不同土地利用方式下洞庭湖退田还湖区土壤物理特性

Soil Physical Properties and Gray Incidence Analysis of Different Land Use Patterns under Converting Polders Back into Wetlands in the Dongting Lake Region

以钱粮湖垸为例,研究了洞庭湖退田还湖区林地（Ⅰ）、园地（Ⅱ）、旱地（Ⅲ）、水田（Ⅳ）、荒地（Ⅴ）等5种土地利用方式下的土壤密度、孔隙状况、水分状况、团聚体组成与分形特征等物理性质,并运用灰色关联分析对土壤物理特性进行了综合评价。研究表明：5种土地利用方式下0-50 cm土层土壤密度为1.02-1.65g/cm^3,毛管孔隙度为33.04%-61.70%,非毛管孔隙度为2.15%-25.35%,总孔隙度为38.40%-64.96%,自然含水量为17.07%-38.33%,毛管持水量为23.22%-64.00%,土壤团聚体平均直径、分形维数分别为1.76-5.09 mm、2.272 8-2.638 8;各土壤物理指标中,非毛管孔隙度变异系数最大（83.51%）,土壤团聚体分形维数变异系数最小（3.61%）;0-25 cm2、5-50 cm土层荒地的土壤密度均最高,而土壤非毛管孔隙度、总孔隙度、自然含水量、毛管持水量均最低,毛管孔隙度仅高于园地;5种土地利用方式下土壤物理特性的关联度排序为Ⅱ（0.776 3）〉Ⅳ（0.762 1）〉Ⅰ（0.698 6）〉Ⅲ（0.659 2）〉Ⅴ（0.618 3）,土壤物理性质以荒地类型最差。

Based upon the case of Qianlianghu polder in the Dongting Lake region,soil physical properties of bulk densities,porosities,water contents,compositions and fractal characteristics of soil aggregates was studied and evaluated synthetically through gray incidence analysis in five typical patterns of land use under converting polders back into wetlands,which included forestland（Ⅰ）,garden land（Ⅱ）,dry land（Ⅲ）,paddy land（Ⅳ） and waste land（Ⅴ）.The results showed that soil bulk densities,capillary porosities,non-capillary porosities,total porosities,soil natural water contents,soil capillary moisture capacities,mean weight diameters and fractal dimensions of soil aggregates in 0～50.0 cm soil layers under different patterns of land use were 1.02～1.65 g/cm3,33.04%～61.70%,2.15%～25.35%,38.40%～64.96%,17.07%～38.33%,23.22%～64.00%,1.76～5.09 mm and 2.272 8～2.638 8,respectively.The biggest variation coefficient（83.51%） was existed in non-capillary porosities and the smallest（3.61%） in fractal dimensions of soil aggregates in all soil physical indexes.In 0～25.0 cm and 25.0～50.0 cm soil layers,the waste land had the highest soil bulk densities,the lowest non-capillary porosities,total porosities,soil natural water contents and soil capillary moisture capacities,and its capillary porosities were higher than that of garden land.The order of gray incidence degrees of soil physical properties were Ⅱ（0.776 3）〉 Ⅳ（0.762 1）〉 Ⅰ（0.698 6） 〉Ⅲ（0.659 2）〉 Ⅴ（0.618 3）,which showed that the soil physical characteristics was the poorest in waste land than that in other land use patterns.