Carbon Stock And Allocation Patterns Analysis Among Components In 4 Ecological Forests In Sub-tropical Area

Forest ecosystems play an important role in mitigation of global climate change due to their high carbon(C)sequestration capacity,large C stocks.Subtropical region of China has diverse forests which contain a diversity of tree species and exhibit a high carbon(C)sequestration capacity.However,with rapid urbanization taking place in China during past 30 years,forests in this area have been going through a serious destruction process.Therefore,conservation and restoration of subtropical ecological forests are the critical part for rebuilding ecological,social and economic values.At present,studies on forest biomass and carbon stocks in ecological forests in subtropical China has not ever been reported.Hence,we decided to select 4 types of subtropical ecological forests(i.e.Cunninghamia lanceolata plantation,Pinus massoniana evergreen coniferous forest,Choerospondias axillaris deciduous broadleaved-forest,and Lithocarpus glaber-Cyclobalanopsis glauca evergreen broadleaved-forest)as the study target to develop species-specific allometric equations for 7 tress species(i.e.namely Pinus massoniana,Alniphyllum fortune,Choerospondias axillaris,Liquidambar formosana,Cyclobalanopsis glauca,Litsea rotundifolia and Schima superba).Based on these species-specific allometric equations,we generalised allometric equations for 3 function groups(i.e.coniferous species,deciduous broadleaved species and evergreen broadleaved species).After this,we used the allometric equations above and relative data collected from 1 hm2 sample plots of the 4 forests,caculated forest stand biomass,C stocks and allocations as well as biomass conversion parameters and expansion factors(BEFs)for C storage.The objectives of this study are as follows:(1)to examine whether parameters of allometric equations of subtropical tree species are consistency;(2)to compare stand biomass,C stocks and allocation in the 4 forests;(3)to investigate plant richness and biodiversity in the 4 forests;and(4)to construct biomass conversion parameters for C storage biomass estimation at regional scale.The main results are presented as follows:1.Tree species significantly affect equation intercepts for all tree components and the slopes for branch,leaf and root biomass,but not significantly affect the slopes for stem,aboveground biomass and total tree biomass.Generalised equations for functional groups perform well with high correlation coefficients(R2>0.7).We recommend the generalised equations can be used for estimating forest biomass at regional scale,and also for estimating stem,aboveground and total tree biomass for these species when species-specific allometric equations are not available at a given site.For branch,leaf and root biomass,species-specific equations are preferred,even though this may require biomass data for additional tree species.2.Total C stocks in the 4 subtropical ecological forests(C.lanceolata plantation,P.massoniana evergreen coniferous forest,C.axillaris deciduous broadleaved forest,L.glaber-C.glauca evergreen broadleaf forest)are at 36.37 t/hm2,84.38 t/hm2,56.05 t/hm2 and 72.38 t/hm2,respectively.The maximum stand component C stocks was found in stems while the minimum stand component C stocks was retaned in leaves.C stocks was larger in roots than branches in C.lanceolata plantation and P.massoniana coniferous forest,wheras C stock was larger in branches than roots in C.axillaris deciduous broadleaved forest and L.glaber-C.glauca evergreen broadleaf forest.The mean value of biomass structure characteristic index of the 4 forests were 1.3166,3.9887,6.7149 and 4.1052 for BNR,0.1042,0.1815,0.2986 and 0.2291 for BNI,5.0992,5.3388,4.5635 and 4.5689 for CRR,0.0479,0.0401,0.0420,and 0.0492 for FC,and 0.8749,0.7740,0.6360,and 0.7201 STR,respectively.3.The 4 subtropical ecological forests consisted of 1 tree species belonging to 1 genues of 1 family for C.lanceolata plantation,42 tree species belonging to 33 genus of 21 families for P.massoniana evergreen coniferous forest,53 tree species belongin gto 40 genus of 25 families for C.axillaris deciduous broadleaved forest,and 40 tree species belonging to 29 genus of 22 families for L.glaber-C.glauca evergreen broadleaf forest.Dominate tree species contained more than half of total biomass in the 4 forests.Margalef richness index of the 4 forests were 0.00,0.04,0.05 and 0.04,respectively.Simpson index of the 4 forests were 0.08,1.41,1.35 and 1.27 while Shannon-Wiener index of these 4 forests were 0.08,1.41,1.35 and 1.27.Ecological dominance index of the 4 forests were 0.96,0.27,0.31 and 0.34,and Plelou evenness index of the 4 forests were 0.12,0.39,0.34 and 0.34.Our results indicated that tree species diversity affected forest biomass and C stocks.4.We investigated relationship between branch biomass and leaf biomass,between aboverground biomass and crown(leaf and branch)biomass,between aboverground biomass and stem biomass,between aboverground biomass and belowground biomass,between photosynthetic organ biomass and nonphotosynthetic organ biomass of the 4 subtropical ecological forests.Bivariate of each component biomass had a strong linear correlation and the coefficient of determination(R2)were larger than 0.5.5.Mean values of wood basic density(WD)of the dominate tree species in the 4 forests(C.lanceonata plantation,P.massoniana forest,deciduous broadleaved forest and evergreen broadleaved forest)from National Forest Inventory in subtropical area were 0.3133 g/cm3,0.4125 g/cm3,0.5021 g/cm3 and 0.5274 g/cm3,respectively;The mean values of the biomass expansion factor(BEF)of these 4 forests were 1.3089,1.2654,1.4233 and 1.3913.The mean values of root:shoot ratio(R)of the 4 forests were 0.1694,0.1772,0.2391 and 0.2635.The conversion parameters varied with stand age,stand density,diameter at breast height(DBH)and tree height(H).The WD values increased with stand age at first and then decreased as stand age increases.The BEF values and R values were negative correlated with DBH and H,and were positive correlated with stand density.The mean values of the BEF of 4 subtropical ecological forests(C.lanceolata plantation,P.massoniana evergreen coniferous forest,C.axillaris deciduous broadleaved forest,and L.glaber-C.glauca evergreen broadleaf forest)were 1.1444,1.3011,1.5919,and 1.3955,while the mean values of the R of these 4 forests were 0.1973,0.1920,0.2259 and 0.2208.