| The mixed broadleaved-Korean pine (Pinus koraiensis) forest is one of the most complex and common vegetation type northeast China. It is well known for its high biodiversity,complex stand structure and unique species composition. Because of timber harvesting practices without measure, the extent of the mixed forest has been greatly reduced and only old-growth forest stands can be found in several natural park and national forest park.Disturbance may change the competition and adaptability of plant, thereby the population dynamics can be changed unpredictablely. The objectives of this study were to explore effects of selective cutting on stand succession and species population of the mixed broadleaved-Korean pine forests in Liangshui national nature reserve, China, after 37 years of selective cutting. We studied the population structure and competitive relationships of the major species in mixed forest both logged and unlogged stands contrastively, and each plots size is 100m×100m. For two plots, We randomly selected 15 living trees were cored and measure each tree's heght, to realize the diameter and vertical growth condition of major tree species.The results showed that:population structure of the major species in the logged stands changed significantly (P<0.01) except Fraxinus mandshurica, which indicates that the selective cutting has caused changes in the population dynamics to a certain extent. Competition index of the major species in the logged stands changed significantly (P<0.01) The increase of competition index was also obvious with the maximum of 7.98 in Betula costata and, the minimum of 0.52 in Pinus koraiensis. Among the major species, only in Abies nephrolepis did the competition index decreased(-1.08). There was a significant negative correlation between the changes of competition index and tolerance index (r=-0.8821, P<0.01). A significant linear relationship between intraspecies competition and aggregation index and number of trees of each species(P<0.01) were noticed. The largest aggregation index was shown in Betula costata and Tilia amurensis in selective cutting area. Because of this, intraspecies competitions are stronger than interspecies competitions in B. costata and T. amurensis, which was in favor of coexistence of different species. The selective cutting depressed Pinus koraiensis's competition on its associated tree species. In contrary, shade-intolerant species's (B. costata, T. amurensis) competition on other species toned up. To conclude:(1) P. koraiensis's competition stress varied little 37 years after selective cutting, which is propitious to its growth and survivorship; (2) Comparative advantages of B. costata and T. amurensis would decrease because of self-thinning. (3) A. nephrolepis's competition pressure was weakened, which is beneficial to recovery of species population. The effect of selection cutting significantly increased survivor's mean annual diameter growth for the five major tree species. (1) Selection cutting had significant effects on radial growth (P<0.01), and the species-specific response grades were related to shade-tolerance(r=-0.79, P<0.01) significantly, also, the increasing rate of the strongest shade-tolerance species (Pinus koraiensis) increased the lowest (39%), meanwhile, the feeblest shade-tolerance species (Acer mono) increased the most(70%). the acceleration caused by selection cutting would sustained for 26-29 years. (2) Selection cutting significantly effected the tree height-diameter rate (P<0.01), moreover, tree height-diameter rate of selective cutting area was smaller than virgin forest area. radial growth, (3) Tree height and diameter were significantly related (virgin forest area:r=0.65*, r=0.58*; selective cutting area:r=0.53*, r=0.48*). radial growth of all diameters of virgin forest were larger than virgin forest area. thereinto, the largest was difference was 20cm |
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