Comparetive Studies On Carbon Density And Carbon Fixation Of Mangroves Of Different Recovery Types In Qi'ao Island

Mangrove ecosystem has the characteristics of high carbon storage and strong carbon sink potential.Selecting high carbon density mangrove tree species and the best combination of tree species for afforestation and stand transformation will maximize carbon storage.In this paper,14 mangroves of different restoration types in Qi'ao Island are taken as research objects.Carbon density and carbon sequestration rate of mangrove vegetation,soil carbon density and carbon sequestration rate are compared and studied.The optimal mangrove restoration types are found to improve carbon sequestration capacity of mangrove wetlands,and to provide basis for rational allocation of mangrove restoration species,so as to promote the restoration of mangrove wetlands and improve wetlands'ecological benefits.The results show that:(1)A biomass model suitable for different regions of Guangdong Province is constructed by using 25 standard analytic trees from eight different regions of Guangdong Province.The biomass model isW = 0.033(D2H)1.002,the determination coefficient is 0.952 and the fitting effect of the model is good.(2)Among the 8 mangrove communities with different tree species,the S.apetala forest has the maximum biomass of vegetation which is 355.54 t·hm-2,the carbon density of vegetation is 159.99 t hm'2,and the carbon fixation rate of vegetation was 9,50 t hm'2?a-1.The carbon fixation capacity of the community was significantly higher than that of the other seven community types.(3)Among the 6 mangrove communities with different underforest recovery,the biomass of S.apetala mixed A.ilicifolius and A.aureum forest is 361.50 t·hm'2,the carbon density of the vegetation is 162.68 t·hm'2,and the carbon sequestration rate of the vegetation is 9.78 t·hm-2·a-1?(4)Among the 8 mangrove communities with different tree species,The maximum content of soil organic carbon appears in 0-20 cm and 20-40 cm soil layers,and the content of soil organic carbon decreased with the increase of soil depth below 40 cm.The minimum soil bulk density appears in 0-20 cm soil layer,the maximum appears in 20-40 cm soil layer and 40-60 cm soil layer.The soil bulk density distribution law of each community below 40 cm is different,and generally decreases with the increase of soil depth.The distribution of soil carbon density in different soil layers of different tree species is obviously different and has its own characteristics(5)Among the 6 mangrove communities with different underforest recovery,The maximum soil organic carbon content appeared in 0-20 cm and 40-60 cm soil layers,and the minimum appeared in 20-40 cm and 60-80 cm soil layers.The minimum soil bulk density appeared in the 0-20 cm soil layer,the maximum appeared in the 20-40 cm soil layer,and in the 20-100 cm soil layer,except for the S.apetala ?A.corniculatum community,the soil bulk density decreased with the increase of soil depth.The distribution of soil carbon density in different soil layers of different communities is obviously different,and has its corresponding distribution law.(6)Among the 8 mangrove communities with different tree species,soil carbon density accounts for the main part of carbon density.Except the S.apetala community,soil carbon density of each community accounts for more than 70%of the total density.Vegetation carbon density of 4 communities of H.littoralis,K.obovata,A.corniculatum and B.gymnorrhiza is between 20.27%and 25.29%,while that of A.ilicifolius,A.aureum and S.alterniflora is lower,accounting for only 0.40%to 1.26%of the total density.The litter carbon density of each community is very small,less than 0.7%of the total density.Soil carbon sequestration rate accounts for the main part of carbon sequestration rate.Except the S.apetala community,the carbon sequestration rate of each community accounts for more than 60%of the total carbon sequestration rate,while the carbon sequestration rate of A.ilicifolius,A.aureum and S.alternifora communities accounts for more than 90%of the total carbon sequestration rate.The carbon sequestration rate of vegetation was higher than that of soil,which was 60.85%and 39.15%respectively.(7)Among the 6 mangrove communities with different underforest recovery,vegetation carbon density accountes for 32.81%-44.41%of total carbon density,soil carbon density accountes for 54.77%-66.85%of total carbon density,while litter carbon density accountesfor a small proportion of total carbon density,0.34%?0.87%.Soil carbon sequestration rate of each community accounted for 48.17%?62.42%of the total carbon sequestration rate,and vegetation carbon sequestration rate accounted for 37.58%?54.42%.Except the S.apetala+A.corniculatum community,the other five communities has lower carbon sequestration rate than the soil carbon sequestration rate.(8)Comparing 14 mangrove communities with different restoration types,it is found that the carbon sequestration rate of S.apetala community and S.apetala-mixed B.gymnorrhiza or with natural restoration community is fast.The total carbon sequestration rates of H.littoralis,K.obovata and B.gymnorrhiza community are similar.The carbon sequestration rates of S.apetala+A.corniculatum community and A corniculatum are slower,similar to those of A.ilicifolius and A.aureum community.The carbon sequestration rate of S.alterniflora is the lowest,significantly lower than those of the other 13 community types.