| The study of forest carbon storage is a hot topic in the global carbon cycle due to its great significance to global warming and maintaining ecological balance.In this study,the plantations of Michelia macclureii and Cinnamomum camphoraa in Xiaokeng National Forest Park(formerly Xiaokeng Forest Farm)in Qujiang County,Shaoguan City,were used as research objects.The biomass distribution patterns of tree,shrub and litter per unit area were analyzed,and the accumulation of carbon and nutrient elements per unit area of artificial forest system(arbor layer,shrub layer,herbaceous layer,soil layer and litter layer)were estimated,and elemental stoichiometric characteristics and soil physicochemical properties of the two plantations were discussed,and the similarities and differences of the two plantations were analyzed and compared in order to provide theoretical basis for the selection of fine carbon sink tree species.The results show that:(1)The biomass regression models were established to estimate organ biomass of M.macclurei and C.camphora plantations.Percentage of M.macclurei organ biomass decreased in the order of stem(50.4±1.10)%>branches(20.3±0.63)%>leaves(17.2±0.16)%>roots(12.1±0.31)%,and that of C.camphora decreased in the order of stem(50.8±3.56)%>roots(26.9±0.24)%>branches(15.8±2.86)%>leaf(6.5±0.86)%.The biomass space distribution decreased in the order of arbor layer>litter layer>herbaceous layer>shrub layer for the plantations.The tree layer biomass of the M.macclurei plantations was larger than that of C.camphora plantations,while shrub layer biomass and herb layer biomass were opposite.(2)There was no significant difference in carbon content of organs in tree layer between the two plantations.Carbon content of tree organs decreased in the order of leaves>stem>branches>roots in M.macclurei plantation and in the order of branches>leaves>stem>roots in C.camphora plantation.The carbon content in tree layer of M.macclurei was significantly higher than that in C.camphora plantation,but their roots organ was vice versa.The order of carbon content in the two plantation systems decreased in the order of tree layer>shrub layer>herb layer>litter layer.The carbon content of litter layer under M.macclurei plantation was higher than that of C.camphora plantation,while that of tree layer,shrub layer and herbaceous layer was opposite.The total carbon storage was 11.04 t/hm~2 in the arbor layer of M.macclurei plantation,and the aboveground carbon storage was about 8.5 times that of underground carbon storage with the order of stem>branches>leaves>roots.The total carbon storage was 6.42 t/hm~2,and aboveground carbon storage was about 3 times of that of underground carbon storage in the arbor layer of C.camphora plantation with the order of stem>branches>roots>leaves.The carbon storage of leaves,branches and stem of M.macclurei plantation was significantly larger than that of C.camphora plantation,but roots is opposite.The aboveground carbon storage of arbor layer,shrub layer and herbaceous layer in the two plantations was larger than that in the underground part,respectively.(3)The total N accumulation decreased in the order of leaves>branches>stem>roots in tree layer of M.macclurei plantation,and in the order of leaves>branches>roots>stem in C.camphora plantation,the total N accumulation of leaves,branches and stem of M.macclurei plantation was significantly larger than that of C.camphora plantation,respectively.The total P accumulation decreased in the order of leaves>stem>branches>roots in tree layer of M.macclurei plantation,and in the order of leaves>roots>branches>stem in C.camphora plantation.The order of total K accumulation decreased in the order of leaves>roots>branches>stem in tree layer of M.macclurei plantation and C.camphora plantation.N,P and K contents of leaves were the highest,whereas those of stem were the lowest among tree organs in the two plantations,and the nutrient accumulation decreased in the order of N accumulation>K accumulation>P accumulation.The accumulation of N,P and K in the aboveground part were higher than those in the underground part in the tree,shrub and herbaceous layers of the two plantations.(4)With increasing soil layer,fluctuation range of soil pH became small with increasing layer in M.macclurei plantation,whereas that tended to slightly increase in C.camphora plantation;the contents of soil C,N,N and available K tended to decrease in the two plantations.There was no significant difference in total P and K content in all layers,but available P content decreased significantly in M.macclure plantation.The contents of P and K decreased slightly in all layers,but the difference of available P content was not significant in C.camphora plantation.(5)Catalase activity did not show significant difference among 0-20cm,20-40cm and 40-60cm soil layers and tended to decrease in 60-80cm and 80-100cm soil layer in M.macclure plantation,whereas that tended to decrease with increasing soil layer in C.camphora plantation.Activities of acid phosphatase and urease tended to decrease with increasing soil layer in the two plantations.Catalase activity in different soil layers,acid phosphatase activity in 60-80cm,80-100cm soil layer and urease activity in 20-40,40-60,60-80 and 80-100 cm soil layers in M.macclure plantation were significantly higher than those in C.camphora woodland.(6)The total soil carbon storage tended to increase with increasing soil layer with the value of 259.26 t/hm~2 in M.macclure plantation and that tended to decrease with increasing soil layer with the value of 203.97 t/hm~2 in C.camphora plantation.The P and K accumulation tended to increase,whereas N accumulation showed a fluctuating trend with increasing soil layer in the two plantations.P accumulation in all layers of M.macclurei plantation were higher than those in C.camphora plantation,but the K accumulation was the opposite.The three soil nutrient elements accumulation decreased in the order of K>N>P in the two plantations.(7)The distribution pattern of carbon storage decreased in the order of soil layer>tree layer>litter layer>herbaceous layer>shrub layer in the ecosystems of M.macclurei and C.camphora.The total carbon storage of M.macclurei ecosystem was significantly larger than that of C.camphora ecosystem,and the carbon storage of tree layer in M.macclurei ecosystem was significantly larger than that of C.camphora tree layer,but there was no significant difference among their shrub,herbaceous and litter layers.The difference of total carbon storage between the two plantations was mainly caused by the difference of soil carbon storage.N,P,K accumulation was 326519.41 and 238533.86 kg/hm~2 in M.macclurei and C.camphora ecosystems,respectively,that decreased in the order of soil layer>arbor layer>litter layer>herbaceous layer>shrub layer in the two ecosystems.The accumulation of N,P and K in M.macclurei tree layer were all greater than those in C.camphora tree layer,whereas those were the opposite in shrub layer.(8)The minimum value of C:N occurred in leaves in the tree layer of the two plantations.Th C:P and C:K of leaves,branches and stem of M.macclurei were higher than those of C.camphora,whereas their roots was opposite.the C:N,C:P and C:K and N:P of M.macclurei tree layer were higher than those of C.camphora tree layer,whereas theirshrub layer and herbaceous layer were opposite. |
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