藏东南色季拉山西坡土壤有机碳库研究

Soil organic carbon pool at the western side of the sygera mountains,southeast Tibet,China

土壤碳是森林生态系统最大的碳库,是其碳循环的极其重要组分。土壤微生物生物量是陆地生态系统碳循环的重要组成部分。为探讨不同森林植被类型对土壤活性有机碳库的影响,以西藏色季拉山(西坡)的高山灌丛(Alpine shrub,AS)、杜鹃林(Rhododendron forest,RF)、急尖长苞冷杉林(Abies georgei var.smithii forest,AGSF)和林芝云杉林(Picea likiangensis var.linzhiensis forest,PLLF)为试验对象,研究了林地土壤有机碳、总氮含量及微生物生物量。结果表明:高海拔植被类型具有较高的土壤活性有机碳含量和分配比例。土壤总有机碳表现在0—10cm均差异显著;在10—20cm和20—40cm无规律性(P<0.05)。土壤全氮表现在0—10cm AS均差异显著,而RF、AGSF和PLLF差异不显著;在10—20cm AS、RF、AGSF与PLLF均相差显著;在20—40cm AS、RF、AGSF与PLLF均相差不显著(P<0.05)。土壤微生物量碳含量与土壤总有机碳含量关系密切,呈显著的正相关。土壤微生物生物量氮含量和比例随微生物生物量碳含量和比例增加而增加。色季拉山土壤微生物量碳含量均随海拔升高而增加。在不同植被类型的生态系统中,土壤总有机碳含量、土壤颗粒有机碳和土壤易氧化碳含量均呈现出随土层深度增加而递减的变化趋势。土壤颗粒有机碳含量占土壤总有机碳含量和土壤易氧化有机碳含量占土壤总有机碳含量的比率范围不同,且随土层深度增加比率减小。土壤活性有机碳与土壤总有机碳显著相关,土壤易氧化有机碳与颗粒有机碳的相关系也比较显著(P<0.05)。

AS a key component of ecosystem carbon budgets, soil carbon is the largest carbon pool of forest ecosystem. Soil microbial biomass carbon is an important component of carbon cycle of the terrestrial ecosystem. In order to explore the effects of different forest types on soil active carbon pool, we chosed Alpine Shrub AS, Rhododendron Forest RF, Abies georgei var. smithii forest AGSF and Picea likiangensis var. linzhiensis forest PLLF as experimental sites in the Sygera Mountainous southeast Tibet. Soil organic carbon SOC, total nitrogen TN and soil microbial biomass were studied at different soil horizon. There is higher LOC （labile organic carbon）at higher-elevation vegetation types in comparison with lower-elevation ones. At 0--10cm soil layer, SOC among the AS, RF, AGST and PLLF were significantly different P〈 0. 05. However, no trend was found for SOC at 10--20cm and 20--40cm. At the AS site, TN were significantly different at 0--10cm soil layer P〈0. 05. There were no significant difference for the AS, RF, AGST and PLLF sites P〈0. 05. At 10--20cm soil layer, there were significant difference for them（ P〈0. 05）. However, no regularity was found for SOC at20-40cm. At different depths, the soil microbial biomass was significantly correlated to soil organic carbon. The SMBC and SMBN was positively correlated with SOC, and the SMBN or its ratio was also positively correlated with the SMBC content and its ratio. The SMBC and SMBN increase with increasing elevationt in the Sygera Mountains. As shown, the total SOC, readily oxidizable carbon and particulate organic carbon decreased with increasing soil horizons. The rations of particulate organic carbon to total SOC content and the readily oxidizable carbon to total SOC content were different in their range. Moreover, their ratios decreased with increasing soil horizons. The active SOC was significantly related to total SOC. In addition, the relationship between readily oxidizable carbon and particulate organic carbon was also significant P〈0.05.