CONTRIBUTIONS OF ABOVEGROUND LITTER, BELOWGROUND LITTER, AND ROOT RESPIRATION TO TOTAL SOIL RESPIRATION IN A TEMPERATURE MIXED HARDWOOD FOREST

Estimating contributions by root respiration and root litter to total soil respiration is difficult owing to problems in measuring each component separately. In a mixed hardwood forest in Massachusetts, we added or removed aboveground litter and terminated live root activity through construction of trenches and root barriers to determine the contribution of aboveground litter, belowground litter, and root respiration to total soil respiration. Annual soil respiration at control plots, measured by the soda-lime technique, was 371 g C - m-2. year-1. We used aboveground litter inputs (1 38 g C - m-2. year-1) and differences in carbon dioxide effluxes among treatment plots to calculate contributions to total soil respiration by live root respiration (33%) and by organic matter derived from aboveground (37%) and belowground (30%) litter. Newly deposited aboveground litter contributed 31% of the carbon dioxide emitted by total aboveground litter. This estimate is consistent with values published in litter decomposition studies. Nearly two thirds of soil respiration in this forest can be attributed to root activity, comparable with a previous study suggesting that live root respiration plus decomposition of root litter contributes 70-80% of total soil respiration across a wide range of forests.