青藏高原样带高寒生态系统土壤有机碳分布及其影响因子

Distribution characteristics and influencing factors of soil organic carbon in alpine ecosystems on Tibetan Plateau transect

沿青藏公路，以跨越山地荒漠、高寒草甸-草原和山地灌丛-针叶林等地带的样带为研究区域，在23个样点采集土样分析土壤有机碳（SOC）分布及其影响因子．结果表明，在样带水平方向，不同植被下整个剖面的SOC含量从高到低依次是森林〉灌丛〉草甸〉草原〉荒漠；在垂直方向上，森林、灌丛和草甸植被0～10cm土层SOC含量、草原植被20cm以上土层SOC含量皆显著高于其下各层，荒漠植被各土层SOC含量分布均一．灰色关联度分析表明；降水是影响样带内SOC分布的主导气候因子，随样带内水热条件的改善，降水对SOC分布的影响逐渐降低；降水和土壤粘粒对表层SOC分布的影响较大，土壤粉粒和砂粒对底层SOC分布影响明显．土壤容重和pH对SOC沿剖面分布的影响逐渐降低；植被生物量是影响不同植被下SOC分布的重要生物因子．

The undisturbed regions along the Qinghai-Tibet road crossing the natural zones of montane desert, alpine meadow-steppe, and montane shrub-coniferous forest were chosen as study area. Soil samples were collected at 23 places and the relations between the influencing factors and distribution of soil organic carbon （SOC） content were studied. The results indicated that the orders of SOC content for the whole soil profile in different vegetation, in the horizontal direction, were showed as below： forest〉shrub〉meadow〉steppe〉desert; all the SOC contents of upper 10 cm soil layers in vegetations of forest, shrub and meadow, as well as that of upper 20 cm soil layers in steppe, in the vertical direction, were higher than that of corresponding lower soil layers. However, the SOC content in desert was uniform. The grey correlative analysis between the climatic factors and SOC content in upper part soil showed that the precipitation was the dominant climatic factor affecting the distribution of SOC on the Tibetan Plateau transect. The influence of precipitation on the horizontal distribution of SOC decreases as the increase of precipitation in the horizontal direction. The vertical distribution of SOC along soil profile was greatly affected by precipitation or soil clay content in upper part of soil, as well as was clearly influenced by soil silt content or sand content in lower part of soil. The influences of both soil bulk density and soil pH on the vertical distribution of SOC along soil profile declined gradually. The plant biomass was the most important biotic factor affecting the distribution of SOC.