中国东部森林土壤有机碳组分的纬度格局及其影响因子

土壤有机碳是森林碳库的重要组成部分,其活性有机碳组分不仅是土壤碳周转过程的重要环节,还是气候变化最敏感的指标。以中国东部南北森林样带(NSTEC,North-South Transect of Eastern China)为对象,选择了9个典型森林生态系统(尖峰岭、鼎湖山、九连山、神农架、太岳山、东灵山、长白山、凉水和呼中),涵盖了我国热带森林、亚热带森林和温带森林的主要类型,测定其0—10 cm土壤有机碳(SOC)、易氧化有机碳(EOC)、微生物碳(MBC)和可溶性有机碳(DOC)含量,结合气候、土壤质地、土壤微生物和植被生物量等因素,探讨了森林土壤有机碳组分的纬度格局及其主要影响因素。实验结果表明:SOC、EOC、MBC和DOC含量分别为23.12—77.00 g/kg、4.62—17.24 g/kg、41.92—329.39 mg/kg和212.63—453.43 mg/kg。SOC、EOC和MBC随纬度增加呈指数增长(P0.05),而DOC则随纬度增加呈指数降低(P0.05)。在不同气候带上,SOC和EOC含量表现为热带森林亚热带森林温带森林(P0.05),DOC含量表现为热带森林亚热带森林温带森林(P0.001)。气候、植被生物量、土壤质地和土壤微生物可解释土壤有机碳组分纬度格局的大部分空间变异(SOC 74%;EOC 65%;MBC 51%和DOC 76%)。其中,气候是土壤有机碳组分呈现纬度格局的主要影响因素,土壤质地是SOC和EOC的次要影响因素,而土壤微生物和植被生物量是MBC和DOC的次要影响因素。

Latitudinal patterns and factors affecting different soil organic carbon fractions in the eastern forests of China

Soil organic carbon (SOC) is one of the most important pools in forest ecosystems. The labile fractions of the SOC pool play critical roles in the SOC turnover processes and are a sensitivity indicator of SOC responses to future climate change. In this study, nine typical forest ecosystems (Jiangfengling, Dinghushan, Jiulianshan, Shengnongjia, Taiyueshan, Donglingshan, Changbaishan, Liangshui, and Huzhong) were selected along the North-South Transect of Eastern China (NSTEC), and covered tropical, subtropical, and temperate climate zones. The SOC, easy-oxidized organic carbon (EOC), microbial biomass carbon (MBC), and dissolved organic carbon (DOC) contents were measured in the 0-10cm soil layer, and climate factors, soil texture, soil microbes, and vegetation biomass were used to explore the latitudinal pattern of SOC fractions in forests and the main factors influencing them. The results showed that the SOC, EOC, MBC, and DOC contents were 23.12-77.00 g/kg, 4.62-17.24 g/kg, 41.92-329.39 mg/kg, and 212.63-453.43 mg/kg, respectively. SOC, EOC, and MBC increased exponentially as the latitude increased (P < 0.05), whereas DOC decreased exponentially as the latitude increased (P < 0.05). The SOC and EOC contents in forest soils were in the following order: tropical forest < subtropical forest < temperate forest (P < 0.05), and the order for DOC content was tropical forest > subtropical forest > temperate forest (P < 0.001). The results of the structural equation modeling showed that climate, soil texture, soil microbe, and vegetation biomass significantly affected the spatial variations in SOC fractions, and they can explain 74%, 65%, 51%, and 76% of the variation in SOC, ECO, MBC, and DOC, respectively. Furthermore, the latitudinal patterns for the SOC fractions were mainly controlled by climate, with soil texture as the sub-dominant factor for SOC and EOC, and soil microbe and vegetation biomass as the sub-dominant factors for MBC and DOC, respectively.