Snags (standing dead trees) are an important habitat component for wildlife in the Sierra Nevada, especially for cavity-using birds and mammals. We estimate that about 31 percent of the bird species, and about 32 percent of the mammal species, that live in the forests of the Sierra Nevada use snags for nesting or denning, foraging, roosting, communication, or perching. Size (diameter and height), tree species, age (time standing since tree death) and condition, and location (exposure, microclimate, and surrounding habitat) are major factors that contribute to the relative value of individual snags to wildlife. The abundance of cavity-nesting birds, in particular, largely depends upon the abundance of suitable snags. Successful management and conservation of snag-using wildlife depend upon maintenance or a sufficient number (unknown at present) of large diameter snags (greater than 15 inches DBH) per acre on a continuing basis. Providing for snag recruitment will be a particular challenge because increased demand for fuel and fiber has led to increased salvage efforts, improved technology for commercial utilization of dead wood, and increased cutting or snags for fuel wood, as other energy sources become more expensive. Improved mill technology allows harvest of smaller trees, which is leading to shorter rotation periods. Short rotations reduce the potential for replacement or large snags unless particular trees or stands are designated and left to grow beyond the normal rotation age. We urge that snags, especially large ones, be retained for wildlife. To provide replacement of snags as they decay and fall, we recommend leaving and/or killing cull trees in coordination with other forest management practices. Unmerchantable trees, damaged or diseased trees, genetically inferior trees, and some seed and shelter wood over-story trees can be left for snags, or killed for snags. In heavily harvested areas a few merchantable trees can be left when needed. Retaining scattered patches of mature forest will provide snags and produce additional wildlife and other forest benefits.
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