Study On The Spatial-temporal Variation Of Soil Respiration In A Subalpine Meadow

With the global climate warming, global carbon cycle has caused the common concerns of biological sciences, earth sciences and social sciences. It had become one of major theme of science programs of the World Climate Research Programme, International Geosphere-Biosphere Programme, DIVERSITAS and the human factor of global environmental change plan (IHDP) and the other projects. Although soil respiration has played an important role in the carbon cycle, its regularity has not been thoroughly understood to the present. Therefore, it is necessary to study the temporal and spatial variability in soil respiration and its influencing factors on soil respiration. It not only would be important for accurately estimating the global carbon budget, but also for developing strategies to cope with global warming problems.Subalpine meadow ecosystem is unique biogeochemical processes and extremely sensitive to the changes of environment and climate. A small change in temperature and humidity can cause the great changes of CO2 efflux in subalpine meadow, and of these changes, in turn, can affect the environment and climate. However, the research on soil respiration in the alpine meadow was resported by a few papers. Furthermore, the reseach on spatial and temporal variability of soil respiration in alpine meadow ecosystem and the roles of environmental factors played on carbon cycle in the system has been rarely reported. Thus, in 2008 and 2009, soil respirations were measured in Shanxi Luliang Pangquangou National Nature Reserve of Yunding Mountain subalpine meadow, and the purpose of the study is to study the characteristics of soil respiration in time and space and the relationship of the seasoanal changes in soil respiration and the envionmantaal factors, such as soil temperature, soil moisture and soil organic carbon. The main results were as follows: (1) Soil respiration of the subalpine meadow showed that there were distinct seasonal variations over the season, but no significant change between years. Soil temperature controled the seasonal variation of soil respiration, and an exponential model better reflects the relationship between soil temperature and soil respiration, but at the low temperatures the model fitted even more better. Annual soil respiration was significantly correlated between years, showing that soil respiration in 2008 and 2009 by the common environmental factors.(2) Soil respiration and soil temperature at 10 cm depth fit the model best and its correlation coefficients were greater than those at 5 cm and 15 cm depth. The soil temperature at 10 cm depth could explain 99% and 77% of variation of the soil respiration, respectively, for 2008 and 2009. The Q10 and R10 values were different from diffrent soil temperature measurement depths, and showed an increase with soil depth increase. The Q10 and R10 values in the two years was also diffrent, the values of Q10 and R10 in 2008 were greater than those in 2009.(3) The relationship of the soil respiration and soil water in the subalpine meadow was not significant, showing that soil water in the alpine meadow was not the limiting factor on soil respiration, but that the effect of extreme drought on soil respiration is very significant. After eliminating the impact of temperature, the correlation coefficien of the fitted eqations of soil respiration and soil moisture increased. It was clear that soil temperature to some extents overshadowed the effect of soil moisture on soil respiration.(4) Soil respiration varied not only in time but also in space. The traditional statistical analysis showed that spatial variation of soil respiration in this area was moderate, and that soil respiration and organic carbon was most correlated. This showed that alpine meadow soil organic carbon on the spatial distribution of soil respiration played a major role. When semivariance analysis of geostatistics was used, the results showed the semivariograms of soil respiration rate could well be described by a linear model. Soil respiration showed moderate spatial autocorrelation, indicating that spatial heterogeneities of soil respiration were resulted mainly by structural factors. The range in soil respiration is 53.15 m, explainning the factors affecting soil respiration within the scale of work in 53.15 m. The isoline map of soil respiration rates produced with the Kriging interpolation method showed that there was moderate spatial heterogeneity of soil respiration which was mainly caused by the differences in soil organic carbon.