Wuyishan Different Altitudes Dynamics Of Soil Respiration

Soil respiration is an important process of soil ecosystem, is the primary pathway through which the element carbon enters into the atmosphere from terrestrial ecosystem and is a key CO₂ source of atmosphere. It is a complex process controlled by biotic and abiotic factors. Like many other soil processes, soil respiration varies strongly with time and space. In order to examine the temporal and spatial variation of soil respiration and its main regulating factors, so as to indicate the response of soil carbon of different elevation gradients to global warming, we measured soil respiration rate, and determined its regulating factors including soil temperature, soil water content, contents of soil organic carbon, soil total nitrogen, soil total sulfur, soil microbe biomass, and fine root biomass along elevation gradients monthly in Wuyi Mountain from April, 2005 to March, 2006. Two treatments (Litter removal and Control) with three repeated plots in each type of vegetation were set up, respectively, totally 24 plots. As follows, we found that:1. Soil respiration decreased along elevation gradients. The annual mean soil respiration rate of EBF (Evergreen Broadleaf Forest), CF(Coniferous Forest, CF), DF(Dwarf Forest), AM(Alpine Meadow) were 3.85, 2.70, 1.90, 2.40μmolCO₂·m^-2·s^-1 in T-treatment and 4.17, 3.19, 1.94, 2.29μmolCO₂·m^-2·s^-1 in C-treatment respectively. There were no significantly different between DF and AM in both treatments.2. By multi-variable regression analysis, we found that annual mean soil temperature could explain 99.79% spatial variation of soil respiration.3. The diurnal variation of soil respiration was significant. Soil respiration peaked 2-4 hours later than air temperature and reached to a minimum at around 2am. However, the result was different in DF in March, 2006.4. Seasonal variation of soil respiration in EBF,CF,DF,AM was significant with maximum in Summer, late July or early August, 6.57, 5.49, 3.13, 5.09μmolCO₂·m^-2·s^-1 in C-treatment and 5.88,5.26,3.10,4.68μmolCO₂·m^-2·s^-1 in T-treatment, respectively, and minimum in Winter, late December or early January 1.04, 0.76, 0.33, 0.30μmolCO₂·m^-2·s^-1 and 1.15,0.68,0.31,0.27μmolCO₂·m^-2·s^-1 in T-treatment respectively.5. Soil temperature, soil water content, litterfall were relation to the seasonal variation of soil respiration, however, soil temperature was the most important regulating factors. In C-treatment, soil temperature at 5cm depth could explain 70-96% of soil respiration, at 10cm depth, 75-97% and at 15cm depth, 78-96%. In T-treatment, soil temperature at 5cm depth could explain 84-97% of soil respiration, at 10cm depth, 82-96% and at 15cm depth, 79-95%.6. Q10 values increased along elevation gradients excluding CF. Q10 values to soil temperature at 5, 10, 15cm of AM, 4.02, 4.40, 4.95 and 3.85,4.16,4.64, were larger than that of EBF, CF, DF in C and T treatments respectively (2.15, 2.36, 2.49 and 2.27, 2.43, 2.53;3.34, 3.65, 3.90 and 3.53, 3.82, 4.08;2.46, 2.65, 2.85 and 3.30, 3.56, 3.83).Our results indicate that soil respiration shows significantly temporal and spatial variation , and soil temperature was the leading factor which regulated temporal and spatial variation of soil respiration. Soil respiration in high elevation soil was more sensitive to the temperature, which suggests that in the future global warming scene, soils in high elevation might release more CO₂ to atmosphere, and furthermore, cause stronger impaction on global climate change.