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 13 CO 2 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., 13 C 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.