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United States Department of Agriculture

Agricultural Research Service

Research Project: DISTURBANCE ASSESSMENT AND MITIGATION OF GREAT BASIN RANGELAND Title: Hydrothermal assessment of temporal variability in seedbed microclimate

Authors
item Hardegree, Stuart
item Cho, Jaepil
item Moffet, Corey -
item Roundy, Bruce -
item Jones, Thomas
item James, Jeremy
item Flerchinger, Gerald
item Clark, Patrick
item Pierson, Frederick

Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 17, 2012
Publication Date: March 1, 2013
Citation: Hardegree, S.P., Cho, J., Moffet, C.A., Roundy, B.A., Jones, T.A., James, J.J., Flerchinger, G.N., Clark, P., Pierson Jr, F.B. 2013. Hydrothermal assessment of temporal variability in seedbed microclimate. Rangeland Ecology and Management. 66:127-135.

Interpretive Summary: Millions of acres of rangeland in the western U.S. have been degraded by wildfire and the proliferation of introduced annual weeds. Restoration practices for these rangelands are often ineffective because low rainfall in this region makes it difficult to establish plants from seed. It is often difficult to determine the value of restoration practices in the field since the weather has to cooperate to get any level of success. What we did in this study is develop a methodology to evaluate weather patterns in a way that produces a numerical index for microclimatic favorability for establishment of desirable rangeland plant species. This index can be used to evaluate historical field plantings, or can be used with long-term weather forecasts to determine the most suitable species to plant in a given year. It can also be used with forecasting to decide not to plant at all in a given year given a prediction of planting failure. Indices of this type could greatly increase the efficiency of field planting by shifting resources to restoration scenarios that have a much higher probability of success.

Technical Abstract: The microclimatic requirements for successful establishment of rangeland species are much more restrictive than those required for maintenance of mature plant communities. We used a 44-year weather record to parameterize a seedbed-microclimate model for estimation of hourly temperature and moisture at seeding depth for a sandy loam soil type at the Orchard Field Test Site in southwestern Ada County, Idaho. Hydrothermal-germination response was measured in the laboratory for 2 seedlots of cheatgrass (Bromus tectorum L.), 4 seedlots of bluebunch wheatgrass [Pseudoroegneria spicata (Pursh) Löve], 3 seedlots of bottlebrush squirreltail [Elymus elymoides (Raf) Swezey], and one seedlot each of Sandberg bluegrass (Poa secunda J. Presl.), big squirreltail [Elymus multisetus (J.G. Smith) M.E. Jones], thickspike wheatgrass [Elymus lanceolatus (Scribn. And J.G. Smith) Gould] and Idaho fescue (Festuca idahoensis Elmer). Germination response models were developed to estimate potential germination rate for 18 subpopulations of each seedlot for every hour of the 44-year simulation period. Seedbed microclimate was assessed seasonally, and for each day, month and year, and germination rate-sum estimates integrated for a numerical index of relative site favorability for germination. The rate-sum-favorability index showed consistent patterns among seedlots for different years, and provides a relatively sensitive indicator for quantification of annual and seasonal variability in seedbed microclimate. This index could be combined with field data to define minimum weather thresholds for successful establishment of alternative plant materials; in conjunction with weather forecast models for making restoration and fire-rehabilitation management decisions for dormant-fall planting; evaluation of potential climate-change impacts on plant community trajectories; and optimization schemes for alternative restoration/rehabilitation management scenarios.

Last Modified: 12/18/2014
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