PARENT SESSION
Oral Session #40: Biodiversity and Ecosystem Function: Do species and species richness matter?. Presiding: R. Dirzo.
Wednesday, August 8, 2001. 8:00 AM to 12:00 PM. Madison Ballroom D.
Partitioning the interactive effects of species assemblage, site, and substrate on cation leaching in a complete factorial experiment using lysimeter mesocosms.
DECKER, KELLY1, WANG, DEANE1, DEHAYES, DONALD1, HUGHES, JEFFREY1, 1
ABSTRACT- Knowledge of abiotic-biotic interactive effects on ecosystem processes is fundamental to our understanding of ecosystems. However, the complexity of natural ecosystems makes it difficult to understand the nature of such interactions. To understand this complexity, we have designed and implemented a replicated 2x2x4 factorial experiment using mesocosms situated in two different Vermont sites, filled with two substrates, and planted with four tree seedling communities with the intention of determining main and interactive effects of site, substrate, and plant community upon soil cation leaching. Leachate has been collected from the mesocosms periodically since 1994 and analyzed for Ca, Mg and K. After two years of seedling growth and soil development, we found that interactions had significant effects on cation leaching. The cumulative interaction effects comprised 7.2 % of the total variation in solution Ca, as opposed to 46.3% and 47.6% for Mg and K, respectively. For Mg, the interaction component of variation was largely due to site x substrate interactions, whereas for K the three-way interaction comprised most of the variation attributable to interaction. For both Mg and K, some of the significant interactions involved factors that had no significant effect when taken out of context and analyzed as 'main effects'. We suggest that taking an approach that focuses upon main effects and relegates interactions into an overarching 'error' term can result in loss of information regarding controls of ecosystem processes.
KEY WORDS: cation leaching, experimental ecosystems, abiotic-biotic interaction, plant assemblages