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Leaf litter density and decomposition in small man-made ponds
  • Kenneth Fortino,
  • Leanna Tacik
Kenneth Fortino
Longwood University
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Leanna Tacik
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Abstract

The input of terrestrial leaf litter into freshwater ecosystems supports aquatic food webs and fuels microbial metabolism. Although the role of leaf litter subsidies to streams have been studied extensively the effect of leaf litter on ecosystem function in lentic systems has received less attention. In particular the impact of leaf litter on trophic dynamics and biogeochemistry of small man-made ponds is virtually unknown, despite the fact that these systems are extremely common and likely represent a substantial modification to watersheds in the North America. We measured the areal density of leaf litter and the rate of leaf litter decomposition in small man–made ponds in central Virginia to determine the size of the leaf litter pool in these systems, the rate at which leaf litter is decomposed, and the extent to which pond characteristics alter leaf litter abundance or processing. We found that the areal density of leaf litter in the ponds ranged between 3.4 and 1179.0 g AFDM m-2. The areal density of leaf litter was significantly greater in the littoral zones, however leaf litter was present in the sediments throughout the pond. There was no relationship between the areal density of leaf litter in the sediments and the percent organic matter of the fine sediments, suggesting that leaf litter input is decoupled from bulk sediment organic matter. The decomposition rate of Liriodendron tulipifera leaves in coarse mesh leaf bags ranged between 0.0025 and 0.0035 d-1, which is among the slowest litter decomposition rates recorded in the literature for ponds and was unrelated to pond characteristics. Our results indicate that leaf litter is an abundant and persistent pool of organic matter in the sediments of small man–made ponds and it is likely to have a substantial effect on the trophic dynamics and biogeochemistry of these systems.