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 post-fire population dynamics of wildlife species remain poorly understood. We used a newly developed unburned island database of the north-western United States from 1984–2014 to assess the post-fire 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 pre- and post-fire male attendance trends at mating locations (leks) differed between burned and unburned areas, and to what extent post-fire habitat composition at multiple scales could explain such trends. Using time-series of male counts at leks together with spatially-explicit fire history information, we modelled 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. Analyses of post-fire habitat composition further revealed that sagebrush vegetation height within 0.8 km around leks, as well elevation within 0.8km, 6.4km, 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. Our results indicate that maintaining areas of unburned vegetation within and outside fire perimeters may be crucial for sustaining sage-grouse populations following wildfire, and requires more attention in wildlife management.
Data tables Dryad potential important unburned islands paper
16-06-2019. Written by Jasper Steenvoorden, University of Amsterdam. Metadata for the supporting data for the article "The potential importance of unburned islands as refugia for the persistence of wildlife species in fire-prone ecosystems", submitted to Ecology & Evolution. WinRAR file contains four files, three for habitat data, one for lek count data. See details of content below. FILE: Lek_Counts_Data.csv. This .csv (comma delimited) file contains information on the observed male attendance on all analysed leks ("Lek_Number", total of 39) between 1984 to 2017. Additional columns include 1) "Fire_year", which indicates the year in which the specific lek or area around the lek was burned, and 2) "Fire_category", which represents the category (fire perimeter, unburned island, small buffer and large buffer) the lek was located in, based on spatial location in or around a fire. "NA" indicates no count was performed at that lek during a specific year. FILE: Habitat_Covariate_Data_0p8km_Scale.csv. This .csv (comma delimited) file contains information on the habitat covariate values at 0.8km scale around leks that were retrieved for the analysis on the effect of post-fire habitat composition on post-fire male attendance trends. Unburned area around each lek is added as a variable but was not used as a predictor variable due to high multicollinearity with vegetation height. Columns in this file are: "Slope_After_Fire" - percentage growth/decline of male attendance per year after lek or area around lek was burned. "Unburned_Area" - percentage unburned area around lek after lek or area around lek was burned. "Vegetation_Height_Value" - average vegetation height around lek after lek or area around lek was burned. "Elevation" - mean elevation of the area around a specific lek at 0.8km scale around lek. "Cheatgrass_Cover_Value" - percentage area around lek with unsuitable cheatgrass cover (>8% cover per pixel). FILE: Habitat_Covariate_Data_6p4km_Scale.csv. This .csv (comma delimited) file contains information on the habitat covariate values at 6.4km scale around leks that were retrieved for the analysis on the effect of post-fire habitat composition on post-fire male attendance trends. Unburned area around each lek is added as a variable but was not used as a predictor variable due to high multicollinearity with vegetation height. Columns in this file are: "Slope_After_Fire" - percentage growth/decline of male attendance per year after lek or area around lek was burned. "Unburned_Area" - percentage unburned area around lek after lek or area around lek was burned. "Vegetation_Height_Value" - average vegetation height around lek after lek or area around lek was burned. "Elevation" - mean elevation of the area around a specific lek at 6.4km scale around lek. "Cheatgrass_Cover_Value" - percentage area around lek with unsuitable cheatgrass cover (>8% cover per pixel). FILE: Habitat_Covariate_Data_18km_Scale.csv. This .csv (comma delimited) file contains information on the habitat covariate values at 18km scale around leks that were retrieved for the analysis on the effect of post-fire habitat composition on post-fire male attendance trends. Unburned area around each lek is added as a variable but was not used as a predictor variable due to high multicollinearity with vegetation height. Columns in this file are: "Slope_After_Fire" - percentage growth/decline of male attendance per year after lek or area around lek was burned. "Unburned_Area" - percentage unburned area around lek after lek or area around lek was burned. "Vegetation_Height_Value" - average vegetation height around lek after lek or area around lek was burned. "Elevation" - mean elevation of the area around a specific lek at 18km scale around lek. "Cheatgrass_Cover_Value" - percentage area around lek with unsuitable cheatgrass cover (>8% cover per pixel).
Data Tables Dryad Potential Important Unburned Islands Paper.rar