DEPAR TMENT OF AGRICULT URE

United States 

Department of 

Agriculture

Forest Service

Pacific Northwest 

Research Station

Research Paper

PNW-RP-589

October 2012

Relations of Native and Exotic 

Species 5 Years After Clearcutting 

With and Without Herbicide and 

Logging Debris Treatments

David H. Peter and Timothy B. Harrington
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Pesticide Precautionary Statement

This publication reports research involving pesticides. It does not 

contain recommendations for their use, nor does it imply that the 

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Authors

David H. Peter is an ecologist and Timothy B. Harrington is a research forester, 

Forestry Sciences Laboratory, 3625 93rd Avenue SW, Olympia, WA 98512-9193.

Cover: Photos show the three sites at 5 years of age. The Molalla site is on top, 

Matlock in the middle, and Fall River on the bottom.
Abstract

Peter, David H.; Harrington, Timothy B. 2012. Relations of native and exotic 

species 5 years after clearcutting with and without herbicide and logging 

debris treatments. Res. Pap. PNW-RP-589. Portland, OR: U.S. Department of 

Agriculture, Forest Service, Pacific Northwest Research Station. 37 p.

To increase timber production and manage other forest resource values, some 

land managers have undertaken logging debris and vegetation control treatments 

after forest harvest. We explored the roles of clearcutting on plant community 

composition and structure at three sites where logging debris was dispersed, piled, 

or removed and vegetation was annually treated or not treated with herbicides for 

5 years. Without vegetation control, a competitive relation was identified between 

exotic and native ruderal (i.e., disturbance-associated) species. When exotic ruderal 

cover changed by 4 percent, native ruderal cover changed by 10 percent in the 

opposite direction. This relation was independent of site, but site was important 

in determining the overall dominance of ruderals. Five annual vegetation control 

treatments increased Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) growth, 

but decreased richness and cover of other species at the rate of one species per 10 

percent reduction in cover. Debris treatment effects were small and found on only 

one site. 

Keywords: Clearcut, invasive species, exotic species, community diversity, 

community structure.
Summary

Clearcutting of Pacific Northwest (USA) forests results in conversion of the 

understory plant community from dominance by shade-tolerant native species to 

dominance by a mixture of native and exotic ruderal (i.e., disturbance-associated) 

species. To increase timber production and manage for other resource values, some 

land managers have undertaken subsequent logging debris and vegetation control 

treatments. We explored the roles of clearcutting with and without logging debris 

and vegetation control treatments on plant community composition and structure at 

three sites with different plant communities and productivity. Logging debris was 

dispersed, piled, or removed. Vegetation was annually treated or not treated with 

herbicides for 5 years. Without vegetation control, a competitive relation was identified between exotic and native ruderal species in which a 4 percent change in exotic 

ruderal cover was associated with an opposite 10 percent change in native ruderal 

cover. This relation was independent of site, but site was important in determining 

the overall dominance of ruderals. Vegetation control increased Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) growth, while it decreased cover and richness of 

other species. Richness declined at the rate of one species per 10 percent reduction 

in cover regardless of site, stand history, or treatment protocol. Nonmetric multidimensional scaling ordination suggested that, although the untreated plant communities were floristically distinct at age 5 years, communities receiving similar 

herbicide treatments become more alike after treatment. Debris treatment effects 

were small and found only on the least productive site. 
Contents

1 Introduction

2 Materials and Methods

2 Study Sites

3 Study Design

5 Field Procedures

7 Analysis

9 Results

9 Species Composition and Diversity

12 Relations Among Native and Exotic Species Groups

12 Canopy Cover and Productivity

12 Relation of Richness to Total Cover

14 Discussion

14 Community Structure and Composition

17 Debris Treatments

17 Vegetation Control

21 Conclusions

21 Acknowledgments

22 English Equivalents

22 References

27 Appendix
This Page Left Blank Intentionally
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Relations of Native and Exotic Species 5 Years After Clearcutting With and Without Herbicide and Logging Debris Treatments

Introduction

Owing to their high levels of light and nutrient availability, early seral communities 

in the Pacific Northwest are dominated by ruderals (i.e., plant species associated 

with disturbance) soon after harvesting, but with some surviving residual forest 

understory species. The residual forest understory species are “stress tolerant” 

(sensu Grime 1977) in that they tolerate the low levels of light and nutrients typical 

of later seral communities while surviving in the understory of the predisturbance 

forest. Thus, while some late-successional species such as western hemlock (Tsuga 

heterophylla (Raf.) Sarg.) may enter the stand much later (relay floristics model), 

early seral communities in the Pacific Northwest follow an initial floristics model 

(Egler 1954) in the beginning. Following establishment of the ruderals, succession in these communities is largely driven by canopy development of Douglas-fir 

(Pseudotsuga menziesii (Mirb.) Franco var. menziesii) or other conifers, but the rate 

of succession and the community composition are affected by site productivity and 

silvicultural management activities. 

Ruderal communities in the maritime Pacific Northwest (USA) have been 

invaded by many exotic (invasive nonnative) plant species. However, very little is 

currently known about the competitive relation that exists between these exotic species and native species. Invasive exotic species can alter hydrologic, nutrient, and 

disturbance regimes (Mack et al. 2000) and may threaten native species (Wilcove 

et al. 1998). However, exotic species are not always a threat to native plants (Davis 

2003), and uncertainty regarding the roles of exotic species in ecosystems hinders 

our ability to know how or even whether to attempt native community restoration. 

Soon after forest harvesting, forest managers may engage in site preparations 

to benefit planted trees. Thus, early community assembly that was initiated by tree 

harvesting may be interrupted by a series of disturbances including logging debris 

treatment and vegetation control for which there are few natural analogues. Because 

organic matter provides a protective barrier against soil disturbance and influences 

nutrient cycling (Smethurst and Nambiar 1990), soil moisture, and temperature 

(Devine and Harrington 2007, Roberts et al. 2005), the recruitment and survival 

of postharvest species could be affected by debris treatments. Most forestry studies have found only small changes in species diversity and composition of ground 

layer vegetation with operational use of herbicides (Boyd et al. 1995, Haeussler et 

al. 2002). For example, in the Pacific Northwest, Stein (1995) found that a single 

glyphosate application caused a shift toward ruderal species with little effect on 

diversity. However, we wondered what effect more rigorous herbicide regimes 

would have on early community composition and structure.
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research paper pnw-rp-589

Because wood products are often not the only and sometimes not the most 

important output desired, land managers need knowledge about the effects of 

silvicultural treatments on entire plant communities. Thus, we evaluated the relations between native and exotic species in three forest productivity studies that were 

initiated by clearcutting. Subsequent vegetation control with herbicides and logging 

debris manipulations were designed to promote Douglas-fir growth in some areas 

and not others. We examined these sites 5 years after clearcutting. Some of the vegetation control treatments were more stringent than what are typically used in forest 

management, although no more stringent than are sometimes used for management 

of road or power line rights-of-way.

We asked how exotic and native floras interact following clearcutting in the 

Pacific Northwest. We were also interested in how postclearcutting logging debris 

and vegetation control treatments further affect plant diversity and composition of 

the community. To this end, we studied three operational studies having similar 

treatments in western Washington and Oregon. Although it is recognized that 

disturbance increases opportunities for ruderal species, we asked if the relation of 

native and exotic ruderals to the residual forest species was similar, and what the 

relation of the two ruderal groups was to each other. We hypothesized that if exotic 

species abundance increased as a result of postclearcutting vegetation control or 

logging debris treatments, there would be a decrease in native species abundance. 

Similarly, but more generally, we hypothesized that an increase in ruderal species 

would be accompanied by a decrease in residual species.

Materials and Methods

Study Sites

Our study sites (Matlock, Molalla, and Fall River) were located in the Western 

Hemlock Zone (Franklin and Dyrness 1988) of western Washington and Oregon. 

These sites were managed for timber production and initially supported uniformly 

stocked stands of 40- to 70-year-old Douglas-fir. At Matlock and Molalla, some 

trees were removed before clearcutting (in a low thinning in 1993 at Molalla and 

by removal of damaged trees after a 1996 ice storm at Matlock). Each stand was 

clearcut (in spring 2003 at Matlock and Molalla and spring 1999 at Fall River) and 

planted with Douglas-fir seedlings (plug+1 stock planted in early 2004 at Matlock 

and Molalla on a 3-m grid; 2+0 stock planted in March 2000 at Fall River on a 

2.5-m grid). Each site was fenced to prevent ungulate browsing of the planted 

seedlings. 

The Matlock site is on nearly level glacial outwash at about 35 m elevation 

25 km west of Shelton, Washington. The soil is deep, somewhat excessively 

We asked how exotic 

and native floras 

interact following 

clearcutting in the 

Pacific Northwest. We 

were also interested in 

how postclearcutting 

logging debris and 

vegetation control 

treatments further 

affect plant diversity 

and composition of the 

community.
3

Relations of Native and Exotic Species 5 Years After Clearcutting With and Without Herbicide and Logging Debris Treatments

drained, very gravelly loamy sand in the Grove Series with 55 to 75 percent coarse 

fragments (Dystric Xerorthent; USDA NRCS 2009a). The water-holding capacity of 

the top 60 cm of soil averaged 55 mm, and the total nitrogen (N) content averaged 

3300 kg/ha in the year following forest harvesting (Devine et al. 2011). The average 

annual precipitation is 2413 mm (USDA NRCS 2000b). The primary plant association of the Matlock site is the Tsuga heterophylla/Gaultheria shallon plant association with some occurrences of the Tsuga heterophylla/Gaultheria shallon-Mahonia 

nervosa association (Henderson et al. 1989). 

The Molalla site is on a gently rolling ridge and upper west-facing slope (0 

to 30 percent slope) between 500 and 570 m elevation about 24 km northeast of 

Molalla, Oregon. The soil is a deep, well-drained cobbly loam of the Kinney Series 

derived from igneous tuffaceous agglomerate with 25 to 35 percent coarse fragments (Andic Dystrudept; USDA NRCS Soil Surv. Staff 2009). The water-holding 

capacity of the top 60 cm of soil averaged 142 mm, and the total N content averaged 

7220 kg/ha in the year following forest harvesting (Devine et al. 2011). The average annual precipitation is 1829 mm (USDA NRCS 2009b). The Molalla site has 

the most topographic variability and correspondingly the most plant associations. 

The four Molalla plant associations in order of importance are Tsuga heterophylla/

Mahonia nervosa/Polystichum munitum, Tsuga heterophylla/Mahonia nervosaGaultheria shallon, Tsuga heterophylla/Polystichum munitum-Oxalis oregana, and 

Tsuga heterophylla/Polystichum munitum (Halverson et al. 1986). 

The Fall River site is located 33 km west-northwest of Chehalis, Washington, 

on a gentle (<15 percent), west-facing slope at 335 m elevation. The soil is a uniform, very deep, well-drained, silty clay loam to silty clay of the Boistfort Series 

derived from volcanic ash and deeply weathered basalt (Typic Fulvudand; USDA 

NRCS 2009a). The water-holding capacity of the top 60 cm averaged 174 mm, and 

the total N content averaged 10 188 kg/ha in the year following forest harvesting 

(Devine et al. 2011). The average annual precipitation is 2159 mm (USDA NRCS 

2009b). The main plant association of the Fall River site is Tsuga heterophylla/

Polystichum munitum-Oxalis oregana (Henderson et al. 1989).

Study Design

We used a randomized complete block design. At Matlock and Molalla, six treatments were replicated four times as a factorial combination of three logging-debris 

treatments by two vegetation-control treatments. Each treatment was randomly 

assigned to four 50- by 60-m (0.3-ha) plots, providing a total of 24 plots per site. 

Blocking was based on aspect (Molalla) and proximity to logging roads (Matlock 
4

research paper pnw-rp-589

and Molalla)—a surrogate for frequency of machine traffic. Machine traffic 

associated with shovel yarding and the logging debris treatments (described below) 

at Matlock and Molalla was confined to designated trails placed at 20-m intervals 

lengthwise through the plots.

At Fall River there were eight replications of three treatments for a total of 24 

plots (Ares et al. 2007). Each Fall River treatment was randomly assigned to two 

30- by 85-m (0.26-ha) treatment plots in each of four blocks. Blocking was based on 

preharvest Douglas-fir volume. All of the plots had similar gentle slopes and west 

exposures. For this study, we looked at only 3 of the 12 treatments conducted at Fall 

River (Ares et al. 2007).

Treatment 

No. Description

1 Logging debris dispersed without vegetation control: removal of 

merchantable logs to a 10- (at Fall River) or 12.7-cm diameter (at 

Matlock and Molalla) top with retention of logging debris in place 

(Matlock and Molalla: four plots per site; Fall River: eight plots).

2 Logging debris piled without vegetation control (piled/no vegetation 

control): removal of merchantable logs and moving of logging debris <12.7-cm diameter into piles 3 to 4 m in diameter (Matlock and 

Molalla: four plots per site).

3 Logging debris removed without vegetation control: removal of 

aboveground portion of trees (boles, branches, and foliage >5-cm 

diameter) (Matlock and Molalla: four plots per site). 

4 Logging debris dispersed with vegetation control: same as treatment 

1, but with five annual herbicide treatments to reduce abundance of 

competing vegetation (described below) (Matlock and Molalla: four 

plots per site; Fall River: eight plots).

5 Logging debris piled with vegetation control: same as treatment 2, 

but with five annual herbicide treatments to reduce abundance of 

competing vegetation (described below) (Matlock and Molalla: four 

plots per site).

6 Logging debris removed with vegetation control treatment: same 

as treatment 3, but with five annual herbicide treatments to reduce 

abundance of competing vegetation (described below). This treatment occurred at all three sites, but at Fall River, all debris > 0.6-cm 

diameter was removed (Matlock and Molalla: four plots per site; 

Fall River: eight plots).

Piling and removing of debris resulted in additional mechanically induced soil 

disturbance. Where debris was dispersed, there was significantly less exposure of 

mineral soil (2 to 3 percent of the total area) than where it was piled or removed 

(4 to 6 percent of the total area) (Harrington and Schoenholtz 2010). The debris 

piles were about 3 m in diameter and 1 m high. There were 105 piles per hectare at 

Matlock and 60 piles per hectare at Molalla (Harrington and Schoenholtz 2010). 
5

Relations of Native and Exotic Species 5 Years After Clearcutting With and Without Herbicide and Logging Debris Treatments

In addition to reducing competition with Douglas-fir seedlings, a goal of the 

herbicide treatments at Matlock and Molalla was to reduce cover of herbaceous 

and woody vegetation to < 20 percent and thereby provide experimental conditions 

for quantifying debris effects on Douglas-fir growth independent of vegetation 

abundance. To this end, an initial vegetation control treatment was applied to all 

plots in late summer 2003 to reduce woody vegetation prior to planting of Douglasfir (table 1). Annual herbicide treatments were applied in the fall or spring of 2003 

through 2008 to the designated vegetation control plots to reduce abundance of 

herbaceous and woody vegetation (Harrington and Schoenholtz 2010). Douglas-fir 

was the only species that was deliberately not sprayed. At Matlock, three additional 

herbicide treatments were applied to all plots to specifically reduce abundance of 

Scotch broom (Cytisus scoparius (L.) Link). These directed applications of triclopyr 

were made to individual broom plants to minimize effects on other vegetation and 

eliminated most of the Scotch broom at Matlock. This highly competitive, exotic 

shrub reproduced prolifically from seed stored in the soil (Bossard 1993) that was 

probably introduced during the 1998 salvage harvest. 

At Fall River, where the goal was to eliminate all vegetation other than the 

planted trees, vegetation control was achieved by one preplanting herbicide application (dispersed/no vegetation control treatment excepted) and five annual applications of preemergent herbicides in the spring with spot applications of postemergent 

herbicides as needed (table 1). Herbicides differed by year at all three sites to 

control selected species as they became dominant and to prevent the development 

of resistance in any of the species of competing vegetation. Both broadcast and spot 

treatments were used to ensure that the desired level of control was achieved.

Field Procedures

Circular 176.6-m2 (7.5-m-radius) vegetation sample plots were located in the center 

of treatment plots at Matlock and Molalla and centered 35 m from the west edge of 

each treatment plot at Fall River. Vegetation measurements were made in year 5 in 

July (Fall River: 2004, Matlock and Molalla: 2008). Vegetation assessment followed 

protocols for reconnaissance plots of the USFS Pacific Northwest Region, Area 1 

Ecology Program (Henderson et al. 1989). Plant cover was ocularly estimated for 

all vascular species except Douglas-fir. Douglas-fir cover was calculated from the 

product of mean cover per tree (based on two crown diameter measurements of 

each tree taken at right angles) and the total count of trees on the plot. Ten systematically selected trees per plot were measured at Fall River. All trees on the plot 

were measured at Matlock and Molalla. Each measured tree was also measured for 

height.
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research paper pnw-rp-589

Table 1—Vegetation control treatment information by year for the three study sites

Study Herbicide(s) active Method of 

Site Month/year yeara ingredient Herbicide rate(s) application

Matlock 09/2003 0 Triclopyr ester 2.8 kg a.i. ha-1 with surfactantb Broadcast

12/2003 0 Sulfometuron 0.2 kg a.i. ha-1c Broadcast

10/2004 1 Triclopyr ester 2.5 percent solution in waterd Directed foliar

04/2005 2 Glyphosate + clopyralid 1.5 percent + 0.75 percent Broadcast

 solution in waterc

04/2006 3 Glyphosate + clopyralid 1.5 percent + 0.75 percent Broadcast

 solution in waterc

04/2007 4 Glyphosate + clopyralid 1.5 percent + 0.75 percent Broadcast

 solution in waterc

06/2007 4 Triclopyr ester 20 percent solution in crop oild Directed basal 

 stem

05/2008 5 Glyphosate + clopyralid 1.5 percent + 0.75 percent Broadcast

 solution in waterc

05/2008 5 Triclopyr ester 20 percent solution in crop oild Directed basal 

 stem

Molalla 08/2003 0 Glyphosate 2.2 kg a.i. ha-1 in water with Broadcast 

 surfactantb

10/2003 0 Sulfometuron 0.2 kg a.i. ha-1 in waterc Broadcast

10/2004 1 Glyphosate + Sulfometuron 1.1 + 0.2 kg a.i. ha-1 in waterc Broadcast

 foliar

05/2006 3 Glyphosate + atrazine 1 percent solution in water Broadcast 

 + 4.9 kg a.i. ha-1c

05/2007 4 Clopyralid + atrazine 0.8 + 4.9 kg a.i. ha-1 in waterc Broadcast

05/2008 5 Triclopyr ester + 2, 2 percent + 2 percent suspension Broadcast 

 4-D ester in water with surfactantc

Fall River 03/2000 1 Sulfometuron 0.2 kg ha-1c Broadcast 2 

 weeks before 

 planting

03/2000 1 Glyphosate 4.67 L ha-1c Broadcast 2 

 weeks before 

 planting

03/2001 2 Atrazine 9.3 L ha-1c Broadcast

04/2001 2 Glyphosate 0.75 percent in waterc Spot

03/2002 3 Atrazine 9.3 L ha-1c Broadcast

03/2002 3 Sulfometuron 0.17 kg ha-1c Broadcast

04–05/2002 3 Clopyralid 1 percent in waterc Spot

06/2002 3 Glyphosate 0.75 percent in waterc Spot

03/2003 4 Hexazinone 7.0 L ha-1c Directed band 

 between rows

04–05/2003 4 Clopyralid 1 percent in waterc Spot to shrubs

06/2003 4 Glyphosate 0.75 percent in waterc Spot

04/2004 5 Hexazinone 5.85 L ha-1c Directed band 

 between rows

a

 Growing seasons since planting Douglas-fir seedlings in early 2004.

b

 Applied to all plots.

c

 Applied to annual vegetation control plots only.

d

 Applied to Scotch broom only.
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Relations of Native and Exotic Species 5 Years After Clearcutting With and Without Herbicide and Logging Debris Treatments

Analysis

We analyzed site and treatment effects on diversity (species richness, Simpson, 

Shannon, and evenness indexes) and canopy cover of plants in three species groups 

or in total. The three species groups were exotic ruderal (ER), native ruderal (NR), 

and native residual forest (RF) species. Ruderal species respond favorably to disturbances such as overstory removal and perform poorly in dense shade. Exotics (as 

contrasted with natives) are species that are now naturalized but were not originally 

present in the Pacific Northwest and were introduced in conjunction with the 

spreading of old-world culture into the area. Most exotic species come from Europe 

or Asia. Most NR species are perennials, whereas most ER species are annuals, 

biennials, or short-lived perennials. Residual forest species are native shade-tolerant 

species typically associated with interior forest settings and are generally long-lived 

perennials. Many of these species regenerated from residual stumps, rhizomes, or 

roots in the clearcut environment. For analyses of canopy cover, individual species’ 

canopy covers were summed for each species group (i.e., ER, NR, RF, and total 

understory) by plot. 

We used PC-Ord computer software (McCune and Mefford 1999) to calculate 

several indicators of species diversity per 176.6-m2

 plot (i.e., species richness, 

Simpson, Shannon, and evenness indexes). Richness is expressed as the number of 

vascular plant species on a plot by species group (ER, NR, RF) or as an overall total 

(all species on a 176.6-m2 plot regardless of group). 

Community composition— 

To examine plant community floristics before and after treatment, we used PC-Ord 

to conduct two nonmetric multidimensional scaling (NMS) ordinations (McCune 

and Mefford 1999) (table 2). One ordination included only plots that had not received vegetation control (n = 32). A second ordination included only plots that 

received vegetation control (n = 40). The response variables were estimated canopy 

covers for all understory species. We set the PC-Ord NMS autopilot for thoroughness, specified use of the Sorensen distance measure, and otherwise used default 

Table 2—Nonmetric multidimensional scaling model performance for the two 

ordinations described in the texta

 Final Number of

Data set Stress Instability Iterations Plots Species

No vegetation control 13.5 <0.00001 74 32 116

Vegetation control 10.3 0.007 500 40 90

a Douglas-fir was not included in these ordinations.

We analyzed site and 

treatment effects on 

diversity and canopy 

cover of plants in three 

species groups or in 

total. The three species 

groups were exotic 

ruderal (ER), native 

ruderal (NR), and native 

residual forest (RF) 

species.
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research paper pnw-rp-589

settings. Default settings included 6 axes, 400 (maximum) iterations, random starting coordinates, reduction in dimensionality of 1 at each cycle with a 0.2 step length 

(rate of movement toward minimum stress), random number of seeds, 40 runs 

with real data, 50 runs with randomized data, and a stability criterion of 0.000010 

standard deviations in stress over the last 15 iterations. We superimposed on our 

ordinations joint plots (McCune and Mefford 1999) of 5-year tree height and crown 

width (measures of productivity) and seven measures of diversity including number 

of NR, ER, and RF species; total richness; Shannon’s index; Simpson’s index; and 

evenness. Joint plots show the direction (angle) and strength (line length) of relations of variables to the ordination scores (correlations). The lines of the joint plots 

emanate from the centroid of all the species data used in the ordination. 

Analysis of variance (diversity and canopy cover)— 

We used analysis of variance (ANOVA) to test the hypothesis that the ordination 

centroids of the three sites were not distinct on each axis of each ordination. We analyzed site-specific effects in canopy cover and diversity variables with two factor 

mixed-model ANOVA (SAS Proc Mixed ) (SAS Institute Inc. 2003) to evaluate 

debris and vegetation control treatments (fixed effects), blocking (random effect), 

and treatment interactions within each site. 

Cover relations among the species groups— 

We used linear regression to test for differences among sites in the cover relations 

of NR and native RF species versus ER species. For each relation, plot values were 

pooled across sites for each of the debris treatments without vegetation control (n = 

8, 12, and 12 for Fall River, Matlock, and Molalla, respectively). Indicator variables 

were specified to test for differences in slopes and intercepts among sites using the 

extra-sums-of-squares approach (Neter et al. 1989). Stepwise regression in PROC 

Reg was used to compare a full model with reduced models having common intercepts, slopes, or both (SAS 2003).

Relation of richness to total cover— 

We used linear regression to test for site differences in the relation of richness to 

total understory cover. Total understory cover (summed over all species except 

Douglas-fir) was used as the measure of intensity of vegetation control as well as an 

indicator of site productivity. Plot values of richness, pooled across sites for each of 

the debris treatments with and without vegetation control (n = 24 for each site), were 

regressed against associated plot values for total understory cover. The extra-sumsof-squares approach was used similarly as described above to test for differences in 

slopes and intercepts among sites for each relation (Neter et al. 1989).
9

Relations of Native and Exotic Species 5 Years After Clearcutting With and Without Herbicide and Logging Debris Treatments

Results

Species Composition and Diversity

Over all plots regardless of treatment at each site (n = 24 per site), we found 82 species at Matlock, 91 species at Molalla, and 52 species at Fall River. On the debrisdispersed treatment plots where no herbicide was used, we found 80 species at Matlock (n = 4), 89 species at Molalla (n = 4), and 49 species at Fall River (n = 8). Thus, 

Fall River was the least diverse site, Molalla had a few more species than Matlock, 

and nearly all species at each site were found in the debris-dispersed plots. 

The dominant species differed among the treatments that lacked vegetation 

control. At Matlock, the three most abundant species were oxeye daisy (Leucanthemum vulgare Lam.; 28 percent cover), hairy cat’s ear (Hypochaeris radicata L.; 27 

percent), and Douglas-fir (8 percent). The most abundant species at Molalla were 

California blackberry (Rubus ursinus Cham. & Schltdl.; 55 percent cover), velvet 

grass (Holcus lanatus L.; 27 percent), and Douglas-fir (12 percent). At Fall River, 

the most abundant species were Douglas-fir (53 percent), hairy cat’s ear (34 percent), and velvet grass (27 percent). The vegetation control treatments were mostly 

dominated by the same species, but with much lower covers except for Douglas-fir, 

which had higher cover.

Our NMS ordinations separated the three sites floristically (fig. 1). Overall 

NMS model performance is provided in table 2 and correlation values (tau) for each 

variable in the joint plots with each axis are given in table 3. Without vegetation 

control, the average location of points from any two sites on either axis was significantly different with the exception of Molalla and Fall River on axis 1. However, 

with vegetation control, all possible site comparisons were significantly different. 

The community floristic affinities are further indicated by the unique sharing of 

10 species between Fall River and Molalla, but only 3 species were uniquely shared 

between Fall River and Matlock. However, Matlock and Molalla had 32 species 

uniquely in common, suggesting even closer affinities between these sites. There 

were no clear patterns in our ordinations attributable to debris treatments except for 

the partial separation of debris removed versus debris dispersed plots at Fall River 

where vegetation control was used (fig. 1b). 

The joint plot in figure 1 (correlation values presented in table 3) suggests that 

two indicators of productivity (crown width and tree height) correlate with the 

floristic differences that separate the three sites in the ordination. Thus, Fall River 

and Molalla (with the largest tree sizes) are separated on axis 1 from Matlock with 

the smallest tree size (fig. 1a). Molalla is further separated from the other sites by 

higher NR species diversity as is Matlock by higher ER species diversity. Figure 

1b shows that the more severely herbicide treated Fall River community separates 
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research paper pnw-rp-589

Table 3—Correlation (tau) of each productivity and diversity 

indicator with each ordination axis

No vegetation Vegetation 

control control

Axis 1 2 1 2

Crown width -0.47 -0.26 -0.48 -0.43

Tree height -0.59 -0.12 -0.55 -0.37

Richness 0.26 0.33 0.62 0.34

Evenness index 0.24 0.06 0.67 0.32

Shannon index 0.30 0.23 0.70 0.28

Simpson index 0.22 0.09 0.69 0.33

Exotic ruderal count 0.52 0.04 0.53 0.39

Native ruderal count -0.01 0.56 0.55 0.51

Residual forest count 0.07 -0.21 0.58 0.19

from the Matlock and Molalla communities on the basis of lower diversity, which is 

inversely correlated with tree size.

Our data suggest that debris treatments have only modest effects on diversity 

and little if any effect on Douglas-fir productivity as measured by 5-year height 

and canopy cover growth (table 4). No debris treatment effect was found for any 

richness or diversity index at Molalla. The Matlock Shannon index was higher for 

the debris-piled treatment than for the debris-removed treatment. At Fall River 

Figure 1—Nonmetric multidimensional scaling ordinations by treatment type at Matlock (M), Molalla (m), and Fall River 

(F) for (a) plots without vegetation control and (b) plots with vegetation control. Superimposed are joint plots showing the 

direction (angle) and strength (line length) of relations of tree size and species diversity measures to the ordination scores. 

Included are Douglas-fir height (ht), Douglas-fir crown width (cw), number of native ruderal (NR) species, number of exotic 

ruderal (ER) species, number of residual forest (RF) species, total richness (ri), Shannon’s index (Sh), Simpson’s index (Si), 

and evenness (ev). In “a,” Simpson’s index, and exotic ruderal (er) count fall on the same angle but are different lengths. 

Similarly, evenness and Si fall on another line. Douglas-fir was not included in these ordinations.

A. Plots without vegetation control B. Plots with vegetation control

Debris treatments have 

only modest effects on 

diversity and little if 

any effect on Douglasfir productivity.
11

Relations of Native and Exotic Species 5 Years After Clearcutting With and Without Herbicide and Logging Debris Treatments

Table 4—Mean 5-year treatment cover and diversity index values with P-values for 

comparisons that were significantly different (α = 0.05)a b c

Matlock

 VC x 

LDD LDP LDR Debris P NVC VC VC P Debris P

n 8 8 8 12 12

Douglas-fir height 195.3 170.6 175.3 163.7 197.1 0.00

Douglas-fir cover 13.3 10.4 10.7 7.7 15.2 0.00

Exotic ruderal cover 38.8 45.9 57.2 0.04* 79.8 14.9 0.00

Native ruderal cover 23.2 13.1 13.2 19.8 13.2

Residual forest cover 30.5 19.4 14.1 <0.01** 22.0 20.7

Total understory cover 92.5 78.4 84.5 121.5 48.8 0.00

Exotic ruderal richness 7.8 8.6 8.1 10.0 6.3 0.00

Native ruderal richness 9.0 8.5 8.0 9.8 7.2 0.01

Residual forest richness 13.6 12.4 11.4 12.7 12.3

Evenness index 0.7 0.7 0.7 0.7 0.7 0.05

Shannon index 2.4 2.5 2.2 0.04*** 2.4 2.3 0.01

Simpson index 0.9 0.9 0.8 0.8 0.8

Molalla

n 8 8 8 12 12

Douglas-fir height 227.4 323.1 227.2 217.3 240.5 0.05

Douglas-fir cover 13.3 15.3 13.8 12.4 15.9 0.01

Exotic ruderal cover 39.6 33.7 40.3 54.2 21.5 0.01

Native ruderal cover 56.3 55.2 57.3 89.3 23.2 0.00

Residual forest cover 21.7 22.7 23.9 32.0 13.5 0.00

Total understory cover 117.6 111.6 121.5 175.6 58.3 0.00

Exotic ruderal richness 6.3 6.3 6.5 7.0 5.7

Native ruderal richness 11.4 11.6 11.0 15.1 7.6 0.00

Residual forest richness 8.9 9.8 8.4 10.7 7.3 0.00

Evenness index 0.6 0.7 0.6 0.6 0.7

Shannon index 2.1 2.2 2.1 2.3 2.0 0.00

Simpson index 0.8 0.8 0.8 0.8 0.8

Fall River

n 16 0 8 8 16

Douglas-fir height 323.9 344.8 310.4 341.1 0.00

Douglas-fir cover 62.5 70.6 53.1 71.3 0.00

Exotic ruderal cover 33.0 2.9 64.8 2.0 0.00

Native ruderal cover 25.5 1.0 50.6 0.7 0.00

Residual forest cover 14.7 1.0 28.1 1.2 0.00

Total understory cover 73.1 4.9 143.5 3.9 0.00

Exotic ruderal richness 4.1 2.5 5.8 2.5 0.00

Native ruderal richness 4.3 2.5 6.9 2.1 0.00

Residual forest richness 8.4 5.0 11.5 5.2 0.00

Evenness index 0.4 0.1 0.03 0.6 0.1 0.00

Shannon index 1.1 0.3 0.04 2.0 0.3 0.00

Simpson index 0.4 0.1 0.01 0.8 0.1 0.00

a Where three values are compared (as in the case of debris treatments), mean separations according to Tukey Honestly Significant 

Difference tests (α = 0.05) are provided at the end of the table.

b Douglas-fir is not included in the richness values.

c

LDD = logging debris dispersed, LDP = logging debris piled, LDR = logging debris removed, NVC = no vegetation control, and 

VC = vegetation control.

Note: * LDD < LDR, ** LDD > (LDR = LDP), *** LDP > LDR.
12

research paper pnw-rp-589

the Evenness, Shannon and Simpson indexes were higher for the debris-dispersed 

treatment than for the debris-removed treatment. Thus, removal of organic matter 

sometimes decreased diversity, but never increased it.

Herbicide treatments decreased diversity while increasing Douglas-fir growth 

(table 4). All indicators of richness and diversity decreased significantly at Fall 

River. Matlock ruderal richness (exotic and native) decreased, but at Molalla native 

species richness (ruderal and RF) decreased. At Matlock, none of the diversity 

indexes changed (evenness, Shannon, Simpson), but at Molalla the Shannon index 

decreased. 

Relations Among Native and Exotic Species Groups

In the absence of vegetation control, there was a strong negative relation (R2 = 0.77; 

P < 0.01, slope = -0.43) between NR cover and ER cover suggesting that species in 

these two groups have overlapping resource requirements resulting in competition 

(fig. 2, table 5). Intercepts, but not slopes, differed among sites for the NR and ER 

relation (fig. 2a), but a common intercept and slope were found for all three sites 

in the relation of RF cover and ER cover (fig. 2b). A weaker relation (R2 = 0.27; P

< 0.01, slope = -0.27) between RF cover and ER cover suggests that ER species 

compete with RF species to a lesser extent than with NR species. Conversely, a lack 

of a relation between RF cover and NR cover suggests little interaction at age 5 

between these two groups (fig. 2c).

Canopy Cover and Productivity

Douglas-fir cover and height were greater with than without vegetation control at 

all three sites (table 4). At Matlock ER cover was higher where logging debris was 

removed than where it had been dispersed. Also, RF species cover was significantly 

higher where logging debris was dispersed than where it had been piled or removed 

at Matlock. No such relation was found among debris treatments at Molalla, and 

owing to experimental design differences, this comparison could not be made at 

Fall River. On debris-dispersed plots without vegetation control, Douglas-fir height 

and canopy cover were greatest at Fall River and least at Matlock (table 4).

Relation of Richness to Total Cover

Over all plots with or without vegetation control, richness had a strong, positive 

linear relation with total understory cover (R2

 = 0.88, P < 0.01; fig. 3). Although the 

site determined the overall level of richness (regression intercepts differed significantly among sites), the rate of species loss owing to vegetation control (regression 

slope) was independent of site, herbicides used, and application protocols that were 

Exotic ruderal species 

compete with residual 

forest species to a 

lesser extent than with 

native ruderal species. 

A lack of a relation 

between residual 

forest cover and native 

ruderal cover suggests 

little interaction at age 

5 between these two 

groups.
13

Relations of Native and Exotic Species 5 Years After Clearcutting With and Without Herbicide and Logging Debris Treatments

A B

C

Figure 2—The relation of cover of native ruderal (NR) species and 

residual forest (RF) species to exotic ruderal (ER) species at the 

Matlock, Molalla, and Fall River sites. Only those plots without vegetation control are shown in these relations. See table 5 for regression 

statistics. Regression lines for fig. 2a solid = Molalla, dashed = Fall 

River, and dotted = Matlock.

Table 5—Regression statistics for the relations of native ruderal cover to exotic ruderal cover (see 

fig. 2), and residual forest cover to exotic ruderal cover (see fig. 2) and species richness to total cover 

(see fig. 3) at the Matlock, Molalla, and Fall River sites

Site Y X Equation R2 S

y.x

n

Matlock Native ruderal cover Exotic ruderal cover Y = 53.8 - 0.43X 0.77 17.5 32

Molalla Y = 112 - 0.43X

Fall River Y = 78.2 - 0.43X

All sites combined Residual forest cover Exotic ruderal cover Y = 45.3 - 0.27X 0.27 12.2 32

Matlock Species richness Total cover Y = 20.7 - 0.098X 0.88 3.23 72

Molalla Y = 15.4 - 0.098X

Fall River Y = 9.6 - 0.098X

Note: Each regression coefficient is significant (p < 0.05). R2 is the coefficient of determination, Sy.x is the standard error of the estimate, and 

n is the sample size.
14

research paper pnw-rp-589

used. Species loss was proportional to the amount of total understory canopy cover 

remaining after treatment (approximately one species lost for each 10 percent reduction of cover).

Discussion

Community Structure and Composition

Our three Western Hemlock Zone (Franklin and Dyrness 1988) sites had distinctive 

environments, floras, and levels of productivity. Indicator species (Halverson et 

al. 1986, Henderson et al. 1989) and our ordinations floristically separate each site 

from the others, but suggest closer floristic affinities between Matlock and Molalla 

than between either of these sites and Fall River. However, based on the ordinations, 

Molalla and Fall River are floristically more similar than are Matlock and Fall 

River. The joint plot suggests that high NR diversity helps to distinguish Molalla 

from Matlock and Fall River while high ER diversity helps to distinguish Matlock 

from the Molalla and Fall River communities. 

The balance of evidence suggests a site productivity gradient of Matlock < 

Molalla < Fall River, which follows the observed ranking in soil water and N availability among the three sites. Matlock had the highest precipitation, but also the 

lowest soil water-holding capacity and the lowest soil N. Fall River had the highest 

soil N, as well as a very deep clay-loam soil providing the largest soil water-holding 

Figure 3—The relation of richness to total understory cover 

for combined plots with and without vegetation control at 

three study sites. Douglas-fir was not included in either richness or cover as it was deliberately not treated with herbicide. 

See table 5 for regression statistics. Regression lines: dotted 

= Matlock, solid = Molalla, and dashed = Fall River.
15

Relations of Native and Exotic Species 5 Years After Clearcutting With and Without Herbicide and Logging Debris Treatments

Table 6—Comparison of means and standard deviations (SD) for Douglasfir height, cover, and plant community diversity indicators for logging 

debris dispersed without vegetation control plots at the three sites

Matlock Molalla Fall River 

n 4 4 8

Mean SD Mean SD Mean SD

Douglas-fir height (cm) 169 20.6 219 9.3 310 16.0

Douglas-fir cover 8.5 0.8 11.4 2.2 53.1 5.3

Exotic ruderal cover 69.7 11.3 58.6 30.7 64.8 30.4

Native ruderal cover 27.9 18.6 87.9 42.7 50.6 16.3

Residual forest cover 33.8 14.2 28.2 8.2 28.1 17.9

Exotic ruderal richness 10.3 1.7 6.8 1.5 5.8 1.4

Native ruderal richness 10.8 2.6 15.8 3.2 6.9 1.5

Residual forest richness 14.8 2.1 10.5 2.4 11.5 3.1

Richness (w/o Douglas-fir) 35.8 6.0 33.0 3.7 24.1 2.9

Evenness index 0.7 0.03 0.6 0.03 0.6 0.03

Shannon index 2.6 0.16 2.2 0.16 2.0 0.13

Simpson index 0.9 0.02 0.8 0.02 0.8 0.02

capacity. Site index values (King 1966) from the preharvest stands suggest Fall 

River is the most productive site (Fall River 41 to 43 m) (Terry et al. 2001), but do 

not distinguish between Matlock and Molalla (both 36 m) (Harrington and Schoenholtz 2010). However, published site index (McArdle and Meyer 1930, base 100 

years) values for the plant associations present on these sites are 38 m for Matlock, 

43 m for Molalla, and 54 m for Fall River (Halverson et al. 1986, Henderson et al. 

1989). Also, the mean 5-year postharvest Douglas-fir tree heights and covers were 

least at Matlock and greatest at Fall River. 

Trends in species richness approximated the inverse of the productivity gradient 

as suggested by the Intermediate Disturbance Hypothesis (Huston 1979). Although 

total richness was greatest at Molalla, richness per unit of canopy cover was greatest at Matlock (least productive) and least at Fall River (most productive) with or 

without vegetation control (fig. 3). Also, all three diversity indexes were apparently 

higher on debris-dispersed plots at Matlock than the other two sites, and total 

richness was lowest at Fall River (table 6). Exotic species were especially important 

contributors to the diversity at Matlock.

The negative relation of ER and RF species covers contrasts with the lack of 

a relation between NR and RF covers, suggesting that ER and NR species groups 

are not only functionally different but have fundamentally different relations to 

RF species as a result. In general, ruderal species (native or exotic) rapidly occupy 

space not already occupied by RF species during early succession. The more RF 

cover surviving the disturbance, the less ruderal cover and thus an inverse relation 
16

research paper pnw-rp-589

develops. However, chronosequence data from Fall River clearly show ER species 

establishing dominance more quickly than NR species (Peter and Harrington 2009). 

The rapid occupancy of open space by ER species obscures what might otherwise 

have been a similar relation of NR to RF species in the past before the invasion of 

ER species. Thus, in the past, a negative relation of NR and RF species probably 

developed, albeit more slowly. The ability of ER species to more rapidly occupy 

these sites than NR species is key to their invasion success and the reason for the 

current obscure relation of NR and RF species. Native ruderal species appear 

to invade and grow more slowly, gradually taking space left as shorter lived ER 

species senesce. Thus, NR cover shows little relation to RF cover at this point in 

succession.

The inverse relation between NR and ER cover suggests niche overlap and competition. Regardless of site, a change of 4 percent cover of ER species was accompanied by an opposite change of 10 percent cover of NR species. However, there was 

apparently no consistent dominance of one group by the other, and, to our knowledge, no localized extinction has resulted, suggesting that our communities are not 

species saturated. Antos and Halpern (1997) found lower root-to-shoot ratios of 

invading annuals (including some ER species) than in NR perennials like fireweed 

(Chamerion angustifolium (L.) Holub). Greater belowground resource allocation of 

NR species suggests a strategy of superior competitiveness for soil resources, but 

at the expense of rapid reproductive capacity and capture of aboveground growing 

space and thus a difference in their niche space relative to ER species. Apparently, 

niche overlap of these groups is sufficient for NR species to have lost some growing 

space to ER species; however, they appear to differ enough in habitat requirements 

that coexistence is possible provided species in both groups have access to the site.

Differences in site characteristics or land use history determined the representation of ruderals. Based on productivity, Fall River might have been expected 

to have the greatest total ruderal cover; however, Douglas-fir attains dominance 

so rapidly on this site that light and root competition partly suppressed the ruderal 

plants by age 5 years, suggesting that high productivity compresses the window of 

availability of suitable habitat for ruderal species. Higher richness of ER species at 

Matlock and the inverse relation of NR to ER species suggests that Matlock is more 

susceptible to invasion by ER species than the other sites. This may result from a 

slower rise in dominance of trees, a slower rate of colonization by NRs owing to 

their more conservative reproductive strategy, and to the slow recovery rate of RF 

species. 

A change of 4 percent 

cover of exotic 

ruderal species was 

accompanied by an 

opposite change of 

10 percent cover of 

native ruderal species. 

Niche overlap of these 

groups is sufficient 

for native ruderal 

species to have lost 

some growing space to 

exotic ruderal species; 

however, they appear 

to differ enough in 

habitat requirements 

that coexistence is 

possible.
17

Relations of Native and Exotic Species 5 Years After Clearcutting With and Without Herbicide and Logging Debris Treatments

Debris Treatments

Ground disturbance, disruption of the litter layer, and top damage to perennial 

native plants associated with logging debris removal and piling likely favored 

fast-growing ERs at the expense of native species. Differences in cover among 

debris treatments were significant at Matlock (ER species: debris dispersed < 

debris removed; RF species: debris dispersed > debris removed or piled). Scotch 

broom also increased where debris was removed at Matlock relative to where 

debris was dispersed (Harrington and Schoenholtz 2010). Ground disturbance also 

promoted ER species invasion elsewhere (Marshall and Buckley 2008, Sumners 

and Archibald 2007). However, at Molalla and Fall River, the debris treatments had 

little effect on abundance of the species groups, similar to some other studies where 

organic matter removal caused only small changes in soil carbon and N (Powers 

2004, Sanchez et al. 2006), microbial communities (Busse et al. 2006), species 

richness (Alban et al 1994, Hauesler et al. 1999) and conifer growth (Fleming et 

al. 2006). We suggest that the low N content and water-holding capacity of soil at 

Matlock slowed recovery or increased mortality of damaged RF species making 

more and longer lasting openings available to invasive exotic species. This also 

accounts for Matlock’s higher ER cover in the debris-removed treatment compared 

to the debris-dispersed treatment.

Vegetation Control

Similar to other studies involving high rates or repeated applications of herbicides 

(Pitt et al. 2004, Wilkins et al. 1993), our vegetation control treatments increased 

tree growth but caused a loss of diversity and plant cover. The more extreme Fall 

River vegetation control treatments clearly overwhelmed all species groups unlike 

the Matlock or Molalla treatments, but even at these sites, cover and diversity were 

lost. The similarity of the richness response to loss of cover at all three sites regardless of substantial differences in flora, productivity, and treatments (one species lost 

for each 10 percent reduction in cover) suggests robustness for this relationship in 

Pacific Northwest forests.

Concern over Scotch broom competition with planted Douglas-fir at Matlock 

prompted an effort to control the broom with individual-plant applications of 

triclopyr in years 1, 4, and 5 on all plots (Harrington and Schoenholtz 2010). Observations by the authors and others (Wearne and Morgan 2004) indicate that Scotch 

broom commonly attains high densities that suppress species diversity. Scotch 

broom would likely turn the predominantly herbaceous-to-tree-dominated succession at Matlock (potentially at the other sites too), into a shrub-to-tree-dominated 

succession while delaying the time required for Douglas-fir to attain dominance. 
18

research paper pnw-rp-589

The extra control measures prevented excessive loss of diversity and tree mortality 

(Harrington and Schoenholtz 2010), and thwarted a potential change in successional 

state. Scotch broom was present at the other sites, but did not achieve high levels of 

dominance there owing to differences in previous stand history, aggressiveness of 

previous control efforts, and possibly differences in soil N. Controlling this shrub 

at Matlock provided a more favorable comparison of the remaining, mostly herbaceous ruderal communities. However, it is important to recognize the potential 

of this and some other species such as red alder (Alnus rubra Bong.) for changing 

the outcome of this study and succession in general with severe consequences 

to the timber crop. Red alder has the potential to be an aggressive competitor at 

Molalla and Fall River, but probably not at Matlock because of limited soil water 

availability.

Plant community composition at Matlock and Molalla, but not Fall River, 

became more similar (shown by ordination) after vegetation control owing to differential reductions in ruderal richness and dominance. The ER richness at Matlock 

and the NR richness at Molalla (and both groups at Fall River) were reduced 

significantly, thus there does not appear to be any tendency of either group toward 

greater herbicide resistance. While Matlock and Molalla vegetation became more 

similar, herbicide treatment decreased their similarity to Fall River. Reduction of 

richness and diversity indexes at Fall River with vegetation control indicates that 

representation of the fewer remaining species became more unequal. Exotic ruderals, although much diminished on vegetation control plots, had more than twice 

the cover of native RF species and four times that of the NRs suggesting a superior 

ability to colonize and grow between herbicide applications. 

The Intermediate Disturbance Hypothesis (IDH) predicts that an optimal 

frequency and intensity of disturbance produces the highest diversity for a given 

community (Connell 1978, Grime 1973). This theory is mainly premised on two 

observations: (1) highly competitive species suppress less competitive species, and 

(2) disturbance may injure or kill highly competitive species as much or more than 

others, thus reducing the advantage that they have. Thus, when the forest overstory 

is removed, the understory is released and space is made available for invaders. 

Damage done to the understory vegetation during timber harvest and site preparation (e.g., debris treatments) creates space for ruderal invasion but rarely eliminates 

the original understory flora, resulting in an increase in diversity. This was the 

case for the plots that did not receive vegetation control. Although we do not have 

preharvest data for our stands, casual observation of adjacent intact forest and 

species lists accumulated for mature and old-growth stands of the plant associations 

we identified (Halverson et al. 1986, Henderson et al. 1989) strongly suggest that 
19

Relations of Native and Exotic Species 5 Years After Clearcutting With and Without Herbicide and Logging Debris Treatments

diversity increased after forest harvesting at all three of our sites wherever vegetation control was not used. Thus, harvesting and debris treatments by themselves 

tend to promote community diversity and thus do not greatly exceed the optimal 

level of disturbance predicted by the IDH.

Foresters typically plant vigorous seedlings of a highly competitive tree species 

(e.g., Douglas-fir) often with vegetation control treatments. This allows the planted 

trees to achieve dominance more rapidly than during natural succession, thereby 

reducing the time that the community spends in a diverse early successional state 

over what would naturally occur. The inverse relation of productivity and diversity 

among our sites suggests that tree growth, even by year 5, may be reducing community diversity at Fall River but not at Matlock. This is also suggested by the relation 

of tree size to community composition in the ordination joint plots and is suggested 

in the findings of Peter and Harrington (2009). Thus, when intermediate levels of 

disturbance stop, or when a single species is allowed to escape the effects of disturbance and grow to dominance, the IDH predicts that species diversity will decline. 

The resulting condition that develops in forests has been refered to as the stemexclusion stage (Oliver 1980) and is widely recognized as having low diversity. It 

is therefore especially important in systems managed on short timber rotations to 

understand how silvicultural treatments affect ephemeral developing understory 

communities where most of the diversity of the developing forest resides.

The vegetation control treatments were effective in accelerating Douglas-fir 

dominance. Douglas-fir responded to reduced competition by growing faster, and at 

Matlock with higher survival (Harrington and Schoenholtz 2010). The magnitude of 

the effect (34 percent increase in crown area) in the productive and predominantly 

herbaceous community at Fall River was notable; however, Douglas-fir benefited 

from vegetation control most at Matlock (56 percent increase in crown area). Even 

so, owing to lower productivity, it will be years before Douglas-fir at Matlock 

achieves the level of dominance expressed at Fall River in year 5, which means 

that early successional diversity will be expressed for a longer period of time at 

this site. However, by accelerating Douglas-fir dominance, ruderal species will be 

suppressed more rapidly with potential landscape-level implications for ruderal 

diversity and wildlife habitat quality where these practices are widespread.

Our annual herbicide treatments reduced richness of three different plant communities at the rate of one species per 10 percent loss of canopy cover regardless 

of site or treatment differences, suggesting a degree of generality for this relation. 

As expected, the more intensive Fall River treatments suppressed diversity and 

cover more than the Matlock or Molalla treatments, but at the same rate relative to 

Our annual herbicide 

treatments reduced 

richness of three 

different plant 

communities at the rate 

of one species per 10 

percent loss of canopy 

cover regardless 

of site or treatment 

differences, suggesting 

a degree of generality 

for this relation. 
20

research paper pnw-rp-589

canopy cover. In the context of the IDH, the powerful effects of herbicide applications pushed the community beyond an “intermediate” level of disturbance and thus 

compromised diversity. 

Although herbicides have few natural analogues, like other disturbances they 

create new growing space, which is colonized by ruderals. Therefore, we expect 

that ruderals, especially ERs will increase upon cessation of herbicide treatments. 

While our research does not indicate what effect more typical single applications 

of herbicides would have on diversity, Stein (1995) found a compositional shift 

toward more ruderal species and little effect on diversity with a single application 

of glyphosate. Stein (1995), however, did not identify all taxa to species, so loss of 

rare species might have been overlooked. Peter and Harrington (2009) found that 

a single treatment at Fall River decreased richness in the year of application while 

further annual applications prevented recovery. Elsewhere, few effects of vegetation 

control with herbicides on diversity have been reported (Boyd et al. 1995, Haeussler 

et al. 2002). However, these and most other forestry herbicide studies monitored 

diversity years after treatment, unlike ours, which monitored diversity during 

the first growing season following treatment. The lesson from these other studies 

appears to be that diversity does recover in time. We plan to continue monitoring 

these sites in the future to measure recovery of diversity and composition in the 

absence of further treatments.

The RF species group was somewhat tolerant of the herbicide control measures 

used. Over all three sites, vegetation control treatments reduced RF species cover 

and richness proportionately less than that of ruderal species. Residual forest species are mostly stress tolerators (Grime 1977) that cope with intense shade and root 

competition from the dominant arboreal overstory as succession proceeds. Many 

RF species have a large root (and rhizome)/shoot ratio, compared to ruderals (Antos 

and Halpern 1997, Lezberg et al. 1999), which is common for stress-tolerant plants 

(Chapin 1980) and an important strategy for surviving unpredictable top loss (Iwasa 

and Kubo 1997). The large underground investment in root and rhizome tissue, and 

the ability to regrow from these organs, allows many forest species to survive a 

variety of disturbances (Halpern 1988). We believe that these characteristics reduce 

the susceptibility of RF species to herbicides by reducing the proportion of tissue 

available for herbicide absorption compared to the total plant biomass (relative to 

most ruderals), resulting in a lower dose received. However, their ability to avoid 

herbicide injury was largely overcome at Fall River by more frequent applications, 

and therefore a higher dose, of herbicides.
21

Relations of Native and Exotic Species 5 Years After Clearcutting With and Without Herbicide and Logging Debris Treatments

Conclusions

Although ER and NR species have considerable niche overlap, ER species are more 

successful at initially occupying disturbed sites. While the response of NR species 

to ER species cover was independent of site or stand history, the overall ruderal 

representation was not. We believe that the kind and quantity of the original forest 

understory together with the level of damage incurred during harvest operations 

and the time sites are open and available (owing to differences in site productivity) 

are largely responsible for differences in the overall ruderal representation after 

clearcutting. Because ER species rapidly invade space not occupied by RF species, 

minimizing damage to the forest understory should decrease ER colonization. 

Intensive debris removal, which also involves ground disturbance further encouraged ER establishment on our least productive site. But the lack of such an effect on 

our other sites suggests that this kind of activity has less impact than clearcutting 

on ruderal representation. The ability of ERs to rapidly invade after herbicide treatments suggests that limiting such activity would favor native species. Early successional species diversity is partly an expression of site potential because species 

richness is inversely proportional to site productivity (Huston 1979), but the degree 

of species saturation may also be important. Intensive vegetation control measures 

aimed at increasing tree productivity reduced richness at the rate of one species per 

10 percent understory canopy cover reduction regardless of site or treatment differences. Understory dominance relations were also changed because of a superior 

ability of ERs to colonize and grow between herbicide treatments and less herbicide 

susceptibility of RF species compared to ruderals.

Acknowledgments

The authors acknowledge the generous support of Green Diamond Resource 

Company, Port Blakely Tree Farms, L.P., and Weyerhaeuser Company, which 

manage the Matlock, Molalla, and Fall River sites, respectively, for providing land 

as well as logistical and technical support for this project. This study is partially a 

product of the Sustainable Forestry Component of Agenda 2020, a joint effort of the 

U.S. Department of Agriculture (USDA), Forest Service, Research and Development Program (R&D) and the American Forest and Paper Association. Funds were 

provided by the USDA Forest Service R&D, Washington office. We also thank our 

many crew members for their diligent and exacting work in data collection, and 

Connie Harrington and Tom Terry for their assistance with the work at Fall River.

Although exotic 

ruderal and native 

ruderal species have 

considerable niche 

overlap, exotic ruderal 

species are more 

successful at initially 

occupying disturbed 

sites.
22

research paper pnw-rp-589

English Equivalents

When you know: Multiply by: To find:

Millimeters (mm) 0.0394 Inches

Centimeters (cm) .394 Inches

Meters (m) 3.28 Feet

Kilometers (km) .621 Miles

Hectares (ha) 2.47 Acres

Kilograms (kg) 2.205 Pounds

Kilograms per hectare (kg/ha) .893 Pounds per acre

References

Alban, D.H.; Host, G.E.; Elioff, J.D.; Shadis, D. 1994. Soil and vegetation 

response to soil compaction and forest floor removal after aspen harvesting. Res. 

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Relations of Native and Exotic Species 5 Years After Clearcutting With and Without Herbicide and Logging Debris Treatments

AppendixTable 7—Species with mean cover by site and treatment for the three study sites a b c

Study site, treatment, number of plots, and species richness

Fall River Matlock Molalla

LDD LDD LDR LDD LDP LDR LDD LDP LDR LDD LDP LDR LDD LDP LDRNVC VC VC VC NVC NVC NVC VC VC VC NVC VC NVC NVC NVC VC VC VC NVC VC

8 8 8 16 4 4 4 4 4 4 12 12 4 4 4 4 4 4 12 12

Scientific name Common name Group 43 29 25 36 62 51 57 45 42 44 73 58 63 61 61 38 38 37 84 51Abies grandis grand fir RF 0 0 0 0 0 0 0 0 0

(Douglas ex D. Don) Lindl.

Abies procera noble fir NR 1 0

Rehder

Acer circinatum vine maple RF 0 6 1 1 11 5 2 2 6 0 0 0 0 0

Pursh

Acer bigleaf maple NR 0 0

macrophyllumPursh

Achlys triphylla sweet after death RF 0 0 0 0 0 0

(Sm.) DC.

Adenocaulon American RF

bicolor Hook. trailplant

Agoseris retrorsa spearleaf agoseris NR 0 0 0

(Benth.) Greene

Agrostis colonial bentgrass ER 0 1 3 3 1 0 2 0 5 1 1 1 0 0 2 0

capillaris L.

Aira silver hairgrass ER 0 1 0 0 0

caryophyllea L.

Aira praecox L. yellow hairgrass ER 0 1 0 0 0 0Alnus rubra Bong. red alder NR 1 1 1

Amelanchier saskatoon RF 5 3 1 3 3 2 3 3

alnifolia (Nutt.) serviceberry Nutt. ex M. Roem.

Anaphalis western pearly NR 8 0 0 0 2 0 0 1 3 1 1 0 0 0 0

margaritacea everlasting (L.) Benth.
28

research paper pnw-rp-589 Table 7—Species with mean cover by site and treatment for the three study sites a b c (continued) Study site, treatment, number of plots, and species richness Fall River Matlock Molalla LDD LDD LDR LDD LDP LDR LDD LDP LDR LDD LDP LDR LDD LDP LDR

NVC VC VC VC NVC NVC NVC VC VC VC NVC VC NVC NVC NVC VC VC VC NVC VC

8 8 8 16 4 4 4 4 4 4 12 12 4 4 4 4 4 4 12 12

Scientific name Common name Group 43 29 25 36 62 51 57 45 42 44 73 58 63 61 61 38 38 37 84 51Anthoxanthum sweet vernalgrass ER 8 2 10 0 7 0 0 0

odoratum L.

Apocynum spreading dogbane NR 1 0 0 0 0

androsaemifolium L.

Athyrium filix-	 subarctic ladyfern RF 0 0 0

femina (L.) Roth ssp. cyclosorumRupr.) C. Chr.

Blechnum spicant deerfern RF 0

(L.) Sm.

Bromus inermis smooth brome ER 0 0

Leyss.

Bromus L. brome NR 0 0 0Bromus pacificus	 Pacific brome NR 0 0

Shear

Bromus vulgaris Columbia brome NR 2 2 1 2

(Hook.) Shear

Campanula pale bellflower NR 0 0 0 1 0 0 0 0

scouleriHook. ex A. DC.

Carex deweyana Dewey sedge RF 0 0 0 0

Schwein.

Carex hendersonii Henderson’s sedge NR 0 0 0 0 0

L.H. Bailey

Carex rossii Boott Ross’ sedge NR 0 0 0 0 0 0 0 0 1 0 0 0 0

Cerastium field chickweed NR 0 0

arvense L.

Cerastium big chickweed ER 1 0 0 0 0 0 0 0 0 0 0 0 0

fontanumBaumg. ssp. vulgare (Hartm.) Greuter & Burdet
29

Relations of Native and Exotic Species 5 Years After Clearcutting With and Without Herbicide and Logging Debris Treatments

Table 7—Species with mean cover by site and treatment for the three study sites a b c (continued)

Study site, treatment, number of plots, and species richness

Fall River Matlock Molalla

LDD LDD LDR LDD LDP LDR LDD LDP LDR LDD LDP LDR LDD LDP LDRNVC VC VC VC NVC NVC NVC VC VC VC NVC VC NVC NVC NVC VC VC VC NVC VC

8 8 8 16 4 4 4 4 4 4 12 12 4 4 4 4 4 4 12 12

Scientific name Common name Group 43 29 25 36 62 51 57 45 42 44 73 58 63 61 61 38 38 37 84 51Chamerion fireweed NR 25 0 0 0 4 2 0 1 3 0 2 1 1 1 4 0 2 0

angustifolium (L.) Holub

Cirsium arvense Canada thistle ER 0 0 0 0 0 0 0 0 0 0

(L.) Scop.

Cirsium vulgare bull thistle ER 0 0 0 0 0

(Savi) Ten.

Claytonia sibirica Siberian RF 0 0 1 1 1 0 0 1 0

L. var. sibirica springbeauty

Clinopodium yerba buena RF 0 0 0 1 0

douglasii(Benth.) Kuntze

Collomia variableleaf NR 0 0 0 0 0 0 0 0 0

heterophylla collomiaDouglas ex Hook.

Cornus bunchberry RF 0 0 0 0

canadensis L. dogwood

Cornus nuttallii Pacific RF 1 0

Audubon ex dogwood 

Torr. & A. Gray

Corylus cornuta California RF 1 0 0 0 0 0

Marsh. var. hazelnutcalifornica(A. DC.) Sharp

Crepis capillaris smooth ER 3 5 12 2 2 2 7 2 1 0 3 2 1 0 2

(L.) Wallr. hawksbeard

Cytisus scoparius Scotch broom ER 0 1 0 0 0 0 1 0 0 0

(L.) Link

Dactylis. orchardgrass ER 1 0 0 0

glomerata L.

Danthonia spicata poverty NR 0 0 0 0 0 0 0

(L.) P. Beauv. oatgrass ex Roem. & Schult.
30

research paper pnw-rp-589Table 7—Species with mean cover by site and treatment for the three study sites a b c (continued)

Study site, treatment, number of plots, and species richness

Fall River Matlock Molalla

LDD LDD LDR LDD LDP LDR LDD LDP LDR LDD LDP LDR LDD LDP LDRNVC VC VC VC NVC NVC NVC VC VC VC NVC VC NVC NVC NVC VC VC VC NVC VC

8 8 8 16 4 4 4 4 4 4 12 12 4 4 4 4 4 4 12 12

Scientific name Common name Group 43 29 25 36 62 51 57 45 42 44 73 58 63 61 61 38 38 37 84 51Dicentra formosa Pacific RF 0 0 0 0

(Haw.) Walp. bleedingheart

Digitalis purple foxglove ER 2 0 0 0 0 0 2 3 2 0 2 0

purpurea L.

Dryopteris spreading RF 0 0 0

expansa woodfern(C. Presl) FraserJenkins & Jermy

Elymus glaucus blue wildrye NR 1 3 7 0 4 0 1 3 2 2

Buckley

Epilobium fringed NR 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0

ciliatum Raf. willowherb

Epilobium chaparral NR 1 0 0

minutum willowherbLindl. ex Lehm.

Equisetum field horsetail NR 0 0

arvense L.

Erechtites coastal burnweed ER 1

minima(Poir.) DC.

Festuca western fescue RF 0 0 1 1 2 1 1 0 1 1 2 5 1 1 2 1 3 1

occidentalis Hook.

Fragaria woodland NR 0 0 0 0 0 0 0 3 8 2 4

vesca L. strawberry

Frangula cascara buckthorn RF 0 0 0 0 0 0 1 0 1 0 0 6 10 10 2 2 7 9 3

purshiana(DC.) Cooper
31

Relations of Native and Exotic Species 5 Years After Clearcutting With and Without Herbicide and Logging Debris Treatments

Table 7—Species with mean cover by site and treatment for the three study sites a b c (continued)

Study site, treatment, number of plots, and species richness

Fall River Matlock Molalla

LDD LDD LDR LDD LDP LDR LDD LDP LDR LDD LDP LDR LDD LDP LDRNVC VC VC VC NVC NVC NVC VC VC VC NVC VC NVC NVC NVC VC VC VC NVC VC

8 8 8 16 4 4 4 4 4 4 12 12 4 4 4 4 4 4 12 12

Scientific name Common name Group 43 29 25 36 62 51 57 45 42 44 73 58 63 61 61 38 38 37 84 51Galium stickywilly NR 0 0 0 0 0 0 0 4 1 0 0 2

aparine L.

Galium triflorum	 fragrant bedstraw RF 0 0 0 0 0 0 0 0 2 2 3 0 0 0 2 0

Michx.

Gaultheria salal RF 7 4 2 9 6 3 4 6 12 11 12 11 4 3 11 6

shallon Pursh

Geranium Carolina NR 0 0

carolinianum L. geranium

Hieracium white hawkweed NR 2 0 0 0 0 0 0

albiflorum Hook.

Holcus lanatus L. common ER 27 0 0 0 3 8 2 0 1 0 4 0 31 13 38 11 14 15 27 13

velvetgrass

Holodiscus oceanspray RF 0 0 0 0 0 0 0 0 2 1

discolor (Pursh) Maxim.

Hypericum common ER 0 0 0 0 0 0 0 0 0

perforatum L. St. Johnswort

Hypochaeris hairy cat’s ear ER 34 1 3 2 28 26 28 4 10 12 27 9 2 1 0 1 5 1 1 2

radicata L.

Ilex aquifolium L. English holy EF 0 0 0 1 0 0

Iris tenax Douglas toughleaf iris NR 0 0 0 1 2 2 0 0 1 0

ex Lindl.

Juncus tenuis poverty rush NR 0 0

Willd.

Lapsana common ER 0 0 0 0

communis L. nipplewort

Leucanthemum oxeye daisy ER 25 23 35 1 4 3 28 3 17 25 17 5 3 2 20 3

vulgare Lam.

Ligusticum celleryleaf NR 0 0 0

apiifolium (Nutt. licorice-root ex Torr. & A.Gray) A. Gray

Lilium Columbia lily NR 0 0 0 0 0 0 0

columbianum Leichtlin
32

research paper pnw-rp-589 Table 7—Species with mean cover by site and treatment for the three study sites a b c (continued) Study site, treatment, number of plots, and species richness Fall River Matlock Molalla LDD LDD LDR LDD LDP LDR LDD LDP LDR LDD LDP LDR LDD LDP LDR

NVC VC VC VC NVC NVC NVC VC VC VC NVC VC NVC NVC NVC VC VC VC NVC VC

8 8 8 16 4 4 4 4 4 4 12 12 4 4 4 4 4 4 12 12

Scientific name Common name Group 43 29 25 36 62 51 57 45 42 44 73 58 63 61 61 38 38 37 84 51Linnaea twinflower RF 3 1 0 0 0 1 0

borealis L.

Lonicera ciliosa orange RF 1 1 0 1 1 1 1

(Pursh) Poir. honeysuckleex DC.

Lotus aboriginus rosy bird’s- NR 1 2 0 0 0 1 0 6 3 7 0 0 0 5 0

Jeps. foot trefoil

Lotus micranthus desert deervetch NR 0 0 0 1 0

Benth.

Luzula comosa Pacific woodrush NR 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

E. Mey.

Luzula parviflora	 smallflowered RF 0 0 0 0 0 0 0

(Ehrh.) Desv. woodrush

Mahonia nervosa Cascade barberry RF 1 1 1 0 1 1 1 1 3 0 0 1 2 1 1 1

(Pursh) Nutt.

Maianthemum feathery false RF 0 0

racemosum lily of the valley (L.) Link

Maianthemum starry false lily RF 0 0 0 0 0 0 0 0 0

stellatum (L.) of the valley Link

Malus fusca (Raf.) Oregon crab NR 0 0

C.K. Schneid. apple

Menziesia rusty RF 0

ferruginea Sm. menziesia

Mycelis muralis wall-lettuce NR 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

(L.) Dumort.

Oemleria Indian plum RF 0 0 0 0

cerasiformis(Torr. & A.Gray ex Hook. & Arn.) Landon
33

Relations of Native and Exotic Species 5 Years After Clearcutting With and Without Herbicide and Logging Debris Treatments

Table 7—Species with mean cover by site and treatment for the three study sites a b c (continued)

Study site, treatment, number of plots, and species richness

Fall River Matlock Molalla

LDD LDD LDR LDD LDP LDR LDD LDP LDR LDD LDP LDR LDD LDP LDRNVC VC VC VC NVC NVC NVC VC VC VC NVC VC NVC NVC NVC VC VC VC NVC VC

8 8 8 16 4 4 4 4 4 4 12 12 4 4 4 4 4 4 12 12

Scientific name Common name Group 43 29 25 36 62 51 57 45 42 44 73 58 63 61 61 38 38 37 84 51Oplopanax devilsclub RF 0 0

horridus (Sm.) Miq.

Osmorhiza sweet cicely RF 0 0 0 0 0 0 0 0

berteroi DC.

Oxalis oregana redwood-sorrel RF 14 1 0 1 0 1 0

Nutt.

Petasites frigidus arctic sweet NR 1 0

(L.) Fr. var. coltsfoot palmatus (Aiton) Cronquist

Phacelia hastata silverleaf NR 0 0 0

Douglas ex phaceliaLehm.

Poa compressa L. Canada NR 0 1 0 1 2 0 1 1

bluegrass

Poa pratensis L. Kentucky NR 0 0 0 0 0

bluegrass

Polystichum western RF 2 0 0 0 1 0 1 0 0 0 0 1 2 4 1 2 1 2 1

munitum swordfern (Kaulf.)C. Presl

Prosartes smithii largeflower RF 0 0 0 0 0 0 0 1 0 0 0

 (Hook.) Utech, fairybells 

Shinwari & Kawano

Prunella. common NR 1 1 2 0 0 2 0 0 0

vulgaris L. selfheal

Prunus sweet cherry EF 0 0

avium (L.) L.

Prunus bitter cherry NR 0 0 0 1 1 0 0 0 0 1 0 1 1 4 1 0 2 0

emarginata (Douglasex Hook.) D. Dietr.
34

research paper pnw-rp-589 Table 7—Species with mean cover by site and treatment for the three study sites a b c (continued) Study site, treatment, number of plots, and species richness

Fall River Matlock Molalla

LDD LDD LDR LDD LDP LDR LDD LDP LDR LDD LDP LDR LDD LDP LDRNVC VC VC VC NVC NVC NVC VC VC VC NVC VC NVC NVC NVC VC VC VC NVC VC

8 8 8 16 4 4 4 4 4 4 12 12 4 4 4 4 4 4 12 12

Scientific name Common name Group 43 29 25 36 62 51 57 45 42 44 73 58 63 61 61 38 38 37 84 51Pseudognaphalium Wright’s NR 0 0

canescens cudweed(DC.) W.A.

Weber ssp. 

thermale (E.E. Nelson)Kartesz

Pseudotsuga Douglas-fir NR 53 72 71 71 9 8 7 18 13 15 8 15 11 12 14 15 18 14 12 16

menziesii (Mirb.) Franco

Pteridium western NR 2 0 0 6 4 1 7 1 7 4 5 16 10 4 1 1 2 10 1

aquilinum brackenfern

(L.) Kuhn

Ranunculus. western NR 0 0 1 0

occidentalis buttercupNutt.

Ribes redflower NR 0 0 0 1 0

sanguineum currant Pursh

Rosa dwarf rose RF 0 0 0 0 0 0 0 0

gymnocarpa Nutt.

Rubus Himalayan ER 0 1 0

armeniacus blackberryFocke

Rubus cutleaf ER 1 0 0 0 0 1 0 1 0 0 0

laciniatus blackberry 

Willd.
35

Relations of Native and Exotic Species 5 Years After Clearcutting With and Without Herbicide and Logging Debris Treatments

Table 7—Species with mean cover by site and treatment for the three study sites a b c (continued)

Study site, treatment, number of plots, and species richness

Fall River Matlock Molalla

LDD LDD LDR LDD LDP LDR LDD LDP LDR LDD LDP LDR LDD LDP LDRNVC VC VC VC NVC NVC NVC VC VC VC NVC VC NVC NVC NVC VC VC VC NVC VC

8 8 8 16 4 4 4 4 4 4 12 12 4 4 4 4 4 4 12 12

Scientific name Common name Group 43 29 25 36 62 51 57 45 42 44 73 58 63 61 61 38 38 37 84 51Rubus whitebark NR 0 1 0 1 0 0 1 0

leucodermis raspberry Douglasex Torr. &

A. Gray

Rubus thimbleberry NR 0 0 0 0 1 1

parviflorusNutt.

Rubus salmonberry RF 1 0 0 0

spectabilisPursh

Rubus ursinus California NR 12 0 1 0 9 5 1 9 2 3 5 5 53 59 55 18 12 24 55 18

Cham. & blackberrySchltdl.

Rumex common ER 0 0 1 0 0 0 0 0

acetosella L. sheep sorrel

Salix scouleriana Scouler’s NR 1

Barratt willowex Hook.

Sambucus red elderberry RF 4 0 0 0 1 0 0 0 0 0 0 1 1

racemosa L.

Senecio stinking willie ER 0 0 0 0 0 0

jacobaea L.

Senecio woodland ER 0 0 0 0 1 4 5 0 3 0 0 0 0

sylvaticus L. ragwort

Stachys Mexican NR 1

mexicana Benth. hedgenettle

Stellaria longstalk NR 0 0 0 0

longipes starwortGoldie
36

research paper pnw-rp-589 Table 7—Species with mean cover by site and treatment for the three study sites a b c (continued) Study site, treatment, number of plots, and species richness Fall River Matlock Molalla

LDD LDD LDR LDD LDP LDR LDD LDP LDR LDD LDP LDR LDD LDP LDRNVC VC VC VC NVC NVC NVC VC VC VC NVC VC NVC NVC NVC VC VC VC NVC VC

8 8 8 16 4 4 4 4 4 4 12 12 4 4 4 4 4 4 12 12

Scientific name Common name Group 43 29 25 36 62 51 57 45 42 44 73 58 63 61 61 38 38 37 84 51Symphoricarpos common RF 5 2

albus (L.) snowberry S.F. Blake

Symphoricarpos trailing RF 3 4 6 1 2 3 4 2

hesperius snowberryG.N. Jones

Thermopsis mountain NR 0 0 0 0

montana Nutt. goldenbanner

Thuja plicata western redcedar RF 0 0

Donn ex D. Don

Trientalis starflower RF 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

borealis Raf.

Trifolium repens L. white clover ER

Trillium ovatum Pacific trillium RF 0 0 0 0 0 0 0 0 0 0

Pursh

Trisetum tall trisetum NR 0 0

canescensBuckley

Tsuga western hemlock RF 0 0 0 0 0 0 0 0 0 0 0 0

heterophylla(Raf.) Sarg.

unknown herb unknown herb ER 0 0

Vaccinium. oval-leaf RF

ovalifolium Sm. blueberry

Vaccinium. red huckleberry RF 0 0 0 0 0 0 0 0 0 0 0 0 1 1 2 0 0 0 1 0

parvifolium Sm.

Vancouveria white insideout RF 1 0 0 0

hexandra (Hook.) flowerC. Morren & Decne.
37

Relations of Native and Exotic Species 5 Years After Clearcutting With and Without Herbicide and Logging Debris Treatments

Table 7—Species with mean cover by site and treatment for the three study sites a b c (continued)

Study site, treatment, number of plots, and species richness

Fall River Matlock Molalla

LDD LDD LDR LDD LDP LDR LDD LDP LDR LDD LDP LDR LDD LDP LDRNVC VC VC VC NVC NVC NVC VC VC VC NVC VC NVC NVC NVC VC VC VC NVC VC

8 8 8 16 4 4 4 4 4 4 12 12 4 4 4 4 4 4 12 12

Scientific name Common name Group 43 29 25 36 62 51 57 45 42 44 73 58 63 61 61 38 38 37 84 51Veronica. germander ER 0 1 1 1 1 1 1 1 1

chamaedrys L speedwell

Vicia americana American vetch NR 0 1 0 0 0 0

Muhl. ex Willd.

Vicia nigricans giant vetch NR 1 0 0 0

Hook. & Arn.ssp. gigantea(Hook.) Lassetter & C.R. Gunn.

Viola evergreen violet RF 3 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

sempervirensGreene

aValues shown as “0” are positive values smaller than 1 percent.bLDD = logging debris dispersed, LDR = logging debris removed, LDP = logging debris piled, VC = vegetation control, NVC = no vegetation control.cColumns labelled simply “VC” or “NVC” incorporate all debris treatments either receiving or not receiving vegetation control respectively. For Fall River only; LDD = NVC. 
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