塔里木盆地北缘绿洲4种土地利用方式土壤有机碳组分分布特征及其与土壤环境因子的关系

为明确干旱区土壤有机碳各组分分布状况,进而合理地开发与利用,解决土地利用效率低下问题,以塔里木盆地北缘盐碱地、天然林、沙地、30 a棉田这4种不同土地利用方式土壤为研究对象,分析不同土地利用方式土壤有机碳、微生物量碳、可溶性有机碳、易氧化有机碳的分布状况,结合冗余分析探索其与土壤环境因子的关系.结果表明,SOC在天然林表现出最高值(1.92 g·kg~(-1)),在沙地随土层增加而增加,在其他土地利用类型整体呈现下降趋势;MBC在天然林表现出最高水平,且随土层深度增加而降低,在其他土地利用类型无明显变化趋势.DOC含量最高值和最低值分别出现在天然林和30 a棉田的80~100 cm层(分别为143.23 mg·kg~(-1)和30.00 mg·kg~(-1)),在天然林中随土层深度增加而增加,在盐碱地中随土层深度增加而降低且不同土层含量均表现出显著差异(P0.05).EOC含量在不同土地利用类型和不同土层中未表现出明显规律.将各有机碳组分进行敏感性分析得出:MBC对不同土层最为敏感,DOC对土地利用变化最为敏感.通过冗余分析得出各有机碳组分与土壤含水量、全氮、p H呈正相关关系,与土壤容重、电导率呈负相关关系.土壤环境因子对各碳组分含量的重要性排序为:土壤容重含水量电导率土壤氮p H,即容重和含水量为影响干旱区有机碳组分的主要因子.

Soil Organic Carbon Components and Their Correlation with Soil Physicochemical Factors in Four Different Land Use Types of the Northern Tarim Basin

In order to clarify the distribution of each component of soil organic carbon (SOC) in arid areas, and to develop methods to rationally solve problems caused by inefficient land use and blind tillage, we studied the effects of different land use patterns on the SOC, microbial biomass carbon (MBC), dissolved organic carbon carbon (DOC), and easily oxidized organic carbon (EOC) on four different land use types: saline soil, natural forest, sandy land, and 30 a cotton field in the northern Tarim Basin. The relationships between different carbon components and soil physicochemical factors were researched by redundancy analysis (RDA). The results showed that the SOC showed the highest value (1.92 g·kg^-1) in natural forests and increased with soil depth, while the other land use types showed a downward trend as a whole. The MBC showed the highest level in natural forests, and decreased with soil depth, but there was no obvious change trends in other land use types. The highest and lowest DOC contents appeared in the 80-100 cm layer (143.23 mg·kg^-1 and 30.00 mg·kg^-1, respectively) in the natural forest and 30 a cotton field, respectively, and increased with soil depth in the natural forest (P<0.05). In the saline soil, the DOC content of the soil decreased with increased depth, and the contents of different soil layers showed significant differences (P<0.05). The EOC content did not show a obvious regularity in different soil layers of different land use types. Sensitivity analysis of each organic carbon component showed that the MBC was the most sensitive to soil layer changes, and the DOC was the most sensitive to different land use patterns. The MBC has a certain indication of soil layer change, which may be due to the fact that microbial biomass C in different layers has different living environments, so the content was significantly different. The DOC has a certain indication of land use types change, which may be due to the adaptation to different situations. Through the RDA, it was found that there was a positive correlation between soil components and soil water content (SWC), total nitrogen (TN) and pH, and a negative relationship between bulk density (BD) and electrical conductivity (EC). The order of importance of environmental factors to the contents of carbon components is as follows: BD > SWC > EC > TN > pH. This indicates that bulk density and water content are the main factors affecting organic carbon components in arid regions.