异速生长法计算秋茄红树林生物量

采用异速生长方法,建立树干基部多分枝型秋茄生物量与分枝直径的函数模型,根据该模型计算了浙江鳌江河口人工秋茄林生物量,并比较了我国不同地区秋茄林生物量差异。结果表明,秋茄生物量(W)与分枝直径(D)之间存在极显著的回归关系,叶片(WL)、树干(WS)、根系和分枝基部(WB)及植株总生物量(WT)与分枝直径(D)的异速生长方程分别为:WL=0.187D1.855(R2=0.612,P<0.0001);WS=0.267D1.906(R2=0.821,P<0.0001);WB=4.6D1.136(R2=0.644,P<0.0001);WT=3.614D1.446(R2=0.801,P<0.0001)。我国不同地区秋茄林地上生物量与林龄和纬度之间存在显著的回归关系:lg(地上生物量)=3.123+0.84×lg(林龄)-2.019×lg(纬度),(R2=0.431,F2,11=4.161,P=0.045)。秋茄种群生物量随着林龄的增加而增加,随着纬度的升高呈现降低趋势。浙江鳌江河口3年、5年和10年龄人工秋茄林生物量分别为7.13、11.32和24.35 t/hm2,其中5年龄秋茄林生物量仅为广东湛江同龄秋茄林(自然湿地生境)生物量的18%。然而,广东深圳的3年龄秋茄林(人工湿地生境)生物量仅为该研究中同龄秋茄林生物量的9.3%。此外,以≤11年龄的人工秋茄纯林为对象,建立了种群密度与种群植株平均生物量的关系:lg(平均单株地上生物量)=8.468-2.1×lg(种群密度),(R2=0.961,F=99.764,P=0.001),秋茄种群密度越小,平均植株生物量越大,平均单株生物量较符合Yoda提出的-3/2自疏定律为快,自疏指数为-2.1。因此,纬度和林龄是秋茄种群生物量的主要影响因子,生境类型、种群密度等因素对红树林种群或群落生物量的积累也至关重要。

An assessment method of Kandelia obovata population biomass

Mangroves are the unique intertidal plant formations growing in sheltered tropical and subtropical coastal areas.The past decade,many measures were undertaken for mangrove forestation in the Aojiang Estuary,Zhejiang Province,with 47 hm2 of existing Kandelia obovata forest.The present experiment was conducted to assess the population biomass of K.obovata in Aojiang Estuary.Mathematical methods that use easily measured variables to predict difficult-to-measure variables are important to mangrove managers.As a result,standard plant methods and allometric equations have been developed for several decades to estimate mangrove biomass.Single-stemed mangrove production was usually estimated by allometry between biomass and stem diameter at breast height.Because mangroves are usually dwarf forests in higher latitude sites,and moreover,the crown bases and multi-stems of dominant individuals may begin within a few decimeters of ground level,estimates of community production that depend on allometry based on single-stemed mangrove may not be accurate.Here,we develop allometric relations to predict total biomass and individual components of biomass(e.g.,leaves,stemts,roots and butts) of K.obovata,a multi-stemmed mangrove,in the Aojiang Estuary,Zhejiang province.This procedure treated each stem as a discrete tree that shared a proportion of the butt and other elements common to all stems.Linear log-log relationships were obtained between biomass and stem diameter at one-tenth of the stem length nearly the ground.Population biomass of artificial K.obovata forest in Aojiang Estuary was calculated according to the function model.We compared the difference on population biomass of K.obovata in different regions of China.The results showed that K.obovata biomass(W) correlated to the stem diameter(D) at a significance level(P < 0.001).The function model between plant biomass(leaf,WL;stem,WS;Root and butt,WB;and total,WT) and stem diameter(D) was as follows: WL=0.187D1.855(R2 =0.612,P < 0.0001);WS=0.267D1.906(R2 =0.821,P < 0.0001);WB=4.6D1.136(R2 =0.644,P < 0.0001);WT=3.614D1.446(R2 =0.801,P < 0.0001).The regression relationship between K.obovata aboveground biomass and stand age and latitude was significant in different regions of China,that is,lg(aboveground biomass)=3.123 + 0.84lg(stand age)-2.019lg(latitude)(R2 =0.431,F2,11=4.161,P =0.045).Population biomass of K.obovata increased with increased stand age,while trend to decrease with increased latitude.Population biomass of 3-,5-and 10-year-old K.obovata forest in Aojiang Estuary was estimated at 7.13,11.32 and 24.35 t/hm2,respectively.The 5-year-old population biomass in this experiment was only of 18% compared with the same age population of K.obovata grown in natural wetlands in Zhanjiang,Guangdong province.However,the biomass of 3-year-old population grown in artificial wetlands in Shenzhen was only 9.3% of the same age population biomass in this experiment.In addition,the regression relationship between population density and mean individual biomass was estimated based on the data of ≤ 11-year-old artificial pure K.obovata forest: lg(mean individual aboveground biomass)=8.468-2.1 × lg(population density),(R2 =0.961,F=99.764,P =0.001).This equation indicates that mean individual biomass increased with decreased population density and the self-thinning index was-2.1,which approximately accorded with the-3/2 power law.Therefore,not only stand age and latitude affect K.obovata population biomass,but habitat types and population density are crucial to K.obovata population biomass accumulation.