不同区段金沙江下游山地失稳性坡面土壤有机碳含量特征

Characteristics of soil organic carbon content in different sections of the unstable slopes of the mountainous area in the lower reaches of the Jinsha River

为探讨不同区段金沙江下游山地失稳性坡面土壤有机碳(soil organic carbon,SOC)含量特征,选择典型流域内温带湿润山岭区、亚热带和暖温带半湿润区和亚热带干热河谷区为研究对象,在各气候区失稳性坡面的不同区段(稳定区、失稳区、堆积区)设置样地,测定不同区段0-20 cm SOC含量,并结合中国科学院东川泥石流观测研究站多年的气象资料,分析气候、区段因素与SOC含量的相关性.结果显示:(1)金沙江下游山地失稳性坡面SOC含量与年均温、夏季均温、冬季均温均存在显著负相关关系(P<0.05),与年降水量、夏季降水量存在显著正相关关系(P<0.05);温带湿润山岭区水热条件良好,整体上各区段SOC含量均高于亚热带和暖温带半湿润区、亚热带干热河谷区;(2)温带湿润山岭区与亚热带干热河谷区SOC含量整体上随着区段稳定程度的降低而下降,呈现稳定区>失稳区>堆积区的变化趋势;(3)金沙江下游山地失稳性坡面SOC含量还受到坡向的影响,具体表现为温带湿润山岭区和亚热带干热河谷区各区段SOC含量均呈现出"阴坡">"阳坡"的变化趋势;(4)气候与区段的交互作用显著影响SOC含量,具体表现为查菁沟阳坡堆积区的SOC含量显著低于温带湿润山岭区与亚热带和暖温带半湿润区(P<0.05).本研究表明气候与区段共同对金沙江下游山地失稳性坡面SOC含量产生影响,且人类活动的干扰作用也不可忽视,具体表现为人类干扰频繁的亚热带和暖温带半湿润区稳定区SOC含量显著低于亚热带干热河谷区(P<0.05),且3个区段SOC含量差异不显著(P>0.05).以上结论可为研究该区域失稳性坡面土壤碳演变规律提供数据支撑和理论参考,同时为生态脆弱区的生态恢复规划提供相应的理论依据.(图2表4参43)

To explore the characteristics of soil organic carbon(SOC) content in different sections of the unstable slopes of a mountainous area in the lower reaches of the Jinsha River, we selected the temperate humid mountain ridge region, subtropical and warm temperate sub-humid region, and subtropical dry-hot valley region as the research areas. Then we divided a stable area, an unstable area, and an accumulation area from the unstable slope of each climatic region as the sample plots. We determined the SOC content of 0-20 cm depth of the different parts of the unstable slope and collected meteorological data from the Dongchuan Debris Flow Observation and Research Station of the Chinese Academy of Sciences to analyze the relationships between climate types, section factors, and SOC content. The results showed that:(1) SOC content in the unstable slope of the lower reaches in the Jinsha River was significantly negatively correlated with average annual temperature, average summer temperature, and average winter temperature(P < 0.05), and significantly positively correlated with the annual precipitation and summer precipitation(P < 0.05). The temperate humid mountain ridge region had better hydrothermal conditions, and, as a whole, the SOC content of each slope was higher than that in the subtropical and warm temperate sub-humid region, and the subtropical dry-hot valley region.(2) The SOC storage decreased with slope stability in the temperate humid mountain ridge and subtropical dry-hot valley regions, following the rule of stable area > unstable area > accumulation area.(3) The SOC content in the unstable slopes of the lower reaches in the Jinsha River was also affected by slope direction, following the rule of "shady slope" > "sunny slope" in temperate humid mountain ridge and subtropical dry-hot valley regions.(4) The interaction between climate types and slope section significantly affected SOC content, indicating that the SOC content of the accumulation area in the Chajing gully sunny slope was significantly lower than in the temperate humid mountain ridge and subtropical and warm temperate sub-humid regions(P < 0.05). The study showed that the climate and slope sections worked together on SOC content in the lower reaches of the Jinsha River. However, human activities cannot be ignored because the SOC content of the stable area in the subtropical and warm temperate sub-humid region with intense human disturbance was significantly lower than in the subtropical dry-hot valley region(P < 0.05), and SOC content was not significant across three slope sections(P > 0.05). Our results can provide data support and theoretical references for soil carbon evolution in unstable slopes and a theoretical basis for ecological restoration planning in ecologically vulnerable areas.