Session Information
| Session | Poster Session | | Date | Monday (2008-04-07) | | Time | 5:00 PM - 7:00 PM | | Room | Grand Terrace |
Presentation Information
| Presenter | Nathan Bristow | | Title | Plant community succession following natural and anthropogenic disturbance events in Great Basin pinyon-juniper woodlands | | Affiliation | Dept. of Natural Resources & Env. Sci., Univ. Nevada, Reno | | Authors | Nathan Bristow, Peter Weisberg, Robin Tausch | | Keywords | Fire effects, Landscape restoration, Remote sensing, Spectral mixture analysis, Succession | | Presentation Type | Poster | Abstract:
Pinyon-juniper (Pinus monophylla and Juniperus osteosperma) woodlands and sagebrush (Artemisia tridentata nutt.) shrubland occupy a majority of the productive regions of the Great Basin. Over the past few centuries the woodlands have gradually increased in range and density, while there has been a corresponding decrease in the extent of sagebrush shrubland. The shifting ecotone between these two vegetation types has led to management concerns over the loss of habitat for sagebrush obligate species and the higher resource requirements of the woodlands. As a result, there has been increasing use of various types of woodland reduction treatments. Prescribed fire and mechanical tree removal by chaining are commonly used to counter the effects of expanding woodlands and simultaneously emulate natural fire, a process believed to have historically controlled pinyon-juniper distribution. Although these methods are often justified by claims that the treatments would emulate natural processes, there have been relatively few studies to compare successional processes following chaining, prescribed fire, and wildfire. Our objective was to quantify and contrast the composition and spatial arrangement of vegetation types and rates of succession following these three disturbance types over a multi-decadal period. Natural fires and chaining and prescribed fire treatments, ranging from forty to thirty years of age, were located in multiple mountain ranges in eastern Nevada. A generalized view of successional pathways in Great Basin mountain ranges considers a progression from herbaceous vegetation to shrubs to open woodland and finally closed woodland. We applied spectral mixture analysis to historical Landsat satellite imagery at 10-year intervals to quantify successional processes with time since disturbance, by modeling the percent cover of herbaceous, shrub, and tree vegetation within each pixel. Results suggest that the rate of succession following chaining treatments is much greater than following wildfire, due to differential effects on survivorship of saplings and small trees. Prescribed fire emulates wildfire much more closely with regard to both the rate of succession and the resulting vegetation structure. |
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