Monday, August 4, 2008

PS 5-79: Cross-site comparison of nutrient budgets in hardwood and conifer stands on contrasting soils

Ruth D. Yanai1, James B. Shanley2, Scott W. Bailey3, Timothy J. Fahey4, Thomas G. Siccama5, Richard A. Hallett3, Robert B. Smith3, and Byung Bae Park6. (1) SUNY-ESF, (2) USGS, (3) US Forest Service, (4) Cornell University, (5) Yale, (6) Korea Forest Research Institute

Background/Question/Methods

In the northeastern US, both hardwood and conifer forests have developed on sites with contrasting parent materials, allowing us to examine the effect of site and forest type on ecosystem nutrient cycling. We measured soil chemistry, above and belowground biomass and production, and litterfall and throughfall fluxes in four northern hardwood and three conifer stands differing in soil acidity at Sleepers River, VT; Hubbard Brook, NH; and Cone Pond, NH.

Results/Conclusions Hardwood stands had greater aboveground biomass and nutrient storage (P = 0.03) and higher nutrient turnover in leaf litter and fine roots (P < 0.01) than the conifer stands, on average. Fine root production was clearly higher in sites with higher base cation status (P = 0.02), due to higher root turnover. Aboveground production, in contrast, was not related to soil acidity. Tissue concentrations of Ca, Mg, and K were sensitive to the gradient in soil base cation availability, while N and P were not. Throughfall and litterfall fluxes of Ca, Mg, and K varied several-fold across the gradient and were positively correlated, though not significantly, to soil base status. Differences among sites in species composition may explain some of the variation. For N and P there was no relation, but litterfall N had a significant inverse correlation (P = 0.03) to soil C:N.