Abstract:

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.

Key words: Populus davidiana, Betula platyphylla, DBH class structure, spatial distribution, spatial association