PROCESSING AND MACROINVERTEBRATE COLONIZATION OF BLACK-CHERRY (PRUNUS-SEROTINA) LEAVES IN 2 STREAMS DIFFERING IN SUMMER BIOTA, THERMAL REGIME AND RIPARIAN VEGETATION

The processing of black cherry (Prunus serotina) leaf packs was studied during the summer of 1992 in two streams, Linesville Creek (LC) and Powdermill Run (PMR). The streams differed considerably in: (1) summer macroinvertebrate (shredder) fauna; (2) thermal regime, and (3) streamside riparian flora. Except for one species (Brillia flavifrons), LC lacked shredders, whereas PMR supported numerous shredder populations during the summer months. Fast- and medium-processed leaf material dominated the LC riparian zone whereas slow-processed leaf material was nearly absent. In contrast, the PMR riparian assemblage was well-represented in each processing category. Leaf packs were processed, as loss of dry mass, in near-equal rates using either days or degree-days as an independent variable. Gathering-collectors (e.g., Polypedilum spp.) and shredders (Tallaperla maria) dominated macroinvertebrate abundance and biomass colonizing the LC and PMR packs, respectively. Our results suggest that: (1) gathering-collectors (e.g., Polypedilum spp.) may compensate for the reduced abundance of shredding detritivores in processing of summer leaf detritus and (2) the absence of slow-processed riparian foliage in small woodland streams (e.g., LC) may prevent the establishment of a spring-summer shredder fauna.