六盘山华北落叶松土壤有机碳沿海拔梯度的分布规律及其影响因素

以六盘山自然保护区华北落叶松林地土壤（海拔范围为1800-2700 m）为研究对象，选取1900、2100、2300、2500 m 4个海拔梯度，研究华北落叶松林土壤有机碳含量、有机碳密度沿海拔梯度的分布规律及其影响因素，以期为准确估算华北落叶松林土壤有机碳储量及其固碳效益评价提供科学依据。结果表明：（1）六盘山不同海拔梯度华北落叶松林土壤粒径范围主要集中在粗粉粒、细粉粒和极细砂粒，粘粒含量最少，不足1%。林地土壤呈中性或弱碱性，pH均值范围为6.74-8.19；除土壤pH外，其他土壤理化指标沿海拔梯度的分布差异不显著（P>0.05）。（2）在1 m的标准土壤剖面内，土壤有机碳含量变化范围为15.80-35.45 g/kg，总有机碳密度的分布在21.34-42.28 kg/m²，且深层（40-100 cm）土壤有机碳含量及其密度在各海拔梯度内的变异程度大于表层土壤。（3）随着海拔的升高，土壤有机碳含量及其密度的表聚现象逐渐不明显；同一海拔高度，土壤有机碳含量和碳密度均随土层深度的增加而逐渐降低；同一土层深度土壤有机碳含量及其密度均随海拔的升高呈先增加后减少的趋势，而在整个土壤剖面上，土壤有机碳含量及其密度在较低海拔区域（小于2100 m）的变异程度较大。（4）冗余分析（RDA）表明：土壤理化性质可以解释华北落叶松林土壤有机碳含量及其密度81.02%的变异，其中电导率是影响华北落叶松土壤有机碳沿海拔梯度变异的主导因子，占环境因子总解释量的67.4%。

Altitudinal distribution rule of Larix principis-rupprechtii forest's soil organic carbon and its influencing factors in Liupan Mountain

The Larix principis-rupprechtii forest soils from four altitudes (1900 m, 2100 m, 2300 m, and 2500 m) in Liupan Mountain Nature Reserve were chosen as the research object to analyze the distribution rules of soil organic carbon content, organic carbon density at different soil depths and its influencing factors. This study provides a scientific basis for the accurate estimation of soil carbon storage and evaluation of carbon sequestration effects in Larix principis-rupprechtii forest. The results showed that:(1) The soil particles in Larix principis-rupprechtii forest are mainly composed of coarse silt, fine silt and very fine sand, clay content was the lowest, less than 1%. The forest land were neutral or alkalescent, and the pH value ranged from 6.74 to 8.19. Except the pH value, the variation of other soil physicochemical properties along the elevation gradient was not significant (P>0.05). (2) In 1m depth standard soil profile, the value of soil organic carbon content ranged from 15.8 to 35.45 g/kg, organic carbon density ranged from 21.34 to 42.28 kg/m², and the variation degree of them in the deep layer (40-100 cm) was greater than that in the surface soil (0-40 cm). (3) With the increase of altitude, the surface accumulation of soil organic carbon was gradually unobvious. During the same altitude gradient, soil organic carbon content and organic carbon density showed a decreasing trend with the increase of soil depth. However, in the same soil depth, soil organic carbon content and organic carbon density tend to increase at first and then decrease with the increase of altitude. In addition, soil organic carbon content and organic carbon density caused the least degree of variation at elevation<2100 m throughout the soil profiles. (4) Results from the redundancy analysis showed that soil physicochemical properties can explain 81.02% total variation of soil organic carbon content and organic carbon density in Larix principis-rupprechtii forest. Among them, electrical conductivity was a main factor driving the variation of soil organic carbon in Larix principis-rupprechtii forest along altitudinal gradients, accounting for 41.21% of total interpretation. This study revealed the change regularity of soil organic carbon in Larix principis-rupprechtii forest along the elevation gradient, and it can provide basis for rational carbon management and sustainable development of plantation.