Year of Award
2025
Document Type
Thesis
Degree Type
Master of Science (MS)
Degree Name
Wildlife Biology
Department or School/College
Wildlife Biology Program
Committee Chair
Chad J. Bishop
Commitee Members
Kelly M. Proffitt, Sarah N. Sells, Joshua J. Millspaugh
Keywords
elk, timber harvest, habitat management, nutritional landscape, resource selection
Subject Categories
Terrestrial and Aquatic Ecology
Abstract
As wildlife and habitats face unprecedented challenges in the form of landscape conversion, shifting disturbance regimes, and climate change, it becomes increasingly important for land and wildlife managers to find avenues for collaboration as they seek to maintain habitat to support robust wildlife populations. Timber harvest may provide one such avenue for collaboration. It has been shown to increase the quality and quantity of ungulate nutritional resources by reverting stands to early successional stages. Additionally, timber harvest may allow for a more precise application of such effects, as managers choose where and how to harvest timber. However, the exact effects of timber harvest on nutritional resources in a given region are difficult to predict, with many inconsistent variables from region to region. This leads to uncertainty regarding its efficacy as a habitat treatment tool for ungulates in understudied areas.
In order to assess the efficacy of a habitat treatment, one must demonstrate both an increase in the desired resource, and increased use of the resource. To that end, we sought to assess the impact of different types of timber harvest on elk (Cervus canadensis) summer nutrition and resource selection in northwestern Montana, and to use these results to inform discussions as to the efficacy of timber harvest as a habitat treatment tool for elk in this and similar regions.
In the first chapter, we created nutritional landscape models for forage biomass and digestible energy using data obtained from 442 random vegetation sampling plots stratified by landcover type, timber harvest strategy, and time-since-harvest. We found that the nutritional resources of harvested sites were higher relative to unharvested sites. Under certain conditions, harvested sites offered some of the best nutrition on the landscape, particularly in late summer. Time-since-harvest drove predictions of forage biomass in both dry and mesic forests, and informed predictions of digestible energy in mesic forests, with nutritional measures being highest in the first five years immediately following harvest and declining through time as forest succession progressed.
In the second chapter, we developed resource selection probability functions for elk during foraging and non-foraging times in early and late summer using the data obtained from GPS radiocollars deployed on 92 adult female elk. We found that elk selected strongly for recently harvested cutblocks associated with higher nutrition during foraging times, especially in late summer. During non-foraging times in late summer, selection switched as elk avoided open landcover types and selected for older cutblocks.
Our research demonstrated both an increase in nutritional resources following timber harvest and preferential use by elk of cutblocks of various harvest strategies and age classes depending on the time of day and season in a densely forested region of Montana. We found that in terms of available nutrition, both even-age harvest strategies and intermediate harvest strategies resulted in appreciable increases to the quality and quantity of elk forage. However, when including considerations of elk landscape use, we found that elk preferred even-age harvest. In this system of dense forests, a relatively small proportion of harvest on the landscape performed at relatively small spatial scales (~0.13 km2 per cutblock) resulted in strong responses in both available nutrition and elk use. Our results suggest that if increasing available nutrition is the goal, then managers can consider either even-age or intermediate harvest strategies, provided they focus their efforts on mesic forests. If increasing elk use is a goal, then managers should prioritize even-age harvest strategies. Overall, our results emphasize the importance of maintaining a mosaic landscape to support the varied needs of elk and show that timber harvest can be used as one tool to maintain such a landscape.
Recommended Citation
Weeks, Trevor C., "In The Clear: timber harvest informs elk summer nutrition and resource selection in a densely forested landscape" (2025). Graduate Student Theses, Dissertations, & Professional Papers. 12543.
https://scholarworks.umt.edu/etd/12543
© Copyright 2025 Trevor C. Weeks