内蒙古典型草原土壤斥水性有机物质促进机理

Soil water repellency is a physical phenomenon resisting wetting, which greatly reduces plant production and induces in environmental and ecological risks as well. There is little understanding on the reasons and mechanisms inducing soil hydrophobicity. We will use the steppe grassland of Inner Mongolia as a study case. We will survey the natures of soil hydrophobicity in the steppe. The spatial and seasonal changes of soil repellency will be involved in the soil with difference degrees of hydrophobicity. The links will be identified between soil hydrophobicity and soil physical, chemical and microbiological parameters, vegetation, grazing intensity and soil degradation as well. It will be investigated for the composition, natures and distribution within soil aggregates of the organic components which are responsible for soil repellency. The hydrophobic compounds will be assayed for the advantageous grasses. And the contribution of these grasses to soil hydrophobicity will be studied through a lab experiment. One test will touch the microbiological mechanism of soil repellency. The aim of this research is : 1) to identify the soil organic components indicating soil hydrophobicity; 2) to establish the method and index for evaluating organic matter equality of the steppe grassland soil based upon soil repellency; 3)to bring forward a vegetation model for reducing soil repellency, but enhancing soil hydrophilicity.

土壤斥水性是水分不能或很难湿润土壤矿物质颗粒表面的物理现象，目前对土壤斥水性原因与机理缺乏了解。本研究以内蒙古典型草原为例，在调查了解土壤斥水性空间变化、季节变化和土壤剖面变化的基础上，深入研究土壤斥水性与土壤理化及生物学性质、植被、优势植物疏水成分、放牧强度、草原退化等之间的内在和外在联系。重点研究斥水性土壤有机物质组成成分和特性，以及在土壤团聚体中分布特点与变化规律；主要优势植物根茎叶中疏水性有机物质组成成分及其在土壤中的分解转化过程，土壤斥水性与微生物群落结构及活性的关系。以期寻找:(1)能够指示土壤斥水强度的土壤有机物质指标，(2)建立基于土壤斥水性的典型草原土壤有机质质量评价指标与标准，(3)提出基于降低土壤疏水性有机物质含量，增强土壤亲水性的植被种群结构模式。

土壤斥水性是水分不能或很难湿润土壤矿物质颗粒表面的物理现象，目前对土壤斥水性原因与机理缺乏了解。本研究以内蒙古典型草原为例，深入研究土壤斥水性与土壤理化、放牧强度等之间的内外在联系。重点研究土壤斥水性有机物质组成成分和特性。主要研究结论如下：.（1）内蒙古不同草地利用类型的土壤表现为低斥水性或无斥水性。土壤斥水性的强度受不同季节降水量变化的影响。放牧强度对不同季节土壤斥水性的变化有一定影响，放牧强度越大土壤斥水性越高。.（2）土壤斥水性与土壤理化因子相关。土壤斥水性与土壤含水量的关系符合正态分布，土壤水含量为约10%时，土壤斥水性是最强；土壤斥水性随着土壤颗粒尺寸的减小而增加，斥水性与土壤粒径呈负相关；土壤斥水性与总氮，速效氮含量和有机质含量呈正相关关系，与草地土壤中速效磷，速效钾和pH的相关性较低。.（3）采用9种提取溶剂对草原斥水性土壤有机物质粗提物进行成分鉴定，共鉴定出50种化合物，主要包括一些酯类、烃类、酸类、酰胺、甾醇、酮类等。进一步对土壤有机物分离纯化及鉴定，分离纯度最高的单一组分的精提物为香草醛。.（4）土壤斥水性与不同草原类型优势植物有关。荒漠草原、典型草原和草甸草原土壤斥水性差异显著，荒漠草原土壤斥水性最大。.（5）不同草原类型土壤微生物特征存在异质性。不同草原类型植物多样性、DOC和TP含量的差异是影响各细菌组分分布的关键因子。真菌在不同类型草原中的分布主要受土壤斥水性、DOC和TP的调控，但是对于固氮菌来说，植被多样性差异和土壤肥力是影响其分布的主要驱动因子。