不同设障年限沙丘土壤粒径和有机碳分布特征

为探讨沙柳沙障对毛乌素沙地土壤粒径和SOC(土壤有机碳)的影响,选取流动沙丘、设障2和7 a的半固定和固定沙丘为研究对象,利用多重分形理论分析不同设障年限沙丘PSD(土壤粒径分布)(以φ计)和w(SOC)的分布特征. 结果表明:设置沙障后,φ(黏粒)、φ(粉粒)与φ(极细砂)增加,φ(细砂)与φ(中砂)下降；土壤粒径的多重分形参数D₁/D₀(D₁为PSD均匀性程度,D₀为PSD宽度)和~f()谱图可以反映沙丘土壤PSD的宽度与均匀性程度,随着设障年限延长,PSD的D₁/D₀均小于流动沙丘,土壤中细粒物质显著增多. D₀表现为设障7 a沙丘(1.01)>流动沙丘(1.00)>设障2 a沙丘(0.93),D₁表现为流动沙丘(0.91)>设障2 a沙丘(0.88)>设障7 a沙丘(0.65). w(SOC)随着设障年限的延长而显著增加,设障7 a沙丘与其他2类沙丘间w(SOC)差异显著；多重分形参数可以表征土壤养分状况与流沙防治状况,设障沙丘上部、下部的w(SOC)与PSD的D₁/D₀之间有明显的相关关系,设障沙丘上部、下部D₁/D₀间呈明显负相关,设障沙丘中部D₁/D₀之间则呈正相关,流动沙丘各部位w(SOC)与D₁/D₀间无显著相关关系. 

Distribution of Soil Particle Size and Soil Organic Carbon in Dunes of Checkerboard Barriers with Different Setting Years

In order to study the effects of Salix psammophila sand barrier on soil particle size distribution (PSD) and soil organic carbon (SOC), multi-fractal features of soil PSD and SOC of a mobile sand dune, a fixed sand dune of a two-year sand barrier and a semi-fixed sand dune of a seven-year sand barrier were analyzed in Maowusu Sandy Land with the multi-fractal method. The results showed that the silt, clay and very fine sand contents of setting sand barrier dunes increased, while those of the fine sand and medium coarse sand decreased. The heterogeneity and width of soil PSD could be reflected by the multi-fractal parameters such as D₁/D₀ (i.e., information dimension/capacity dimension) and -f() (i.e., multi-fractal spectrum). The ratios of D₁/D₀ of the fixed dune and semi-fixed dune were higher than that of the mobile dune, and the decreasing order of D₀ was:sand dune with seven-year sand barrier (1.01) > mobile sand dune (1.00) > sand dune with two-year sand barrier (0.93). The order of D₁ was mobile sand dune (0.91) > sand dune with two-year sand barrier (0.88) > sand dune with seven-year sand barrier (0.65). The multi-fractal parameters were obviously related with the soil clay content. The soil plasma content increased when the soil heterogeneity was large. There was an obvious decreasing trend in SOC content of the three different types of dunes. There was a strong correlation between the SOC content and D₁/D₀ of PSD. Therefore, the multi-fractal soil parameters can be used as an indicator to reflect the concentration of soil nutrients. There was an obvious increasing trend of SOC content for the three different types of dunes with the setting years, and the SOC content of the seven-year sand barrier was significantly different from the other two sand dunes. Additionally, there was a significant correlation between the SOC content and the multi-fractal parameters of PSD. Therefore, the multi-fractal parameters can be used to interpret the change of soil nutrient status.