The Study Of The Carbon Gain Of Eucalyptus Dunnii Plantation And The Relationship Between Vegetation And Carbon Gain

CO₂emissions of excessive has increased, leading to climate warmingphenomenon more and_more serious, has become the world’s environmentalproblem. The forest ecosystem is the largest carbon pool in terrestrialecosystems, accounting for46%of the global terrestrial carbon storage and animportant part of the global carbon cycle, it plays a key role in preventing thewarming of the atmosphere and has an important impact on the climatechange and the global carbon balance In the present and the future. Scientificmanagement of forests, not only can increase the forest carbon stocks, canalso slow the rate of increase of CO₂in atmospheric, can inhibit thegreenhouse effect; therefore, researching on forest ecosystem carbonsequestration capacity is necessary. This paper aims to establish themathematical model which show the relationship between eucalyptus dunniibiomass, volume, weight, carbon gain and the tree measured factors, providesa theoretical basis for the accurate estimation of the carbon gain of eucalyptusdunnii plantation; further determines the stand elements of the eucalyptusdunnii plantation Including vegetation type, diversity index, evenness, richnessand so on, and has explored the relationship between them and the carbongain，the main research results are as follows:（1） The allocation ratio of the carbon gain of the eucalyptus dunniiplantation vegetation layer is as follows: shrub layer<herb layer<litterlayer<tree layer, the tree layer carbon gain accounting for stand biomass of83.83%, the shrub layer accounting for the smallest proportion, accounting foronly stand biomass of0.27%; The allocation ratio of the carbon gain in thevarious organs of eucalyptus dunnii is as follows: leaves <branches <roots<trunk, trunk carbon gain is for34.55kg/plant, accounting for79.33%of thewhole plant carbon gain, and the trunk is the main part of the timber, whichindicates that the value of eucalyptus dunnii as artificial cultivation offast-growing timber forest is very obvious.（2） In eucalyptus dunnii plantation, the R/S ratio of the tree layer is theminimum,0.183, the R/S ratio of the shrub and the herb layers are0.435and0.778, which also shows that the tree layer can make better use of light thanthe shrub and herb layer and is the main producer of the stand; the R/S ratio ofthe shrub and the herb layers is much larger than the R/S ratio of the tree layer,which shows that the understory vegetation has certain competition ability onthe moisture and nutrient, the absorption and utilization of water and nutrientsby the inhibition of the principal is very small（3） Using the principal component analysis to establish the volumeregression equation of eucalyptus dunnii, specific for:V=0.0433124H [d_m/F（x_m）]²,where H is the height, d_mis the diameter ofthe tree where high h_m, F （x）=0.377+0.168x0.253x^0.50.273x², x_m=h_m/H, and through the precision detection, finding that by0.5H diameter of the highestaccuracy assess volume, system error is only0.3%,so the effect of the methodto assess the volume of eucalyptus dunnii by principal component analysis isideal.（4） Based on eucalyptus dunnii standard wood biomass, respectively, anddiameter at breast height （D）, tree height （H） and D²H to establish theregression equation of eucalyptus dunnii organ biomass:W_roots=0.026（D²H）^0.848,W_branches=0.001+0.003（D²H）+0.003（D²H）²,W_trunk0.140（D²H）0.899,W_leaves=0.004-0.088D+0.582D²-0.843D³,W_whole=0.175（D²H）^0.868, the equation decision coefficient R²are all above0.946,which shows that the fitting degrees of the equations are higher，so theycan more accurately estimate the biomass of each organ of the eucalyptusdunnii.（5） Established two models of the eucalyptus dunnii carbon gain, used thecarbon gain as the dependent variable and the volume as the independentvariable to establish the carbon gain model of each organ:C_branches=0.694+1.047V+16.283V²-8.674V³,C_trunk=128.946V^0.856，C_leaves=0.147-0.474V+17.869V²-17.103V³,C_roots=23.408V^0.850C_whole=5.022+136.398V+111.754V²ï¼›used the carbon gain as the dependentvariable, the tree measurement factorsas the independent variable to establishthe carbon gain model of each organ:C_trunk=2113.946D^2.304，C_leaves=0.142-0.045（D²H）+2.780（D²H）²1.093（D²H）3，C_roots=373.812D^2.284，C_branches=0.646+1.148（D²H）+1.435（D²H）²,C_whole=5.753+56.774（D²H）+17.654（D²H）²the fitting degrees of the equations are all higher, their decision coefficient R²are as low as0.985, we can reasonably choose a estimation model underdifferent conditions, or different requirements.（6） The species composition of the tree layer species composition ineucalyptus dunnii plantation is relatively simple,29shrub species,9herb species, the diversity of shrub layer is the highest, but overall, because as theartificial pure forest, the eucalyptus dunnii plantation species is relativelysimple. Forest carbon gain and vegetation elements are closely related,carbon gain and biomass, volume and density are positively related torelationship; the carbon gain and the diversity index and richness arenegatively related to relationship within a certain range, when diversity indexand richness reaches a certain level, the carbon gain and the diversity indexand richness are positively related to relationship; the carbon gain and speciesevenness are positively related to relationship.