| As one of the relatively superior measures to cultivate the large diameter material abroad,the target tree management has started late in the domestic practice,and the mechanism has not been fully explained.In order to reveal the changing characteristics of the target tree management and the soil under the forest,the best measures for cultivating the large diameter lumber were sought in order to optimize the forest micro-environment while optimizing the structure of artificial forest ecosystem and improving ecosystem services.In this paper,the plantation of Pinus massoniana Lamb.in 30 a and 33 a in low mountainous area of Sichuan province was studied.The forest was thinned by the management measures of target tree and to explore the initial response of the forest growth for 3-4 years,the forest soil carbon storage and the soil active organic carbon pool to the target tree of the 100 plants/hm~2?150 plants/hm~2?100 plants/hm~2.To evaluate the comprehensive effect of target tree management on Pinus massoniana Plantation,it is of great practical and strategic significance to understand and quantitatively evaluate the change of carbon sequestration potential and nutrient cycling in local and similar areas after the management of target tree.It also provides some reference and practical significance for how to exert forest“sink”potential and ecological compensation better in the process of vegetation tending in this area.The results of the study are as follows:(1)The effect of the target tree on the growth structure of Pinus massoniana forest is as follows:After the target tree operation,the diameter of the forest was significantly higher than that of the control group(P<0.05),in which the average annual growth rate of breast diameter reached 0.3 cm,and the main source and target tree of the growth rate of each treatment;After the operation of the target tree,the diameter of the forest at the breast is typical normal distribution,in which the proportion of the larger diameter trees is higher than that of the control stands,and the large-scale tree distribution without the control stands has a great advantage for the cultivation of the large-diameter-order timber target tree;After the operation of the target tree,the trees grow rapidly due to the decrease of competition timber.The average annual growth of the volume reaches the 0.0063 m~3,in which the average annual growth of the target tree is higher than that of the general tree,excluding the accumulative loss of thinning,the actual accumulative growth of each treatment is significantly higher than that of the control forest(P<0.05).Among them,150plants/hm~2 performed best.(2)The average annual growth of carbon storage in each organ of Pinus massoniana was higher than that in the control group after the operation of the target tree,in which the average annual increment of the trunk was the largest,3.22 kg was reached,and the average annual growth rate of total carbon storage was highest in 200 plants/hm~2 target trees,5.46 kg;The increasing trend of carbon storage in each layer is arbor layer,>shrub layer>herbaceous layer>coarse woody remnant layer>litter layer.In addition to the tree layer,the variation both in the ground vegetation(shrub and herb)is highest,the processing of the ground vegetation carbon capacity variation is significantly higher than control(P<0.05),the processing of soil carbon reserves change was not significant(P>0.05),but lower than the control forest;Target tree processing of internal and external integration of carbon deposits in the case of trees reduced total 3-4 years compared with the stand,and compared the thinning stands before the internal and external integration of carbon reserves increase,the management of forest carbon sequestration ability target tree has a promoting effect.Stand for carbon sinks.(3)The target tree management changes the seasonal variation between the organic carbon pool,and the target tree region is more significant.Among them,target tree management changed the seasonal distribution of EOC in the target tree area of 0-5 cm,and the seasonal distribution of SOC and DOC in the target tree area of 5-20 cm,with no significant impact on FLOC(P>0.05).The target tree operation has increased the CPMI,and the correlation analysis shows that there is a strong correlation between the efficient nitrogen,the efficient phosphorous and the organic carbon bank,which means that the physical and chemical properties of the soil are very close to the carbon stability.In conclusion,target tree management not only improves the individual growth of target tree and provides large diameter material,but also significantly changes the growth structure of forest stand,promotes the development of forest stand carbon sink function,provides theoretical basis for the implementation of China's timber strategic reserve,and also provides feasible methods for improving the function of plantation ecosystem.The results showed that the accumulation of 150 plants/hm~2 was the best among all the treatments and could cultivate more large diameter materials than other treatments.The integrated internal and external carbon storage of 150 plants/hm~2 and 200 plants/hm~2 has reached a high level.At the same time,the target tree has changed the dynamic change of organic carbon storage after operation.Both available nitrogen and soil active organic carbon showed significant difference(P<0.01).The difference between available phosphorus and soluble organic carbon was very significant(P<0.01).It is advisable to implement 150 plants/hm~2 in similar conditions. |
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