Effects Of Close-to-nature Forest Reconstruction On Distribution Patterns Of Carbon Storage In Young And Middle Age Forests In Ningbo Area

As the largest carbon storage in terrestrial ecosystems,forests play an irreplaceable role in mitigating climate warming and maintaining global carbon balance.Many experimental studies have confirmed that reasonable forest management measures can effectively improve forest carbon sink capacity and potential.Close-to-nature transformation is a multi-objective forest management model originating in Germany,which emphasizes that forestry activities should be carried out according to the law of forest self-development.Since the introduction of near-natural forest theory in China in the 1980 s,many researches have discussed the theory of close-to-nature transformation and the feasibility of its application.However,there is still a lack of unified understanding of the impact of close-to-nature transformation on forest carbon storage dynamics and its mechanism.Taking Yuwang and Tingxia forest close-to-nature management demonstration plots that set up by the National Tiantong Station in Ningbo as the research object,the carbon storage in tree layer,litter layer and soil layer of the close-to-nature transformation was observed for one year.The content of soluble organic carbon,microbial biomass carbon and fine roots in soil were measured by collecting soil and fine root samples.The effects of near-natural forest transformation on carbon storage dynamics and root turnover of forest ecosystem components were analyzed.The main results are as follows:(1)In the early stage of close-to-nature transformation,seasonal dynamics of soil soluble organic carbon in different surface layers were significantly different;compared with the control plots,soil soluble organic carbon and microbial biomass carbon content in different soil layers of the close-to-nature transformation plots did not change significantly.(2)After close-to-nature transformation,the carbon storage of tree layer in Yuwang and Tingxia demonstration sites increased by 27.0% and 37.80% respectively,and the growth rate was significantly higher than that of the control plots;the carbon storage of litter layer on the surface and its change did not respond significantly to the close-to-nature transformation forests;the growth rate of total carbon storage of soil in different types of close-to-nature transformation forests was lower than that of the control plots,but it do not reached the significant level.(3)Close-to-nature transformation has a certain impact on the distribution of carbon storage in tree layer organs and components of ecosystem.The specific performance is that close-to-nature transformation improves the allocation ratio of carbon storage in vegetation branches,leaves and roots,and decreases the proportion of carbon storage in trunk.After transformation,the proportion of carbon storage in tree layer of Yuwang plot increased,while the distribution of carbon storage in tree layer of Tingxia plot was lower than that of the control plots.(4)Fine root stock decreased after the close-to-nature transformation,but there was no significant difference between the transformation and control plots.Close-to-nature transformation significantly increased the fine root production and turnover rate of surface soil in Yuwang plot,but had no significant effect on Tingxia plot.In conclusion,close-to-nature transformation can significantly increase the growth rate of biomass and carbon storage of various organs in forest tree layer,and the production and turnover rate of fine roots in surface soil layer,but it has no significant effect on soil active organic carbon,litter layer and soil layer carbon storage.The results of this study can provide a scientific basis for the ecological restoration and sustainable development of subtropical forests and the impact of close-to-nature transformation on forest carbon sequestration function.