桂林新寨花岗岩地区4种植被下土壤有机碳分解速率研究

【目的】研究花岗岩地区不同植被下土壤有机碳分解速率特征，为土壤碳汇效应提供科学依据。【方法】通过室内土壤培养法，选择桂林新寨花岗岩地区林地、旱地、果园和灌丛4种植被下0～20、20～40和40～60 cm三个深度的土壤，测定土壤有机碳在25℃和70%田间持水量条件下培养100 d分解释放的CO2-C含量。【结果】4种植被下土壤有机碳分解速率总体上随着土层加深而递减，分解速率在前期比较快，后期缓慢，最后达到平衡；累积释放的CO2-C含量均是0～20 cm〉20～40 cm〉40～60 cm。土壤有机碳分解释放的CO2-C占各自总有机碳的比值以旱地最高，达3.34%～4.84%，其次为林地和果园，分别为1.82%～2.88%和1.91%～2.16%，最低的是灌丛，为1.77%～1.98%。4种植被下土壤有机碳库与土壤全氮、有机质、脲酶呈显著正相关，灌丛的活性碳平均周转时间最长，旱地的缓效性碳平均周转时间最短。【结论】林地、果园和灌丛有机碳库所含难分解物相对较多，土壤有机碳相对较稳定，具有碳汇效应。

Decomposition rates of soil organic carbon under four kinds of vegetations in granite area of Xinzhai Village in Guilin, China

【Objective】The characteristics of decomposition rates of soil organic carbon under different vegetations in granite area were studied to provide scientific references for soil carbon sequestration effect. 【Method】Through indoor soil culture, the 0-20, 20-40 and 40-60 cm soil layer of 4 types of vegetations （woodland,dry land,orchards and shrubs） were chosen in Xinzhai Village of Guilin. Cultured for 100 days at 25℃ under the conditions of 70% water content in field, the content of CO2-C released from the soil organic carbon was determined. 【Result】The decomposition rates of soil organic carbon under 4 types of vegetations generally descended with the increase of soil layer depth, more specifically, the decomposition rates was initially faster, slower later, and finally leveled. The sequence of accumulative content of CO2-C released in soil layer was 0-20 cm〉20-40 cm〉40-60 cm. Regarding the proportion of CO2-C released by soil organic carbon decomposition to their total organic carbon,the highest ratio was the dry land,up to 3.34%-4.84%,followed by the woodland （1.82%-2.88%） and the orchard （1.91%-2.16%）. The lowest was the shrub （1.77%-1.98%）. The soil organic carbon of 4 types of vegetation was significantly positively correlated to total nitrogen,organic matter content,and soil urease activity. Concerning the average turnaround time of activated carbon,the longest one was the shrub,and for the average turnaround time of slow carbon,the slowest one was the dry land. 【Conclusion】Since the soil organic carbon pools of the orchard,shrub and woodland relatively contain more components difficult to decompose,and soil organic carbon under the three kinds of vegetations is relatively stable with effect of carbon sinks.