Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 22, 2010
Publication Date: September 1, 2010
Citation: 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. Interpretive Summary: Western juniper now dominates over 8 million acres of rangeland in the western United States. Over 95% of existing trees, however, have expanded beyond their historical habitat to invade 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. In this study, we developed methodology to fuse Landsat and LiDAR remote sensing data to classify juniper invasion status and trajectory. This technique had 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 and assessment, and identification of priority areas for juniper control treatments that will restore historical plant communities and enhance rangeland productivity.
Technical Abstract: Juniper encroachment into shrub steppe and grassland systems is one of the most prominent changes occurring in rangelands of western North America. Most studies on juniper change are conducted over small areas, although encroachment is occurring across large regions. Development of image-based methods to assess juniper encroachment over large areas would facilitate rapid monitoring and identification of priority areas for juniper management. In this study, we fused Landsat 5 TM- and Light Detection and Ranging (lidar)-based juniper classifications to evaluate juniper expansion patterns in the Reynolds Creek Experimental Watershed of southwestern Idaho. Lidar applications for characterizing juniper encroachment attributes at finer scales were also explored. The fusion-based juniper classification model performed well (83% overall accuracy). A comparison of the resulting juniper presence/absence map to a 1965 vegetation cover map indicated 85% juniper expansion, which was consistent with tree-ring data. Comparisons of current and previous canopy-cover estimates also indicated an increase in juniper density within the historically-mapped juniper distribution. Percent canopy cover of juniper varied significantly with land cover types highlighting areas where intensive juniper management might be prioritized.