间伐强度对柚木林土壤质量及生长的影响

目的 探究不同间伐强度对柚木人工林土壤理化性质、酶活性及林木生长的影响，为柚木大径材高效培育和林地可持续经营提供理论依据。 方法 以15年生柚木纯林为研究对象，设置轻度、中度、重度间伐和对照4个处理。间伐3.5 a后，测定柚木生长量、土壤理化性质和酶活性等指标，分析不同间伐强度处理下各指标的差异。采用冗余分析法（RDA）分析柚木生长指标及土壤酶活性与土壤理化性质指标之间的关系。 结果 间伐对土壤理化性质及酶活性的影响主要表现在0～20 cm土层，间伐提高了土壤含水率，降低了表层土壤pH值；土壤有机质、碱解氮的含量随间伐强度的增大而增加，中度、重度间伐林分0～20 cm土层有机质含量比对照显著提高了18.2%和19.0%，碱解氮含量显著增加了15.7%和16.6%；间伐后土壤全氮和交换性钙含量也均增加。间伐显著增强了0～20 cm土层的蔗糖酶活性，而脲酶、酸性磷酸酶和过氧化氢酶活性变化无显著差异。柚木林分的平均胸径和单株材积随间伐强度的增大而增加，林分断面积和蓄积也均高于对照；重度间伐处理的林分各生长指标年均增量最大，并显著高于对照，平均单株材积和蓄积增量分别提高了80.0%和90.2%。土壤有机质、有效磷含量与柚木各生长指标呈正相关，田间持水量、土壤密度及总孔隙度是影响土壤酶活性的主要环境因子。 结论 间伐改善了土壤养分和水分状况，促进了柚木生长，林地生产力得到明显提高。间伐提高了与N、P循环相关酶的活性，显著增强了与C循环相关的蔗糖酶活性。对15年生柚木人工林进行间伐，适宜的间伐强度为40%～45%。

Effects of Thinning Intensity on Soil Quality and Growth of Teak Plantation

Objective To explore the effects of thinning intensity on the growth of teak, on soil physicochemical properties and on enzyme activity. Method Taking 15 years old pure forest of teak (Tectona grandis) as trial object, four thinning intensity treatments, including low, moderate, heavy thinning and the control were set. The growth, soil properties and enzyme activities of teak plantation were measured 3.5 years after thinning, and the difference of these indexes with different intensity treatment was analyzed. Redundant analysis method (RDA) was used to study the relationship between tree growth, soil enzyme activity and soil property. Result The effects of thinning on soil physicochemical properties and enzyme activities were showed mainly in 0-20 cm soil layer. The soil moisture content of the surface soil increased and soil pH reduced after thinning. The contents of soil organic matter and alkali-hydrolyzed nitrogen was positively correlated with the intensity of thinning treatment, In 0-20 cm soil layer, the organic matter contents under moderate and heavy thinning increased by 18.2% and 19.0% compared with the control, and the alkali-hydrolyzed nitrogen content was respectively 15.7% and 16.6% higher than that of the control. The contents of total nitrogen and exchangeable calcium also increased after thinning. The activity of invertase and acid phosphatase in 0-20 cm soil layer was significantly enhanced by thinning, but there was no significant difference in urease and catalase contents. The average breast-height diameter and the volume of individual trees of teak plantation increased with the intensity of thinning treatment, and the stand basal area and volume were higher than those of the control. Under heavy thinning treatment, the annual increment of growth indexes of teak was the largest and significantly higher than that of the control, while both the individual volume and stand volume increment were higher than of the control by 80.0% and 90.2% respectively. There was a positive correlation between soil organic matter, available phosphorus and tree growth indexes. Soil water holding capacity, density and total porosity were the main environmental factors affecting soil enzyme activity. Conclusion Thinning can improve soil nutrient and water status, promotes the growth of teak, and the productivity of forest land can increase obviously. Thinning significantly enhances the C cycle-related invertase activity and increases the activity of N, P cycle-related enzymes. Total nitrogen, soil bulk density are the key factors affecting enzyme activity. The suitable thinning intensity of 15-year-old teak plantation is 40%-45%.