US-IALE 2018

AUTHORS: Allie V. Schiltmeyer*, David A. Wedin – School of Natural Resources, University of Nebraska-Lincoln; Dirac Twidwell, Department of Agronomy and Horticulture, University of Nebraska-Lincoln

ABSTRACT: Nebraska’s Wildcat Hills support an intact mosaic of ponderosa pine forests, woodlands, and mixed-grass prairie. It is home to one of Nebraska’s Rocky Mountain bighorn sheep populations and contains several thousand hectares of public land. The Wildcat Hills face multiple threats including climate change, wildfire, drought, pine beetles, and invasive species. In particular, ponderosa pine (Pinus ponderosa) woodlands have experienced extreme wildfires throughout the western US in recent decades. Today, less than one percent of Nebraska’s woodlands and grasslands are burned in a given year. Conservation strategies encouraged by the Nebraska Natural Legacy Project include incorporating a fire return interval of 5-10 years on land within the Wildcat Hills. However, the threat of juniper (Juniperus spp) encroachment deters landowners from incorporating fire into their management routines. Substantial fuel loads and juniper flammability can lead to crown fires within ponderosa pine stands. Simple land cover classifications provided by state and federal agencies are the only data available to evaluate preliminary wildfire models. Neither of these assessments has evaluated the population density, age structure, and regeneration of ponderosa pine and juniper. The age and size structure of Wildcat Hills woodlands affect ecology and potential fire behaviour at both the stand and landscape scale. We did not find evidence of extensive juniper establishment in the grassland matrix surrounding ponderosa pine patches, but a threshold exists for woodland density beyond which juniper establishment increased significantly. This will be important for managing the growing threat of juniper encroachment and wildfire regimes in Nebraska’s ponderosa pine regions.