Atmospheric nitrate deposition and enhanced dissolved organic carbon leaching: Test of a potential mechanism

Atmospheric NO3- deposition has the potential to disrupt litter decomposition in temperate forests by suppressing enzymes responsible for lignin degradation. A reduction in phenol oxidase activity could potentially trigger an increase in soluble phenolic compounds, which in turn are known to decrease the activity of cellulolytic enzymes like beta-glucosidase. Our study investigated whether the inhibition of lignin degradation by experimental NO3- deposition could increase soluble phenolics in soil, suppress beta-glucosidase activity, and potentially explain a greater export of dissolved organic C (DOC) from northern hardwood ecosystems. We found no evidence that the suppression of phenol oxidase by NO3- additions increased soluble phenolics in mineral soil, nor did we rind a strong inverse relationship between soluble phenolics and beta-glucosidase activity. It appears that reductions in mineral soil lignolytic activity induced by experimental deposition are not responsible for greater DOC export from soil.