Respirations and Response in Temperature of Salt Marsh Soil in Different Types of Wetlands Along the Coast of Yancheng

Soil respiration rates (SRR) of the salt marsh soils in the wetlands under different types of vegetation, i.e. Phragmites australis (PHS), Spartina alterniflora (SPS) and Suaeda salsa (SUS) along the coast of Yancheng were determined separately in the field and soil samples collected for laboratory incubation and measurement of respiration rates at specific temperatures, and further for analyses of soil responses to changing temperature in respiration. Results show that:(1) during the experiment period, the salt marsh soils were sources of CO₂. The mean SRR under PHS, SPS and SUS was 323.67, 499.51 and 150.41 mg·m^-2·h^-1, respectively. The SRRs followed a seasonal rhythm of summer > spring > autumn. (2) In the field experiments it was found that SSR peaked at times when the soil temperature reached 28, 22 and 20℃ in the soil under PHS, SPS and SUS, respectively. In the laboratory incubation experiment, it was found that SRR was significantly and positively related to soil temperature (P<0.05), and the three types of soils displayed an order of PHS (2.19)>SUS (2.15)>SPS (1.58) in sensitivity of SRR responding to changing environmental temperature (Q₁₀ value). (3) During the experiment period, cumulated field SRR was estimated at 3 400 g·m^-2·a^-1 in SPS, 2 330 g·m^-2·a^-1 in PHS and 1 082 g·m^-2·a^-1 in SUS, and followed a seasonal rhythm of summer > spring > autumn.