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 comp onent separately. In a mixed hardwood forest in Massachusetts, we adde d or removed aboveground litter and terminated live root activity thro ugh construction of trenches and root barriers to determine the contri bution 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 use d aboveground litter inputs (1 38 g C - m-2. year-1) and differences i n carbon dioxide effluxes among treatment plots to calculate contribut ions to total soil respiration by live root respiration (33%) and by o rganic matter derived from aboveground (37%) and belowground (30%) lit ter. Newly deposited aboveground litter contributed 31% of the carbon dioxide emitted by total aboveground litter. This estimate is consiste nt with values published in litter decomposition studies. Nearly two t hirds of soil respiration in this forest can be attributed to root act ivity, comparable with a previous study suggesting that live root resp iration plus decomposition of root litter contributes 70-80% of total soil respiration across a wide range of forests.