Factors Affecting The Biomass Conversion And Expansion Factor For Masson Pine In Fujian Province

Identifying the problems,which how stand characteristic factors,topographic factors and soil factors synergistically affect biomass conversion and expansion factor(BCEF)and how many relative influences of multiple factors affecting BCEF are,can provide a more accurate scientific basis for estimating biomass and carbon storage.In this study,the boosted regression trees(BRT)method was used to analyze the main factors that influenced the BCEF of foliage(BCEFfo),BCEF of branch(BCEFbr),BCEF of bark(BCEFbk),BCEF of wood(BCEFwd),BCEF of stem(BCEFst),BCEF of crown(BCEFcr),BCEF of aboveground(BCEFab),BCEF of blowground(BCEFbb)and BCEF of total tree(BCEFwt)of Masson pine.Data from the permanent sample plot of the 8th Chinese National Forest Inventory for Fujian Province was used.The main conclusions are as follows:(1)Stand characteristic and topographic factors were the most important factors for all kinds of BCEF.The cumulative relative influences of stand characteristic and topographic factors on the BCEFfo,BCEFbr,BCEFbk,BCEFwd,BCEFst,BCEFcr,BCEFab,BCEFbb and BCEFwt were 87.04%?87.38%?86.69%?88.25%?89.00%?87.08%?87.20%?86.59%and 87.80%,respectively.(2)Among the stand characteristic factors,the age group was dominant,respective contributing to 42.21%?40.91%?41.08%?41.94%?41.13%and 41.07%of the BCEFfo,BCEFbr,BCEFbk,BCEFcr,BCEFab and BCEFwt differences that decreased with an increase in the age group,and 42.82%?43.23%and 41.54%of the BCEFwd,BCEFst and BCEFwt differences that increased with an increase in the age group.(3)Among the topographic factors,slope aspect was the key variable,respective contributing to 13.28%?13.91%?14.43%?13.58%?14.52%and 14.52%of the BCEFfo,BCEFbr,BCEFbk,BCEFcr,BCEFab and BCEFwt differences,which were the highest at the southeast slope and the lowest at the southwest slope,and 13.06%and 15.16%of the BCEFwd and BCEFwt differences,which were the lowest at the southeast slope and the highest at the southwest slope.Besides,elevation contributed to 16.83%of the BCEFst differences that decreased with an increase in elevation and gradually inclined to stable while the elevation was more than 1000 meter.(4)In addition,soil factors had a lower effect on all kinds of BCEF.The cumulative relative influences of soil factors on the BCEFfo,BCEFbr,BCEFbk,BCEFwd,BCEFst,BCEFcr,BCEFab,BCEFbb and BCEFwt were 12.96%?12.62%?13.31%?11.74%?11.00%?12.92%?12.80%?13.41%and 12.20%,respectively.Among the soil factors,the thickness of the humus layer was the key variable,contributing to 8.89%?9.28%?9.42%?8.02%?7.85%?8.97%?9.02%?9.13%and 8.62%of the BCEFfo,BCEFbr,BCEFbk,BCEFwd,BCEFst,BCEFcr,BCEFab,BCEFbb and BCEFwt differences.Among all influencing factors,age group had the highest effect on all kinds of BCEF.Consequently,the ways,such as calculating BCEF based on age group or building universal BCEF models of all age,could achieve a better precision of biomass and carbon storage.