九连山自然保护区土壤有机碳时空变异的耦合效应

Coupling effect of spatial-temporal variation in soil organic carbon in the Jiulianshan National Nature Reserve

土壤有机碳动态的研究有助于评估陆地生态系统的固碳增汇功能,但土壤有机碳随海拔和土层的空间变异与随发育时间的互作即空间与时间变异耦合效应少有报道,因而研究不同海拔梯度下各土壤层次有机碳的时空变异对评估亚热带森林生态系统的固碳效应有重要意义。以九连山主峰黄牛石不同海拔的典型森林、灌丛和草甸土壤剖面为对象,对比分析自然保护区设立初(1982年)至2015年间各土壤层次(0~10 cm,10~20 cm,20~40 cm)有机碳含量及碳储量的变化,探讨封山育林33 a后九连山有机碳变化及其影响因素。33 a前后有机碳含量和碳储量变化在0~40 cm土层内均随着海拔的升高而呈现线性增大的趋势,随海拔的升高,土壤有机碳含量和碳储量变化的累积速率随土层加深而逐渐增大,即20~40 cm土层的有机碳含量和碳储量变化累积速率最大;杜鹃林0~10 cm和10~20 cm土层的有机碳含量变化及0~10 cm土层的有机碳储量变化显著地高于人工林,高山草甸和杜鹃林20~40 cm土层的有机碳含量和碳储量变化显著高于其他植被类型,高山草甸20~40 cm土层的有机碳含量变化显著地高于0~10 cm。混合线性模型结果表明各土壤层次有机碳变化不受年份的显著影响,但均受到海拔的显著影响,植被类型对0~10 cm土壤有机碳的影响强于10~20 cm和20~40 cm。高海拔地区的杜鹃林、高山草甸的有机碳变化可能是导致各土壤层次有机碳33 a变异的主要原因。在全球气候变暖背景下,高海拔地区杜鹃林、高山草甸在33 a后由于温度上升导致其光合作用和生长速度提高,碳固定增加,因此气候变化和植被的生长过程可能对土壤有机碳的源汇动态产生显著影响。

Understanding the organic carbon dynamics of soil is helpful when assessing carbon sequestration and accumulation in terrestrial ecosystems;however,the coupling effect between the spatial and temporal variations in soil organic carbon across altitudes and the soil layers is rarely reported.Therefore,this study aims to evaluate the carbon sequestration of a subtropical forest ecosystem.Soil profiles were taken from forests,shrubs,and meadows at different altitudes on Huangniushi Mountain,the tallest peak in the Jiulianshan National Nature Reserve.In 1982,the surrounding hills were enclosed for natural afforestation.Therefore,the organic carbon content and storage among different soil layers(0-10 cm,10-20 cm,20-40 cm)were analyzed to explore the changes over time.In the entire soil range(0-40 cm),the organic carbon content and storage increased linearly with altitude.The organic carbon accumulation rate gradually increased with increasing altitude and soil depth(i.e.,the 20-40 cm layer had the fastest accumulation rate).Changes in the organic carbon content were significantly higher in the Rhododendron forests than in the artificial forests in the 0-10 cm and 10-20 cm soil layers,and the change in organic carbon storage between the Rhododendron forest and the artificial forests was significantly higher in the 0-10 cm soil layer.The greatest changes in organic carbon content and storage were observed between the alpine meadow and Rhododendron forest in the 20-40 cm soil layers,and the carbon storage change in the alpine meadow 20-40 cm soil layer was significantly higher than that in the 0-10 cm layer.The mixed linear model results showed that time did not influence the organic carbon changes in the soil layers,but altitude had a significant effect.Vegetation type also had a significant effect on the 0-10 cm soil layer.The organic carbon changes in the Rhododendron forest and the alpine meadow at high altitudes may be the reason for the overall changes in the soil layers.Despite global climate change,the Rhododendron forest and the alpine meadow at high altitudes have significantly improved their growth rates,photosynthesis,and carbon sequestration.Therefore,climate change and plant growth may have a significant impact on the source and sink dynamics of soil organic carbon.