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 studie d 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) strea mside 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 dom inated the LC riparian zone whereas slow-processed leaf material was n early absent. In contrast, the PMR riparian assemblage was well-repres ented in each processing category. Leaf packs were processed, as loss of dry mass, in near-equal rates using either days or degree-days as a n 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 result s suggest that: (1) gathering-collectors (e.g., Polypedilum spp.) may compensate for the reduced abundance of shredding detritivores in proc essing of summer leaf detritus and (2) the absence of slow-processed r iparian foliage in small woodland streams (e.g., LC) may prevent the e stablishment of a spring-summer shredder fauna.