John and Becky distributing leaf packets at Coweeta.
The Effects of Leaf Litter Species Diversity on Decomposition in a Riparian Zone in the Southern Appalachians
Ball, B.A., Kominoski, J.S., Hunter, M.D., Coleman, D.C., and Pringle, C.M.
Decomposition of organic material is a fundamental ecological process that has influences on nutrient cycling and energy flow and thus the structure and dynamics of terrestrial and aquatic ecosystems (Swift et al. 1979, Odum 1971). Both biotic and abiotic factors, including chemical composition of litter, temperature and moisture, and the activity of microbes and invertebrates, influence rates of decomposition and nutrient cycling (Aerts et al. 1997, Melillo et al. 1982, Seastedt 1984). As different leaf species have different decay rates, the temporal and spatial bioavailabilty of the nutrients and microhabitat provided are variable. It has often been debated that ecosystem processes, such as decomposition, may be a function of species diversity (Tilman et al. 1996, Wardle et al. 1997, Bardgett and Shine, 1999). Change in land use is a potential threat to diversity, and thus perhaps decomposition. The Southern Appalachian region is experiencing an increase in land-use change, due to population growth, urbanization, and abandonment of agriculture (Wear and Bolstad 1998). There is a need to understand the mechanisms by which species diversity affects decomposition in order to predict the possible effects of land-use change on this basic process. In this three-year study, decomposition over a gradient of species diversity (one to four dominant species of varying quality) will be analyzed in a riparian zone at Coweeta Hydrologic Laboratory. We will assess the effect of species diversity on chemical identity, soil fauna (microbial and invertebrate), and decay rate (k) on a temporal scale. I hypothesize that increased species diversity will increase decay rate, chemical identity, and soil fauna, though perhaps not additatively. It is important to remember that aquatic and terrestrial ecosystems are not two separate systems, as they are commonly studied, but interact with one another. To study the land-water interface, the same data will be gathered on the adjacent stream for comparison. We're using comparable aquatic and terrestrial methods to detect patterns in decomposition that may (or may not) be similar between the two systems.
SPECIES DIVERSITY AND LEAF LITTER DECOMPOSITION: THE INFLUENCES OF LAND-USE CHANGE
Kominoski, J.S., B.A. Ball, C.M. Pringle, M.D. Hunter, and D.C. Coleman. Institute of Ecology, University of Georgia, Athens, GA 30602
Abstract. Decomposition of organic material is a fundamental ecological process that influences nutrient cycling and energy flow in ecosystems. In forested streams, allochthonous organic matter is a primary food resource. In forested streams, allochthonous organic matter is a primary food resource. The structure and dynamics of these ecosystems are directly linked to the availability and quality of leaf litter inputs. Leaves with decreased lignin, lower tannin and phenolics, and higher C:N exhibit faster rates of decay and are more bioaccessible to consumers. Since different leaves have different decay rates, the temporal and spatial bioavailability of different leaf species as food sources to aquatic micro- and macroconsumers is variable. Changes in land-use are a potential threat to species diversity. This experiment will attempt to qualify and quantify the relationship between species diversity and leaf litter decomposition in order to predict the effects of land-use change of this process. A 183d study conducted at the Coweeta Hydrologic Laboratory will assess the effect of leaf litter species diversity on decay rate (k), chemical diversity, microbial biomass, and macroinvertebrate community composition in the stream-riparian interface. As a means of examining the land-water interface as one ecosystem, comparable methods will be used to detect patterns in decomposition between terrestrial and aquatic ecosystems. My hypotheses are: 1) leaf litter packs composed of a heterogeneous species mixture will support a higher diversity of fauna and may exhibit altered decomposition rates than packs composed of a single species, and 2) the impact of species diversity on litter processing will follow similar patterns in both ecosystems, but at different time scales.
John and Becky distributing leaf packets at Coweeta.
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