Effect Of Forest Closed On Biomass And Carbon Storage In Several Kinds Of Stands

The Yangtze River is the key ecological protection area in China. During CPRWRP project implementation, forest closed was an important technical measure for ecological restoration in this region. So to assess the effect of forest closed on forest carbon sequestration accuratly was very important. To estimate forest biomass and carbon storage could not only reflect the forest ecological system function, but also it was important means of evaluation the benefit of ecological restoration after hillsides closing.Six representative counties (cities) in the project implementation area, Macheng, Wanzhou, Yongchuan, Bijie, Yaoan and Yongshan, have been taken as study area. A representative small watershed in which the project be implement for5years had been selected for every counties, both plots and CK plots had been established as well.Forest types in study were Pinus elliottii stand in Macheng, Pinus massoniana in both Wanzhou and Yongchuan, Cryptomeria fortunei in both Bijie and Yongshan, and Pinus yunnanensis in Yaoa. They were mainly coniferous and mixed coniferous. Based on data of both plots an CK plots, regressions between biomass and DBH had been obtained for main tree species; biomasses and C orages for trees and shrubs, herbaceous, litter and soil layer of a stand had also been calculated; effects of hillsides closing or not on biomasses and C storages of a stand had been analyzed as well.Comments and suggestions had been given for regional ecological restoration and reconstruction based on the ecological benefit from hill closing. The main results were:The tree layer biomass accounted for more than50%, and tree root biomass for10%-20%, the litter biomass for less than6%of total biomass of a stand, and the proportion of shrub to herb was floating as the stand development. In early stage of a plant community both the shrub layer and herb layer were growing rapidly, but with the forest crown density increasing, the proportion of shrub layer to herb layer decreased gradualy.The vegetation layer C storage accounted for about30%, litter C storage for about1%, and soil C storage for about70%of total C storage of a stand, which indicated that the soil was a huge carbon pool.It was very obvious that the effect of forest closed on stand characteristics from a comparative analysis on both forest closed stand and CK stand.The technical measures of forest closed promoted tree growth, for instance, DBH, tree height, canopy density and tree density in main stand layer. The forest closed benefit depended on dominant tree species, forest growth stage and the disturbance intensity by human.The herbaceous biomass depended on canopy density, stand growth stage and herbaceous species composition. Although the technical measures of forest closed made the stand canopy density increased, it made shrubs and herbs growth decreased.The technical measures of forest closed promoted litter biomass accumulation. The litter biomass increased year by year converted to humus in soil surface effectively. The litter biomass was affected by stand age, density, species composition and the interference degree by humane.As humus quantity in soil increased year by year the soil structure and soil fertility were improved gradually:soil with high organic matter content, loose and porous, quantity of soil aggregate increasing, moisture and so on.The technical measures of forest closed made the forest C storage of different forest type increased2times, and the soil C storage was the maximum in whole stand C storage. The technical measures of forest closed made the C storage of every layer increased, and the C storage of the vegetation layer was bigger than that of soil. With the forest age and canopy density increasing, the C storage of both and soil layer were increaseing, however, the C storage of soil was bigger than that of the vegetation layer.The technical measures of forest closed meant this action had being kept damage from human, prohibited deforestation, which made a progress for a forest community succession and the ecological benefit increased gradually.