| 其他摘要 | Terrestrial ecosystem constitutes one important carbon sink and source to the atmosphere. Its responses and feedbacks to global change are focuses of global change research. Soil carbon budget is of predominance in terrestrial carbon budget, making itself one important part of global carbon cycle. Net GHG emissions are influenced by land use, soil tillage management and external environmental change, which also change the global GHGes’ budget. Karstic ecological systems are the important components of the Earth’s surface system, playing important roles in the regional carbon cycle and balance. It is important to study soil GHG fluxes’ response to or impact on global change under different land use in karst area. It is the scientific base of adaptabilities and optimization of ecosystems in karst area. Biochar is one carbon-rich, stable solid product, which is pyrolyzed in oxygen-deficient environment. As one soil conditioner and carbon sequestrator, biochar can sequestrate C, decrease GHG emissions and improve soil fertility, attracting extensive attentions worldwide. The interaction mechanism between biochar and soil is still unclear so far and biochar’s effect on GHG emissions is lack of universality. Accordingly, it is one urgent task to perform the study in different soils, with different kinds of biochar and at different addition levels, which can help the evaluation of biochar on soils, environment and crops, provide reference for the practical widespread application. Taking three different land use types, namely, rotated upland field, shrub forest and peddy-upland rotation field in Kaiyang country of Guizhou province as our study object, we used static enclosed chamber coupled with GC to observe the soil CO2, CH4 and N2O fluxes’ seasonal changes for one year. The main results are as follows: 1. Different land use types affected greenhouse gas fluxes evidently. The CO2 fluxes of rotated upland field, shrub forest and paddy-upland rotation field were 271.09, 342.98, and 546.92mg CO2?m-2?h-1, respectively. And the order of soil respiration intensity was: paddy-upland rotation field >shrub forest > rotated upland field. The CH4 flux of rotated upland field, shrub forest and paddy-upland rotation field were－36.86、－103.22 and 70.77μg CH4?m-2?h-1, respectively. Paddy-upland rotation field mainly acted as a source of atmospheric CH4 during the rice growing period, and a sink of atmospheric CH4 during the whole vegetable growing season. The N2O fluxes of rotated upland field, shrub forest and paddy-upland rotation were 24.53, 4.33 and 18.71 mg N2O?m-2?h-1, respectively. The N2O flux varied with land use changes; the order of soil N2O flux was: rotated upland field > paddy-upland rotation field > shrub forest. The GWP varied with land use change and the order was paddy-upland rotation field > shrub forest > rotated upland field. Comparing to forest land of other areas of China, soil CH4 flux of shrub forest in study area exhibited distinct zonal features was in a higher range. CH4 flux from peddy-upland rotation field soil was obviously lower than results of other regions, mainly caused by zonal variations of water management, soil, fertilization and climatic factors, etc. 2. There were significant positive correlations between upland field soil CO2 flux and temperature in both diurnal changes and seasonal fluctuations. The seasonal CO2 flux fluctuations from upland field were positively exponentially correlated to atmospheric temperature and soil temperature significantly, indicating that temperature was the potent driving factor. The relationship between CO2 flux and soil water content was not statistically significant, but the soil water content and temperature took effect on soil respiration in a synergetic way. The traditional ploughing could promote the CO2 emission and decomposition of soil organic matter in short period. The CO2 flux was positively correlated with soil pH significantly, which meant that increased pH in a certain range could promote the activity of bacteria and therefore increase the soil. |
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