Seasonal drought in North America’s sagebrush biome structures dynamic mesic resources for sage‐grouse

Abstract

The North American semi‐arid sagebrush, Artemisia spp., biome exhibits considerable climatic complexity driving dynamic spatiotemporal shifts in primary productivity. Greater and Gunnison sage‐grouse, Centrocercus urophasianus and C. minimus, are adapted to patterns of resource intermittence and rely on stable adult survival supplemented by occasional recruitment pulses when climatic conditions are favorable. Predictions of intensifying water scarcity raise concerns over new demographic bottlenecks impacting sage‐grouse populations in drought‐sensitive landscapes. We estimate biome‐wide mesic resource productivity from 1984 to 2016 using remote sensing to identify patterns of food availability influencing selective pressures on sage‐grouse. We linked productivity to abiotic factors to examine effects of seasonal drought across time, space, and land tenure, with findings partitioned along gradients of ecosystem water balance within Great Basin, Rocky Mountains and Great Plains regions. Precipitation was the driver of mesic resource abundance explaining ≥70% of variance in drought‐limited vegetative productivity. Spatiotemporal shifts in mesic abundance were apparent given biome‐wide climatic trends that reduced precipitation below three‐quarters of normal in 20% of years. Drought sensitivity structured grouse populations wherein landscapes with the greatest uncertainty in mesic abundance and distribution supported the fewest grouse. Privately owned lands encompassed 40% of sage‐grouse range, but contained a disproportional 68% of mesic resources. Regional drought sensitivity identified herein acted as ecological minimums to influence differences in landscape carrying capacity across sage‐grouse range. Our model depictions likely reflect a new normal in water scarcity that could compound impacts of demographic bottlenecks in Great Basin and Great Plains. We conclude that long‐term population maintenance depends on a diversity of drought resistant mesic resources that offset climate driven variability in vegetative productivity. We recommend a holistic public–private lands approach to mesic restoration to offset a deepening risk of water scarcity.

Sage‐Grouse Population Dynamics are Adversely Affected by Overabundant Feral Horses

“…During the sage‐grouse brood‐rearing period, specifically later months in summer, riparian vegetation communities are important resources for chicks (Casazza et al 2011, Gibson et al 2016). These areas constitute a small proportion of western lands, but are some of the most productive and ecologically important areas of sagebrush ecosystems (Svejcar 1997, Donnelly et al 2018). Feral horses within the Great Basin often relocate to higher elevations during the brood‐rearing period from late spring to early fall (Pellegrini 1971, McInnis 1985) seeking riparian areas (Crane et al 1997) because of the relatively higher water intake needs of horses compared to other ungulates (Groenendyk et al 1988).…”

Using satellite‐derived estimates of plant phenological rhythms to predict sage‐grouse nesting chronology

“…First, within these dry habitats, sage‐grouse seek the relatively more productive sites during the brood‐rearing phase to extend access to succulent vegetation (Kane, Sedinger, Gibson, Blomberg, & Atamian, 2017). To mitigate plant desiccation birds can select wetland habitats (Donnelly et al., 2018; Donnelly, Naugle, Hagen, & Maestas, 2016), or in areas of high topographic relief, track succulent vegetation upslope or across aspects (Dahlgren, Messmer, et al, 2016). Importantly, year‐to‐year variability in the onset of phenological dates diminished with increasing elevation.…”

Integrating Ecosystem Resilience and Resistance Into Decision Support Tools for Multi-Scale Population Management of a Sagebrush Indicator Species

“…Specifically, growth rates increased more strongly following warm and wet conditions in higher elevation sites but declined with warmer conditions in lower elevation sites. Dynamic patterns in precipitation can also have strong, differential impacts on annual availability and drought resiliency of mesic resources across elevational and mid-scale ecoregional gradients (Donnelly et al, 2018). Models such as these that quantify modifications of static predictions of sagebrush engineering resilience by interannual variation in precipitation and temperature can further help parameterize decision-support tools for sage-grouse given that sage-grouse populations respond positively to pulses of above average precipitation at local- (Blomberg et al, 2012) and mid-scales (Coates et al, 2016a;Donnelly et al, 2018).…”