土地利用方式对雅江中游土壤理化性质及颗粒分形特征的影响

Effects of Land Use Types on Soil Physicochemical Properties and Fractal Characteristics of Soil Particles in Middle Reaches of Yajiang River

采取野外调查和室内试验相结合方法,分析了雅江中游4种土地利用方式基本理化性质,并运用土壤颗粒体积分形维数模型研究了不同土地利用方式土壤颗粒分形特征及与土壤粒径、性状关系。结果表明:(1)不同土地利用方式0~30 cm土壤理化性质差异显著(P<0.05),土壤容重表现为稀疏灌丛>农耕地>荒草地>人工林地,随着土壤层次增加,土壤容重呈增大趋势。总孔隙度、毛管孔隙度、饱和持水率、毛管持水率均与容重规律相反;(2)4种土地利用方式主要以粉粒、砂粒为主,黏粒含量仅占到0.36%~4.27%,土壤质地偏砂性;(3)0~30 cm土壤颗粒体积分形维数平均值的顺序为:农耕地>荒草地>人工林地>稀疏灌丛。人工林地具有较好的土壤结构,相对疏松、通透性好。而稀疏灌丛受到砾石影响,分形维数最小,但在保水保肥能力上最弱;(4)土壤颗粒体积分形维数与砂粒体积百分含量呈极显著负相关(r=–0.873,P<0.01);与粉粒体积百分含量呈极显著正相关(r=0.860,P<0.01);与黏粒体积百分含量呈极显著正相关(r=0.913,P<0.01)。这表明,一定程度上,研究区分形维数可作为评估水土流失的指标;(5)土壤颗粒体积分形维数与各土壤单一物理性质具有不同程度相关性,其中与总孔隙度、毛管孔隙度、饱和含水量、毛管含水量均为正相关关系,而与容重、有机质呈负相关关系。

The effects of four land use types on soil physicochemical properties in the middle reaches of Yajiang River were studied by field investigation and laboratory measurement and volume fractal characteristics soil particles and their relation with soil particle size distribution and soil properties were studied and discussed. The results showed that physicochemical properties of 0-30 cm soil varied greatly under different land use types（P〈0.05）, soil bulk densities under different land use types increased with the increase of soil depth and showed an order of sparse shrub 〉 farmland 〉 wild grass ground 〉 artificial forest land, while total porosity, capillary porosity, saturated moisture capacity and capillary water content showed inverse trends. Silts and sands were predominant in soils under four land use types, the percentages of clays only ranged from 0.36% and 4.27% , and soil textures were dominated by sand. In 0-30 cm soil, average volume fractal dimensions were in an order of farmland〉wild grass ground 〉 artificial forest land 〉 sparse shrub. The artificial forest had best soil structure, which were relatively loose with good permeability, while fractal dimension of the sparse shrub was the smallest are affected by the gravel and with the weakest water and fertilizer retention capacities. The volume fractal dimension of soil particles had an extremely significant negative correlation with the volume percentage of sands （r = -0.873, P〈0.01） while an extremely significant positive correlation with the volume percentage of silts and clays（r = 0.860, P〈0.01; r = 0.913, P〈0.01）, which indicated that, to some extent, the fractal dimension of soil particles can be used as an index to assess soil erosion in the studied area. The volume fractal dimension of soil particles was positively correlated with total porosity, capillary porosity, saturated water content and capillary moisture content, but negatively correlated with bulk density and organic matter.