United States Environmental Monitoring

Environmental Protection Systems Laboratory

Agency Las Vegas, NV 89193-3478

E AP Project Summary

Research and Development EPA/620/SR-94/015 July 1994

Environmental Monitoring and

Assessment Program—

Arid Ecosystems 1992 Pilot

Report

study results, and discusses planned

future studies.

Introduction

In 1992 the Arid Ecosystems Resource

Group conducted a pilot study in the southeastern Utah portion of the Colorado Plateau. The purpose of this EMAP group is

to measure and report on the extent, condition, and trends of several resource

classes in the biogeographical provinces

of nearctic and neotropical North America

within the United States.

The study focused on four objectives:

• Assessment of sampling variance—

Evaluation of the EMAP-Forests Resource Group sampling plot design

relative to the selected indicators.

• Indicator sensitivity—Evaluation of the

sensitivity of the indicator measures

to independent evaluations of site condition as designated by various land

management.

• Sampling frame and extent—Evaluation of the utility of using classified

TM imagery and other data acquired

from the U.S. Fish and Wildlife Service (FWS) Gap Analysis Program

(GAP) to select frame materials for

the pilot study and future studies and

to provide data for extent estimation

of arid ecosystems.

• Quality assurance, information management, and logistics—Evaluation of

the quality assurance, information

management, data analysis, logistiThe U.S. Environmental Protection

Agency (USEPA) and its collaborators

have initiated a long-term, policy-relevant research project, the Environmental Monitoring and Assessment Program (EMAP), focused on evaluating

ecological conditions on regional and

national scales. In 1992 the EMAP Arid

Ecosystems Resource Group (one of a

number of EMAP resource groups) conducted a pilot study in the southeastern Utah portion of the Colorado Plateau. This report describes this first

field activity for arid ecosystems. The

1992 pilot study was developed to

evaluate sampling plot design and the

sensitivity of selected indicators. The

study focused on four objectives related to plot design, indicator development, sampling frame material, quality

assurance, information management,

and logistics. The primary categories

of indicators selected for evaluation in

the 1992 pilot study were vegetation

composition, structure, and abundance;

spectral reflectance; soil properties;

and soil erosion. Data were collected

on 29 sites within two major resource

classes—desertscrub and conifer

woodland. Indicator measurement

methods and the study results for each

of the four objectives are explained in

this report. Each of these sections includes recommendations based on the

1992 study. The final section summarizes the major conclusions and recommendations drawn from the 1992 pilot study, draws implications from the

Susan E. Franson
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cal, and reporting requirements and

constraints based on the pilot study

area.

1992 Pilot Study Area

The Colorado Plateau is an arid and

semi-arid tableland in the southwestern

U.S. The entire 130,000-square mile region of the Colorado Plateau is much more

extensive than needed to fulfill the requirements of the intended indicator evaluation pilot; therefore, only a portion of the

plateau was chosen for data collection.

This region is predominantly managed as

federal lands, (i.e., Bureau of Land Management, National Park Service, and Forest Service, and part of Navajo Nation,

state, and private lands). The diversity of

ownership and jurisdiction promoted interagency participation in the pilot implementation. The area is bisected by the Colorado River and includes many canyon

lands that allowed for evaluation of logistical requirements in some of the most difficult terrain that EMAP-Arid activities will

likely face. The area includes two resource

classes which are prevalent within the

Colorado Plateau (desertscrub and conifer woodlands) that were chosen for indicator evaluation.

Indicator Measurement

Methods

Vegetation Composition,

Structure, and Abundance

Vegetation composition and structure

have been evaluated for decades in arid

ecosystems and are well established as

important indicators of ecosystem condition. The difficult decision for the 1992

pilot was to determine what type of measurement technique best fit within the

EMAP approach. Numerous vegetative

sampling techniques were evaluated including plot sampling, belt transects, and

line intercept techniques. Most of the vegetative sampling techniques have been

developed for measuring forage supplies

for big game and other herbivores. The

literature was reviewed and the EMAPArid researchers decided to use a modified Daubenmire (1968) approach because

it provides the ability not only to measure

vegetation attributes about species richness and diversity, but also to keep open

options for relating this information to wildlife habitat in future pilots.

Spectral Reflectance

A remote sensing approach to collect

information about a site offers a number

of advantages for indicator development

such as producing spatially explicit estimates of ecological condition over entire

regions in a cost-effective manner. A number of researchers have developed strong

relationships between measurements and

indices derived from remote sensing and

ecosystem variables. The Normalized Difference Vegetation Index (NDVI) is such

an index and researchers have shown

very high relationships between NDVI developed from satellite and ground measurements and leaf area index. The leaf

area index correlates strongly with a number of other extremely important ecosystem variables such as primary productivity

and biomass. The NDVI was selected as

a candidate indicator for the 1992 pilot

study because it has both a demonstrated

relationship to vegetation parameters and

a lack of sensitivity to atmospheric conditions; in addition, it has been used to

monitor phenological (vegetation) variables

on regional, continental, and global scales.

The Landsat TM satellite data were used

to determine NDVI because the waveband

location for deriving information concerning vegetation parameters is superior to

multispectral scanner (MSS) data and the

pixel size of 30 by 30 m correlates more

easily with field-based measurements than

does the 1.1- by 1.1-km pixels of the Advanced Very High Resolution Radiometer.

Soil Properties and Soil Erosion

Soil properties were selected because

they were determined to be critical in evaluating ecosystem health and interpreting

vegetative information. The literature provided the rationale for looking at (physical, chemical, and biological crusts) soil

parameters and focusing on their implications to management options, plant growth

and the water balance. Soil erosion was

also included in the 1992 pilot because

most of the data required for estimating

erosion were collected in the soil profile.

These data could then be used as inputs

to the Revised Universal Soil Loss Equation (RUSLE) erosion models for evaluating the relationship between soil erosion

and site condition. Several researchers

have identified a positive correlation between increased runoff and erosion with a

decrease in the seral stage of arid ecosystems and have evaluated the sensitivity of the models.

Assessment of Sampling

Variance

The process of collecting samples can

produce extraneous variability in the indicator measurements in addition to the variability associated with the resource condition. The EMAP survey design protocols

include annual visits to sampling sites

throughout the region and will require multiple sampling crews to procure the measurements within adequate time frames.

The utility of indicators of resource condition to some extent depends upon the

degree to which these extraneous sources

of variation inhibit the ability of the indicator measurement to describe resource

characteristics. Knowledge of these variance values is necessary not only to construct confidence intervals for the measured indicators but also to evaluate the

viability of the measurements as indicators. The magnitude and influence of each

of these components of variability must

be evaluated by the EMAP-Arid program

as it progresses through the indicator development process. Variance components

that continue to require a high level of

investigation include those associated with

the year, crew, measurement, and plot

design.

The evaluation of indicator measurement variances associated with the sampling units that potentially could be used

in a common plot design for monitoring

EMAP-Arid extensive resources was a primary objective of the 1992 pilot study.

Year and crew components of variance

were not considered for investigation in

the 1992 pilot study and will be determined from larger and long-term studies

in the future. Measurement variances are

discussed in Section 7 of the report.

Measurements considered most influential for the spectral, vegetation, and soils

indicator categories were selected as candidates for evaluation of their variance

properties. The variable selected for the

spectral measure was the NDVI; the variables selected for vegetation measurements were total vascular plant cover,

shrub cover, and tree cover; and the soil

variables analyzed were the clay, silt, sand,

and very fine sand percentages; organic

matter; the soil erodibility factor (K); and

the length-slope (LS) steepness factor.

The variables for this analysis also were

selected to represent measurements acquired from different components of the

plot design. The selected variables are

each representative of uniquely different

types of statistical variables which affect

how the indicator variables are used in

the analyses. Each category of indicator

measurements is discussed separately.

It is recommended that a study be conducted to determine an optimal integrated

response design for EMAP-Arid monitoring. Such a study should be conducted

using a uniform sampling grid that allows

a wide range of arrangements of the basic measurement units from linear

transects of varying lengths to varying

shapes and sizes of rectangular arrays of

the units. The relationships of the arrange-
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ments to their respective variances can

be used to craft efficient sampling designs

at a site. Also, this type of study would

result in data to estimate the level of spatial correlation that can be expected from

the measurements. Knowledge of the spatial correlation would indicate the need for

any spatial separation among the measurement units to increase the amount of

independent information acquired from the

units.

Indicator Sensitivity

One of the primary aims of the indicator

evaluation process is to evaluate the degree to which individual indicators represent a range of ecological condition. This

is often referred to as evaluation of indicator sensitivity. Two general types of indicator sensitivity are commonly evaluated:

the grouping or clustering of indicator values across an environmental gradient and

the degree to which an indicator varies

within a known range of conditions.

The first type of sensitivity analysis normally involves recognition of patterns or

clusters (pattern recognition or detection)

of values of indicators across an environmental gradient. The study is designed to

determine if indicator values will separate

or cluster into one or more groups and

whether the groups correspond to the environmental gradient. This design allows

an evaluation of indicator sensitivity to a

range of environmental conditions, even if

standards (desired conditions) for evaluating condition are not known.

The second type of sensitivity analysis

generally involves selecting sample sites

based on a range of “known” or “desired”

conditions and evaluating the degree to

which indicators vary across those conditions. This type of sensitivity analysis requires an a priori agreement on what constitutes condition (nominal, marginal,

subnominal) and knowledge of the geographic range of the condition (so that

representative sites can be selected).

Initially, the EMAP-Arid researchers had

intended to evaluate indicator sensitivity

relative to known or desired conditions as

determined by existing information available from federal land management agencies. The EMAP-Arid team decided to conduct this initial pilot study in the Colorado

Plateau due to the wealth of information

available from this area. Discussions were

held with a number of management agencies and these discussions led to the understanding that EMAP-Arid could obtain

congruous determinations of site condition for the Colorado Plateau area. However, the EMAP team discovered significant differences in agency descriptions of

the condition of a site. This difference was

substantial enough in several cases that

no consistent rating of a site could be

established. Recently, similar concerns

have also been reported by the NRC in

their review of rangeland health. As a

result of these factors, the 1992 pilot study

was not able to address the objective to

evaluate indicator sensitivity against sites

of “known” condition. Results presented in

this report are only indicative of patterns

in the Colorado Plateau and the actual

range condition, delineated in these patterns, is not known. However, it is reasonable to assume the sites were different

and represented at least a partial range in

condition.

Frame Materials

The EMAP-Arid group definitions of vegetation resource classes, as well as biogeographic provinces have been established. A method, or set of methods, to

estimate extent of arid resources needs to

be developed, with the idea that an area

sampling technique will provide a better

estimate of extent.

An evaluation of the FWS GAP information was conducted to determine how

well the satellite-derived data base identified plant communities found at the pilot

study sample points. It is important to

note that the GAP data used were considered “preliminary”, and have been improved since the initial comparison was

made.

The evaluation of the GAP data was

inconclusive partly because, for a comprehensive evaluation, more sites are

needed, and, some discrepancies appeared to exist. If the EMAP-Arid group

wants to consider using GAP data in the

future to select frame materials and to

provide data for extent estimation of arid

ecosystems, then a further assessment of

the accuracy of the GAP data must be

performed. This assessment should be

done on the second generation (or the

most recent version) of the GAP data and

must include a sufficient sample number

for each land cover type.

Quality Assurance, Information

Management, and Logistics

Quality assurance (QA), information

management, and logistics are integral

components of EMAP field activities. In a

program of the magnitude of EMAP, overlooking or ignoring even apparently minor

issues or details may eventually jeopardize the success of the program. Planning

and documenting QA, information management, and logistics activities are essential. The report documents these activities for the 1992 pilot study.

Conclusions and

Recommendations

The 1992 pilot study was the first EMAPArid field study, and addressing the objectives developed for this study is essential

to full implementation of the program.

Questions related to these objectives will

continue to be important elements in planning for future pilot studies. During the

1992 pilot study, the EMAP-Arid team was

successful in partially addressing these

objectives but, more importantly, the planning and implementation of this study uncovered issues that were not fully understood or perceived in initial design efforts.

For example, the original assumptions that

the EMAP-Forest design would be applicable to EMAP-Arid indicator measurements or that independent site condition

assessments from land management

agencies could readily be used to evaluate sensitivity of indicators were inaccurate. Only as the 1992 field work progressed were these difficulties pinpointed.

The USEPA, through its Office of Research and Development (ORD), funded

and collaborated in the research described

here. It has been peer-reviewed by the

Agency and approved as an EPA publication. Mention of trade names or commercial products does not constitute endorsement or recommendation for use.
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Susan E. Franson (also the EPA Project Officer, see below) is with the Environmental

Monitoring Systems Laboratory, Las Vegas, NV. 89193-3478.

The complete report, entitled “Environmental Monitoring and Assessment Program—

Arid Ecosystems 1992 Pilot Report,” (Order No. PB94-176898/AS; Cost: $27.00;

subject to change) will be available only from:

National Technical Information Service

5285 Port Royal Road

Springfield, VA 22161

Telephone: 703-487-4650

The EPA Project Officer can be contacted at:

Environmental Monitoring Systems Laboratory

U.S. Environmental Protection Agency

Las Vegas, NV 89193-3478

• •

United States

Environmental Protection Agency

Center for Environmental Research Information

Cincinnati, OH 45268

EPA/620/SR-94/015

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