氮添加对亚高山针叶林土壤结构及水分入渗性能的影响

为探究大气氮沉降增加导致的土壤团聚体结构变化规律及其对土壤水分入渗性能的影响，在贡嘎山针叶成熟林和中龄林内分别设计2种氮肥形态(NH₄)₂SO₄、KNO₃]和4个浓度水平(0,10,20,40 kg/(hm²·a)N)的添加试验，研究不同形态大气氮沉降对亚高山森林土壤团聚体结构和土壤水分入渗特征的影响。结果表明：(1)随施氮量增加，中龄林土壤大团聚体含量逐渐增加，土壤持水量、孔隙度和水分稳定入渗率逐渐增大；成熟林土壤大团聚体含量、土壤持水量、孔隙度和水分稳定入渗率均表现出先增加后降低的趋势；(2)不同形态氮添加对土壤团聚体结构、孔隙度及水分稳定入渗率的作用无显著差异；(3)土壤持水能力、孔隙度和团聚体结构是土壤入渗性能的主要影响因子，外源氮添加增加中龄林土壤持水量和孔隙度，改善中龄林土壤团聚体结构稳定性和水分入渗性能。

Effects of Nitrogen Addition on Soil Structure and Water Infiltration of Subalpine Coniferous Forest

In order to investigate the changes in soil aggregates due to increased atmospheric nitrogen deposition and its effect on soil water infiltration, two kinds of nitrogen fertilizer ((NH₄)₂SO₄ and KNO₃) with four concentration levels (0, 10, 20, 40 kg/(hm²·a)N)were respectively added in mature and middle-aged coniferous forests at Mount Gongga, aims to investigate the effect of different forms of atmospheric nitrogen deposition on the structure of soil aggregates and the infiltration characteristics of soil water in a subalpine forest. The results showed that: (1) With the increase of nitrogen application, the proportion of large macroaggregate, soil water holding capacity, soil porosity and water stable infiltration rate in middle-aged stands gradually increased; the proportion of large macroaggregate, soil water holding capacity, soil porosity and water stable infiltration rate in mature stands showed a trend of first increasing and then decreasing; (2) The effects of different nitrogen forms on soil aggregate structure, soil porosity and water stable infiltration rate showed no significant difference; (3) Water infiltration was mainly affected by water holding capacity, soil porosity and aggregate formation. Nitrogen addition increased water holding capacity and soil porosity, and enhanced soil aggregation and water infiltration in middle-aged stands.