An exceptionally powerful storm struck southwestern Washington in December 2007 causing large debris flows in two adjacent streams. The two affected streams had been studied prior to the storm, providing a rare opportunity to examine ecosystem recovery. We monitored the streams and their riparian zones for six years after the disturbances to determine whether recovery rates of biota, physical habitat, and water temperature differed, and if so, what factors affected resilience. Along both streams, the debris flows removed wide swaths of soil, rock, and coniferous riparian forests, widening the active channel and increasing solar exposure and summer water temperatures. Initially depauperate of vegetation, after four years red alder trees dominated the riparian plant communities. The warmer water, greater solar radiation, and unstable substrates likely contributed to variable benthic insect and tailed frog tadpole densities over time, although benthic insect communities became more similar after three years. The debris flows also decreased channel slopes and removed channel step barriers such that cutthroat trout were able to rapidly occupy habitats far upstream, but sculpins were slower to recolonize and both fish species exhibited some differences in recovery between the two streams. Crayfish were severely impacted by the debris flows; this may be due to attributes of their life history and the timing of the flows. Overall, we found that recolonizing aquatic species exhibited varying levels of resilience and recovery after the disturbances being related to the influence of physical habitat conditions, species dispersal ability, and the presence of nearby source populations.
Millipedes are a diverse and ancient group of poorly known terrestrial organisms. While recent advances in their taxonomy and distribution have occurred in some areas of the world, our knowledge about the distribution and ecology of many taxa in the Pacific Northwest is limited. We review the ecology of taxa we observed and present results from a field study relating millipede abundance and community composition to environmental conditions of geology, vegetation, and climate. Millipedes of southwest Washington State were surveyed in the spring and fall of 2005 and 2006 along twelve headwater streams in forested landscapes. Overall, we observed 10 families of millipedes, with confirmed identification of 15 species. Millipede community composition differed strongly between seasons and across sites. For each season, we report family-specific multiple regressions relating millipede abundance/presence to environmental conditions. Given the ecological importance of millipedes as detritivores, more information on taxonomy and environmental relationships is needed. This research provides insight into the patterns and distribution of riparian-associated millipedes in the Pacific Northwest.
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