林草恢复对热水河小流域侵蚀区土壤团聚体稳定性与有机碳氮特征的影响

Effects of forest and grass restoration on soil aggregate stability,and organic carbon and nitrogen characteristics in an eroded area of the Reshui River

土地利用类型影响土壤团聚体稳定性及碳氮分布,进而改变土壤碳氮循环过程。本研究对热水河小流域草地、灌丛和林地3种不同林草恢复措施下0-100 cm剖面土壤团聚体、碳氮及其他理化性质进行了系统研究,以探索适宜的林草恢复措施。结果表明:不同林草恢复对侵蚀区土壤团聚体分布、稳定性和碳氮特征具有显著的影响。在0-10、10-30和30-60 cm各土层中,草地>2 mm粒级团聚体含量显著大于灌丛和林地(P<0.05),而在60-100 cm土层中,则表现为灌丛>林地>草地(P<0.05);土壤团聚体重量平均直径(mean weight diameter,MWD)和几何平均直径(geometric mean diameter,GMD)分布趋势与大于0.25 mm粒级团聚体(the ratio of>0.25 mm aggregate,R_(0.25))相似。在0-10和10-30 cm土层中,草地总氮和有机碳含量显著大于灌丛和林地(P<0.05);但随土层加深,草地深层土壤碳氮含量分布减少,在30-60和60-100 cm土层中,土壤总氮和有机碳含量分布趋势表现为灌丛>林地>草地(P<0.05);此外,草地碳氮计量比在3种土地利用中始终处于较低水平。土壤团聚体稳定性、碳氮含量与土壤pH、土壤机械组成等土壤性质密切相关。MWD与pH极显著正相关(P<0.01),GMD与pH和粉粒含量显著正相关(P<0.05),而R_(0.25)与土壤机械组成极显著相关(P<0.01),与总氮和有机碳含量则显著相关(P<0.05);土壤总氮和有机碳含量与pH和粉粒含量极显著负相关(P<0.01),与砂粒含量极显著正相关(P<0.01)。本研究结果表明,在表层土壤中草地具有较好的稳定土壤结构,具有稳固碳氮的作用,而在较深土层中,灌丛和林地等植被恢复措施的团聚体稳定性较强,碳氮含量也较高。本研究为干热河谷地区的生态修复提供了数据支持。

Land use affects the stability of soil aggregates and the distribution of carbon and nitrogen,thereby changing the process of soil carbon and nitrogen cycling.In this study,soil aggregates,carbon,nitrogen,and other physical and chemical properties in 0-100 cm soil profiles of grassland,shrubland,and forestland were systematically studied in a small watershed of the Reshui River under three different forest and grass restoration measures.This was done to explore suitable forest and grass restoration measures.The results showed that the distribution,stability,and carbon and nitrogen characteristics of soil aggregates were significantly affected by different forest and grass restoration measures.In the 0-10 cm,10-30 cm,30-60 cm soil layer,the aggregate content(>2 mm)in the grassland was significantly higher than that in the shrubland and forestland(P<0.05).In the 60-100 cm soil layer,the performance followed the trend of shrubland>forestland>grassland(P<0.05).The distribution trends of soil aggregate mean weight diameter(MWD)and geometric mean diameter(GMD)were similar to the distribution trend of the ratio of>0.25 mm aggregate(R_(0.25)).In the 0-10 cm and 10-30 cm soil layers,the total nitrogen and organic carbon contents of the grassland were significantly higher than those of the shrubland and forestland(P<0.05).However,with the deepening of the soil profile,the distribution of carbon and nitrogen contents in the deep soil layer of grassland decreased.In the 30-60 cm and 60-100 cm soil layers,the distribution trend of total nitrogen and organic carbon contents of the soil was in the order of shrubland>forestland>grassland(P<0.05).In addition,the carbon and nitrogen stoichiometric ratio of the grassland was always at a low level among the three land uses.Soil aggregate stability,and carbon and nitrogen contents were closely related to soil pH,soil particle composition,and other soil properties.The MWD was significantly and positively correlated with pH(P<0.01),GMD was significantly and positively correlated with pH and silt contents(P<0.05),and the correlation between R_(0.25) and soil particle composition was extremely significant(P<0.01).Additionally,the correlation between the total nitrogen and organic carbon contents was significant(P<0.05).Soil total nitrogen and organic carbon contents were both significantly and negatively correlated with pH and silt content(P<0.01),and positively correlated with sand content(P<0.01).The results of this study showed that grassland had a better role in stabilizing soil structure,and stabilizing carbon and nitrogen in the soil surface.However,in the deeper soil layer,the stability of aggregates in shrubland and forestland was better than that in the grassland,and the contents of carbon and nitrogen were also higher.This study provides data to support ecological restoration in dry-hot valley areas.