Sagebrush Demography on the Idaho National Laboratory
Investigators and Affiliations
Amy D. Forman, Plant Ecologist, Environmental Surveillance,
Education and Research Program, S.M. Stoller Corporation, Idaho
Falls, ID
Roger D. Blew, Ecologist, Environmental Surveillance, Education and
Research Program, S.M. Stoller Corporation, Idaho Falls, ID
Funding Sources
U.S. Department of Energy Idaho Operations Office
Background
As more and more sagebrush steppe habitat in good ecological
condition is lost, it becomes increasingly important to understand
the ecosystem dynamics of that vegetation type, especially the
biology of the dominant species, sagebrush. An understanding of the
population dynamics, or demography, of sagebrush should allow land
managers to make better decisions about remaining healthy sagebrush
steppe vegetation. An understanding of what the historical
population dynamics of a sagebrush stand may have been like will
also allow land managers to begin to understand how to make
improvements in sagebrush steppe communities that are in somewhat
degraded conditions.
At the INL, the DOE is responsible for the stewardship of 2300 km2
of relatively pristine sagebrush steppe habitat. This land comprises
one of the largest remnant of this type of ecosystem that has been
largely exempt from anthropogenic disturbance. Some of the primary
issues DOE must address as a land manager include: fire risk and
fuel management, post-fire vegetation recovery, rangeland health,
wildlife habitat management (including habitat critical to the
survival of threatened, endangered, and sensitive species), and land
use planning. Sagebrush is an important component of managing for
all of these issues. Unfortunately, the population biology of
sagebrush is not well understood. In particular, very little
information is available on the typical age structure of sagebrush
stands, the frequency of recruitment events, the dynamics of shrub
die-off, and the typical lifespan of sagebrush.
The overarching goal of this proposed study is to describe sagebrush
stand age structure for a representative sample of sagebrush stands
and to identify the population dynamics that influence that
structure at the INL. Characterizing sagebrush stand age structure
is a critical component to managing sagebrush steppe ecosystems, and
understanding some of the basic biology of sagebrush can add
tremendously to DOE’s ability to make knowledgeable land management
and land use decisions. A simple study to establish a working
knowledge of the age dynamics of sagebrush stands can yield
information useful to those land management issues listed above.
Many of the results from this study may also be applied to sagebrush
stands with similar climatic conditions and disturbance regimes
range-wide, allowing range managers throughout the West to use these
data.
Objectives
The working knowledge of the dynamics of stand age structure gained
from this study will allow managers to better address all of the
land management issues mentioned above. The specific objectives for
this project are:
To determine the typical stand age structure or range of
stand age structures for mature sagebrush stands.
To investigate how stand age structure relates to
stand condition and shrub die-off for sagebrush.
To examine the dynamics of sagebrush stand
replacement in the absence of wildland fire.
By addressing these goals, the proposed study will facilitate
a comprehensive understanding of sagebrush population biology on
the INL and on climatically similar rangelands. That improved
understanding of sagebrush ecology will include the normal age
structure of sagebrush stands, the typical range of variation of
sagebrush stand age structure, how age structure of a sagebrush
stand relates to stand condition, the dynamics of shrub die-off,
the typical lifespan of sagebrush, the frequency of recruitment
events, and the relationship between recruitment and
disturbance.
The expected deliverables for the project will support the
development of the Conservation Management Plan and include (1)
specific habitat management recommendations for sagebrush at the
INL and (2) guidance for assessing the status of sagebrush
habitat health on the INL.
Accomplishments through 2006
During 2006, 14 stands of Wyoming big sagebrush (Artemisia
tridentata ssp. wyomingensis) were sampled. The
vegetation data collected as a component of this study included;
shrub cover, sagebrush density, and individual shrub rank data
for use in developing criteria for measuring stand condition. At
each stand, cross section samples of sagebrush were also
collected. The cross sections were labeled and archived in
preparation for sanding and ring counts.
Results
Because data collection was initiated in 2006 and no data
analyses have yet been completed, no results are reported here.
