Landscape Assessment and Monitoring of Semi-Arid Woodlands in the Little Mountain Ecosystem
Timothy J Assal
Patrick J Anderson
U.S. Geological Survey
The Little Mountain Ecosystem in southwestern Wyoming has been identified as a priority area for conservation by the BLM and the WGFD. The woodlands of the Little Mountain Ecosystem have been affected by multiple disturbance types over the last 20 years. Active management of these ecologically important woodlands has sought to rejuvenate decadent aspen stands and reduce conifer expansion in successional aspen stands through prescribed fire and mechanical thinning. The area also experienced wildfires and multiple drought years over the last decade.
The BLM Rock Springs Field Office asked the USGS to conduct research that provides baseline information on the Little Mountain Ecosystem woodlands. This project is designed to acquire information on woodland cover type and the extent and timing of various disturbance types and their effects on woodland productivity. A long-term objective of this research is to determine the feasibility of developing a program for monitoring both abrupt and gradual forest and woodland change by using the archive of satellite imagery that covers large areas of southwestern Wyoming. We expect this work to generate multiple datasets for the USGS and WLCI partners. Outcomes will help WLCI Local Project Development Teams with evaluating and prioritizing aspen treatments, allow us to delineate effects of natural disturbance and identify long-term trends in woodland productivity at a landscape scale, and identify areas of the landscape that are most susceptible to change. Finally, a broad aim of this work is to identify ecosystem response to disturbance and climate variability and to contribute to the literature of recent ecosystem change.
In FY2014, we secured funding to purchase digital plant-canopy imagers for rapid assessments of vegetation treatments and structural changes. Each unit consists of a digital hemispheric (fisheye) camera, a global positioning system, and a radiation sensor (for measuring the light available for photosynthesis). We revisited the majority of our 2013 field plots and collected nine canopy photos per plot from which we will calculate canopy cover and leaf area index. This information provides a permanent record of each plot and will be used to assess canopy condition of woodland stands. The 2013 and 2014 data will be used to model (relate) ground measurements with recent satellite data. After model calibration, we will apply this information to a time series of satellite data to identify areas of stability and change.
Products Completed in FY2014
- Compiled and analyzed 2013 and 2014 field data on stand and canopy structure.
- Established field protocol for using digital plant-canopy imagers in Effectiveness Monitoring.
- Calibrated preliminary models (logistic regression) used to produce maps of deciduous and coniferous woodlands at a 10-meter resolution.
- Assembled a 27-year Landsat satellite imagery record of the project area to use in a trend analysis.
Projects Completed in 2013
- Maps and data, presented to WLCI partners at the Southwest Wyoming Aspen Workshop on Little Mountain.
- Field data collected to relate woodland condition to reflectance measured by satellite images.
- GIS maps of woodland cover type were finalized and distributed to WLCI partners.
- Datasets from satellite imagery archives and long-term climate data were assembled.
- Assal, T.J., Anderson, P.J., and Urza, A.K., 2012, Assessment and monitoring of semi-arid woodlands in the Little Mountain Ecosystem, presented at the Wyoming Landscape Conservation Initiative Science Workshop, May 14-17, 2012, Rock Springs, Wyo., workshop summary available for download.