HR: 1330h
AN: NB33I-07    [Abstracts]
TI: Influence of Initial Leaf Pack Size on Estimates of Breakdown Rates in Streams
AU: * McTammany, M E
EM: mmctamma@bucknell.edu
AF: Bucknell University, Biology Department, Lewisburg, PA 17837 United States
AU: Gallo, T M
EM: tgallo@bucknell.edu
AF: Bucknell University, Biology Department, Lewisburg, PA 17837 United States
AB: Experiments to determine the influence of leaf pack size on estimates of breakdown rates were conducted in Stony Run, a moderately hardwater stream in central Pennsylvania draining mature second-growth forest. We deployed 5-mm mesh bags containing different initial amounts (2, 5, 10, 20, and 50 g) of white oak leaves at 3 sites in Stony Run during October 2004. Bags have been retrieved monthly and were processed to determine ash-free dry mass remaining and abundance of shredder-detritivores in the bags. Breakdown rates varied from 0.018 d^-1 in 50 g bags to 0.015 d^-1 in 2 g bags and were strongly correlated with initial weight of leaf litter (log₁₀ initial leaf mass vs. breakdown rate r = 0.99). Total invertebrate abundance was initially higher in heavier leaf bags, and proportion of shredders increased as leaf mass declined throughout the study. Shredder abundance was positively correlated with leaf pack size (r = 0.76) and breakdown rate (r = 0.82), which indicates that shredders were more important in determining breakdown rates than mechanical fragmentation or microbial activity. These results suggest that models of stream organic matter dynamics should incorporate distribution of natural leaf packs and higher breakdown rates associated with densely packed leaves.
DE: 4239 Limnology
DE: 4804 Benthic processes/benthos
DE: 4806 Carbon cycling
DE: 4815 Ecosystems, structure and dynamics
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly