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United States Department of Agriculture

Agricultural Research Service

Related Topics


Location: Northwest Watershed Management Research

2011 Annual Report

1. Hydrologic vulnerability of sagebrush steppe following pinyon and juniper encroachment. Woodland encroachment on western rangelands has altered the vegetative structure and hydrologic function of large expanses of historic shrub steppe. ARS researchers at the Northwest Watershed Research Center in Boise, Idaho, conducted rainfall simulation and concentrated-flow experiments that measured infiltration, runoff, and erosion in these encroaching plant communities. Small (0.5 m2) and large (13 m2) plot scales were used to document relative hydrologic stability of areas underneath tree canopies. Shrub-interspaces between trees exhibited higher water and soil loss vulnerability as tree density increased. As tree density increases, understory vegetation decreases and when ground cover falls below 40-50%, runoff and erosion dramatically increases. These results provide a basis for land managers to better assess and predict Great Basin sagebrush steppe hydrologic and erosional responses to woodland encroachment.

2. Characterizing western juniper expansion via a fusion of LandSat 5 thematic mapper and Light Detection and Ranging (LiDAR) data. Western juniper now dominates over 8 million acres of rangeland in the western United States. Over 95% of existing trees have expanded beyond their historical habitat and invaded adjacent sagebrush-bunchgrass rangeland. There is a critical need to develop remote sensing tools to assess the distribution of this invasive species in order for management agencies to assign treatment priorities for allocation of rangeland restoration funds. ARS researchers at the Northwest Watershed Research Center in Boise, Idaho, developed a methodology to fuse LandSat and LiDAR remote sensing data to classify juniper invasion status and trajectory. This technique was demonstrated to have relatively high accuracy and was used to evaluate juniper invasion at the ARS Reynolds Creek Experimental Watershed. This improved technology can be used by land management agencies for rapid monitoring, assessment, and identification of priority areas for juniper control treatments that will restore historical plant communities and enhance rangeland productivity.

Review Publications
Pierson Jr, F.B., Williams, C.J., Kormos, P.R., Hardegree, S.P., Clark, P., Rau, B.M. 2010. Hydrologic vulnerability of sagebrush steppe following pinyon and juniper encroachment. Rangeland Ecology and Management. 63(6):614-629.

Glenn, N.F., Spaete, L.P., Sankey, T.T., Derryberry, D.R., Hardegree, S.P., Mitchell, J.J. 2010. Errors in LiDAR-derived shrub height and crown area on sloped terrain. Journal of Arid Environments. 75(4):377-382.

Spaete, L.P., Glenn, N.F., Derryberry, D.R., Sankey, T.T., Hardegree, S.P. 2011. Vegetation and slope effects on accuracy of a LiDAR-derived DEM in the sagebrush steppe. International Journal of Remote Sensing. 2(4):317-326.

Sankey, T.T., Glenn, N.F., Ehinger, S., Boehm, A.R., Hardegree, S.P. 2010. Characterizating western juniper expansion via a fusion of Landsat 5 thematic mapper and LiDAR data. Rangeland Ecology and Management. 63(5):514-523.

Last Modified: 7/24/2014
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