Browsing Rangeland Ecology & Management, Volume 67, Number 5 (September 2014) by Subjects
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Response of Conifer-Encroached Shrublands in the Great Basin to Prescribed Fire and Mechanical TreatmentsIn response to the recent expansion of piñon and juniper woodlands into sagebrush-steppe communities in the northern Great Basin region, numerous conifer-removal projects have been implemented, primarily to release understory vegetation at sites having a wide range of environmental conditions. Responses to these treatments have varied from successful restoration of native plant communities to complete conversion to nonnative invasive species. To evaluate the general response of understory vegetation to tree canopy removal in conifer-encroached shrublands, we set up a region-wide study that measured treatment-induced changes in understory cover and density. Eleven study sites located across four states in the Great Basin were established as statistical replicate blocks, each containing fire, mechanical, and control treatments. Different cover groups were measured prior to and during the first 3 yr following treatment. There was a general pattern of response across the wide range of site conditions. There was an immediate increase in bare ground and decrease in tall perennial grasses following the fire treatment, but both recovered by the second or third growing season after treatment. Tall perennial grass cover increased in the mechanical treatment in the second and third year, and in the fire treatment cover was higher than the control by year 3. Nonnative grass and forb cover did not increase in the fire and mechanical treatments in the first year but increased in the second and third years. Perennial forb cover increased in both the fire and mechanical treatments. The recovery of herbaceous cover groups was from increased growth of residual vegetation, not density. Sagebrush declined in the fire treatment, but seedling density increased in both treatments. Biological soil crust declined in the fire treatment, with no indications of recovery. Differences in plant response that occurred between mechanical and fire treatments should be considered when selecting management options. © 2014 The Society for Range Management.
Short-Term Butterfly Response to Sagebrush Steppe Restoration TreatmentsAs part of the Sagebrush Steppe Treatment Evaluation Project (SageSTEP), butterflies were surveyed pretreatment and up to 4 yr posttreatment at 16 widely distributed sagebrush steppe sites in the interior West. Butterfly populations and communities were analyzed in response to treatments (prescribed fire, mechanical, herbicide) designed to restore sagebrush steppe lands encroached by piñon-juniper woodlands (Pinus, Juniperus spp.) and invaded by cheatgrass (Bromus tectorum). Butterflies exhibited distinct regional patterns of species composition, with communities showing marked variability among sites. Some variation was explained by the plant community, with Mantel's test indicating that ordinations of butterfly and plant communities were closely similar for both woodland sites and lower-elevation treeless (sage-cheat) sites. At woodland sites, responses to stand replacement prescribed fire, clear-cutting, and tree mastication treatments applied to 10-20-ha plots were subtle: 1) no changes were observed in community structure; 2) Melissa blues (Plebejus melissa) and sulfurs (Colias spp.) increased in abundance after either burning or mechanical treatments, possibly due to increase in larval and nectar food resource, respectively; and 3) the juniper hairstreak (Callophrys gryneus) declined at sites at which it was initially present, probably due to removal of its larval food source. At sage-cheat sites, after prescribed fire was applied to 25-75-ha plots, we observed 1) an increase in species richness and abundance at most sites, possibly due to increased nectar resources for adults, and 2) an increase in the abundance of skippers (Hesperiidae) and small white butterflies. Linkages between woody species removal, the release of herbaceous vegetation, and butterfly response to treatments demonstrate the importance of monitoring an array of ecosystem components in order to document the extent to which management practices cause unintended consequences.