Zhong Qicheng et al. creator text xx Plant and Soil 2013 9999 monographic und

print

487-502 Background and Aims: The reclamation of natural salt marshes for agricultural use is expected to profoundly inf;uence the effects f predicted global warming on the carbon balance of coastal areas globally. This study was undertaken to understand the potential for soil respiration changes in a disturbed coastal ecosystem under future atmospheric warming.Methods:An in situ simulated warming experiment was conducted in a reclaimed salt marsh on Chongming Island in the Yangtze Estuary, China. Open-top chambers(OTCs) were applied to simulate air-warming conditions.Results: Based on the 2-year study, we found the following: (1) Averaged across the entire study period, the OTCs significantly increased the mean air temperature by 1.53+=0.17 degree celcius. (2) The air warming resulted in no significant stimulation of the mean soil rrespiration averaged across the entire study period. Warming had no significant effect on soil respiration in the growing season. (3) Air waming had no significant effect on the mean soil temperature or volumetric moisture at a 5 cmdepth, but it increased the mean soil porewater salinity by 119;averaged across the entire study period. (4) Air warming had no significant effect on total organic carbon, total nitrogn or the molar C/molar N ratio of the soil in the uppermost 10 cm layer during the 2 years of soil respiration measurement. The warming treatement also had no significant effect on aboveground biomass or fine root (2< mm) density during the second year of soil respiration measurement. (5) Soil temperature accounted for 81.0;and 79.0;of the temporal variations of soil respiration in the control(CON) and evevated temperature (ET) plots, respectively. No significant correlation between soil volumetric moisture and soil respiration was obseved in either CON or ET. Soil porewater salinity was positively correlated with soil respiration in CON, but such a positive correlation was not found in ET. No change of the temperature sensitivity of soil respiration (Q10 value) was obseved.Conclusions: Based on above results, we speculate that soil porewater salinity was the key factor controlling the effects of air warming on soil respiration in the reclaimed salt marsh. Our results suggest that an air warming of approximately 1.5 degree celcius over the next few decades may not lead to a higher soil respiration in reclaimed salt marshes. Carbon sinks Global warming Land reclamations Salt marshes Yangtze Estuary 220216