| P. bournei (Hemsl.) Yang is not only a beautiful large evergreen broad-leaved trees,but also an endangered species.It was listed as the two level national protected wild plants,P. bournei (Hemsl.) Yang has a very high economic value and ecological significance.This paper using inventory and laboratory analysis studies three kinds of forest ages Hunan P. bournei (Hemsl.) Yang plantation ecosystem’s biomass,carbon content rate and the distribution characteristics of carbon density.The main research results are as follows:(1)The12a,25a,38a P. bournei (Hemsl.) Yang plantation ecosystem’s biomass were52.52t/hm2,210.45t/hm2,347.44t/hm2,respectively;Most biomass (95.09%-97.19%)of P. bournei (Hemsl.) Yang plantation were concentrated in the tree layer,by ages from small to large were49.95t/hm2,205.22t/hm2,337.67t/hm2,respectively;next was the litter layer,made up2.03%to4.68%;Shrub and herb layers biomass contributed smallestjust made up0.23%to0.46%;The biomass of the trunk occupied the greatest proportion of tree layer,which made up53.06%to62.63%and this proportion increases with ages;Root had a relatively stable biomass,which accounted15.97%to17.78%;Branches and leaves made up10.47%to15.33%,7.08%to8.75%,respectiv ely,and with the increasing age, the proportion of branches and leavese gradually reduced;12a,25a,38a P. bournei (Hemsl.) Yang plantation forest average net productivity were:6.73t/hm2-a,17.35t/hm2-a,24.60t/hm2·a, respectively.(2)The average carbon content of tree layer12years old P. bournei (Hemsl.) Yang sort of different seasons is spring(49.45%)>winter(46.04%)> autumn (45.61%)> summer (44.25%).The annual average carbon content sort of different organs are leaves(48.41%)>root(46.98%)>bark(46.98%)>branch(45.20%)>trunk>(44.02%).Thre e kinds of forest age of P. bournei (Hemsl.) Yang average carbon content of various organs roughly as follows:leaves(48.45%)>root(46.09)>trunk(46.07%)>bark (44.41%)> branch (44.38%).The difference between the average carbon content of the root of each component is small. The average carbon ratio P. bournei (Hemsl.) Yang tree layer also increased with the increasing age,38years(46.99%)>25years (46.38%)>12years (44.64%).Carbon content P. bournei (Hemsl.) Yang plantation vegetation layer decreases from top to bottom,three kinds of forest age are tree layer> shrub layer> herb layer.The rates of soil carbon content decreased with increasing soil depth in three plots.The carbon content within the three plots0-60cm soil increases with ages,but haven’t reach an significant differences,which were12years(5.86%)<25years (6.34%)<38years(7.05%).The carbon content in different layers of the soil with nitrogen rate was significantly correlated,and parts of significantly correlated with total phosphorus.(3)P. bournei (Hemsl.) Yang plantation tree layer of carbon density is increasing with the increasing stand age,12years old,25years old and38years old were22.05t/hm2,95.62t/hm2and159.5t/hm2,respectively,which accounted the entire ecosystem rates were18.76%,48.22%,58.87%,respectively.Shrub and herb layers accounted the entire ecosystem carbon density ratio is less than1%, the proportion of litter layer of less than2%.Average annual net carbon seqestration in P. bournei (Hemsl.) Yang plantation forest ecosystems by the age from small to large were2.17t/hm2-a,5.01t/hm2-a,6.10t/hm2-a,respectively.Tree layer accounted for more than60%,by the age from small to large were1.84t/hm2·a,3.82t/hm2·a,4.20t/hm2·a, respectively.Litter layer’s average annual net carbon sequestration also accounted for a large part,0.28t/hm2·a,0.95t/hm2-a and1.51t/hm2·a, accounted the total of12.90%,18.96%and24.75%,respectively. |
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