Rainfall driven transport of carbon and nitrogen along karst slopes and associative interaction characteristic

Transportation of carbon and nitrogen during rainfall events is highly important within karst ecosystems and has particular relevance to understand decoupling relation between carbon and nitrogen cycles. The ability of the karst ecosystem to sequester carbon is currently unknown but has potential to be an important residual terrestrial carbon sink. We hypothesis that the runoff response to rainfall events will vary according to whether the slope belongs to karst area, and carbon and nitrogen have imbalanced outputs response to runoff. Hence, a series of in-situ simulated rainfall experiments at three sites (two karst slopes with different carbonate matrixes and one non-karst slope without a carbonate matrix) were conducted in a typical karst zone in southwest China. We measured runoff discharge, and dissolved carbon and nitrogen during the experiments. The results show that the total runoff discharge increased positively with rainfall intensity, with the carbonate matrix making an important contribution to rainfall reallocation. The dissolved carbon loss from runoff plots is much higher than the dissolved nitrogen, with the dissolved C/N revealing the decoupling relation of carbon and nitrogen cycles in this critical karst zone. This initial carbon migrated by runoff at catchment scale is critical to carbon budgets in rivers. Furthermore, nitrogen leaching from the system is crucial as a nitrogen shortage at karst area in southwest China.