冀北土石山区天然次生林山杨、白桦种群的空间分布格局

Spatial Distribution Pattern of Populus davidiana and Betula platyphylla Populations in a Typical Natural Secondary Forest in Rocky Mountain Area of Northern Hebei

分析冀北土石山区典型天然次生阔叶林中的山杨、白桦种群的径级结构、空间分布格局及种内/种间的空间关联。结果表明:山杨、白桦均以中径木为主,林下缺乏可供更新的幼苗、幼树,种群呈现衰退趋势;山杨、白桦的全部个体在本研究尺度上呈聚集分布,随尺度的增大其聚集强度先增大后减小,并趋于随机分布;山杨、白桦种群随龄级增大,聚集强度减小,以幼树的聚集强度最大;不同生长阶段同种个体间的关联性随尺度的变化,出现正关联、负关联和相互独立的空间关系,以负关联为主;不同生长阶段的山杨和白桦种群间未出现正关联,大多数种对在本研究尺度上为负关联或者在大部分尺度上为负关联;山杨、白桦的种内/种间竞争激烈,群落整体结构不稳定,处于演替初期向中期过渡阶段。

In this paper,we investigated class structure of the diameter at breast height(DBH),spatial distribution pattern and intraspecific /interspecific spatial association of Populus davidiana and Betula platyphylla populations.The results showed that trees with intermediary diameter of Populus davidiana and Betula platyphylla dominated the populations.The populations lacked regenerative saplings,which indicated the populations were in declining trend.In the study scale,all individuals of the two species populations were significantly clustered,and with scale increase the clustering intensity first increased and then decreased to a random distribution.At different growth stages,clustering intensity decreased with age-class increase.The saplings had the maximum clustering intensity.Spatial association of intraspecific individuals of Populus davidiana and Betula platyphylla at different growth stages depended on the scales,and presented positive,negative and independent,among which the negative association was dominant.However,spatial association of interspecific individuals did not present positive one,and most of trees had a negative association on the scale of this study,or most of scales exhibited a negative association.The results showed that there existed fierce competition in intraspecific /interspecific of Populus davidiana and Betula platyphylla populations,the structure of the communities was unstable,and the communities were in transition stage of succession from prime to interim.