黄土高原不同植被带人工刺槐林土壤团聚体稳定性及其化学计量特征

Soil Aggregate Stability and Its Stoichiometric Characteristics in Robinia pseudoacacia Forest within Different Vegetation Zones on the Loess Plateau, China

为研究黄土高原不同植被带对土壤团聚体稳定性及团聚体化学计量变化特征的影响,本研究选取黄土高原不同植被带人工刺槐林地土壤为研究对象,分析了不同粒径团聚体含量,团聚体化学计量及稳定性指标.结果表明,> 2 mm和0. 25～2 mm粒径团聚体含量,机械团聚体的平均重量直径(E_(MWD))和机械团聚体的几何平均直径(E_(GMD))表现为森林带>森林草原带>草原带,而0. 053～0. 25 mm粒径团聚体含量和可蚀性因子K呈现相反的变化特点;各粒径团聚体有机碳和全氮含量在3个植被带整体表现为森林带显著高于森林草原带和草原带,而全磷含量在各植被带间无明显变化规律;有机碳和全氮含量在草原带以<0. 053 mm和0. 25～2 mm粒径占绝对优势,在森林草原带以0. 053～0. 25 mm和0. 25～2 mm粒径为主,而森林带各粒径间均无显著差异;草原带和森林草原带<0. 053 mm粒径全磷含量最高,而森林带全磷含量在各粒径间无显著差异;<0. 053 mm和0. 053～0. 25 mm粒径团聚体C∶N值以草原带和森林草原带高于森林带,而0. 25～2 mm和> 2 mm粒径在3个植被带间无显著差异;各粒径C∶P和N∶P值以森林带显著高于森林草原带和草原带.综上可见,土壤团聚体稳定性和团聚体化学计量在3个植被带间存在较大差异,团聚体稳定性和团聚体有机碳、全氮含量整体表现为森林带显著高于森林草原带和草原带.

With the aim of studying the effects of different vegetation zones on soil aggregate stability and its stoichiometric characteristics,the soils under Robinia pseudoacacia plantations located within different vegetation zones on the Loess Plateau were selected as the research object. Indicators including the content,stoichiometry,and stability of different aggregate fractions were analyzed. The results showed that the content of > 2 mm and 0. 25-2 mm,the mean diameter(EMWD),and the geometric mean diameter(EGMD) of aggregate fractions were in the order of forest zone > forest-steppe zone > grassland zone. However,the stability proxies of aggregate fractions across the three vegetation zones indicated that the content and erodibility(K factor) of 0. 053-0. 25 mm exhibited an opposite trend. The overall trend of the soil organic carbon and total nitrogen of aggregate fractions among the three vegetation zones was that the forest zone significantly overtopped the forest-steppe zone and grassland zone,while the content of total phosphorus showed no significant differences among the three vegetation zones. Additionally,the content of soil organic carbon and total nitrogen of < 0. 053 mm and 0. 25-2 mm was the highest among the different fractions in the grassland zone,while that of 0. 053-0. 25 mm and 0. 25-2 mm was the highest in the forest-steppe zone. In contrast,there were no significant differences in the content of organic carbon and total nitrogen in the forest zone among the different aggregate fractions. The total phosphorus content topped in < 0. 053 mm fractions in the grassland zone and the forest-steppe zone,while that in the forest zone had no significant differences among the different aggregate fractions. Besides,the C∶ N ratios of < 0. 053 mm and 0. 053-0. 25 mm in the steppe zone and the forest-steppe zone were higher than that in the forest zone,while that of 0. 25-2 mm and > 2 mm had insignificant differences among the three vegetation zones. The C∶ P and N∶ P ratios of fractions in the forest zone were significantly higher than that in the forest-steppe zone and steppe zone. Overall,the stability and stoichiometry of soil aggregate fractions exhibited relatively significant differences among the three vegetation zones. Additionally,the stability,soil organic carbon,and total nitrogen content of aggregate fractions in the forest zone were generally higher than those in the forest-steppe zone and grassland zone.