1. The effects of leaf litter species diversity on decomposition in a forested watershed Becky A. Ball, Mark A. Bradford, David C. Coleman, Mark D. Hunter, John S. Kominoski, Catherine M. Pringle Institute of Ecology, University of Georgia, Athens, GA 30602 Introduction: There is currently much debate about the effect of species diversity on ecosystem functions, and many theories exist about the relationship between the two. For decomposition, no clear patterns have emerged (see Hättenschwiler et al. 2005, Gartner and Cardon 2004), though an idiosyncratic relationship is commonly found. Such results likely arise due to the way in which diversity is defined. Species diversity can be defined by species richness (the number of species involved) and composition (the identity of species involved). Composition can be further defined as having additive effects (where a mixture reflects the average of the species involved) and non-additive effects (where mixture behaves differently than would be expected by the average). In order to separate richness and composition when researching species diversity, a full factorial design is necessary. This project utilizes a full factorial design to determine the effects of leaf litter species diversity on decomposition and nutrient cycling in a forested riparian zone in the southern Appalachians. Questions: 1.Is there a significant effect of species richness on decomposition? 2.Is there an effect of species composition on decomposition? If so, is it additive or non-additive? 3.What does this tell us about nutrient cycling? Methods: Site: Lower Ball Creek, Coweeta Hydrologic Lab, Otto, NC Leaf Species: Liriodendron tulipifera (L), Acer rubrum(A), Quercus prinus (Q), Rhododendron maximum(R) L LALAQ LAQR A LQ LAR Q LR LQR R AQ AQR AR QR Litterbag method to study decomposition over 3 years Assays: AFDM (k rate) C:N:P Phenolics -Total phenolics -Condensed tannins -Hydrolysable tannins Acknowledgements: NSF Award #0218001 Coweeta LTER Institute of Ecology Graduate Students and undergraduate work-study students Institute of Ecology Analytical Lab Dr. Keller Suberkropp, University of Alabama Lower Ball Creek, November 2003 J. Kominoski Results: Decay rate: Mass loss: Chemistry: Discussion: Mass Loss No significant effect of richness on mass loss No significant non-additive effect of composition on mass loss There are additive interactions based on the presence or absence of certain species Chemistry No significant effect of richness on chemical properties of litter It is composition for which we see significant effects, being non- additive for the nutrients N and P. Implications There are possible effects of litter diversity (through composition) on nutrient movement, both additively and non-additively. Species identity has a significant impact in this forested system. Fiber -Cellulose -Hemicellulose -Lignin Fauna -Bacteria (DAPI) -Fungi (Ergosterol) -Nematodes -Arthropods Literature Cited: Hättenschwiler et al. 2005. Ann. Rev. Ecol, Evol and Syst. 36:191-218. Gartner and Cardon. 2004. Oikos 104:230-246. P = 0.61 Composition P = 0.00 Composition * time P = 0.46 Richness P = 0.31 Richness * time P = 0.97 Richness P = 0.41 Composition P = 0.00 Richness P = 0.73 Composition P = 0.04 Full factorial ANOVA explores effect of composition and richness independent of the presence/absence of each species Richness P = 0.61 Composition P = 0.98