| Soil water and water-soluble calcium are indispensable for vegetation growth,and soil water-calcium relationships can better indicate soil water content and soil water-soluble calcium availability.However,less attention has been paid to the characteristics of soil water-calcium relationship in karst areas,and it has failed to reveal the soil water-calcium relationship and its influencing factors in this area.Through in situ sampling,correlation analysis and redundancy analysis,the distribution characteristics of soil water content and soil water-soluble calcium in typical karst areas of Guizhou were studied to reveal the soil water-calcium relationship and the influencing factors in the area,with a view to providing reference for soil water and calcium resource management in karst areas.The main research findings are as follows:(1)The moisture content in soils of typical karst areas in Guizhou varies widely.The average soil moisture content in karst plateau area is28.38%,and the soil moisture content increases with the increase of soil depth.The average soil water content in the canyon area is 34.67%,and the soil moisture increases with the depth of the soil layer.Soil moisture content was mainly influenced by soil internal factors such as soil capillary porosity,non-capillary porosity,soil clay particles,soil sand particles and soil gravels,which were positively correlated with soil capillary porosity and soil clay particles and negatively correlated with the rest of factors.Among the external factors,the factors that have greater influence on soil moisture are elevation,slope direction and vegetation cover.Vertically,the main controlling factors of soil water content are soil capillary porosity and soil sand content.Horizontally,the main controlling factors of soil water content are soil capillary porosity and soil particle distribution.(2)In general,soils in typical karst areas of Guizhou are in a state of water-soluble calcium deficiency and can be supplemented with watersoluble calcium content in soils.The soil water-soluble calcium content varies greatly in different distribution directions.The average soil watersoluble calcium content in karst plateau area is 32.38mg/kg,and the soil water-soluble calcium content decreases with the increase of soil depth.The average soil water-soluble calcium content in the karst canyon area was 29.07 mg/kg,and the soil water-soluble calcium content increased with the increase of soil depth.Soil water-soluble calcium content in karst plateau area and canyon area is mainly influenced by soil properties such as soil non-capillary porosity,soil p H,soil organic matter,soil sand,soil gravel,soil total calcium,soil exchangeable calcium,etc.to a higher degree,and positively correlated with these soil properties,and less influenced by environmental factors.In the vertical direction,soil water-soluble calcium content is mainly influenced by soil internal factors such as soil capillary porosity,soil sand and gravel content,soil total calcium,exchangeable calcium content,and soil p H.Horizontally,soil water-soluble calcium content is mainly influenced by soil property factors such as soil sand and gravel content,soil capillary porosity,and non-capillary porosity.(3)The analysis of water-calcium relationship shows that the soil of typical karst region in Guizhou can further increase the supply of soil water-soluble calcium under the premise of maintaining the supply of soil water content.The characteristics of soil water-calcium relationship vary greatly in different karst areas.The average soil water-calcium coupling degree of vegetation in the karst plateau area is 0.67,and primary coordination is dominant.The average water-calcium ratio is 31.54,and the soil water-soluble calcium supply can be further increased compared with the soil water supply.The soil water-calcium coupling of vegetation in the karst canyon area was 0.66 on average,with primary coordination and an average soil water-calcium ratio of 227.34,which could increase the supply of soil water-soluble calcium compared with soil water supply.Soil water-calcium coupling degree and water-calcium ratio in typical karst areas of Guizhou are mainly influenced by water-soluble calcium content,and less influenced by other soil properties and environmental factors.Through the study,the main controlling factors affecting soil water content and soil water-soluble calcium distribution were identified,and a method to quantify soil water-calcium relationships in karst areas was found,and the results of the study can provide reference for local vegetation construction and agricultural development practices. |
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