西北黑河流域土壤pH与CaCO_3相当物含量关系研究

干旱-半干旱地区的石灰性土壤中pH与CaCO_3相当物含量之间有一定关系,但目前黑河流域土壤中pH与CaCO_3相当物含量之间的关系及其影响因素尚不明确。从区域、海拔、土壤母质、土壤类型、土地利用方式五个方面分析了我国西北黑河流域土壤中pH与CaCO_3相当物含量之间的关系。结果表明,黑河流域土壤pH与CaCO_3相当物含量之间存在显著的非线性相关,pH随着CaCO_3相当物含量的增加而逐渐升高,当CaCO_3相当物含量升高到某一阈值后,pH增幅迅速降低,最终趋于稳定;不同区域、海拔、土纲、成土母质和土地利用方式下,pH与CaCO_3相当物含量之间的相关程度不同,表现为上游土壤pH与CaCO_3含量呈显著正相关,不同的海拔高度区间pH与CaCO_3含量之间具显著正相关,人为土、盐成土、均腐土、雏形土的pH与CaCO_3含量显著正相关,冰碛物、残积-坡积物、湖积物发育的土壤pH与CaCO_3含量具有极显著正相关,土地利用方式对pH与CaCO_3含量的关系影响较小;不同区域、海拔、土纲、成土母质和土地利用方式下,pH与CaCO_3相当物含量的最佳回归模型不同,有幂函数模型、一元二次模型、一元三次模型和线性模型。

Relationships Between pH and Content of Calcium Carbonate and Equivalents in Soil of the Heihe River Valley, Northwest China

[Objective] Content of calcium carbonate and equivalents and pH are two important properties of the soil,which will affect availabilities of soil elements and nutrients,and consequently soil fertility and quality.It was demonstrated in previous studies that content of CaCO3 and equivalents did affect soil pH and some other soil properties.Generally speaking,with increasing content of CaCO3 and equivalents,soil pH gradually rises and levels off in the end.What's more,their relationship could be described with an inverse function model.This study was carried out in the Heihe River Valley,which is the second largest inland river valley and a typical one,located in the western part of the Hexi Corridor in the arid region of Northwest China.In this area,the relationship between soil pH and content of CaCO3 and equivalents may vary and was therefore analyzed from the aspects of region,altitude,soil parent material,soil type and land use.[Method] Based on the data gathered during the 2012-2013 soil survey of the valley,correlation analysis and regression analysis were performed of variation of soil pH with content of content of CaCO3 and equivalents.[Result] Results show that soil pH had a significant nonlinear relation with content of CaCO3 and equivalents as previous studies disclosed,i.e.,soil pH gradually rises with the increasing content of the substance,declined in its rising rate when the content reached a certain level,and leveled off in the end.However,the relationship between the two varied in degree with region,altitude,soil parent material,soil type and land.Specifically,soil pH was significantly and positively related to content of CaCO3 and equivalents in the valley as a whole and in the upstreams of the river,and in anthrosols,halosols,isohumosols and cambisols,regardless of elevation and land use.However,no significant relationship was found in soils derived from aeolian,diluvial and alluvial deposits.In addition,the optimal regression model for analysis of relationship between the two varied with the region,altitude,soil parent material,soil type and land use,and may be a power function model,a quadratic model,a cubic model or a linear model,instead of a simple inverse function model as obtained in previous studies.[Conclusion] The relationship between soil pH and content of CaCO3 and equivalents in the Heihe River Valley is complex,which may be related to its vast spatial span,great altitude gradient,different soil forming factors and diversified soil types.