Soil disturbance and elemental dynamics in a Northern Hardwood forest soil, USA

Abstract

Loss of soil nutrients due to disturbance may serve as an index of the homeostasis of biogeochemical cycling and ecosystem stability. Soil and the surrounding root system were disturbed during the installation of Soil Containment Systems (SCSs) in the hill slope at the Bear Brook Watershed in Maine (BBWM). The SCSs were constructed from high density PVC pipe (24 cm i.d. and 30 cm height) implanted at field. Leachate cations and anions, soil organic matter and exchangeable cations were analyzed. Leachate NO3− was higher by an order of magnitude compared to undisturbed soils from the same research site and other hardwood forest soils in the northeast U.S. The concentrations of cations in the leachate from SCSs were also higher and loss of NO3− was positively correlated with the loss of most cations. Calcium was the dominant cation representing 55% of the base cation composition of soil leachate. Monthly losses of Ca2+, Mg2+ and K+ were 1.8, 1.6 and 1.2% of total exchangeable pools, respectively. Disturbance of the BBWM soil ecosystem caused high rates of NO3− leaching which markedly changed the soil biogeochemistry. These results and other supporting data from watershed mass balances and experimental chemical additions suggest that BBWM may be N saturated.