Spring Phenology of Aquatic Emergence and Terrestrial Insect Activity in the H.J. Andrews Experimental Forest, Oregon, USA

We have been studying emerging aquatic and flying terrestrial insect activity as part of a cross-taxa phenology study at the H.J. Andrews Experimental Forest since 2009.  Our goals are to understand how climate variation influences springtime phenology and to better anticipate taxa specific and food web responses to changing climate. We are particularly interested to what extent phenological events may be staggered or coherent within and across taxa in mountainous terrain with complex topography and patchy microclimates. At 6 headwater streams with different thermal regimes (related to elevation, riparian cover and groundwater input), emerging aquatic insects responded more consistently to accumulation of degree days than did terrestrial insects collected in associated riparian and upslope habitats. In each year, total aquatic insect emergence rates in cooler streams lagged behind those in warmer streams; similar patterns were observed for selected ubiquitous aquatic species. Although we experienced unusual weather during the first 3 years of sampling, we found greater differences in timing of onset of activity among sites within a year than between years for individual sites. These phenological responses of insects are now being evaluated in context of plant development and songbird activity.