半干旱黄土丘陵沟壑区水平阶整地人工油松林种内竞争研究

以吴起县胜利山水平阶整地模式的20龄人工油松林为研究对象,采用逐步扩大范围的方法确定影响对象木的最佳竞争范围,探讨了不同径级基株所受的邻体竞争强度与邻体范围的关系.结果如下,(1)该区人工油松纯林对象木的最佳竞争距离为2.8m,其中小径级对象木的最佳竞争距离为4m,随着径级的增大,该取值范围变化趋势不明显;(2)总体竞争强度随着距离的增加逐渐增大,但增大的趋势随着距离的增加而减小.邻体范围与基株竞争强度的关系模型为倒数关系Cl=a+bL-1;(3)油松邻体竞争强度随对象木胸径的增大而减小,呈现幂函数关系Cl=aD-b.其中当油松基株胸径在0—2cm这个阶段中,油松之间的竞争比较激烈.该林地可以选择以2.8m为间距对小径级植株进行间伐择伐,减轻植株间的竞争消耗,实现植被群落达到健康稳定状态.

Intraspecies Competition Among Chinese Pine(pinus tabulaeformis)in a Level Terraced Forest of China’s Hilly and Gully Loess Plateau

Forests with level terracing in Wuqi were chosen to study intraspecies competition among Chinese pine(pinus tabulaeformis)trees using an improved individual competition model.Results indicated the following:(1)within the pine plantation,the optimal growth distance was 2.8m,which of 0—2cm lower diameter size was 4.0m,but it did not change obviously with the diameter size increasing;(2)as the spacing increased,the number of neighbor trees became more and the total intraspecies competition intensified,but the trend of intensified became weaker.Model of the total competition intensity and interference zone was:Cl=a+bL-1;(3)The competition intensity decreased gradually with the DBH increasing,the model was Cl=aD-b.The competition between the pines was greatest among trees with diameters of up to~2cm.Findings indicated that trees in this size range should thinned to a spacing pattern of approximately 2.8m,which will improve the health and stability of the pine forest.