Growth Characteristics Of Juvenile Korean Pine Planted In Secondary Forest

Zonal climax Korean pine (Pinus koraiensis) and broadleaved species mixed forest in Northeast China has been changed regressively into secondary forest with almost no conifers. Planting Korean pine tree under the canopy of secondary forest is a feasible approach for recovering Korean pine and broadleaved species mixed forest. For establishing an effective growth promotion method for under-canopy planted juvenile Korean pine trees.An experiment of individual growth space adjustment was conducted on the juvenile Korean pine trees planted in 1989 (A) and 1982 (B), relying on Opening Degree (K) combined with contagion (U), species mingling (M) and size differentiation (W) at the stages of K=1, K=1.5 and K=2, including the CK. Studying on the forest structure, the suitable environment, and the biomass distribution to solve the slow growth of juvenile Korean pine trees under the canopy of secondary forest, coordinate the relationship between broadleaved species and juvenile Korean pine trees, and make a management project in this growth stages. Following the results:After the numerical adjustment, the structure of broadleaved species trend to accord. The broadleaved trees in the east, northwest, southeast, and above the juvenile Korean pine trees were cut, and the contagion (U = 0 or U = 0.25), species mingling (M=0.5), and size differentiation (W=0.5) were fixed. The retain trees are with small leaves and sparse branches.The advantages of growth in both stages are significant, in the A stage, the net growth of mean basal diameter and the height of juvenile Korean pine trees in the A1 (K=1) management during past 4 years were the highest, and they were higher than ACK 63.4% and 68.5% respectively, then A3 (K=2)>A2 (K=1.5)>ACK. In the B stage, the mean diameter at the breast height was the B1 management, higher than BCK 82.7%, but height in the B3 (K=2)management was higher than BCK 80.6%, then B1 (K=1), B2 (K=1.5) were higher than BCK 70.5%.The height under the first branch in both stages was low. Especially in the B stage, the ratio of dead branches on the trunk was higher, and the natural pruning capacity of juvenile Korean pine was 0.242 in average. The crown width was longest in the east in both stages. In the A stage, The normal form quotient of CK was biggest, and then A1 (K=1), A2 (K=1.5), A3 (K=2), and B1 (K=1)>B2 (K=1.5)>B3 (K=2)>BCK (0.648) in the B stage.The specific leaf area became bigger in both stages, while the open degrees were lager. The current year leaves had the biggest specific leaf area, which means that the forest adjustments are suitable. The biomass models in the two stages are W=aD₀^bå’ŒW=aD_1.3^b respectively. The results showed that the biomass of juvenile Korean pine in the K=l management was higher than any other management in both stages, they were A1 (K=1) =1.328 t/hm² and B1 (K=1) =22.302 t/hm². In A stage, the average biomass per plant were A3 (K=2)>A1 (K=1)>A2 (K=1.5)>ACK(0.018 t/hm²); In B stage, the average biomass per plant were B1 (K=1)>B2 (K=1.5)>B3 (K=2)>BCK(0.255 t/hm²). The current needles biomass was the highest in different age classes.Among the biomass structural characteristics, A1 (K=1) =46.7% and B1 (K=1) =46.7% management had the higher trunk biomass in the two stages, and they also had the lowest ratio of bark. In A stage, the ratio of branch was higher in the A2 (29.1%) management, but in the B stage only B2 (K=1.5) was significantly different from the others.Above all, the synthesis effect of K=1(open degree) management showed better than the others in planting Korean pine tree under the canopy of secondary forest between 15 and 25 years, which is the best way to manage this kind of forests.