Category: Ecological Research
Title: Fact Sheet: Long-term Herbivore Exclusion for Recovery of Buckbrush Populations During Restoration of Ponderosa Pine Forests in Northern Arizona
Author: * Huffman, D.W.
Subject: Herbivore Exclusion, Buckbrush (Ceanothus fendleri)
Abstract: Open conditions created by restoration activities in ponderosa pine (Pinus ponderosa Laws.) forests of the American Southwest can lead to increases in understory plant productivity but also attract large ungulate herbivores. New plant growth stimulated by tree thinning and prescribed fire can provide greater forage quantity and quality for herbivores, but grazing pressure on the recovering understory may be high. Some management options during the period when understories are recovering include excluding herbivores from the site or protecting individual plants for a number of years following restoration treatments. Short-term protection of grazed species may provide opportunity for their escape through development of mass or structural defenses such as spines or thorns. For example, Huffman and Moore (2003) showed that two years after forest treatments buckbrush (Ceanothus fendleri Gray) plants protected from mule deer and Rocky Mountain elk had greater stem number, longer stems, and greater current-year biomass than unprotected plants. In contrast, branches of unprotected plants were heavily browsed and just 8 percent of these plants produced flowers. Herbivory pressure also may be lessened with increasing plant community diversity and as more forage options become available to herbi-vores. However, it is unclear how long protection of grazed plants is needed. Chancellor et al. (2008) showed that buckbrush plants exposed to herbivores after seven years of protection had similar stem lengths and stem numbers as plants that continued to be protected. Leaf area and leaf biomass, however, were sig-nificantly less on the recently exposed plants than on protected plants. In this study, we wanted to determine if long-term protection from herbivores was required to restore buck-brush abundance and potential reproduction after forest restoration treatments that were comprised of tree thinning and prescribed fire Buckbrush is a shrub common in ponderosa pine forests of the southwestern U.S. It is important for soil nutrient budgets, understory structure, and habitat for wildlife. We re-measured buckbrush plots (10.8 ft2 (1 m2) in size) in the following groups: 1) unprotected (never protected from herbi-vores); 2) short-term protection (exclosures installed in 1999, removed in 2006); and 3) long-term protection (exclosures installed in 1999 and maintained throughout the 12-year study period).
Type: Fact Sheet
Source: ERI - Fact Sheet
Publisher: Ecological Restoration Institute