Natural Resources, School of


First Advisor

David A. Wedin

Second Advisor

Dirac Twidwell, Jr.

Date of this Version



SCHILTMEYER, A.V. (2018). Assessment of the Ponderosa Pine Woodlands in Nebraska's Wildcat Hills: Implications for Juniperus Encroachment and Management. University of Nebraska-Lincoln.


A THESIS Presented to the faculty of The Graduate College at the University of Nebraska In partial fulfillment of the requirements For the degree Master of Science, Major: Natural Resource Sciences, Under the supervision of Professors David A. Wedin and Dirac Twidwell, Jr. Lincoln, Nebraska: July, 2018

Copyright (c) 2018 Allie Victoria Schiltmeyer


Ponderosa pine (Pinus ponderosa) is a dominant tree species across western North America. Its eastern distribution includes three populations in western Nebraska. This study assesses the distribution, structure and age of ponderosa pine woodlands in one of those regions, the Wildcat Hills. The Wildcat Hills have escaped severe wildfires seen in recent decades in other ponderosa pine regions. Nevertheless, the Wildcat Hills woodlands face multiple threats including climate change, wildfire, drought, pine beetles, and invasive species. Key to these threats is the stand structure of pine woodlands, which have increased in density across much of ponderosa pine’s range. These changes in stand density are associated with high recruitment of young pines or the encroachment of other woody species, e.g. eastern redcedar (Juniperus virginiana). This study examined whether these changes are occurring in the Wildcat Hills by conducting an inventory of trees, regeneration, and understory vegetation in 63 plots across a 630-hectare study area. 51 of the ponderosa pines were aged using dendrochronological techniques. The study found that 65% of the study area has open (/hectare) or savanna (/hectare) with few or no juniper trees and seedlings. In contrast, 35% of the study area was classified as woodland. Over 50% of the trees in woodlands were small junipers. Identifying and understanding thresholds for woodland resilience and management in the Wildcat Hills provides insights into their current functional dynamics and directions for future research regarding their fate.

Advisors: David A Wedin and Dirac Twidwell, Jr.