低山丘陵区土壤硒、镉空间分异对土地利用景观特征的响应

Responses of spatial variation of selenium and cadmium to landscape features of land use in surface soil

为明确低山丘陵区土地利用景观特征和景观格局对土壤硒(Se)、镉(Cd)含量空间分异的影响.以重庆市江津区为研究区,采集和测定了247件表层土壤样品,将研究区划分为3519个1 km×1 km网格单元,再基于30 m土地利用数据测算了每个网格单元土地利用景观特征指数和景观格局指数,并运用冗余分析(RDA)和双变量空间自相关(Moran’s I),定量探讨了景观格局对表土Se、Cd含量分异的影响.结果表明:(1)江津区表土Se(0.36 mg·kg^(-1),算术均值,下同)、Cd(0.27 mg·kg^(-1))含量高于渝西地区土壤背景值,但表土Cd含量略低于全国农用地风险筛选值.(2)林地表土Se含量(0.43 mg·kg^(-1))显著高于耕地(0.34 mg·kg^(-1)),而水田(0.29 mg·kg^(-1))、旱地(0.27 mg·kg^(-1))土壤Cd含量高于林地(0.25 mg·kg^(-1)).(3)受成土母质影响,空间上林地景观聚集度与土壤Se含量呈负相关,耕地景观聚集改变土壤理化性质间接影响土壤Se含量.(4)研究区景观多样性和均匀度与表土Se、Cd含量呈正相关,景观格局是土壤Cd空间分异的主要因素,土壤Se含量更多受控于成土母质.从景观格局角度,定量分析了低山丘陵区土地利用景观特征与土壤Se、Cd的关系,可为优化富硒土壤开发和控制土壤镉污染提供参考.

To clarify the effects of land use landscape features and patterns on the spatial differentiation of soil selenium(Se)and cadmium(Cd)contents in the hilly area,247 topsoil samples were collected and measured in the Jiangjin District of Chongqing City,which,as the study area,is divided into 3519 grid units of 1 km×1 km.Based on 30 m land use data,land use landscape feature index and landscape pattern index of each grid unit were measured.Redundancy analysis(RDA)and bivariate spatial autocorrelation analysis(Moran’s I)were used to quantitatively explore the effects of landscape pattern on Se and Cd contents differentiation of topsoil.Results showed that:①The Se(0.36 mg·kg^(-1),arithmetic mean,same as below)and Cd(0.27 mg·kg^(-1))contents of the topsoil in the study area were higher than the background values of soils in the western part of Chongqing,while the Cd content was slightly lower than the national risk screening value for agricultural land.②The topsoil Se content of forested land(0.43 mg·kg^(-1))was significantly higher than that of cultivated land(0.34 mg·kg^(-1)),while the soil Cd contents of paddy land(0.29 mg·kg^(-1))and dry land(0.27 mg·kg^(-1))were higher than that of forested land(0.25 mg·kg^(-1)).③Affected by the parent material,the spatial degree of forest landscape aggregation was negatively correlated with topsoil Se content in space,and cultivated land landscape aggregation indirectly affected soil Se content by changing soil physical and chemical properties.④The diversity and uniformity of landscape in the study area were positively correlated with the Se and Cd contents in topsoil,and the landscape pattern was the main controlling factor of soil Cd spatial differentiation,while the soil Se content was more controlled by the parent material.From the perspective of landscape pattern,the relationship between land use landscape characteristics and soil Se and Cd in a typical hilly area was quantitatively analyzed,which could provide reference for optimizing Se-rich soil development and controlling soil Cd pollution.