Soil infiltration mechanisms under plant root disturbance in arid and semi-arid grasslands and the response of solute transport in rhizosphere soil.

The symbiotic relationship between plant roots and soil infiltration is of great significance for sustainable development of the agriculture and forestry. Through detailed summary of the relationship between root morphological parameters and soil infiltration rates in arid and semi-arid grasslands mainly with leguminous herbs, gramineous herbs and shrubs, the mechanisms that key parameters (root length density, surface area density, diameter, biomass density, architecture, secretion and decay rate) disturb soil infiltration through affecting soil structure such as porosity, soil bulk density and soil organic matter (SOM) are elucidated. Furthermore, the degree of root disturbance on soil structure and infiltration rates are partially clarified by constructing quantitatively structural equation modeling path diagrams. The results show roots have the most significant effect to increase soil infiltration rates through increasing non-capillary pores, contributing to >50 % of the positive effect. In contrast, the increased SOM influenced by roots can obstruct soil infiltration and offset about 25 % of the positive effects. In addition, the impact of root disturbance on transport of nutrients, pesticide and pathogenic microorganisms in rhizosphere soil is also discussed to analyze the potential influence on food and water environmental safety. The presence of roots reduces the amount of leachate-prone nutrients, but their disturbance increases the rate of soil infiltration thus accelerates transport of solutes into deeper soil. Meanwhile, the rhizosphere alters the environmental behavior of pesticides and pathogenic microorganisms, increasing risk of plant roots exposure to them. At present, systematically quantifying the interference of plant roots on soil structure and soil infiltration capacity remains a major challenge. It is necessary to further improve the research methodology and strengthen the study of root soil interaction mechanisms, providing scientific basis and technical support for sustainable agricultural development and ecological environment protection.