Persistence of tree cavities used by cavity‐nesting vertebrates declines in harvested forests

Abstract

Abstract An abundant supply of cavity‐bearing trees is important for maintaining wildlife communities in harvested forests. During harvesting, suitable trees and cavities are directly removed, and the longevity of cavities in retained trees may be reduced by increased exposure to wind and other disturbance factors. We examined patterns of cavity survival in retained trembling aspen ( Populus tremuloides ) trees in harvested stands compared with those in unharvested mature stands by monitoring the persistence of individual cavities. We followed 930 cavities in 3 harvest treatments for up to 17 years in pre‐cut and uncut forest, and up to 13 years post‐harvest (reserve patches and dispersed retention), in temperate‐mixed forests of interior British Columbia, Canada. Average annual cavity loss rates were 5.6% in pre‐cut and uncut forest, 7.2% for cavities in trees retained in reserves, and 8.1% for cavities in retained trees dispersed throughout cuts. Correspondingly, median cavity longevity was 15 years for cavities in pre‐cut and uncut forest, 10 years for cavities retained in reserves, and 9 years for those in dispersed retention. Risk of loss increased most for cavities in living trees (factor of 2.17), but we found no detectable difference for cavities in recently dead trees and trees with advanced decay. We suggest retention of a range of aspen size and decay classes to allow for future cavity‐tree recruitment in harvested stands. Inclusion of wildlife reserves as part of an overall forest management plan will also help to mitigate the effects of windthrow and maintain long‐lived cavity resources required by a large portion of forest wildlife. © 2013 The Wildlife Society