 0.21

Smith/Siuslaw 0.55 0.22 0.23 0.44 0.33 0.23

Weighted average 0.536 0.286 0.178 0.460 0.362 0.178

ACS = Aquatic Conservation Strategy.
72

GENERAL TECHNICAL REPORT PNW-GTR-937

Table 11—Weighted average percentage of interim riparian reserves (IRR) allocated among different 

management objectives from six case-study watersheds on Bureau of Land Management lands in western 

Oregona

Weighted average percentage of interim riparian reserves 

allocated among management objectives

Option A Reclassified 

to allow 

matrix goals

Option B Reclassified 

to allow 

matrix goals

ACS 

goals

Dual 

goals

Matrix 

goals

ACS 

goals

Dual 

goals

Matrix 

goals

Allocation of IRR in matrix 53.6 28.6 17.8 46.0 36.2 17.8

Weighted by percentage of 

 matrix (52 percent)

27.8 14.9 9.3 23.9 18.8 9.3

Allocation of IRR in reserves

 outside matrix

100 0 0 100 0 0

Weighted by percentage of

 reserves outside matrix

 (48 percent)

48 0 0 48 0 0

Weighted average allocation

 of IRR

75.8 14.9 9.3 24.2 71.9 18.8 9.3 28.1

ACS = Aquatic Conservation Strategy. 

a

Assumes that Bureau of Land Management matrix and reserves (outside of matrix) in western Oregon have the same proportion in 

 interim riparian reserves.

reduces the forest available for harvest from what is estimated here. Matrix near 

the coast has the potential for being designated as additional critical habitat for 

the marbled murrelet as more sites are found, further reducing the area of matrix 

available for harvest. “Survey and Manage” requirements are also likely reduce 

the harvestable area of matrix. Thus, our estimate here of 52 percent matrix likely 

overestimates matrix area and underestimates reserve area.

Using this percentage of matrix and reserves (outside matrix), approximately 76 

percent of the interim riparian reserve area on BLM western Oregon lands under 

option A and 72 percent under option B would remain devoted solely to the goals of 

the ACS (table 11). An additional 15 percent and 19 percent under options A and B, 

respectively, could contribute both to ACS goals and to matrix goals such as timber 

production. The overall reduction in the amount of interim riparian reserve area on 

the landscape would be 9 percent under both options (table 11). 

Seventy six percent 

under Option A and 72 

percent under Option 

B of interim riparian 

reserve on BLM lands 

in western Oregon 

remain devoted solely 

to achieving ACS 

goals.
73

Potential Options for Managing Riparian Reserves of the Aquatic Conservation Strategy of the Northwest Forest Plan

Rates and Intensities of Harvest in the Reclassified Interim 

Riparian Reserve

Reclassification of the interim riparian reserves affects the rate and type of harvest 

permitted in these areas. We estimate that approximately 24 to 28 percent of existing 

interim riparian reserves could potentially have timber production as a goal under 

the two options evaluated here (table 11). About one-third of that area would be 

returned to matrix prescriptions; the other two-thirds will retain its ACS goals but 

could have timber production as an added goal. Commercial thinning up to age 80 in 

moist forests and beyond 80 years (to reduce fuels) in dry forests is already allowed 

in the interim riparian reserves, although moderated by concerns about threatened 

fish stocks. We would expect thinning to continue, although the rate and intensity 

might increase somewhat, especially on the portion of the interim riparian reserves 

returned to matrix. A potentially more controversial change concerns the application 

of variable-retention harvest in moist forests, a silvicultural practice not permitted in 

interim riparian reserves. We will focus our discussion here on the potential magnitude of that change.

Variable-retention harvest followed by a few decades of diverse early-successional ecosystems (figs. 2 and 3) would emphasize the provision of habitat for 

early-seral species, a different goal than attempting to create diversity in existing 

stands and speeding development of late-successional forests. Also, variable-retention harvest would provide more harvest volume per acre than thinning, and would 

change the appearance of the forest more dramatically. 

We would expect that the outer portions of the interim riparian reserves that 

could be available for timber harvest under options A or B would be harvested 

at about the same rate as the uplands. The BLM estimated that implementation 

of the No Action alternative (the NWFP) would result in an average amount of 

variable-retention harvest of approximately 43,932 ac per decade for the first two 

decades in matrix areas (USDI BLM 2015, p. 277). Across an estimated 691,998 ac 

of matrix lands (USDI BLM 2015, p. 29), approximately 6.3 percent of the matrix 

would be harvested per decade. Using our watershed case studies and estimates of 

the distribution of interim riparian reserves between matrix and late-successional 

and other reserves, we estimate that 24 to 28 percent of the interim riparian reserve 

area across the landscape would be reclassified to allow timber production as a 

management goal under options A and B, respectively (table 11). With a 6.3-percent 

variable-retention harvest rate per decade, 3 to 4 percent of the total interim riparian 

reserve area could receive a variable-retention harvest over the first two decades.8

8 Calculated as 24.1 × 6.3 × 2 = 3.0 percent for option A and 28.1 × 6.3 × 2 = 3.5 percent for 

option B.
74

GENERAL TECHNICAL REPORT PNW-GTR-937

9 “Private lands,” as defined in our study, include Coquille tribal lands in the 

Coquille watershed.

Distribution of Stream Classes Between Landowner Groups 

The relative proportion of “most ecologically sensitive” streams varies between 

federal and nonfederal (private) lands,9 as well as by watershed, and both ownership 

types contain significant numbers of these streams (table 9). When private lands lie 

in the lower portions of the watershed, such as in Myrtle Creek, a greater proportion of “most ecologically sensitive” fish-bearing streams are found on private lands 

(table 9; fig. 12A; fig. 17). When federal and private lands are more intermingled in 

the lowlands, as in the Coquille and Smith/Siuslaw (table 9; figs. 12B and 12F; fig. 

17), landowners share more equally in the proportion of “most ecologically sensitive” fish-bearing streams. 

Potential Impacts on Terrestrial Biodiversity

Many terrestrial species use the area near streams for at least part of their lives, as 

acknowledged in FEMAT (1993) and the documents associated with the Northwest 

Forest Plan (USDA and USDI 1994, RIEC and IAC 1996). These documents discuss 

the “size” of the riparian reserves as being important for some mammals and 

amphibians, and the FEMAT summary (p. II-31) describes riparian reserves serving 

as dispersal habitat for the northern spotted owl. There is also reference to riparian 

reserves being important for connecting late-successional reserves for organisms 

with limited dispersal capabilities (e.g., fungi, plants, flightless insects, amphibians, 

mollusks) (p. IV-187), and a paragraph in the aquatic section (p. V-34) that describes 

the importance of riparian reserves as travel and dispersal corridors for terrestrial 

animals and plants. Thus, potential changes to riparian reserves need to consider 

the effects on these organisms. 

We surmise that, in general, effects on terrestrial species of adopting either 

option A or option B will be minimal for the following reasons: 

1. In the development of the Northwest Forest Plan, much of the evaluation of 

effects of different management options on species centered on harvest of 

mature and old-growth stands (FEMAT 1993). A number of factors make 

harvest of these stands unlikely to any significant degree, including recommendations for their retention in the new Northern Spotted Owl Recovery 

Plan (USFWS 2011), prescriptions associated with ecological forestry (box 

1), and the approach herein that limits harvest within one tree-height of 

streams to stands currently less than or equal to 80 years of age. 

In some watersheds, 

private lands contain 

the majority of “most 

ecologically sensitive” 

streams.
75

Potential Options for Managing Riparian Reserves of the Aquatic Conservation Strategy of the Northwest Forest Plan

Figure 17—Proportion of fish-bearing and non-fish-bearing stream length categorized as most ecologically sensitive and other in the six 

study watersheds, by ownership. Note that a large proportion of the most ecologically sensitive fish-bearing streams are on private lands. 

(A) Myrtle Creek; (B) Applegate; (C) Coquille; (D) North Umpqua; (E) McKenzie; (F) Smith/Siuslaw.

0

80

40

20

60

100

120

140

BLM matrix BLM LSR Private

A. Myrtle Creek B. Applegate

C. Coquille D. North Umpqua

BLM matrix BLM LSR Private

Stream length (river miles) Stream length (river miles)

Ownership/allocation

Ownership/allocation

BLM AMA BLM LSR

BLM AMR

FS AMA FS LSR Private

0

50

100

150

200

250

300

350

400

450

0

100

200

300

400

500

600

700

800

900

0

100

200

300

400

500

600

700

800

900

BLM matrix

BLM AMA

BLM LSR FS matrix

FS AMA

FS LSR Private

Non-fish-bearing, other

Non-fish-bearing, most ecologically sensitive

Fish-bearing, other

Fish-bearing, most ecologically sensitive

Stream category
76

GENERAL TECHNICAL REPORT PNW-GTR-937

2. Most of the forest area in the Northwest Forest Plan’s interim riparian 

reserves (within two site-potential tree-heights of fish-bearing streams or 

one site-potential tree-height of non-fish-bearing streams) would be unaffected by adoption of options A or B. 

3. Use of ecological forestry in the riparian conservation areas (one treeheight along both fish-bearing and non-fish-bearing streams under options 

A and B) includes aggregate retention patches that can be placed to aid 

movement of organisms with low dispersal capabilities, including mollusks, 

mosses, fungi, and lichens (Olson et al. 2007), and can increase the width of 

the protected area along the stream beyond what is specified in the option. 

4. A relatively low rate of regeneration harvest in the interim riparian reserves 

would likely occur. 

0

200

400

600

800

1,000

FS FS LSR Private

matrix

BLM 

LSR

BLM 

matrix

E. McKenzie F. Smith/Siuslaw Stream length (river miles)

0

200

400

600

800

1,000

1,200

BLM 

matrix

BLM AMA

BLM

LSR

FS matrix

FS AMA

FS LSR

FS AMR

Private

Ownership/allocation

Ownership/allocation

Non-fish-bearing, other

Non-fish-bearing, most ecologically sensitive

Fish-bearing, other

Fish-bearing, most ecologically sensitive

Stream category

Figure 17—Continued.
77

Potential Options for Managing Riparian Reserves of the Aquatic Conservation Strategy of the Northwest Forest Plan

5. Although the forest near streams on federal lands has been highlighted as a 

potential movement corridor for some species, the fragmented (often checkerboard) nature of the BLM’s western Oregon forests makes it difficult to 

maintain continuous streamside forest across the landscape no matter what 

management policies are chosen for federal lands. On the other hand, connectivity along diagonals of the checkerboard ownership has been proposed 

(Olson and Burnett 2013, Olson and Kluber 2014) and warrants assessment.

Research Implications

Criteria used to design the riparian conservation area for options A and B rely 

heavily on science derived since development of the NWFP, including empirical 

studies of the effects of riparian buffers and models of landscape habitat suitability 

or processes that may affect aquatic systems. Research needs include further development of these relevant science themes, as well as monitoring the effects of option 

implementation on specific elements named in ACS objectives. Research on and 

monitoring of option implementation can lead to informed adaptive management 

to improve the efficacy of riparian management for aquatic-riparian restoration. 

Some key research areas include:

1. Assessing the effects of riparian conservation area implementation on ACS 

attributes at the spatial scale of whole watersheds. The ACS attributes of interest include instream habitat and water quality, along with aquatic, riparian, and 

terrestrial species of concern, including abundance, habitat quality assessment, 

habitat use, and dispersal. Specific questions include:

▪ What are the differential effects of riparian conservation areas under 

option A or B, with ecological forestry implemented upslope? 

▪ Are there cumulative effects if implementation is clustered among 

adjacent watersheds in a small area of the NWFP?

2. Validating landscape models with field-derived data for down-wood recruitment 

including tree-tipping, thermal loading, and landslide potential. Specifically:

▪ Do riparian conservation areas under option A or B with ecological 

forestry implemented upslope change any assumptions for dynamics 

of wood recruitment (e.g., is blowdown more likely?), thermal loading, 

or sedimentation processes? 

▪ What site-specific contexts may need consideration for model 

accuracy?

▪ Is a no-entry zone in the portion of the riparian conservation area specified for ACS goals necessary, for example to reduce erosion potential?

Monitoring the 

effects of option 

implementation is 

imperative.
78

GENERAL TECHNICAL REPORT PNW-GTR-937

▪ What temporal considerations are needed for tree-tipping to maximize 

efficacy of large wood recruitment to streams?

3. Assessment of efficient placement of aggregated patches of green-tree retention. 

For example: 

▪ What stream, riparian, or upland ecosystem services can be addressed 

by patch placement?

▪ Can patches aid local distribution of sensitive species or habitat 

attributes?

Conclusions 

It was expected that the boundaries of the interim riparian reserves of the Northwest Forest Plan could and would be modified as a result of watershed analysis. 

However, as described previously, this has not happened for a number of reasons 

and, as a result, relatively little management has occurred in the reserves, especially 

within one tree-height of streams (Reeves 2006). To help provide understanding 

of recent scientific information and analysis tools in a management context, we 

did an initial ecological evaluation of two potential options that reduce the area of 

interim riparian reserves needed to meet the goals of the ACS of the Northwest 

Forest Plan, while providing opportunities to achieve other management goals, such 

as increased timber harvest and associated revenue from a portion of these lands. 

These options fall within the bounds of what was expected by the developers of 

the ACS (FEMAT 1993) and the ROD (USDA and USDI 1994), and are based on 

science produced since the ACS was developed. 

Based on our summary of new science and evaluation of these potential 

options, the ACS should continue to be met under either potential option. Both 

options employ tree-tipping to ensure that thinning inside riparian reserves does not 

reduce the amount of wood falling into the stream. This technique should increase 

the compatibility of timber harvest or thinning for restoration and aquatic goals 

throughout the area of the Northwest Forest Plan. We also expect that the portion of 

the riparian conservation areas managed solely for the goals of the ACS in matrix 

in each option is sufficient to maintain water temperatures and microclimate within 

ecologically acceptable ranges and minimize the potential for excess erosion. These 

options are novel ideas that could be considered for the BLM lands, and are unlikely 

to compromise the goals of the ACS. They should be viewed as working hypotheses, much like the interim riparian reserves. Any implementation and subsequent 

evaluation of these or similar options would benefit from an adaptive management context to assess their effectiveness in meeting ACS goals and for continual 

improvement as additional information becomes available over time.

Aquatic Conservation 

Strategy goals should 

continue to be met 

under either potential 

option.
79

Potential Options for Managing Riparian Reserves of the Aquatic Conservation Strategy of the Northwest Forest Plan

Placement of a stream reach in the “most ecologically sensitive” category is a 

function of achieving a certain threshold value for any one of our three criteria for 

fish-bearing streams (intrinsic potential, temperature, or susceptibility to erosion) 

or one criterion for non-fish-bearing streams (susceptibility to debris flows) (table 

3). We justified our threshold values earlier in this report, but initial sensitivity 

analysis suggests that the choice of other threshold values can affect, somewhat, the 

segments classified as most ecologically sensitive. Policymakers and managers may 

wish to set the thresholds differently, however. For example, IP values of >0.7 could 

be used—the value for “high” IP areas (Burnett et al. 2007). This threshold would 

identify stream segments with the greatest potential to contribute to conservation 

and the recovery of ESA-listed fish species. Additionally, the threshold for inclusion 

of a non-fish-bearing stream based on the potential of debris flows to deliver materials to fish-bearing streams could be adjusted from the top 25 percent level that we 

used. Burnett and Miller (2007) suggested that greater conservation benefits accrue 

with a greater proportion of streams with high debris-flow potential being devoted 

to conservation than to timber harvest. However, the use of tree-tipping as one of 

the management actions along these streams would help ensure that wood recruitment into them continues, and that wood is available for delivery to fish-bearing 

streams from all headwater streams. 

Our analysis also suggests that it could be difficult to rely solely on federal 

lands to recover and conserve freshwater habitat for native salmonids, including 

the ESA-listed coho salmon in western Oregon, given the significant proportion 

(approximately half [table 9]) of “most ecologically sensitive” stream segments 

that are found on nonfederal lands. The type of analysis done here using NetMap 

(Benda et al. 2007) can potentially be useful to watershed councils and others in 

identifying where to most effectively direct resources aimed at the protection and 

restoration of aquatic ecosystems across the landscape.

Although climate change was not considered in the development of the ACS, 

the potential options considered here should provide conditions for organisms to 

meet the challenges presented by a warming planet. Freshwater resources, including those in the NWFP area, are among the most vulnerable resources to climate 

changes (Bates et al. 2008). One of most immediate and pronounced impacts 

of climate change will be increased air temperatures (Mote et al. 2003). Water 

temperatures are projected to increase as a result (Isaak et al. 2012), although the 

extent of change will vary widely (Arismendi et al. 2012). Recent research (Cristea 

and Burges 2010, Lawrence et al. 2014, Perry et al. 2015) suggests that adequately 

sized and stocked riparian areas can offset the potential effects of climate change on 

water temperatures. 
80

GENERAL TECHNICAL REPORT PNW-GTR-937

Our analysis focused on how different-sized buffers along fish-bearing streams 

in matrix would change the amount of solar radiation (a surrogate for stream temperature) that could reach the water surface. The one site-potential tree-height buffer on fish-bearing streams in option A should be sufficient to prevent any increases 

in water temperature. In option B, susceptibility to increases in the amount of solar 

radiation reaching the stream was one of the ecological sensitivity criteria: we limited buffer reductions on fish-bearing streams on matrix lands to those that showed 

less than a 10-percent increase in the estimated amount of solar radiation that could 

reach the stream on the hottest day of the year. This is a conservative threshold 

for changes that could affect water temperature, thus minimizing the potential for 

adverse increases in water temperature. Currently, about two-thirds of fish-bearing 

streams in matrix on federal lands across our case-study watersheds would retain a 

riparian conservation area of one site-potential tree-height. As a result, the riparian 

conservation areas should be sufficient to prevent, and potentially offset, increases 

in water temperature related to climate change in many systems. 

Winter precipitation and flows (Mote et al. 2003, Tague and Grant 2009) are 

also likely to increase as a consequence of climate change, which will in turn 

increase landslides and debris flows. The potential options focus on increasing the 

occurrence of large trees by limiting management to stands ≤80 years of age, using 

tree-tipping into streams, retaining larger riparian conservation areas on non-fishbearing streams with the high probability to deliver wood and sediment to fishbearing streams, and restricting activities in the more erosive portions of the stream 

network. These provisions should help sustain key ecological processes that create 

and maintain suitable habitat for fish and other aquatic and riparian-dependent 

species through time. 

Assuming that the other components of the ACS, including key watersheds, 

watershed analysis, monitoring, and standards and guidelines would not change 

and that interim riparian reserves in LSRs and other reserved and withdrawn lands 

would remain in place, the options evaluated here provide examples of potential 

ways to implement the ACS while meeting other management goals and the challenges of climate change. As estimated above (table 11), 72 to 76 percent of the area 

in NWFP interim riparian reserves in the BLM’s western Oregon lands would still 

be devoted solely to achieving the goals of the ACS, depending on which option 

was chosen. Therefore, we assess the potential for these options to reverse the 

progress of the ACS to date or to retard its continued achievement of the ACS goals 

as minimal. However, as with the interim riparian reserves, such options should be 
81

Potential Options for Managing Riparian Reserves of the Aquatic Conservation Strategy of the Northwest Forest Plan

not be viewed as immutable and, therefore, implementation and evaluation in an 

adaptive management context (Stankey et al. 2005) would be prudent to enable a 

response and adjustments to unforeseen effects in a timely manner.

Acknowledgments

This report benefited from discussions with Paul Anderson, Lee Benda, Peter Bisson, Kelly Burnett, Deann Carlson, Deanna Olson, and students in Norm Johnson’s 

2013 forest policy class at Oregon State University. It was also improved by the 

comments from Deanna Olson, Susan Alexander, Katherine Smith, Cynthia Miner, 

and Borys Tkacz, and six anonymous reviewers. Debora Johnson of Applegate 

Forestry and Kelly Christiansen of the Pacific Northwest Research Station contributed several of the maps. Kathryn Ronnenberg provided invaluable editorial and 

graphical assistance. Ideas and concepts presented in this report are solely those 

of the authors and are not necessarily endorsed by any management or regulatory 

agencies. 

Metric Equivalents

When you know: Multiply by: To find:

Inches (in) 2.54 Centimeters (cm)

Feet (ft) 0.305 Meters (m)

Miles (mi) 1.609 Kilometers (km)

Acres (ac) 0.405 Hectares (ha)

Miles/1,000 acres 3.9728 Kilometers/1000 ha

Trees per acre 2.47 Trees per hectare

Degrees Fahrenheit 0.56 (°F – 32) Degrees Celsius

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GENERAL TECHNICAL REPORT PNW-GTR-937

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