PARENT SESSION
Poster Session # 14: Forest Ecology.

Wednesday, August 6 Presentation from 5:00 PM to 6:30 PM. SITCC Exhibit Hall B.

Nutrient and fine root heterogeneity in forested wetlands with contrasting hydrologic regimes.

Neatrour, Matthew^{*,1, 2}, Jones, Robert¹, Golladay, Stephen², ¹ Department of Biology, Blacksburg, VA² Joseph W. Jones Ecological Research Center, Newton, GA

ABSTRACT- Nutrient heterogeneity and fine root distribution are related in upland forests of southeastern United States. However, it is not clear whether these relationships exist in forested wetlands where lack of oxygen can limit fine root growth. We used a combination of univariate, multivariate, and geostatistical techniques to investigate how nutrient heterogeneity affects fine root distribution in three types of forested wetlands: floodplain swamps, river swamp sloughs, and depressional swamps. Floodplain swamps and river swamp sloughs are alluvial ecosystems and receive nutrient subsidies from streams during flood pulses. Depressional wetlands, in contrast, are hydrologically isolated from streams and receive most of their nutrients via precipitation. We measured standing fine root biomass and nutrient availability (N-NO₃, N-NH₄, and P-PO₄) in one representative site of each wetland type and predicted that fine root biomass would be more strongly related to nutrient availability in alluvial swamps. Fine root biomass was not related to nutrient availability at any of the sites. Multiple regression analyses showed that nutrient availability explained little of the variation in fine root biomass. In addition, fine root variability, as indicated by the coefficient of variation (CV), was relatively low at all of sites (33-50%) and did not match nutrient CV (53-209%). Semivariograms showed that fine root biomass and nutrient availability were spatially autocorrelated. These data suggest that fine root biomass and nutrients are patchily distributed in these forested wetlands; however, fine root biomass and nutrients are not congruent.

Key words: heterogeneity, fine root, wetland