Temporal dynamics of large woody debris in the Foothills of Alberta

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In Alberta, the current management strategy protects riparian forests from disturbance to reduce risk of adversely affecting streams and aquatic ecosystems. However, riparian zones are not immune to natural disturbance, some of which may be vitally important to maintain stream function. For example, the recruitment and retention of logs in riparian zones alters stream geomorphology and hydrology resulting in critical habitat for invertebrates and fish. This study, a collaboration of the Tree-Ring Lab at the University of British Columbia (UBC), Foothills Model Forest (FMF), Hinton Wood Products (West Fraser) and ANC Timber Ltd. (Alberta Newsprint Company (ANC)), will quantify recruitment and decay rates and residence times of large woody debris (LWD) in pine- and spruce-dominated riparian forests, surrounding small first order streams in the upper and lower foothills sub-regions of western Alberta. Three interconnected projects will use multiple lines of evidence to quantify the dynamics of LWD, as follows. (1) Tree-ring analyses will determine the time since death of logs in various stage of decay and in forests of different ages. These results will be used to calculate rates LWD recruitment and develop predictive models of LWD persistence and rates of decay. (2) Tree-ring analysis of snags and logs in permanent sample plots in upland forests will quantify decay processes for terrestrial coarse woody debris. We will use this information to determine the rate of decay and rate of outer ring erosion in order to improve the accuracy of age estimates of LWD. (3) We will develop models to test for differences in decay rates and processes between upland and riparian woody debris. The outcome of this research will have value to both theoretical ecology and applied forest management in the foothills of Alberta and other montane and boreal forests. We will work with the Foothills Model Forest to develop tools for ensure that new knowledge gained from this research is effectively integrated into forest management practices and policy.