Spatial structure diversity of semi-natural and plantation stands of larix gmelini in Changbai Mountains, northeastern China.

The objective of this study was to study the recovery and protection of over-logged forests. Based on survey data of two plots, the structure of larch-spruce-fir stands and natural spruce-fir and broadleaf mixed forests was analyzed using traditional approaches, species spatial diversity and a bivariate distribution of three commonly used diversity indices, i.e. uniform angle index (W), dominance (U) and mingling (M). The results indicated that: 1) The diameter distribution of the spruce-fir and broadleaf mixed forests was similar to a “J-shaped” curve. The diameter distribution of the larch-spruce-fir stands was similar to a multimodal “J-shaped” curve and showed the characteristics of stands of the same generation. The value of species spatial diversity of larch-spruce-fir stands (4.149 4) was smaller than that of spruce-fir and broadleaf mixed forests (5.546 0). 2) There were no significant differences in the structure of the bivariate distribution between the two plots. As for two indices DBH and height, the frequency of the trees with random distribution pattern and middle dominance degree was 14% for DBH and 13% for height in the larch-spruce-fir stands, and 11% for DBH and 13% for height in the spruce-fir and broadleaf mixed forests. As for the same indices, the frequency of the trees with high mingling and middle dominance degree was 12% for DBH and 10% for height in the larch-spruce-fir stands, and 13% for DBH and 14% for height in the spruce-fir and broadleaf mixed forests. 3) The frequency of trees with different dominance and mingling degree was different in the larch-spruce-fir stands. Trees with same mingling degree were almost the same between different dominance degrees in spruce-fir and broadleaf mixed forests. There was also little difference in DBH and height. The natural spruce-fir and broadleaf mixed forests were in a relatively stable state. Immediate measures are needed to improve spatial structure diversity in the larch-spruce-fir stands. The results of our research could be used for the design and tending of larch-spruce-fir stands and adjustment of its structure, and thus to achieve the effects of structure-based forest management of larch-spruce-fir stands.