Microclimate complexity in temperate grasslands: implications for conservation and management under climate change

As climate change advances, there is a need to examine climate conditions at scales that are ecologically relevant to species. While microclimates in forested systems have been extensively studied, microclimates in grasslands have received little attention despite the climate vulnerability of this endangered biome. We employed a novel combination of iButton temperature and humidity measurements, fine-scale spatial observations of vegetation and topography collected by unpiloted aircraft system, and gridded mesoclimate products to model microclimate anomalies in temperate grasslands. We found that grasslands harbored diverse microclimates and that primary productivity (as represented by normalized difference vegetation index), canopy height, and topography were strong spatial drivers of these anomalies. Microclimate heterogeneity is likely of ecological importance to grassland organisms seeking out climate change refugia, and thus there is a need to consider microclimate complexity in the management and conservation of grassland biodiversity

Quantifying multiple breeding vital rates in two declining grassland songbirds

Many studies of reproductive success in North American songbirds have focused on nesting success, while relatively few have evaluated breeding-season adult survival and post-fledging survival. Grassland songbirds are among North America's most rapidly declining avian groups, and knowledge of factors that influence vital rates is needed to address declines, develop management strategies, and accurately model population limitation. We concurrently monitored nesting success, breeding-season adult survival, and post-fledging survival of two grassland obligates, Baird's Sparrow and Grasshopper sparrow, breeding in western North Dakota and northeastern Montana. Nesting success was monitored by locating and visiting nests at regular intervals while adult and post-fledging survival were assessed by daily telemetry tracking of radio-tagged birds. We analyzed the three variables using logistic exposure and modeled climate, temporal, and vegetative covariates to explain variation in rates. Cumulative nesting success, breeding-season adult survival, and post-fledging survival were 37%, 78%, and 25%, respectively, for Baird's Sparrow and 16%, 74%, and 55% for Grasshopper Sparrow. Both nesting success and post-fledging survival in Baird's Sparrow were responsive to environmental covariates including temporal effects and vertical vegetation structure. Conversely, vital rates of Grasshopper Sparrow were largely unresponsive to covariates we modeled, perhaps because of the species' broader habitat niche relative to Baird's Sparrow. Breeding season adult survival in both species showed little annual variation and was high relative to overwintering survival estimates for the same species, while post-fledging survival in Baird's Sparrow was low and may be a management concern. We suggest as a next step the formal comparison of vital rates across life-stages in an integrated population model capable of identifying sources of population limitation throughout the full annual cycle of the species