We compared the export of aquatic invertebrates (drift), dissolved organic carbon (DOC) and fine particulate organic carbon (FPOC) from headwater streams directly affected by logging to that of control streams. Twenty-four high elevation (1055 m ? 1575 m) streams were selected for sampling in two study areas in the southern interior of BC. Streams were categorized into three treatment types: new clearcuts logged less than three years previous, old clearcuts logged three to five years previous, and controls. Discharge rates ranged from 0.064 to 16 L sec-1 and drift density ranged from 0.013 to 0.32 individuals L-1. The mean DOC and FPOC concentrations in new clearcut streams were elevated over control streams; however, the differences were not significant. Mean DOC and FPOC concentrations in old clearcuts were also not significantly different from those of new clearcut or control streams. Old and new clearcut streams had significantly higher biomass of true flies than controls (p=0.047, 0.028). Abundance of a common stonefly family, Nemouridae, was higher in control streams than in pooled clearcut streams (p=0.034). Proportions of the functional feeding groups shredders and collectors differed significantly between controls and pooled clearcut streams (0.040, 0.028). Control streams had an increased EPT/D index, calculated as sums of number of organisms, over new and old clearcut streams (p=0.009, 0.009). Other than these differences, there were no significant differences in densities of invertebrates, aquatic insects, or mayflies, stoneflies, caddis flies and true flies orders and families among and between treatments. These data suggest both logged and unlogged headwater streams support a considerable number of macro-invertebrates.
Brian A. Heise
Forest Investment Account (FIA). 2004. Effects of logging on export of organic matter from headwater streams. Forest Investment Account (FIA) - Forest Science Program. Forest Investment Account Report. FIA2004MR212