SREL Reprint #1841





Interspecific leaf interactions during decomposition in aquatic and floodplain ecosystems


Savannah River Ecology Laboratory, University of Georgia, Drawer E, Aiken, South Carolina 29802 USA

Abstract. An experiment was designed to test the importance of the potential interaction (inhibition or enhancement) between slow and fast decaying leaf species on processing rates in a stream and its floodplain. The decomposition of water oak (Quercus nigra) and sweetgum (Liquidambar styraciflua) in single-species packs was compared with water oak plus sweetgum in mixed-species packs within three habitats (stream snags, floodplain pools, and elevated floodplain surfaces) at three sites in coastal plain streams. Fast-decaying sweetgum leaves did not enhance the rate of oak decomposition. Sweetgum leaves in mixed packs decomposed more slowly than single species packs in seven out of nine comparisons. Increases in bacterial density on leaves were depressed in mixed species packs relative to single-species sweetgum packs. Fungal hyphae could not be observed in mixed or single-species packs. The effect of oak leaves on sweetgum leaves was affected by frequency and period of inundation. Macroinvertebrate shredders were rare or absent from most leaf packs collected from stream snags and floodplain pools. Over 40% of leaf packs placed in the stream contained no shredders, while another 28% contained <0.001 g shredders/g leaf dry weight. Therefore, shredders were too rare to influence overall leaf processing rates. These studies suggest that microbial processing accounts for most leaf decomposition and oak leaf leachate is shown to be inhibitory to microbial processing of sweetgum leaves.

Key words: decomposition, inhibitory compounds, bacteria, shredders, flood frequency

SREL Reprint #1841

McArthur, J.V., J.M. Aho, R.B. Rader, and G.L. Mills. 1994. Interspecific leaf interactions during decomposition in aquatic and floodplain ecosystems. Journal of the North American Benthological Society 13:57-67.

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