State-and-Transition Simulation Models to explore post-fire habitat restoration in three greater sage-grouse (Centrocercus urophasianus) Priority Areas for Conservation, USA (2018-2068)

Wildfires are increasingly modifying wildlife habitat in the western United States and managers need ways to scope the pace and degree to which post-fire restoration actions can re-create habitat in dynamic landscapes. We simulated post-fire revegetation and greater sage-grouse (Centrocercus urophasianus) habitat restoration using a spatially explicit state-transition simulation model (STSM) developed for sagebrush ecosystems. The STSM represented the vegetation dynamics of the sagebrush ecosystem and included annual fires, annual grass invasion, conifer encroachment, and sagebrush revegetation restoration. We compared simulated vegetation output with sage-grouse perennial grass and sagebrush cover habitat needs and evaluated trajectories of potential habitat for three sage-grouse Priority Area for Conservation (PACs) populations located along the northwestern, central, and eastern edge of the Great Basin. This data release is organized into two general datasets: the ST-Sim library and the associated projections of potential sage-grouse habitat (organized by population). Habitat layers illustrate a time series of potential habitat and 50-year potential change in habitat classification for sage-grouse across space and time. The structure of these data follow: A) STSM Model – contains the ST-Sim library, input, and output files; SagebrushSteppeRestoration.ssim, B) KLAM Habitat Data – contains habitat data for the Klamath Oregon/California PAC (located in the northwestern region of the Great Basin), C) NWINV Habitat Data – contains habitat data for the NW Interior Nevada PAC (located in the central region of the Great Basin), and D) STRAW Habitat Data – contains habitat data for the Strawberry Utah PAC (located along the eastern edge of the Great Basin). The STSM was built using the Syncrosim ST-Sim platform with the software's integrated stock-flow submodel to simulate and track continuous vegetation component cover changes caused by annual growth, natural regeneration, and post-fire sagebrush seeding and planting restoration. Thirteen restoration scenarios representing a combination of three revegetation alternatives (no restoration, seeding, planting) under three effort levels (average, double, maximum), and two durations (single-year, multi-year) were simulated for each PAC landscape. Seeding and planting effort levels were based on historic treatment area polygon data (median size) for sagebrush seeding (6 km2) and planting (4 km2). Area was used as a measure of effort that represented an annual fire response equivalent to average effort, double effort (2x area median), and maximum effort (45 km2). The ‘maximum effort’ scenario represented a hypothetical management response 7-11 times larger than average post-fire revegetation treatment area sizes. Planting scenarios represented the sagebrush cover gains of planting 4 plants/m2 (low-density; LD planting) and 8 plants/m2 (high-density; HD planting). A combination seeding-planting scenario representing single-year gains from seeding and multi-year gains from HD planting (two additional years of sagebrush cover gains) and a passive no restoration scenario equivalent to ‘no effort’ were simulated to compare with single- and multi-year seeding or planting scenarios. Habitat layers were generated at 10-year intervals using the simulated vegetation outputs from the five best restoration scenarios of each type (no restoration, seeding, LD planting, HD planting, multi-year) for each PAC landscape. Sagebrush and perennial grass cover from projected continuous component cover values tracked in the STSM stock-flow (SF) submodel were used to characterize potential habitat based on sage-grouse seasonal life stage cover requirements. Habitat distinctions were based on a given pixel meeting minimum cover amounts and classified pixels as suitable, marginally suitable, and unsuitable relative to seasonal spring (i.e., breeding period), summer (i.e., brood-rearing period), and winter sagebrush and perennial grass cover requirements. The three PAC study sites represented the range of vegetation composition and dynamics present in sagebrush-steppe systems and contained variable amounts of annual grass and pinyon-juniper cover that exemplified degraded sagebrush shrubland (Klamath Oregon/California PAC), at-risk of annual-grass invasion (NW-Interior Nevada PAC), and at-risk of juniper encroachment (Strawberry Utah PAC) landscapes.