Effects of precipitation exclusion and warming on soil soluble carbon and nitrogen in a young Cunninghamia lanceolata plantation

Abstract

Soil soluble carbon and nitrogen play important roles in soil carbon and nutrient cycles and are highly sensitive to climate change, as they can be directly used by microorganisms. We used Tension Lysimeter to collect soil solution in 50% precipitation exclusion (P) and warming (5 ℃) plus 50% precipitation exclusion (WP) treatments in a 2 year-old Cunninghamia lanceolata plantation in subtropics, to examine the effects of precipitation and temperature on soil soluble carbon and nitrogen concentrations in soil profile. Results showed that neither P treatment nor WP treatment changed seasonal dynamics of soil dissolved organic carbon (DOC) concentration, with maximum value at October among all treatments. DOC concentration was increased in both P and WP treatments in the whole soil profile, especially in 60 cm soil depth. Compared with the control, DOC concentration was increased by 30.4%-88.7% and 32.8%-137.6% in P and WP treatments, respectively, with the most obvious difference being found in October. DOC concentration was decreased with the increases of soil depth in the control, but no significant difference among different soil layers were found in P and WP treatments. NO3--N concentration was increased by 221.1%-931.0% in WP treatment. Therefore, precipitation reduction might increase losses of C and N from soil solution in subtropical forest, due to improvement of soil permeability by the increases of fine roots grown into deep soil, which might stimulate soil microorganism activities and soil organic matter decomposition. Furthermore, warming would exacerbate the risk of C and N losses.