亚热带森林透冠雨对林下土壤水稳性团聚体结构的影响

Effects of Throughfall in Subtropical Forests on the Structure of Water Stable Aggregate in Understory Soils

透冠雨不仅是森林土壤水分补给的主要形式,而且通过水力作用对土壤团聚体结构进行破碎和重组,但相关过程并不清晰。以亚热带森林林下土壤为对象,对照林外降雨,研究森林透冠雨对土壤水稳性团聚体粒径组成结构和稳定性的影响规律。结果表明:1)经过一年的原位培养实验,相较于林外降雨,透冠雨促进了土壤中大团聚体(>0.25 mm)百分比(R_(0.25))、土壤团聚体平均重量直径(MWD)和土壤团聚体几何平均直径(GMD)的增加。2)R_(0.25)、MWD、GMD在雨季主要表现出减少趋势,而旱季主要体现为增加趋势,且雨季的变化幅度较旱季更大。相对于林外降雨,透冠雨在雨季对土壤中R_(0.25)、MWD、GMD减小幅度更加明显,在旱季的增加幅度也更加显著。3)降雨量显著影响R_(0.25)、MWD、GMD。透冠雨量减少提高了土壤中的R_(0.25)、MWD、GMD,而林外降雨量减小对于土壤中R_(0.25)、MWD、GMD的提高较小,其中MWD、GMD与雨量大小呈显著负相关关系。综合上述结果,相较于林外降雨,透冠雨能维持较好的土壤团聚体结构,对森林土壤土壤结构稳定性具有明显的积极作用。

Throughfall is not only the main form of forest soil moisture recharge,but also can break and reorganise soil aggregate structure through hydraulic action,but the related process is unclear.Taking subtropical forest understory soil as an object,this study investigated the influence of forest throughfall on the particle size composition structure and stability of soil water stable aggregates against the rainfall outside the forest.The results show that,1)after one year of in situ incubation experiments,compared with rainfall outside the forest,throughfall promoted an increase in the percentage of large soil aggregates(>0.25 mm)(R_(0.25)),the mean weight diameter(MWD),and the geometric mean diameter(GMD)in the soil.2)R_(0.25),MWD,and GMD mainly showed a decreasing trend in the rainy season,while the dry season mainly reflected an increasing trend,and the magnitude of change was greater in the rainy than in the dry season.Compared with rainfall outside the forest,throughfall decreased R_(0.25),MWD,and GMD in soil more significantly in the rainy season and increased them more significantly in the dry season.3)Rainfall significantly affected R_(0.25),MWD and GMD,while reduced rainfall throughfall increased R_(0.25),MWD and GMD in soil,while reduced rainfall outside the forest increased R_(0.25),MWD and GMD less,with MWD and GMD significantly and negatively correlated with rainfall.Taken together,compared with rainfall outside the forest,throughfall can maintain a better soil aggregate structure,which has an obvious positive effect on the stability of soil structure in forest soils.