Leaf and wood breakdown in cave streams

Cave streams lying near the surface are important ecotones connecting energ y sources from the terrestrial environment to deep groundwater. We examined leaf and wood breakdown and transport in 5 cave streams with, and 2 withou t, large openings that allow litter input from the surface. White oak (Quer cus alba) leaf breakdown rates in cave streams spanned the range of values reported for white oak leaves in surface streams. Leaf breakdown was faster in streams with leaf-shredding invertebrates, and leaf breakdown rates wer e positively correlated with shredder density in leaf packs. Wood breakdown rates were fast, partly a result of the wood veneer we used, and did not d iffer among streams. Microbial colonization of leaves and wood followed a p attern typical of surface streams: fungal biomass and microbial respiration peaked within 62 d and then declined on leaves, but biomass and respiratio n on wood gradually increased to a plateau. Coarse particulate organic matt er (CPOM) breakdown and microbial colonization in cave streams were not acc elerated by the absence of litter, unlike surface streams, apparently becau se nutrients were not limiting in cave streams. Nutrient levels were high i n all streams, so nutrient enrichment had little effect on microbial biomas s and respiration on wood in cave streams. Leaf and stick transport distanc es were short and, when combined with breakdown rates, suggest that CPOM is efficiently retained near its entry point.