川西沿海拔梯度典型植被类型土壤活性有机碳分布

研究土壤活性有机碳含量及分配比例是揭示土壤碳库周转及调控机理的重要途径,通过利用高锰酸钾氧化法获得易氧化有机碳、湿筛法获得颗粒有机碳和密度分离法获得轻组有机碳3项指标探讨沿海拔梯度不同植被类型间(山地常绿阔叶林、常绿落叶阔叶混交林、落叶阔叶林、针阔混交林、暗针叶林)土壤活性有机碳含量差异及调控因子,结果表明:随土层加深,土壤颗粒和轻组有机碳含量及分配比例均降低,土壤易氧化有机碳含量降低而分配比例保持较稳定水平。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。不同活性有机碳含量之间均呈显著线性相关(P0.05)表明活性有机碳起源的类似。活性有机碳与土壤粘粒+粉粒含量百分比呈显著负相关(P0.05)表明活性有机碳趋向分布于土壤大团聚体当中。年均温与不同植被类型间表层土壤活性有机碳含量和分配比例成负相关趋势,但可能由于取样点较少的缘故而在统计上不显著。年均温与土壤非保护性有机碳向保护性有机碳的转化速率常数(K)接近于显著负相关(P=0.062)。

Labile soil organic carbon distribution on influenced by vegetation types along an elevation gradient in west Sichuan, China

Labile soil organic carbon (LOC) is an indicator in terms of evaluating soil organic matter quality and dynamics. Fractionation of soil organic matter (SOM) implies the separation of the total SOM into different soil physical fractions that are thought to be functionally homogeneous with respect to physicochemical properties and turnover rate, and the organic matter dynamics based on turnover time will be further understood. In this paper, Labile soil organic carbon, evaluated by three indicators obtained from oxidation and physical fractionation methods, was found varies with vegetation types (Mountainous evergreen broad-leaved forest, mixed evergreen and deciduous broadleaved forest, deciduous broad-leaved forest, mixed coniferous and broadleaved forest, sub-alpine dark coniferous forest) distributed along an elevation gradient. A 333mM KMnO4-chemical oxidation method was used to determine the easily oxidized carbon (EOC), and another two physical methods including wet sieving through a 0.053 mm sieve and flotation in aqueous NaI (1.8g?cm-3) were used to determine the particulate organic matter carbon (POC) and light fraction organic carbon (LFOC) respectively. POC and LFOC contents as well as their proportions decrease with the increasing soil depth, similar result was found in EOC content, while there is no decrease in the proportion of EOC. Compared with lower-elevation vegetation types, higher ones were found significantly higher in their LOC content and proportion. EOC and POC show positive correlations with LFOC (P<0.05), indicates the similar origin of EOC, POC and LFOC. In contrast, negative correlation between LOC and silt+clay(%) content indicates that more LOC are contained in the macroaggregate. EOC, POC and LFOC contents of surface soil layer as well as their proportions decrease with mean annual temperature (MAT), however, no significant was found for the fewer samplings. And a marginal positive correlation was found between MAT and the rate constant for C transfer from the unprotected to the protected soil pool (K) (P=0.062).