北京通州平原生态林空间结构特征

林分空间结构直接反映林木间资源竞争情况和生长空间分配状况,对掌握生态林生长状况、制定林分结构调控措施,提升森林质量和生态服务具有重要作用。本文以北京市通州区油松林、白蜡林、旱柳林、毛白杨林、国槐林、刺槐林和垂柳林7种平原生态林为对象,采用聚集度、角尺度、大小比数、开敞度、树冠指数、竞争指数、边缘效益和空间结构综合指数评价了平原生态林的空间结构特征。结果表明: 研究区林分水平分布格局良好,聚集度处于0.32～1.41,角尺度都分布在0.4左右,大小比数主要分布在0.5附近。林分垂直分布格局有待改善,开敞度介于0.19～0.52,大部分树冠指数在0.7左右,竞争指数均大于50,整体居于高位状态。除刺槐林空间结构综合评价指数为Ⅲ级外,其他6种林分均为Ⅱ级,林分开阔程度较低,生活力一般,各林分空间结构综合评价指数从大到小为刺槐林>垂柳林>油松林>旱柳林>白蜡林>国槐林>毛白杨林。

Spatial structure characteristics of plain ecological plantation in Tongzhou District,Beijing, China

Forest spatial structure (FSS) directly reflects resource competition and growth space distribution among different trees. The characteristics of FSS play an important role in mastering the growth status of ecological forest, formulating stand structure regulation measures, and improving forest quality and ecological services. In this study, seven plain ecological plantations including Pinus tabuliformis, Fraxinus chinensis, Salix matsudana, Populus tomentosa, Sophora japonica, Robinia pseudoacacia, and Salix babylonica in Tongzhou District, Beijing were selected as the research objects. The spatial structure characteristics of plain ecological plantations were evaluated by aggregation degree, angle index, neighborhood comparison, open degree, canopy index, competition index, edge benefit, and spatial structure comprehensive index. The horizontal distribution pattern of stand was well, with the aggregation degree of 0.32-1.41, the angle index of 0.4, and the neighborhood comparison mainly around 0.5. The vertical distribution pattern of stand was not well and needed to be improved, with the open degree of 0.19-0.52, most canopy indexes of about 0.7. The competition index presented a high competitive status with the all values of >50. Except the comprehensive evaluation index of R. pseudoacacia plantation presented in grade Ⅲ, the other six kinds of plain ecological plantations fell to grade Ⅱ, with low stand openness and low vitality. The comprehensive evaluation indices of FSS followed the order of R. pseudoacacia > S. babylonica > P. tabuliformis > S. matsudana > F. chinensis > S. japonica > P. tomentosa.