Long-Term Vegetation Transects (2011)

Long-Term Vegetation Transects (2011)


Investigators and Affiliations

  • Amy D. Forman, Plant Ecologist, Environmental Surveillance, Education, and Research Program, Gonzales-Stoller Surveillance, LLC, Idaho Falls, Idaho
  • Roger D. Blew, Ph.D., Ecologist, Environmental Surveillance, Education, and Research Program, Gonzales-Stoller Surveillance, LLC, Idaho Falls, Idaho
  • Jackie R. Hafla, Natural Resource Specialist, Environmental Surveillance, Education, and Research Program, Gonzales-Stoller Surveillance, LLC, Idaho Falls, Idaho.


Funding Source: U.S. Department of Energy-Idaho Operations Office

Background: The Long-Term Vegetation (LTV) Transects and associated permanent plots were established on what is now the Idaho National Laboratory (INL) Site in 1950 for the purposes of assessing impacts of nuclear energy research and production on surrounding ecosystems (Singlevich 1951). Initial sampling efforts focused on potential fallout from nuclear reactors and the effects of radionuclides on the flora and fauna of the Upper Snake River Plain. After several years of sampling, however, the concentrations and any related effects of radionuclides on the sagebrush steppe ecosystem of the INL Site were determined to be negligible (Harniss 1968).

Because the LTV plots were widely distributed across two transects which bisect the INL Site (Figure 9-5) and vegetation abundance data had been collected periodically since their establishment, their utility as a basis for monitoring vegetation trends in terms of species composition, abundance, and distribution was eventually recognized. Accordingly, vegetation abundance data collection has continued on the LTV plots on a semi-regular basis; about once every 5 years. Eight-nine LTV plots are still accessible and many have now been sampled on 12 occasions between 1950 and 2011, making the resulting dataset one of the oldest, largest, and most comprehensive for sagebrush steppe ecosystems in North America.

In many ways the LTV plots are still used to assess the impacts of energy research and development on the INL Site. The mission of the INL Site has moved beyond a strict focus on the development of nuclear energy to activities which pertain to securing energy-related infrastructure, further development of non-nuclear based energy technologies, and the cleanup of legacy waste. As the mission has grown and changed, so too have the potential impacts of mission-related activities on the vegetation of the INL Site. Potential ecological impacts of energy development at regional, national, and global scales are also of greater concern than they were when the LTV plots were established more than 60 years ago. Accordingly, issues currently addressed by the LTV dataset include; habitat quality for sensitive species, effects of exotic species invasions, increased rates of disturbance, habitat fragmentation, climate change, and the resilience of sagebrush steppe plant communities to various stressors.

The most recent sampling effort was conducted during the 2011 growing season. In addition to collecting and analyzing abundance data on the permanent plots, we will also include analysis on an ancillary vegetation data set in the report associated with the 2011 sampling effort. Prompted by sustained declines in big sagebrush (Artemisia tridentata) cover across the LTV plots since the late 1970s, a demography study was initiated to better understand population- level mechanisms which may be causing the declines. Data for this study were collected on 14 plots located in the central portion of the INL Site (Figure 1) in 2006 and sample processing continued through 2011. Results from this ancillary study and their implications on the biology of big sagebrush will be interpreted within the context of long-term trends in sagebrush-dominated communities represented by the LTV dataset.
Figure 1
Figure 9-5. Map of the INL Site with Plot Locations for the LTV Permanent Plots and the Ancillary Sagebrush Demography Study Plots.


We will approach data analysis and organize the technical report associated with the 2011 data collection effort according to five primary objectives. These objectives reflect a continuation of the vegetation trend analyses on which the LTV has been historically based, and the use of some new datasets and novel analyses of older datasets to identify specific mechanisms influencing overall vegetation trends. Results from the current analysis and reporting effort will allow us to make specific recommendations about conservation management goals and the likely effects of potential habitat management actions.

The first two objectives include updating trend analyses previously performed on the LTV dataset using the current 2011 dataset. Objective 1 is focused on native, primarily perennial species, and addresses long-term abundance trends in functional groups and individual species of interest, as well as the stability of total community vegetative cover and species composition through time. Objective 2 emphasizes trends in the abundance and distribution of non-native species and will include updating several analyses presented in the report associated with the 2006 sample period (Forman et al. 2010), such as tracking cheatgrass (Bromus tectorum) abundance and distribution on the LTV plots through time.

The purpose of Objective 3 is to characterize the rate of community change, in terms of species composition, at the local scale. Results from previous analyses of the LTV data suggest that although good-condition native plant communities at the INL Site change relatively slowly when abundance data are analyzed by functional group and are averaged across many plots, changes in individual species’ abundance at the plot scale can be quite dynamic over relatively short time periods. By addressing this objective, we hope to gain a better understanding of the natural range of variability in these semi-arid communities both spatially and temporally.

Objective 4 includes analysis and interpretation of the Sagebrush Demography data. We will use these data to identify the mechanisms which have potentially caused the long-term, persistent declines in big sagebrush cover at the INL Site, as well as the effects of stochastic events on population structure and big sagebrush abundance.

Objective 5 is a synthesis of many of the analyses conducted during this sample period and the results presented in previous LTV reports. We will present a paradigm for sagebrush population and community dynamics at the INL Site which can be used to inform interpretations of vegetation monitoring data and to evaluate the efficacy of proposed management actions for improving sagebrush habitat.

Accomplishments through 2011:

The primary LTV Database was updated prior to data collection in 2011. We revised the species metadata table to reflect changes in taxonomy between the 2006 and 2011 sample periods using the Plants National Database (USDA, NRCS 2011). A 2011 LTV Project Database was created to mirror the primary LTV Database. We used the 2011 LTV Project Database for daily data processing and associated Quality Assurance/Quality Control procedures. Once all of the data in the 2011 LTV Project Database are verified and validated to insure the integrity and completeness of the 2011 dataset, the 2011 LTV Project Database will be integrated back into the primary LTV Database. All of the 89 active LTV plots were sampled during the 2011 growing season according to the standardized protocols outlined in previous reports (e.g. Forman et al. 2010). We incorporated all of the resulting data into the 2011 LTV Project Database and completed all Quality Assurance/Quality Control procedures and data verification and validation processes on those data.

Shrub abundance data and big sagebrush cross sections for ring counts were collected for the Sagebrush Demography study in 2006. The sagebrush cross sections were processed and ring counts were completed throughout 2010 and early 2011. A formalized database was designed and populated with all data collected to support this project.

We had not yet initiated data analysis on either the LTV or Sagebrush Demography datasets in 2011; results are forthcoming.

Plans for Continuation
The primary LTV Database will be updated with the data in the 2011 LTV Project Database and the Sagebrush Demography database will be finalized prior to data analysis. The databases will be complementary to one another through corresponding metadata table structures. Analysis and reporting to address the five objectives discussed above will be completed in 2012.

Final databases for both datasets and a technical report detailing data analyses, results, and management implications will be provided.


  • Forman, A. D., R. D. Blew, and J. R. Hafla. 2010. The Idaho National Laboratory Site Long- term Vegetation Transects: A Comprehensive Review. STOLLER-ESER-126. Environmental Surveillance, Education and Research Program, Idaho Falls, ID.
  • Harniss, R. O. 1968. Vegetation changes following livestock exclusion on the National Reactor Testing Station, Southeastern Idaho. Utah State University, Logan, UT.
  • Singlevich, W., J. W. Healy, H. J. Paas, and Z. E. Carey. 1951. Natural radioactive materials at the Arco Reactor Test Site. Radiological Sciences Department, Atomic Energy Commission, Richland, WA.
  • USDA, NRCS. 2011. The PLANTS Database (http://plants.usda.gov, 14 March 2011). National Plant Data Center, Baton Rouge, LA 70874-4490 USA.