1
Chapter
2
Site Characterization
The purpose of this section is to describe approaches and resources for identifying current and
historical conditions and associated ecological processes. Since a basic goal of restoration is to bring a
site back to a more functional state or trajectory, an original or presumed functional historical condition
should be defined to the maximum degree possible. Accurate information regarding current and
historical conditions and impacts is critical to setting realistic goals, selecting plant species, and
identifying management approaches that will promote or sustain restored conditions. As such, it is
important to also characterize the conditions that allowed for the historical functional vegetation to
develop and sustain itself (such as climate, soils, disturbance regimes, etc). This section provides
instructions on how and where to gather site attributes that help to define the site potential. This
information should be assembled into a Restoration Project Documentation File (See Appendix X of this
document for an example) to keep track of the many site characteristics and its relation to site potential,
which can affect the success of a restoration project
SITE HISTORY
To ensure the highest rate of success possible for a restoration project, it is important to determine the
project site’s level of variance from desirable conditions as well as the processes by which the site
came to its present condition. This will help characterize the level of restoration needed, identify
possible challenges and limitations to successful restoration, and allow the procession of the most
informed planning and implementation for the project.
In order to get a full picture of the reasons behind the current condition of the restoration site, a full
understanding of both natural and anthropogenic site history is essential.
Natural History
Historic vegetation structure and abundance is a function of historic site attributes that include climate,
soils, herbivory, disturbance regimes and other factors. Characteristics of these natural systems
fluctuate in space and time as a result of variations of these historic conditions, and thus oscillate
through a range of characteristics. In order to re-construct a potential range of natural variability, it is
necessary to consider the site’s attributes, the degree to which they may have changed over time, how
these changes have occurred, and the major influences behind the changes. This information will
generate a greater understanding of the current condition of the site as well as what the ecological
potential of the site may be. From the difference in attributes between current and potential condition
prioritization of restoration sites will be more effective as a clearer understanding of the time, effort and
money each restoration site may demand.
SITE POTENTIAL
Each subject heading below plays into site potential and stability (thus ecosystem resistance and
resilience) and should be evaluated prior to the restoration project to understand the influence of each
element in the overall ecosystem.
CLIMATE
Characteristics such as elevation, timing and amount of precipitation, and temperatures affect soil
moisture and productivity, and thus vegetation composition. Important aspects of climate include mean
annual precipitation and air temperature as well as the annual distribution of these characteristics. This
information will help when planning weather dependent activities (such as soil ripping, seeding, etc), as
well as plant community characteristics such as periods of highest productivity and likely seed
production times.
Sources of Information for climate
Local climate summaries can be downloaded from the Western Region Climate Center to determine
local rainfall and temperature patterns.
Record annual precipitation and its historic timing in the Restoration Project Documentation Form.
PHYSICAL FEATURES
The combination of simple physical characteristics such as soil type, slope, elevation and aspect have
strong effects on how a site can respond to restoration efforts. Considerations of soil characteristics
such as soil texture and depth should be noted for evaluations of moisture retention and erosion
potential. In addition, it is important to pay close attention to site aspect as effective precipitation and
thus soil moisture can be noticeably different on south and north facing slopes. Furthermore, the
steepness of a site can have strong effects on erosion potential, and can be exacerbated by soil
textures that are particularly susceptible to erosion. As a result, a different suite of species will be better
suited for each aspect, slope and soil type and multiple iterative combinations of each. Soils are
discussed further in the Soils and Vegetation section below.
ECOLOGICAL PROCESSES
Ecological processes such as fire, floods, wind storms, landsides, herbivory and insect outbreaks often
serve to develop or maintain vegetation communities. The disruption of those processes, when it leads
to a significant departure from historic conditions, is identified as a risk. In cases where disturbances
like fire or flooding were important development and/or maintenance factors, it is useful to determine
what the typical return intervals were for such events. In cases where the reestablishment of historic
processes is not likely, full restoration may not be possible.
For information on ecological processes, some Ecological Site Descriptions (available from the NRCS)
include brief descriptions of ecological processes that historically maintained plant communities. If the
proper ESD is not available, other resources are described below.
Ecological Site Descriptions (ESDs)/ Major Land Resource Areas (MLRAs)
Ecological Site Descriptions (ESDs) have been pulled together by the NRCS for many vegetation types
within Major Land Resource Areas (MLRAs). Ecological site maps can be downloaded from the Web
Soil Survey . Once the Ecological Site has been identified, Ecological Site Descriptions (ESDs) can be
downloaded. The following steps can be used to retrieve Ecological Site Descriptions:
Access the NRCS' Web Soil Survey, than start the Web Soil Survey (WSS), and follow the steps
below:
a. Define an Area of Interest using the interactive map
b. Select the Soil Data Explorer tab. There are several sub-tabs within this page with
information about site soils. A site-specific soil report can be printed or downloaded.
c. Select the Soils Report tab. The report will include Ecological Site names and numbers.
d. Select the Ecological Site Assessment tab
e. View, print or download the Ecological Site Map and Ecological Sites by Map Unit
Component table to see how Ecological Sites are thought to have covered the land.
f. Select each of the Ecological Site tabs on the lower left portion of the page
g. Print or download reports directly from the site if available
h. If the reports are not available go to NRCS Major Land Resource Area Explorer web site
or go to the state NRCS page
i. Select the state and county of interest OR click the location or select the area of interest on
the Locator Map
j. Click which component(s) of the MLRA description desired, then create report
k. Open the Ecological Site Descriptions folder (bottom one)
l. Select the Major Land Resource Area (MLRA) with numbers corresponding to the first three
numbers in the Ecological Site. (For example MRLA B007 will contain the Ecological Site
Description for R007XY401WA)
m. Download applicable Ecological Site Descriptions
ESDs contain detailed information of many vegetation types such as a list and relative abundance of
plant species grouped by functional type. These were created by averaging the species found in similar
relict sites across the region (Major Land Resource Area per NRCS). Therefore, local forb species lists
may not be accurate at a site-specific scale, or forbs are identified only to genus. It should be noted that
percent composition listed in ESDs is based on forage production rather than more common ecological
metrics like canopy coverage, as ESDs are primarily used as a planning tool for grazing management.
ESDs also provide critical information on historic disturbance regimes, and the degree of disturbance
necessary to significantly change the vegetation community.
State and Transition Concept
Much ecological research and theory have been undertaken to fully understand where (or if) a project
site lies within its historic range of characteristics. The ‘State and Transition’ (Laycock 1991) concept is
used to demonstrate an ecosystem’s tendency and ability to
move to and from different conditional states (e.g. states I, II,
and III in diagram). This tendency is based in the level of
ecosystem stability, which is in turn defined by the resistance
and resilience of plant communities to disturbance. Features of
the disturbance include the duration, extent and consistency of
perturbation that causes the vegetation to shift dominance
State and Transition
and/or composition to give rise to a different stable state. Once
Ecological thresholds are denoted A
such a threshold is crossed to a new stable state, the ecosystem
and B that lead the ecosystem to
typically does not return to its previous state without active
different stable states I, II, and III.
management. It is important to evaluate the threshold(s) the site
Laycock, W.A 1991. Stable states and thresholds of
range condition on North American rangelands: a
in question has crossed in order to evaluate the time, money and
viewpoint. Journal of Range Management 44:427433.
effort restoration may take.
Below is a schematic from USDA-NRCS to show states and
transitions of an upload loam site with a pinyon-juniper woodland. Schematics like this generally also
have additional information that outlines other site features that affect the tendency and ability of a site
to move from one stable state to another (e.g. soils, elevation, climate, etc).
Figure X. State and Transition Model for Pinyon- Utah Juniper Community
SOILS AND VEGETATION
Climate, slope and soil attributes combine to form expected vegetation community patterns across the
landscape. As vegetation is the main component of restoration projects, it is critical that the potential or
reference vegetation be understood to the greatest degree possible. Information on historic and natural
disturbances such as fire or floods should be investigated to understand their role in the stability of the
vegetation type.
Sources of Information for soils and vegetation
THE FIELD
There is truly nothing equivalent to taking a walk in the proposed project area to get a feel for the
condition of the site. Take notes on plant composition (percent cover (and species) of dominant shrubs,
perennial grasses, perennial forbs, annual grasses, annual forbs, and bare ground), notes on types
and intensity of current land use, soil characteristics, plant vigor, and invasive weeds present. Record
an educated guess of how the site may deviate from its highest potential.
It is best to gather quantitative monitoring data on the site prior to any restoration work to be able to
compare the current vegetation community with the restored community. Details on establishing a
suitable monitoring program for a project are given in Chapter X.
OTHER RESOURCES
If the potential desired plant community is unknown or more information is needed to complete the site
characterization, several other resources are available to describe the potential vegetation composition
for a restoration site. Many of these sources include soil descriptions and the potential influences of the
soil as it pertains to plant community annual production. However, some sites include plant community
description, plant community composition and structure, ground cover and ecological dynamics of the
site (such as transitional pathways between plant community condition). Resources with this
information are detailed below.
Nationally Accepted Vegetation Community Descriptions
If an Ecological Site Description is not available for a particular site, there are other sources of
information regarding potential vegetation community composition and structure. For instance, the
Southwest ReGAP project was completed as an effort to develop a seamless land cover map for the
southwest United States (Prior-Magee et al. 2007). However, in addition to mapping land cover, the
project involved the collection of a variety of other pertinent bio-physical spatial data. Thus, the SW
ReGAP data was merged with other regional land cover products (GAP and LANDFIRE) to create a
national land cover currently being served through the GAP analysis Programs Land Cover Viewer
(http://gapanalysis.usgs.gov/gaplandcover/viewer/).
Moreover, since the original map legends used by GAP and LANDFIRE Projects were based on the
Ecological Systems Classification (Comer et al 2003), it was prudent to make those products consistent
with the national Vegetation Classification System (FGDC 2008). Therefore, a cross-walk between the
Ecological Systems Classification and the Macrogroup level of the NVC Standard was completed. This
allows users to view the maps either at the ecological system level of detail, or at the Macrogroup or
coarser level of the NVC.
Further descriptions of each of these communities can be found at:
SW ReGAP: Report on legend descriptions (http://earth.gis.usu.edu/swregap/legend_desc.html)
NatureServe Explorer: Ecological Community Descriptions
(http://www.natureserve.org/explorer/servlet/NatureServe?post_processes=PostReset&loadTemplate=
nameSearchEcol.wmt&Type=Reset)
Reference sites
If more site specific information is desired than what can be found in the above resources, it is possible
to characterize a reference site that has been chosen to be representative of the ecological potential of
a restoration site. While pristine reference sites may no longer exist, close approximations of the
potential plant community can be found in a number of places. Areas less likely to be affected by
anthropic disturbance can be found within livestock exclosures, areas naturally isolated from livestock
access such as steep hillsides, protected areas, and isolated areas without livestock water access
(Shinneman et al. 2008). It is important to recognize, however, that relatively undisturbed-looking sites
may have been substantially altered by past grazing, modified fire regimes, hydrological alterations or
other processes. At a minimum, however, such sites indicate what native plants successfully compete
under current conditions.
The following information should be collected from reference sites:
es
Percent composition of all species should add up to 100%.
For some who have not previously performed vegetation monitoring, estimating composition may seem
like a daunting task. It may be helpful to bring along a vegetation monitoring quadrat, and practice
estimating composition within a smaller, defined area, before extrapolating to the site level.
Anthropogenic history
In addition to natural historical perturbations causing shifts in vegetation cover, lands can be modified
as a result of a variety of land management practices ranging from historic fire suppression, modified
fire regimes, historic grazing, unmanaged recreation, and/or energy development. These land use
practices can cause a variety of changes on the landscape, such as reductions of native vegetation,
species diversity, vegetation structural diversity, biological soils crust, and resistance to noxious weed
invasions.
These characteristics can lead to accelerated erosion, reduced native seed bank, and a potentially nondesirable suite of species capable of invading and persisting associated with an associated reduction of
desirable species. Many combinations of these impacts can lead to less functional ecosystems, and an
associated increase in the amount of effort to return them to a more functional state.
 Agency files
Both BLM and USFS typically keep files on activities they have either conducted or permitted on the
lands they manage. Records of permitted activities, such as livestock grazing, mineral development,
and some recreation uses are generally maintained in local offices and provide invaluable background
information, and often site-specific characterization of historical activities and impacts on those
landscapes. These offices often have historical images (photographs) as well as data that document
conditions at one or more times in the past. Historically, the U.S. Forest Service conducted detailed
rangeland inventories on allotments they managed. Other inventories have been conducted on public
lands and one should investigate what files may be on site or that can be accessed through archived
materials. Some offices have old SCS (now NRCS) range site maps and/or soils maps that predate
ecological site or terrestrial ecological unit inventories.
 Literature and historical records review
There are numerous publications and databases that describe vegetation or wildlife habitats along with
the ecological processes that maintain them. Local historical records include survey records, journals
and old photographs that can provide valuable insights into the historical conditions. Universities often
house historic records as well. Caution is advised when using journals and other historical records as
authors may not have been trained in recording quantitative objective observations. Other locations that
may have pertinent historic records include wildlife agency records or others in the community with
historical knowledge of the local area.
 Expert Opinion
Another potential source for local historic ecological knowledge for is expert opinion, generally from
staff with local range management, wildlife, fish, soils, ecology and botany backgrounds and
experience. Agency land managers, private lands biologists, and other Lands Division employees often
have considerable botanical knowledge. In addition, other agencies and entities (private vegetation
consultants, Native Plant Societies) could be consulted on native species composition in challenging
situations.
Climate Change
Whether considered anthropogenic or natural, climate change is occurring at an ever-increasing rate
and must be considered when addressing site potential and natural range of variability. The Colorado
Plateau is particularly vulnerable to climate change (Schwinning et al 2008)1 and thus research into the
latest science on predicted changing precipitation patterns and increases in temperature should be
completed as site potential is considered.
With the consistent increase in human use of the Colorado Plateau, there has been a corresponding
increase of invasive species, alteration of fire regimes and nutrient (C and N) cycles, and significant
changes in soil structure and function. All of these relatively recent changes on the Colorado Plateau
have altered ecosystem function and should be carefully considered when attempting to rehabilitate the
landscape. The high aridity and extreme temperatures of the Plateau combine to form a relatively
1
Schwinning, S., J. Belnap, D. R. Bowling, and J. R. Ehleringer. 2008. Sensitivity of the Colorado Plateau to change: climate, ecosystems, and society.
Ecology and Society XX(YY): ZZ. [online] URL: http://www.ecologyandsociety.org/volXX/issYY/artZZ/
resistant ecosystem – one that has evolved over millennia to adapt to periodic severe droughts as well
as higher than normal precipitation years. It is postulated that multi-decadal patterns of drought and
high moisture periods may have been associated with changes in specific vegetation components and
overall plant cover, but did not fundamentally reorganize the vegetation community. Thus, the
ecosystem is generally resistant to external pressures. In that same line of theory, however, this
translates into an ecosystem that is correspondingly not resilient - or has difficulty in returning to its
previous state after a perturbation. The high resistance and low resilience of the Colorado Plateau
poses a particularly difficult challenge for restoration projects, especially in light of climate change
projections.
PRECIPITATION AND TEMPERATURE
As a sobering note, there is currently a 19 model consensus that forecasts megadrought events by the
second half of the 21st century for the western United States (Schwining et al 2008). Moreover,
projected decreases in winter precipitation is likely to have a negative effect on plant productivity,
particularly perennials. Winter precipitation determines annual primary productivity in perennials
(Caldwell 1985). Contrarily, pulses of summer precipitation is available mostly to plant species with an
active shallow root system such as grasses and late summer annuals (Schwinning et al 2003). Plant
species with a combined deep tap root and shallow root system are particularly well suited to take
advantage of differing precipitation patterns. It should be noted that some woody shrubs with deep
roots in the Colorado Plateau have an estimated life span of well over 100 years as shown by some
repeat photography (Bowers et al 1995).
SOILS
Soils on the Colorado Plateau are often dominated by biological soil crusts and can sometimes
represent up to 70% of the living cover (Belnap 1995). These crusts can heavily influence ecosystem
function as they are an important source of carbon for subsurface soil organisms because soil carbon is
limited in desert soils (Belnap 2003a). Soil crusts are critical in nutrient cycling and uptake as well. For
instance, nitrogen is fixed only when the cyanobacteria are wetted and have sufficient carbon
compounds (Paul and Clark 1996) present. Up to 70% of the fixed nitrogen is taken up by surrounding
organisms, including plants, fungi, actinomycetes and bacteria and can be reabsorbed by the
cyanobacteria or lichen (reviewed in Belnap 2003b). The crusts also help maintain nutrients in plantavailable forms, which is especially important in the typically high pH desert soils.
Furthermore, biological soil crusts contribute to ecosystem health due to their influence on desirable
soil physical properties such as increasing soil aeration and porosity and reducing wind and water
erosion rates (Belnap and Gardner 1993). They also provide a protective cover to the soil surface to
slow evaporation to increase associated soil moisture retention times (George et al 2003).
It has been shown that impacted soils have a 40-70% decrease in soil carbon and nitrogen when
compared with less impacted soils (Neff et al 2005, Fernandez et al 2006). The consistent use of the
Colorado Plateau in the last century has decreased its productivity as well as decreased its ability to
rebuild from these depletions. After drought years or other uses, rapid returns to what has been
accepted as ‘normal’ agricultural activities has not allowed for proper ecosystem recovery.
Given the climate change projections as well as the resistance and resilience of the ecosystems of the
Colorado Plateau, it is important to carefully consider potential changes to vegetation patterns on the
landscape and thus species choices for restoration projects.
Potential Site Challenges
The presence of one or more challenges such as weed infestation or high soil alkalinity will temper
expectations and restoration goals; rarely, they may even preclude restoration completely, or
suggest shifting limited funding to a more promising site.
Site histories, along with an analysis of current site conditions, can typically be used to plan for,
mitigate, or avoid potential pitfalls. Highlighting some common site challenges encountered by area
managers. The narrative of each section will include common causes, symptoms, and potential
solutions.
Specific site challenges and discussion of common causes, symptoms and potential solutions may help
to overcome these issues and are discussed in Chapter 4 in more detail.