Long-Term Vegetation Study


 

The Long-Term Vegetation (LTV) Transects and associated permanent vegetation plots (see map below) were established on what is now the Idaho National Laboratory (INL) Site, in 1950 for the purpose of assessing the impacts of nuclear energy research and production on surrounding ecosystems. Vegetation abundance data were first collected in 1950 for inclusion in an ecological characterization of the Site. Samples of plant and animal tissues were also collected from these plots and analyzed for radionuclide concentrations on an annual basis for several years. The effort to collect tissue samples was eventually discontinued because the effects of fallout from nuclear reactors were determined to be negligible, at least
in terms of radionuclide concentrations in the environment. However, collection of vegetation abundance data has continued on a regular basis for nearly sixty years.
 

 

The data generated from the LTV Transects comprises one of the oldest, largest, and most comprehensive vegetation data sets for sagebrush steppe ecosystems in North America. Since their establishment, the LTV Transects have been used extensively for various tasks to support the INL Site mission and have been the basis for major milestones in understanding practical and theoretical ecology of sagebrush steppe vegetation dynamics. Applications of the LTV data include:

  • Plant community classification and mapping,

  • Assessing the effects of drought and livestock grazing,

  • Understanding fire history and recovery,

  • Characterizing species invasion patterns,

  • Testing theories of vegetation succession and change,

  • As a basis for habitat suitability modeling for sensitive species,

  • Supporting NEPA processes,

  • Making appropriate land management recommendations, and

  • Developing specific revegetation recommendations.

In addition to the functions listed above, the LTV data set is still used to assess the impacts of energy development on the environment, as was intended in 1950. However, impacts beyond radioactive fallout, such as exotic species invasion, habitat fragmentation, and global climate change are of current interest.

 

Objectives

 

The eleventh LTV data set was collected during the summer of 2006.  Two tasks were undertaken in association with the 2006 data collection.  The first task involves a major effort in updating and describing the data archives.  The second includes summarization and analysis of the 2006 and all previously collected abundance data.

 

The last attempt at organizing and archiving the LTV data was completed in the early 1980s.  Although care has been taken to format and store data collected since 1983 in a manner consistent with the protocol established at that time, the data archives have become outdated.  The software available for archiving and processing data has improved substantially over the past 25 years, necessitating an update of the LTV data files.  A considerable amount of the work associated with entry and summary of the 2006 data included designing and populating a relational database for all of the LTV data from 1950-2006.  Additionally, the specific sampling protocol will be documented and a thorough history of the LTV will be included as part of the reporting effort.

 

Analyses on the 2006 and previous data can be summarized under two focus areas.  The first includes characterizing general plant abundance and community composition trends, similar to analyses described in previous LTV reports.  The second group of analyses will concentrate on characterizing patterns of exotic species invasion and determining the effects of invasion on vegetation cover and composition of native plant communities subsequent to invasion.

 

Accomplishments through 2009

 

Accomplishments through 2009 include collection of the 2006 data and completion of quality assurance/quality control procedures on that data set.  The 2006 data were also summarized, formatted, and imported into a comprehensive relational database.  The database was thoroughly documented and verification/validation routines were performed on the data contained therein.  Verification and validation processes were used to ensure the integrity and completeness, as well as to resolve issues associated with taxonomic classifications and scaling, of the historical data set.  A specific protocol for use in collecting LTV data was designed and drafted in association with the 2006 data collection effort. 

 

Analyses summarizing INL Site vegetation trends over the past 56 years were completed in 2009.  Changes in abundance and composition through time were addressed by comparing absolute cover at the species level over the past decade and changes in the total cover of functional groups and key shrub species over the entire 56-year data set.  Patterns of exotic species invasion were investigated using a mapping exercise to identify changes in the presence and abundance of cheatgrass and other non-native annual species across the LTV plots through time.  Results of the mapping exercise were compared to changes in mean density and frequency of the target species or group of species between sample periods in an effort to characterize general spatial/temporal patterns of invasion on the INL Site.    

 

Five chapters were outlined for inclusion in the final report, and drafts of each were completed by spring 2009.  The five chapters include: (1) a brief introduction, (2) a comprehensive history of the LTV permanent plots and associated vegetation studies, (3) a detailed protocol to be used to guide data collection efforts and maintain continuity in future data collection efforts, (4) a thorough documentation of the updated database structure, and (5) results of analyses addressing long-term plant community change and invasive species patterns.  The entire report was submitted for review in 2009.       

 

Results

The database includes seven raw data and metadata tables.  The general structure of the database is depicted in Figure 13.  The metadata tables include information about plant species on the INL Site, information about each of the permanent plots on the LTV Transects, and information about the sampling history on the LTV plots.  Of the four data tables contained within the database, three tables are comprised of vegetation abundance data and one includes information about plot photos.  The abundance data tables contain density/frequency data, cover data estimated using line interception, and cover data estimated using point interception.  The photograph specifications data table was designed to consolidate data associated with photos taken during LTV data collection efforts including photo dates, exposure, aperture, camera angle, etc.  The photo data table was designed such that the record of each photo can include a hyperlink to a digital copy of that photo.  Accordingly, all of the historical photos were digitized as part of the update to the LTV archive.  The photograph specification data table was not populated as a part of the current effort; however, the historical photos have been properly archived in a digital format to streamline integration as part of future efforts.

 

Flow chart showing seven data and metadata tables and the relationships of those tables to one another in the LTV database.

 

Results from analyses on trends in species composition and abundance indicate that although the cover of major functional groups remains relatively stable through time, the cover of species within those groups can vary dramatically over just a decade.  Species composition, it terms of absolute cover, from the 2006 sampling effort are shown in Table 8.  Cover of big sagebrush (Artemisia tridentata) has continued to decline through the 2006 sampling effort, and the cover of crested wheatgrass (Agropyron spp.) is increasing rapidly, albeit at a local scale.  Results from the analyses on trends of invasive species indicate that the spatial distribution of cheatgrass has increased over the study period; however, the mean density and frequency have not increased as predictably as expected.  The abundance and distribution of other non-native annuals, specifically, desert madwort (Alyssum desertorum) is increasing far more rapidly (Forman et al. 2010).    

 

 

Mean percent cover of the vascular plants sampled on 43 LTV plots using point-intercept methods during the 2006 sample period.  Species are listed in order of descending cover values within each functional group.  Cover is reported for each species having an absolute cover value > 0.1%.  Constancy indicates the number of plots in which a species occurred and cover normalized by constancy indicates the mean cover of a species averaged across only the number of plots in which it occurred.

Plant Species

Absolute Cover (%)

Constancy

Cover (%) Normalized by Constancy

Shrubs

 

 

 

 

   Chrysothamnus viscidiflorus

6.902

41

7.238

 

   Artemisia tridentata ssp. wyomingensis

4.885

30

7.002

 

   Artemisia tridentata ssp. tridentata

2.495

11

9.753

 

   Grayia spinosa

0.999

9

4.772

 

   Linanthus pungens

0.807

18

1.929

 

   Tetradymia canescens

0.415

7

2.548

 

   Krascheninnikovia lanata

0.366

5

3.144

 

   Ericameria nauseosa

0.101

5

0.867

 

   Others (n = 5)

0.130

 

 

 

   Total Shrub Cover

17.10

 

 

 

Perennial Graminoids

 

 

 

 

   Hesperostipa comata

3.238

31

4.491

 

   Achnatherum hymenoides

1.159

38

1.311

 

   Elymus lanceolatus

1.003

31

1.391

 

   Agropyron desertorum

0.952

6

6.824

 

   Elymus elymoides

0.935

29

1.387

 

   Pascopyrum smithii

0.824

10

3.544

 

   Poa secunda

0.450

28

0.690

 

   Others (n = 6)

0.202

 

 

 

   Total Graminoid Cover

8.76

 

 

 

Perennial Forbs

 

 

 

 

   Schoenocrambe linifolia

0.775

32

1.042

 

   Phlox hoodii

0.453

26

0.750

 

   Eriogonum ovalifolium

0.264

16

0.708

 

   Astragalus lentiginosus

0.189

15

0.541

 

   Stephanomeria spinosa

0.119

5

1.022

 

   Others (n = 24)

0.836

 

 

 

   Total Perennial Forb Cover

2.64

 

 

 

Succulents

 

 

 

 

   Opuntia polyacantha

0.40

33

0.52

 

Native Annuals and Biennials

 

 

 

 

   Lappula occidentalis

0.357

24

0.639

 

   Eriogonum cernuum

0.249

16

0.670

 

   Gayophytum diffusum

0.230

16

0.618

 

   Eriastrum wilcoxii

0.167

19

0.377

 

   Cordylanthus ramosus

0.121

6

0.870

 

   Others (n = 13)

0.377

 

 

 

   Total Native Annual/Biennial Cover

1.50

 

 

 

Introduced Annuals and Biennials

 

 

 

 

   Alyssum desertorum

2.672

26

4.419

 

   Bromus tectorum

0.771

27

1.228

 

   Salsola kali

0.525

10

2.256

 

   Descurainia sophia

0.141

11

0.551

 

   Sisymbrium altissimum

0.137

7

0.841

 

   Halogeton glomeratus

0.121

6

0.870

 

   Tragopogon dubius

0.006

3

0.093

 

   Total Introduced Annual/Biennial Cover

4.37

 

 

 

   Total Vascular Plant Cover

34.77

 

 

 

 

Plans for Continuation

The LTV report will be finalized and publicly available in calendar year 2010.  Two peer-reviewed publications containing results from the current LTV data set will also be prepared and submitted as time and funding allow.

 

Publication:  STOLLER-ESER-126 - The Idaho National Laboratory Site Long-Term Vegetation Transects: A Comprehensive Review - Amy D. Forman, Roger D. Blew, Jackie R. Hafla - June 2010