Vegetation control on soil organic matter dynamics

Soil organic matter (SOM) formation is one of the least understood steps of the global carbon cycle. An example is uncertainty around the role of plan t communities in regulating SOM formation and turnover. Here we took advant age of the highly controlled conditions at the San Dimas lysimeter installa tion to quantify the influence of oak and pine vegetation on SOM dynamics. SOM turnover rates, estimated using total C and C-14 content of litter and physically separable soil fractions, were faster under oak than under pine. In contrast to the rapid turnover for the oak litter (<2 years), the delay in litter incorporation into the mineral soil under pine was a controlling factor of SOM fluxes. (C) 2001 Published by Elsevier Science Ltd.