|Forest Investment Account|
|Abstract of FIA Project Y051049|
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Green tree retention: a tool to maintain ecosystem health and function
|Author(s): Grayston, Sue J.||Imprint: Vancouver, B.C. : University of British Columbia, 2005||Subject: Forest Investment Account (FIA), Silvicultural Systems, British Columbia, Experiments, Soil Fertility, Soil Management||Series: Forest Investment Account (FIA) - Forest Science Program|
This project is assessing the potential of green tree retention as a management tool to maintain soil health and functioning and site productivity after harvesting. This project brings together a unique multi-disciplinary group of researchers to apply a range of novel techniques to quantify changes in soil microbial and faunal diversity and function in response to harvesting. The research is using the existing STEMS 2 installation at Elk Bay, Vancouver Island, for the study. STEMS is a large, multi-disciplinary field experiment that compares the ecological, biological and socio-economic effects of seven silvicultural systems including clear-cut, uncut, group selection, patch cuts, dispersed retention and aggregated retention and is an exceptional resource for this purpose in that it allows us to examine the same soils pre- and post-harvest. We will use 4 sizes of aggregated retention patches (5m, 10m, 20m and 40m diameter) in our study. Our investigations will determine how soil communities change, whether key species are lost, and if retention of green trees of different aggregate sizes and density ameliorate modifications of these communities. Changes in rates of soil processes will be concurrently measured to determine if the observed alterations in soil communities have serious consequences for soil functioning. This year we have sampled the STEMS 2 site pre-harvest for baseline information on soil microbial and faunal community diversity and activity. We sampled what will be the center of each retention patch and at the edge of each patch and then 30 m out from what will be the retention patch edge into the clear-cut. Microbial diversity and activity has been characterized by phenotypic and molecular methods and function determined using biochemical analyses. DNA was extracted from forest floor and mineral soil and the bacterial and fungal community profiled through PCR-DGGE analysis of ribosomal RNA genes (rDNA). Primers for genes characteristic of specific functional groups (e.g. NH4 oxidizers, N2 fixers, denitrifiers) were used to assess diversity of functional genes in the samples by T-RFLP. Microbial activity and catabolic diversity were assessed using basal and substrate induced respiration using a variety of C sources. To assess ectomycorrhizal fungal community structure, surveys of basidiomycete fruiting bodies were conducted on site. Soil macro, meso and microfauna were extracted from the soil and have been identified to species or morphospecies. Nutrient availability in the field has been determined close to each sampling point using ion-exchange membranes (PRS probes) for both anions and cations. The composition of the ectomycorrhizal mushroom community was typical of western hemlock or Douglas-fir dominated second growth forest in north coastal North America. Analysis of the bacterial and fungal diversity in the soils is on-going, preliminary analysis has shown that samples contained approximately 5-15 unique bands. The three most abundant groups of soil fauna were the Nematoda , the Acari and the Collembola, whilst the larger elements of the fauna (earthworms, millipedes, centipedes, beetles) were relatively lacking in abundance and diversity at the site. There were no underlying pre-harvest differences in soil nutrient availability, microbial activity, total mite or collembolan densities that could confound our proposed post-harvest analyses of the effects of patch size and distance from patch centre on the abundance of these groups. Likewise, for soil nutrient availability, microbial activity, collembola and mite densities, there were no significant differences between future Green Tree Retention Area (TU7) and either the control (TU3) or future clearcut area (TU2).
Updated May 30, 2006
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