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Extension of the effects of logging on export of organic matter from headwater streams
Heise, Brian A.
This proposed project is an extension of an ongoing FSP funded program which is currently researching the effects of logging on export of organic matter from headwater streams. To date there is no information in interior BC that quantifies how the export of organic matter is being affected by logging activities. Recent research has looked at the effects of clear-cut logging on aquatic invertebrates at various locations in BC and the Pacific Northwest (ex., Price et al. 2003, Hernandez et al. 2005); however, what remains poorly understood is the ecological connectivity from small, headwater streams to larger, downstream systems (Gomi et al. 2002). The input and flow of organic matter in a stream ecosystem provides the primary source of energy for stream food webs. Small, headwater streams are subjected to high inputs of organic matter due to their close association with riparian vegetation and surrounding soils (Vannote et al. 1980). As a result, headwater streams can function as important exporters of nutrients and energy and are thus intimately connected to downstream reaches (Gomi et al. 2002, Wipfli 2004). Fine particulate organic matter (FPOM) and dissolved organic carbon (DOC) are two highly mobile components of organic matter that are transported downstream and play both direct and indirect roles in the detrital food web (Suberkropp 1998). The movement (or drift) of aquatic invertebrates in headwater streams can provide both a source of colonization and a direct food source for resident fish in downstream reaches. This relationship was demonstrated most recently by Wipfli and Gregovich (2002) in southeastern Alaska. Their results indicated that forested headwater streams provided a year-round source of organic matter and invertebrates to downstream habitats. In order to protect the integrity of larger order fish-bearing reaches, the effects of land-use practices on the export of these variables must be better understood. In 2005-2006, we applied a BACI (Before, After, Control and Impact) design to determine the effects of clear-cut logging under current riparian management guidelines on the export of organic matter in high elevation headwater streams in the BC interior. During pre-harvest conditions in 2005, drifting aquatic invertebrates, FPOM and DOC were measured from 21 streams (9 control and 12 treatment) in the Cariboo forest region. In summer 2006, after logging took place, data was again collected from all but 3 treatment streams. Due to the pine beetle epidemic, unpredictable changes in logging plans resulted in the delayed harvesting of 3 of our study streams. In addition, modifications to the original design greatly improved the study but substantially increased processing time in the laboratory. As a result, this proposed extension will request funding to 1) complete processing of additional spring and fall samples that were collected in 2006, 2) collect 24 hour drift, FPOM and DOC data from 3 post-impact streams that were not logged by the summer of 2006, plus 3 matching control streams to monitor environmental variability 3) Provide a second year of post-impact DOC data from all 21 streams and 4) provide additional extension of project results. REFERENCES CITED: Gomi, T., R.C. Sidle, and J.S. Richardson. 2002. Understanding Processes and Downstream Linkages of Headwater Systems. Bioscience 52(10): 905-916. Hernandez, O., R.W. Merritt, and M.S. Wipfli. 2005. Benthic invertebrate community structure is influenced by forest succession after clearcut logging in southeastern Alaska. Hydrobiologia 533: 45-59. Price, K., A. Suski, J. McGarvie, B. Beasley, J.S. Richardson. 2003. Communities of aquatic insects of old-growth and clearcut coastal headwater streams of varying flow persistence. Canadian Journal of Forest Research. 33: 1416-1432. Suberkropp, K.F. 1998. Microorganisms and organic matter decomposition. In River ecology and management. Eds. R.J. Naiman and R.E. Bilby. Springer Verlag, New York. Vannot ...
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