Effect of defoliation on patterns of carbon exudation from Agrostis capillaris

Grassland ecosystems are important global sinks and sources of atmospheric carbon (C). In this study, we used an in-situ 13CO2 tracer approach to quantify differences in short-term C exudation from defoliated and non-defoliated Agrostis capillaris (L.) plants subjected to natural diurnal light and temperature regimes and rainfall events. Results showed: 1. There was no significant difference in overall carbon exudation from the plants as a result of defoliation; 2. defoliation significantly increased exudation of recent photosynthate (i.e., 13C labeled); 3. there was a distinct and statistically significant diurnal trend in C exudation with root C exudation increasing during the day and early evening and decreasing during the night and early morning. The importance of light/temperature and defoliation as drivers of patterns of root C exudation and the contribution of recent assimilate C to atmosphere-plant-soil carbon flow are discussed.