黄土高原典型植被根系对土壤团聚体及其有机碳组分的影响

Effects of Typical Vegetation Roots on Soil Aggregates and Their Organic Carbon Fractions on the Loess Plateau

为探究植被根系作用下不同粒径团聚体内碳组分含量的相对变化及其主要影响因素,以黄土高原地区自然生长的直根系植物铁杆蒿(Artemisia gmelinii Web.)和须根系植物长芒草(Stipa bungeana Trin.)典型植被为研究对象,以退耕1年撂荒地为对照样地(CK),测定各粒径团聚体质量占比及其土壤有机碳(SOC)、颗粒态有机碳(POC)、矿物结合态有机碳(MAOC)含量,分析土壤基本理化性质和根系特征参数与不同粒径团聚体碳组分特征间的相互关系。结果表明:(1)与撂荒地相比,铁杆蒿和长芒草样地均显著提高POC和MAOC含量,POC含量变化幅度均大于MAOC。铁杆蒿和长芒草样地显著提高各粒径团聚体碳组分含量,>0.25 mm大团聚体中POC和MAOC含量增幅较微团聚体更大,分别为7.44~8.26倍和3.76~4.37倍。(2)大团聚体有机碳含量与POC、MAOC均为极显著相关,小团聚体有机碳含量与POC显著相关,微团聚体有机碳含量与MAOC显著相关。团聚体对POC的包裹和对MAOC的结合作用共同存在,同时二者以不同的影响方式作用于团聚体有机碳变化,继而影响土壤总有机碳,其中,小团聚体有机碳含量是最主要的影响因素。(3)土壤团聚体碳组分与植被根系参数显著相关,根表面积密度(RSAD)和根生物量密度(RWD)是影响团聚体碳组分的主要因素,其解释方差分别为50.5%,17.0%。通过碳组分对各粒径土壤团聚体有机碳的影响,植物根系能够有效提升土壤有机碳含量并改善土壤质量。该研究结果为黄土高原地区土壤固碳与植被恢复提供参考。

In order to investigate the changes of organic carbon content fractions in aggregates of different particle sizes under the effects of vegetation roots and their main influencing factors,two typical vegetation species(Artemisia gmelinii Web.and Stipa bungeana Trin.)growing naturally on the Loess Plateau were were chosen as subjects,while abandoned land for one year served as control(CK).The mass ratio of each particle size aggregates and their soil organic carbon(SOC),particulate organic carbon(POC)and mineral associated organic carbon(MAOC)contents were determined and the relationships between the basic properties of the soil,the characteristics of the root system and the carbon fractions of each different particle size aggregates were analyzed.The results revealed the following findings:(1)Compared to CK,contents of POC and MAOC were significantly higher in Artemisia gmelinii Web.and Stipa bungeana Trin,with POC contents varying more than MAOC.The experimental land of Artemisia gmelinii Web.and Stipa bungeana Trin.significantly increased the carbon fraction contents of macro-aggregates(>0.25 mm)by 7.44~8.26 times and 3.76~4.37 times respectively,which had the bigger increase than that of the micro-aggregates.(2)The organic carbon content of large macro-aggregates was significantly correlated with POC and MAOC,that of small macro-aggregates was significantly correlated with POC,and that of micro-aggregates was significantly correlated with MAOC.The inclusive effects of POC and the binding effects of MAOC by the aggregates coexisted,and both of them acted in different ways to influence the changes of organic carbon in aggregates,and then affected the total organic carbon of the soil,of which the organic carbon content of small aggregates was the most important influencing factor.(3)Soil aggregate carbon fractions were significantly correlated with vegetation root parameters,where root surface area density(RSAD)and root weight density(RWD)played major roles in influencing the aggregate carbon fractions,explaining variance of 50.5%and 17.0%respectively.Through the effects of carbon fractions on organic carbon in soil aggregates of all particle sizes,plant roots can effectively enhance soil organic carbon contents and improve soil quality,and the results of this study provide a reference for soil carbon sequestration and vegetation restoration in the Loess Plateau region.