Fire legacies in eastern ponderosa pine forests

Fire-driven landscape heterogeneity shapes habitat selection of bighorn sheep

Patterns in disturbance severity and time since fire can drive landscape heterogeneity that is critical to conservation; however, there is limited understanding of how wildlife interact with the spatial–temporal complexities of disturbance outcomes and at what scales. We conducted multiscale modeling of habitat selection for male and female Rocky Mountain bighorn sheep (Ovis canadensis canadensis) over an 8-year period. We aimed to identify the spatial scales at which bighorn sheep responded to various habitat features and determine how fire severity and time since fire can shape habitat selection by bighorn sheep over different seasons and between sexes. With the exception of litter cover, spatial scales that extended beyond the finest spatial grain (i.e., a 30-m pixel) to include the surrounding landscape were better at predicting habitat selection. Escape terrain, elevation, fire severity, year, perennial and annual forb and grass cover, and shrub cover occurred in every best-supported model. Associations with escape terrain, elevation, and perennial and annual forb and grass cover varied by sex and season. In contrast, bighorn sheep were consistently positively associated with low- and high-severity fire. Females increased use of low- and high-severity burned areas with greater time since fire, while males tended to decrease use of areas that burned at high severity with greater time since fire. Our results support the importance of landscape heterogeneity created by fire severity and time since fire for Rocky Mountain bighorn sheep and reinforces calls to integrate disturbance-driven heterogeneity into our assessments and management of wildlife.

Woody Plant Encroachment and the Sustainability of Priority Conservation Areas

Woody encroachment is a global driver of grassland loss and management to counteract encroachment represents one of the most expensive conservation practices implemented in grasslands. Yet, outcomes of these practices are often unknown at large scales and this constrains practitioner’s ability to advance conservation. Here, we use new monitoring data to evaluate outcomes of grassland conservation on woody encroachment for Nebraska’s State Wildlife Action Plan, a statewide effort that targets management in Biologically Unique Landscapes (BULs) to conserve the state’s natural communities. We tracked woody cover trajectories for BULs and compared BUL trajectories with those in non-priority landscapes (non-BULs) to evaluate statewide and BUL-scale conservation outcomes more than a decade after BUL establishment. Statewide, woody cover increased by 256,653 ha (2.3%) from 2000–2017. Most BULs (71%) experienced unsustainable trends of grassland loss to woody encroachment; however, management appeared to significantly reduce BUL encroachment rates compared to non-BULs. Most BULs with early signs of encroachment lacked control strategies, while only one BUL with moderate levels of encroachment (Loess Canyons) showed evidence of a management-driven stabilization of encroachment. These results identify strategic opportunities for proactive management in grassland conservation and demonstrate how new monitoring technology can support large-scale adaptive management pursuits.

Ponderosa Pine Regeneration, Wildland Fuels Management, and Habitat Conservation: Identifying Trade-Offs Following Wildfire

Increasing wildfires in western North American conifer forests have led to debates surrounding the application of post-fire management practices. There is a lack of consensus on whether (and to what extent) post-fire management assists or hinders managers in achieving goals, particularly in under-studied regions like eastern ponderosa pine forests. This makes it difficult for forest managers to balance among competing interests. We contrast structural and community characteristics across unburned ponderosa pine forest, severely burned ponderosa pine forest, and severely burned ponderosa pine forest treated with post-fire management with respect to three management objectives: ponderosa pine regeneration, wildland fuels control, and habitat conservation. Ponderosa pine saplings were more abundant in treated burned sites than untreated burned sites, suggesting increases in tree regeneration following tree planting; however, natural regeneration was evident in both unburned and untreated burned sites. Wildland fuels management greatly reduced snags and coarse woody debris in treated burned sites. Understory cover measurements revealed bare ground and fine woody debris were more strongly associated with untreated burned sites, and greater levels of forbs and grass were more strongly associated with treated burned sites. Wildlife habitat was greatly reduced following post-fire treatments. There were no tree cavities in treated burned sites, whereas untreated burned sites had an average of 27 ± 7.68 cavities per hectare. Correspondingly, we found almost double the avian species richness in untreated burned sites compared to treated burned sites (22 species versus 12 species). Unburned forests and untreated burned areas had the same species richness, but hosted unique avian communities. Our results indicate conflicting outcomes with respect to management objectives, most evident in the clear costs to habitat conservation following post-fire management application.