Soil respiration dynamics in typical tidal flat wetlands of Hangzhou Bay, China

Abstract

Coastal wetlands are important carbon pools around the world, and soil respiration is a key process that releases carbon into the atmosphere. In this study, the soil respiration rates of different wetland vegetation zones (Phragmites australis, Spartina alterniflora, Scirpus mariqueter, and a bare mudflat) were investigated in Hangzhou Bay over 12 consecutive months. The wetland soil respiration rate was high in the daytime and low in the nighttime in summer, similar to the diurnal dynamics of soil temperature, and formed an obvious unimodal curve. The seasonal dynamics of soil respiration also formed a unimodal curve: summer > autumn > spring > winter; the soil respiration rates of the vegetation zones were in the rank of P. australis > S. alterniflora > S. mariqueter > bare mudflat, under all diurnal and seasonal conditions. The soil respiration rate had no significant correlation with soil water content but did have a significant exponential correlation with air and soil temperatures. The correlation between the soil temperature and respiration rate in P. australis, S. alterniflora, and bare mudflat was greater than that between the air temperature and respiration rate, while thatin S. mariqueter was quite different. Calculations showed that the Q10 value, a temperature-sensitive coefficient of soil respiration, was 2.59 ± 0.58 in the study area, and was greater in bare mudflat than in soil with vegetation. Soil CO2 emissions in P. australis, S. alterniflora, S. mariqueter, and bare mudflat were 6483.40, 5228.96, 2295.48, and 975.48 gm–2 yr–1 respectively.