Abstract: Pinus tabulaeformis is not only one of representative tree species in warm temperate zone, but also an important afforestation tree species in northern China. The population structure and spatial patterns of main woody plant species were studied. The results showed that the population structure of P. tabulaeformis was a reverse pyramid type. The age structure of the population was declining due to lack of seedlings and saplings. The population structure of other 5 broadleaved populations, such as Quercus liaotungensis, Acer tegmentosum and etc, was a spindle type and the age structure of these populations was ascending. As to the distribution pattern, the P. tabulaeformis, Q. liaotungensis, Prunus armniaca, Populus davidiana and Crateagus pinnatifida population were clump in all research scales. Betula platyphylla and Acer ginnala population patterns were the same, clump for small scales, random for middle and large scales. The spatial pattern of Acer tegmentosum population was random for middle scales, but clump for small and large scales. As to Acer mono population, the spatial distribution pattern was random in all scales. Varied with scales, the spatial patterns of Alnus japonica changed from clump to regular. The spatial patterns of the woody plant population in upper and lower layers were also analyzed. The result showed that the spatial patterns of upper layer's and lower layer's tree species were all clump tendency, whereas the latter varied from clump to random. The population spatial pattern was decided mainly by long-term interactions among the biological, ecological characteristics and its environmental conditions, which showed the survival strategy and adaptive mechanism in certain degree.

Key words: natural Pinus tabulaeformis forests, size-class structure, spatial pattern, point pattern analysis