Nutrient fluxes in litterfall and decomposition in four forests along a gradient of soil fertility in southern Ohio

Abstract

To determine how soil nutrient availability influences nutrient cycling, fluxes of nutrients through litterfall and decomposition were determined for four forest stands similar in all respects except soil nutrient availability and microclimate, within Neotoma Valley, a small watershed in southern Ohio, U.S.A. Litterfall varied from 10 to 60% among sites while nutrient concentrations and masses in new leaf litter varied as a function of extractable soil nutrient levels. Mass loss from litterbags was significantly higher in more fertile sites. Stepwise regression indicated that initial litter nitrogen and phosphorus concentrations were strongly correlated with relative decomposition rate while lignin concentration and microclimate variables were only correlated weakly. Thus, both litterfall nutrient transfers and decomposition rates were under the control of soil nutrient levels. Nitrogen was immobilized in litter at all sites during the 1st year of decay; litter from more fertile sites mineralized nitrogen during the 2nd year, while that from less fertile sites continued to immobilize nitrogen. Phosphorus and calcium mineralization rates were strongly correlated with the availability of these elements in the soil. Magnesium and potassium were leached rapidly from litter; amounts mineralized were correlated with amounts in litterfall. Interrelations among soil fertility, litterfall, and nutrient mineralization, as well as litter redistribution, are discussed as processes important in the development and maintenance of the soil fertility gradient in this watershed.