Characterizing the Response of Piñon-Juniper Woodlands to Mechanical Restoration Using High-Resolution Satellite Imagery

In northern New Mexico, complex interactions among climate, land use, and the associated reduction of surface fire in forest and savanna communities facilitated the expansion of piñon-juniper woodlands. Because increasing tree cover can outcompete herbaceous vegetation (e.g., forbs and grasses), woodland expansion resulted in reduced herbaceous cover and increased soil exposure, leading to increased runoff and erosion. To improve hydrologic function in these degraded woodlands, an overstory thinning and slash-mulch treatment was applied to more than 1 000 hectares within Bandelier National Monument (New Mexico, United States) between 2007 and 2010. Our objective was to develop a remote sensing strategy to quantify land-cover changes following mechanical treatment of piñon-juniper woodlands. In this study, we 1) established a simple and repeatable method for assessing treatment effectiveness using high-resolution satellite imagery, 2) quantified vegetation response at six times since treatment (from 0.5 to 3.5 years), and 3) delineated areas of degraded woodland before and after treatment. We classified a 2006 QuickBird satellite image (before treatment) and a 2011 WorldView image (after treatment) to map tree cover, herbaceous cover, bare soil, and shadow with average overall accuracies of 95.0% and 94.7% for the 2006 and 2011 images, respectively. Following treatment, average tree cover, bare soil, and bare soil patch size decreased 9%, 4%, and 18%, respectively, while herbaceous cover increased 14%. Overall, the total amount of woodland area classified as degraded decreased by 34% post treatment. By comparison, control areas remained relatively unchanged across the same time period. Our results demonstrate the utility and promise of highresolution satellite imagery to inform rapid and objective assessments of landscape-scale restoration treatments. © 2016 The Society for Range Management. Published by Elsevier Inc. All rights reserved.The Rangeland Ecology & Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information

The potential importance of unburned islands as refugia for the persistence of wildlife species in fire-prone ecosystems

1. The persistence of wildlife species in fire‐prone ecosystems is under increasing pressure from global change, including alterations in fire regimes caused by climate change. However, unburned islands might act to mitigate negative effects of fire on wildlife populations by providing habitat in which species can survive and recolonize burned areas. Nevertheless, the characteristics of unburned islands and their role as potential refugia for the postfire population dynamics of wildlife species remain poorly understood.  2. We used a newly developed unburned island database of the northwestern United States from 1984 to 2014 to assess the postfire response of the greater sage‐grouse (Centrocercus urophasianus), a large gallinaceous bird inhabiting the sagebrush ecosystems of North America, in which wildfires are common. Specifically, we tested whether prefire and postfire male attendance trends at mating locations (leks) differed between burned and unburned areas, and to what extent postfire habitat composition at multiple scales could explain such trends. 3. Using time‐series of male counts at leks together with spatially explicit fire history information, we modeled whether male attendance was negatively affected by fire events. Results revealed that burned leks often exhibit sustained decline in male attendance, whereas leks within unburned islands or >1.5 km away from fire perimeters tend to show stable or increasing trends. 4. Analyses of postfire habitat composition further revealed that sagebrush vegetation height within 0.8 km around leks, as well elevation within 0.8 km, 6.4 km, and 18 km around leks, had a positive effect on male attendance trends. Moreover, the proportion of the landscape with cheatgrass (Bromus tectorum) cover >8% had negative effects on male attendance trends within 0.8 km, 6.4 km, and 18 km of leks, respectively. 5. Synthesis and applications. Our results indicate that maintaining areas of unburned vegetation within and outside fire perimeters may be crucial for sustaining sage‐grouse populations following wildfire. The role of unburned islands as fire refugia requires more attention in wildlife management and conservation planning because their creation, protection, and maintenance may positively affect wildlife population dynamics in fire‐prone ecosystems