Simulating Current Successional Trajectories in Sagebrush Ecosystems With Multiple Disturbances Using a State-and-Transition Modeling Framework |
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| Authors: | Louisa B Evers Richard F Miller Paul S Doescher Miles Hemstrom Ronald P Neilson |
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| Institution: | 1. Fire Ecologist, Bureau of Land Management, Oregon State Office, Portland, OR 97204, USA.;2. Plant and Fire Ecologist Emeritus, Eastern Oregon Agricultural Research Station, Oregon State University, Corvallis, OR 97331, USA.;3. Restoration Ecologist, Department of Forest Ecosystems and Society, Oregon State University, Corvallis, OR 97331, USA.;4. Research Ecologist (retired), US Forest Service Pacific Northwest Research Station, Portland, OR 97204, USA.;5. Bioclimatologist (retired), US Forest Service Pacific Northwest Research Station, Corvallis, OR 97331, USA.;1. Director and Rangeland Extension Specialist, Sierra Foothills Research and Extension Center, University of California Agriculture and Natural Resources, Browns Valley, CA 95918, USA.;2. Rangeland Ecologist USDA-NRCS Eastern Oregon Agricultural Research Center, Burns, OR 97720, USA.;3. Research Leader, USDA-NRCS Eastern Oregon Agricultural Research Center, Burns, OR 97720, USA.;1. US Geological Survey, Southwest Biological Science Center, Moab, UT 84532, USA;2. Department of Physical and Environmental Sciences, Colorado Mesa University, Grand Junction, CO 81501, USA;3. US Geological Survey, Forest and Rangeland Ecosystem Science Center, Corvallis, OR 97330, USA;1. Supervisory Research Ecologist and Ecologist, Jornada Experimental Range, USDA Agricultural Research Service, Las Cruces, NM, USA;2. Supervisory Rangeland Management Specialist, Las Cruces District Office, USDI Bureau of Land Management, Las Cruces, NM 88033, USA |
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| Abstract: | Disturbances and their interactions play major roles in sagebrush (Artemisia spp. L.) community dynamics. Although impacts of some disturbances, most notably fire, have been quantified at the landscape level, some have been ignored and rarely are interactions between disturbances evaluated. We developed conceptual state-and-transition models for each of two broad sagebrush groups—a warm-dry group characterized by Wyoming big sagebrush (Artemisia tridentata Nutt. subsp. wyomingensis Beetle & Young) communities and a cool-moist group characterized by mountain big sagebrush (Artemisia tridentata Nutt. subsp. vaseyana Rydb.] Beetle) communities. We used the Vegetation Dynamics Development Tool to explore how the abundance of community phases and states in each conceptual model might be affected by fire, insect outbreak, drought, snow mold, voles, sudden drops in winter temperatures (freeze-kill), livestock grazing, juniper (Juniperus occidentalis var. occidentalis Hook.) expansion, nonnative annual grasses such as cheatgrass (Bromus tectorum L.), and vegetation treatments. Changes in fuel continuity and loading resulted in average fire rotations of 12 yr in the warm-dry sagebrush group and 81 yr in the cool-moist sagebrush group. Model results in the warm-dry sagebrush group indicated postfire seeding success alone was not sufficient to limit the area of cheatgrass domination. The frequency of episodes of very high utilization by domestic livestock during severe drought was a key influence on community phase abundance in our models. In the cool-moist sagebrush group, model results indicated at least 10% of the juniper expansion area should be treated annually to keep juniper in check. Regardless, juniper seedlings and saplings would remain abundant. |
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