Submitted to: Biological Invasions
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/24/2008
Publication Date: 9/3/2009
Citation: Holly, D.C., Ervin, G.N., Jackson, C.R., Diehl, S.V., Kirker, G.T. 2009. Effect of an Invasive Grass on Ambient Rates of Decomposition and Microbial Community Structure: A Search for Causality. Biological Invasions Volume 11, Issue 8 (2009), pg 1855. Interpretive Summary: Decomposition rates of above and below ground plant biomass of native (Andropogon glomeratus) and invasive (Imperata cylindrica) grass species were compared over a 12 month period. Below ground biomass of I. cylindirca always decomposed faster than A. glomeratus. A. glomeratus also decayed faster when placed within a stand of I. cylindrica. Microbial community analysis indicated that site invaded by I. cylindrica differed by both species composition and functional enzyme composition. The results support the growing consensus that invasion by I. cylindrica alters normal ecological processes and highlight a possible mechanism (alteration of microbial assemblages) by which I. cylindrica may alter rates of decay in invaded ecosystems.
Technical Abstract: In sutu decomposition of above and below ground plant biomass of the native grass species Andropogon glmoeratus (Walt.) B.S.P and exotic Imperata cylindrica (L.) Beauv. (cogongrass) was investigated using litter bags over the course of a 12 month period. The above and below ground biomass of the invasive I. cylindrica always decomposed faster than that of the native A. glomeratus. Also, below ground biomass of both species decomposed at a consistently faster rate when placed within an invaded area consisting of a monotypic stand of I. cylindrica as opposed to within a native plant stand assemblage. However, there was no similar such trend observed in the above ground plant material. The microbial communities associated with the invaded sites often differed from those found in the native vegetation and provide a causal mechanism by which to explain the observed differences in decomposition rates. The microbial communities differed not only compositionally, as indicated by ordination analyses, but also functionally with respect to enzymatic activity essential to the decay process. This study supports the grwoing concensus that invasive plant species alter normal ecological processes and highlights a possible mechanism (alteration of microbial assemblages) by which I. cylindrica may alter an ecosystem process (decomposition).