USDA Forest Service, Rocky Mountain Research Station, http://www.fs.fed.us/rmrs/
Abstract
Plant population models are valuable tools for assessing ecological tradeoffs between forest management approaches. In addition, these models can provide insight on plant life history patterns and processes important for persistence and recovery of populations in changing environments. In this study, we evaluated a set of ecological restoration alternatives for their long-term effects on buckbrush (Ceanothus fendleri Gray), a shrub common in understories of ponderosa pine (Pinus ponderosa Laws. var. scopulorum Engelm.) forests of the southwestern United States. The field data were collected from a set of forest restoration units located on the Fort Valley Experimental Forest. We constructed simple stage-based models in order to simulate 25-year population dynamics. Results showed that scenarios that included overstory thinning, herbivore protection, and prescribed fire resulted in buckbrush populations with significantly greater numbers of aboveground stems than populations in the other alternatives. Vegetative stem recruitment, flowering, and seedling emergence were important in producing these results. For alternatives that included protection from herbivores, burning at 2-year frequencies resulted in populations with significantly greater numbers of aboveground stems than scenarios with longer intervals between burning. In contrast, frequent burning in alternatives without herbivore protection resulted in population decline. These results indicate that protecting buckbrush from large herbivores allowed plants to complete life cycles and fully express these life history traits. This research demonstrates that population modeling can help illuminate ecological tradeoffs associated with land management alternative
