Examining historical and current mixed-severity fire regimes in ponderosa pine and mixed-conifer forests of western North America.

There is widespread concern that fire exclusion has led to an unprecedented threat of uncharacteristically severe fires in ponderosa pine (Pinus ponderosa Dougl. ex. Laws) and mixed-conifer forests of western North America. These extensive montane forests are considered to be adapted to a low/moderate-severity fire regime that maintained stands of relatively old trees. However, there is increasing recognition from landscape-scale assessments that, prior to any significant effects of fire exclusion, fires and forest structure were more variable in these forests. Biota in these forests are also dependent on the resources made available by higher-severity fire. A better understanding of historical fire regimes in the ponderosa pine and mixed-conifer forests of western North America is therefore needed to define reference conditions and help maintain characteristic ecological diversity of these systems. We compiled landscape-scale evidence of historical fire severity patterns in the ponderosa pine and mixed-conifer forests from published literature sources and stand ages available from the Forest Inventory and Analysis program in the USA. The consensus from this evidence is that the traditional reference conditions of low-severity fire regimes are inaccurate for most forests of western North America. Instead, most forests appear to have been characterized by mixed-severity fire that included ecologically significant amounts of weather-driven, high-severity fire. Diverse forests in different stages of succession, with a high proportion in relatively young stages, occurred prior to fire exclusion. Over the past century, successional diversity created by fire decreased. Our findings suggest that ecological management goals that incorporate successional diversity created by fire may support characteristic biodiversity, whereas current attempts to "restore" forests to open, low-severity fire conditions may not align with historical reference conditions in most ponderosa pine and mixed-conifer forests of western North America.

Influence of Diversionary Food on Red Squirrel Populations and Damage to Crop Trees in Young Lodgepole Pine Forest.

This study was designed to test the hypothesis that large-scale provision of diversionary food (sunflower seeds) would reduce red squirrel (Tamiasciurus hudsonicus) feeding damage to lodgepole pine (Pinus contorta) crop trees. Study areas with managed lodgepole pine stands were located near Vernon and Quesnel in south-central British Columbia, Canada. Large-scale applications of sunflower seeds were conducted on a manual basis in 1989, and by manual and aerial means in 1990, and an operational level by aerial means in 1991. Feeding damage to crop trees was assessed in control and treatment blocks. Populations of the red squirrel, northwestern chipmunk (Eutamias amoenus), and Columbian ground squirrel (Spermophilus columbianus) were sampled intensively by live-trapping on control and treatment blocks in 1990. Manual application of seed (clumped distribution) significantly reduced damage in the treatment block (11.3% of trees damaged) compared with the control (57.5% of trees damaged). Aerial application of seed (uniform distribution) also significantly reduced damage in replicated treatment vs. control blocks. Provision of diversionary food resulted in a temporary increase in the overall number of red squirrels caught on the treatment areas followed by a return to control levels within 6 wk. This increase was primarily the result of an increased number of transients in the trapped sample. The population density of resident (transients excluded) red squirrels did not increase when diversionary food was added. Similarly, we could not detect differences in reproduction, body masses, or survival of squirrels between control and food-supplemented areas. Northwestern chipmunks and Columbian ground squirrels also showed a temporary increase in density when food was added. Application of sunflower seed on an operational basis significantly reduced damage by squirrels in replicated study areas covering three different forest ecological zones. Provision of diversionary food is an effective strategy to protect intensively managed stands of lodgepole pine from red squirrel feeding damage.