Soil respiration dynamics in Cinnamomum camphora forest and a nearby Liquidambar formosana forest in Subtropical China

Abstract

Climate change can significantly affect carbon cycling of forest ecosystems. The diurnal and seasonal dynamics of soil respiration (R s) in Cinnamomum camphora and Liquidambar formosana forests were investigated by using infrared gas exchange analyzer of Li-Cor 6400-09 each month in 2006. Soil temperature and moisture were also measured. Diurnal variations in R s varied with daily soil temperature in the two forests. Across the growing season, soil respiration peaked on July 28 due to higher soil temperature and moisture conditions. Seasonal R s variations were predominantly influenced by soil temperature. Seasonal soil respirations in C. camphora and L. formosana forests were strongly related to soil temperature (x) at 5-cm depth (R s = 0.1598e0.1377x (R 2 = 0.9289, P = 0.001) and R s = 0.2177e0.0962x (R 2 = 0.927, P = 0.000)), while annual mean R s rate was 2.614 and 1.397 μmol m−2 s−1 and Q 10 values was 3.96 and 2.62 for the two forests, respectively. However, R s was not influenced by seasonal changes in soil moisture (w) in the two forests in 2006. We developed two equations (R s = −0.020w 2+0.497w+0.562 (R 2 = 0.109, P > 0.05), R s = −0.001w 2+0.072w+0.731(R 2 = 0.053, P > 0.05)) to describe the relationship between R s and soil moisture. A positive relationship between R s and soil moisture were observed when soil moisture was below 12.43% and 18.00%, but when soil moisture exceeded threshold values of 12.43% and 18.00%, soil moisture became the restraint factor for R s. Long-term observations of soil respiration and moisture are required to understand the temporal dynamics of soil respiration.