华北落叶松人工林生长对抚育间伐的响应及其与土壤因子的关系

目的 探讨不同间伐强度对林木生长的影响并找出影响林分生长的关键土壤因子。 方法 在山西省沁源县好地方林场华北落叶松人工林设置12块抚育间伐试验样地，开展轻度（间伐强度15%）、中度（间伐强度35%）、重度（间伐强度50%）抚育间伐并设置对照样地，以树木平均胸径、平均树高、平均枝下高、平均冠幅、乔木层生物量与生产力为林木生长指标，利用方差分析与多重比较分析不同间伐强度林分生长特征，结合土壤因子运用相关性分析研究林木生长量与土壤因子的关系。 结果 表明：华北落叶松人工林经中度、重度间伐2年与4年后，各树木生长指标与对照样地相比均显著增加；间伐在减少林分内乔木层生物量的同时能显著提高乔木层生产力，各时间段及间伐强度下乔木层生产力均表现为重度>中度>轻度>对照；间伐可提高土壤有机碳（SOC）、土壤全氮（TN）、土壤全磷（TP）含量，减缓土壤养分的流失；华北落叶松人工林平均胸径生长量与SOC、TN呈显著正相关，平均冠幅生长量与土壤含水率（MC）、SOC、TN、TP显著正相关。 结论 间伐可促进华北落叶松人工林单株林木胸径和冠幅生长，增大林木单株冠径比与生产力，在本研究的3个间伐强度中，50%的重度间伐是最适间伐强度。华北落叶松人工林内土壤有机碳与土壤全氮含量较为丰富，土壤全磷含量较少，土壤pH为弱酸性，SOC、TN、TP是影响华北落叶松人工林生长的重要土壤因子。

Response of Larix principis-rupprechtii Plantation Growth to Thinning and Its Relationship with Soil Factors

Objective To explore the effects of different thinning intensity on tree growth and identify the key soil factors affecting forest growth. Method Twelve thinning test plots and control plots were set up in the Larix principis-rupprechtii plantation with mild (thinning intensity 15%), moderate (thinning intensity 35%), severe (thinning intensity 50%) thinning in Haodifang Forest Farm in Qinyuan County, Shanxi Province, and take the average DBH, average tree height, average branch height, average crown width, tree layer biomass and productivity as the tree growth indicators. Variance analysis and multiple comparisons were used to analyze the growth characteristics in the stands with different thinning intensities, and were combined with soil factor to study the relationship between forest growth and soil factors by utilizing correlation analysis. Result The tree-growth index of the L. principis-rupprechtii plantation significantly increased compared with the control after two and four years of moderate and severe thinning. Thinning significantly increased the productivity of the arbor layer while reduced the biomass of the arbor layer in the stand. The productivity of arbor layer in all the period and thinning intensities followed the pattern of severe thinning > moderate thinning > mild thinning > the control. Thinning increased the content of soil organic carbon (SOC), soil total nitrogen (TN) and soil total phosphorus (TP), and reduced the loss of soil nutrients. The average DBH growth of L. principis-rupprechtii plantation was significantly positively correlated with SOC and TN. The average crown growth was significantly positively correlated with soil water content, SOC, TN and TP. Conclusion Thinning can promote the growth of DBH and crown width of individual trees in L. principis-rupprechtii plantation and increase the ratio of crown to diameter and productivity of individual trees. Among the three thinning intensities, the severe thinning intensity is the optimal. Soil organic carbon and soil total nitrogen content in L. principis-rupprechtii plantations are abundant, the soil total phosphorus content is less, and the soil pH is weakly acidic. SOC, TN, TP are crucial factors affecting the growth of L. principis-rupprechtii plantation.