陇中黄土高原温性荒漠不同草地型土壤团聚体稳定性及有机碳分布特征

Distribution Characteristics of Soil Aggregate Stability and Organic Carbon of Different Grassland Types in the Temperate Desert of Longzhong Loess Plateau

土壤团聚体稳定性和有机碳(SOC)是反映土壤结构和质量的重要指标,在温性荒漠土壤质量改善中起着关键作用.为探究温性荒漠不同草地型土壤团聚体分布规律、稳定性和团聚体SOC含量的变化特征及相互关系,以陇中黄土高原温性荒漠的4种草地型(盐爪爪型、红砂型、珍珠猪毛菜型和合头藜型)为研究对象,采用湿筛法测定土壤的团聚体粒径分布特征,通过计算团聚体稳定性指标与团聚体粒径SOC对全土SOC含量的贡献分析土壤团聚体的稳定性,采用相关分析、主成分分析和线性拟合方程揭示土壤团聚体和团聚体粒径SOC与土壤稳定性的关系.结果表明,盐爪爪型草地各土层(0~10、10~20和20~30 cm)>0.25 mm团聚体含量(R0.25)、平均重量直径(MWD)、几何平均直径(GMD)和全土SOC含量均显著高于红砂型和合头藜型草地(P<0.05);盐爪爪型草地各土层0.053~0.25 mm和<0.053 mm粒径SOC含量显著高于合头藜型草地(P<0.05);表层和亚表层土壤(0~10 cm和10~20 cm)的0.25~2 mm粒径SOC对全土SOC含量的贡献显著最高(P<0.05);且随着土层加深,盐爪爪型草地R0.25、MWD、GMD、全土和团聚体SOC含量呈现先升后降趋势,10~20 cm含量最高;盐爪爪型草地团聚体含量以0.25~2 mm团聚体为主,其他3种草地型以0.053~0.25 mm团聚体为主.此外,全土SOC含量与R0.25、MWD、GMD和ELT呈显著相关(P<0.01),且团聚体0.25 mm是正负相关的临界点;R0.25、MWD、GMD和ELT值是影响草地全土SOC的关键因素;全土SOC含量与GMD的拟合方程更适合描述SOC含量与团聚体稳定性间的关系.因此,相较于其他草地型,盐爪爪型草地对土壤团聚体稳定性和土壤质量具有促进作用.

Soil aggregate stability and organic carbon(SOC)are important indicators of soil structure and quality and play a key role in the improvement of soil quality in temperate deserts.This study aimed to investigate the distribution patterns,stability of soil aggregates,and variation characteristics of the content of aggregate organic carbon in different grassland types in temperate deserts and their interrelationships.Four grassland types in a temperate desert(Kalidium foliatum type,Reaumuria songarica type,Salsola passerina type,and Sympegma regelii type)in the Longzhong Loess Plateau as research objects,and the soil aggregate particle size distribution characteristics were determined using the wet sieving method.The stability of soil aggregates was analyzed by calculating aggregate stability indicators and the contribution of aggregate particle size SOC to bulk soil SOC content.Correlation analysis,principal component analysis,and linear fitting equations were used to reveal the relationship between the soil aggregate content and aggregate particle size SOC and aggregate stability.The results showed that the content of>0.25 mm aggregates(R0.25),mean weight diameter(MWD),geometric mean diameter(GMD),and bulk soil SOC content in each soil layer(0-10,10-20,and 20-30 cm)of the K.foliatum type grassland were significantly higher than that of the R.songarica type and S.regelii type(P<0.05).The SOC content of 0.053-0.25 mm and<0.053 mm particle size in each soil layer of the K.foliatum type grassland were significantly higher than that of the S.regelii type(P<0.05).Surface and subsurface soils(0-10 cm and 10-20 cm)had the significantly highest contribution of 0.25-2 mm particle size SOC to the bulk soil SOC content(P<0.05).Additionally,as the soil layer deepened,the R0.25,MWD,GMD,bulk soil,and aggregate SOC contents of the K.foliatum type grassland showed a tendency to increase first and then decrease,with the highest contents from 10-20 cm.Kalidium foliatum type grassland aggregate content was dominated by 0.25-2 mm aggregates,whereas the other three grassland types were dominated by 0.053-0.25 mm aggregates.In addition,bulk soil SOC content was significantly correlated with R0.25,MWD,GMD,and ELT(P<0.01),and the 0.25 mm aggregate was the critical size of positive and negative correlation.R0.25,MWD,GMD,and ELT values were the key factors influencing bulk soil SOC in grassland.The equation fitted to bulk soil SOC content,and GMD was the most suitable to describe the relationship between SOC content and the stability of soil aggregates.Therefore,compared with other grassland types,K.foliatum type grassland had a promoting effect on the soil aggregate stability and the improvement of soil quality.