Elizabeth L. Kalies

Community occupancy responses of small mammals to restoration treatments in ponderosa pine forests, northern Arizona, USA.

In western North American conifer forests, wildfires are increasing in frequency and severity due to heavy fuel loads that have accumulated after a century of fire suppression. Forest restoration treatments (e.g., thinning and/or burning) are being designed and implemented at large spatial and temporal scales in an effort to reduce fire risk and restore forest structure and function. In ponderosa pine (Pinus ponderosa) forests, predominantly open forest structure and a frequent, low-severity fire regime constituted the evolutionary environment for wildlife that persisted for thousands of years. Small mammals are important in forest ecosystems as prey and in affecting primary production and decomposition. During 2006-2009, we trapped eight species of small mammals at 294 sites in northern Arizona and used occupancy modeling to determine community responses to thinning and habitat features. The most important covariates in predicting small mammal occupancy were understory vegetation cover, large snags, and treatment. Our analysis identified two generalist species found at relatively high occupancy rates across all sites, four open-forest species that responded positively to treatment, and two dense-forest species that responded negatively to treatment unless specific habitat features were retained. Our results indicate that all eight small mammal species can benefit from restoration treatments, particularly if aspects of their evolutionary environment (e.g., large trees, snags, woody debris) are restored. The occupancy modeling approach we used resulted in precise species-level estimates of occupancy in response to habitat attributes for a greater number of small mammal species than in other comparable studies. We recommend our approach for other studies faced with high variability and broad spatial and temporal scales in assessing impacts of treatments or habitat alteration on wildlife species. Moreover, since forest planning efforts are increasingly focusing on progressively larger treatment implementation, better and more efficiently obtained ecological information is needed to inform these efforts.

A meta-analysis of management effects on forest carbon storage

ABSTRACT Forest management can have substantial impacts on ecosystem carbon storage, but those effects can vary significantly with management type and species composition. We used systematic review methodology to identify and synthesize effects of thinning and/or burning, timber harvesting, clear-cut, and wildfire on four components of ecosystem carbon: aboveground vegetation, soil, litter, and deadwood. We performed a meta-analysis on studies from the United States and Canada because those represented 85% of the studies conducted worldwide. We found that the most important variables in predicting effect sizes (ratio of carbon stored in treated stands versus controls) were, in decreasing order of importance, ecosystem carbon component, time since treatment, and age of control. Management treatment was the least important of all the variables we examined, but the trends we found suggest that thinning and/or burning treatments resulted in less carbon loss than wildfire or clear-cut. This finding is consistent with recent modeling studies indicating that forest management is unimportant to long-term carbon dynamics relative to the effects of large-scale natural disturbances (e.g., drought, fire, pest outbreak). However, many data gaps still exist on total ecosystem carbon, particularly in regions other than North America, and in timber production forests and plantations.

Small mammal community maintains stability through compensatory dynamics after restoration of a ponderosa pine forest

Ecosystem stability has been of increasing interest in the past several decades as it helps predict the consequences of anthropogenic disturbances on ecosystems. Species may exhibit stability through compensation, with greatly fluctuating populations year to year but a consistent density response over time. Stability is increased when species with similar functional roles compensate for one another by responding differently to environmental change. In restoration projects, the objective is to restore stability by altering ecosystem composition, structure, and function to resemble natural (‘‘reference’’) conditions. We assessed the success of ecological restoration treatments by examining the structural and functional responses of the small mammal community before and after treatment, and compared to reference conditions. We used Royle density models to examine the responses of eight species of small mammals to restoration (thinning) treatments in ponderosa pine forests to determine if the community maintained total density, biomass, and function (represented by ectomycorrhizal fungi dispersion) after disturbance. Community composition differed in each of 6 years following treatment, but total density and biomass remained constant, suggesting the community is a stable prey base for predators. In addition, goldenmantled ground squirrels (Spermophilus lateralis) and gray-collared chipmunks (Tamias cinereicollis) appeared to play a similar role in dispersing ectomycorrhizal fungi across different forest structures. Both total species density and biomass were greater after thinning than in unthinned stands, and were similar to reference stands. These results suggest that although species composition changes from year to year after disturbance, restoration treatments can maintain ecosystem stability in terms of small mammal community-level properties.