Soil Respiration in a Subtropical Mangrove Wetland in the Jiulong River Estuary, China

Abstract

The diurnal and seasonal variations of soil respiration (SR) were studied at a subtropical mangrove wetland in the Jiulong River Estuary from May 2010 to April 2011. SR rates were measured continuously from 08:00 to 06:00 local time (24-h time system) on July 8–9 and October 3–4, 2010; and January 15–16 and April 11–12, 2011. Similar patterns in the diurnal variation of SR were observed on October 2–3 and April 11–12, with the maximum values at 14:00 and the minimum at 00:00. However, the diurnal dynamics of SR on July 8–9, 2010 and January 15–16, 2011 showed different patterns, with the maximum values at 08:00–10:00 on above sampling dates and the minimum at 22:00 on July 8 and at 04:00 on January 16. The daily mean values of SR approximated to the values measured at 08:00. SR fluctuated with distinct seasonal patterns. The seasonal variation was characterized by a mono-peak pattern, with the highest rate (6.18 µmol CO2 m−2 s−1) in July and the lowest rate (0.36 µmol CO2 m−2 s−1) in December. The results showed that the variation of SR in mangrove wetland was mainly controlled by soil temperature, and there was no significant correlation between SR and soil water content. It also implied that the model of SR in mangrove wetland should not only consider the effect of soil temperature, but also incorporate other factors, such as water level, precipitation, microbial activity and photosynthesis, which also could affect SR.