Utah State University Water Initiative – Spring Runoff Conference
One of the most critical goals in wetland restoration is to enhance or recover the multitude of ecosystem functions (ecosystem multifunctionality) rendered by wetlands. Previous research has not investigated the role of genetic diversity as a driver of multifunctionality in wetlands. In a mesocosm study, we evaluated how genotype richness in three native bulrush species (Schoenoplectus acutus, S. americanus, and Bolboschoenus maritimus) impacts multifunctionality, including resistance to invasion by the introduced lineage of the common reed, Phragmites australis. We evaluated genotype richness effects under two nutrient levels because nutrient conditions are known to greatly effect plant growth and nutrient enrichment can shift the competitive balance in favor of invasives. We performed a fully factorial, outdoor mesocosm experiment in which we manipulated genotypic richness (2,4,8 genotypes), nutrient enrichment (low, high), and seeding of competing Phragmites (no seeds, high density). We measured quantified traits of four functions with a variety of response variables: primary productivity (bulrush aboveground biomass production), invasion resistance (performance of invading Phragmites: cover and biomass), habitat provisioning (bulrush seed production), and C storage (soil bulk density and percent organic matter). We examined direct and indirect effects on multifunctionality including genotypic richness, nutrient enrichment, and seeding of competing Phragmites using structural equation modeling. Preliminary analysis indicates nutrients and the different bulrush species had a stronger effect on primary productivity, invasion resistance, habitat provisioning, and carbon storage than bulrush genotype richness. Based on these findings, we suggest that, depending on nutrient conditions. bulrush species selection may be as important as genotype richness levels in supporting these ecosystem functions.