A Comparative Study On Carbon Storage In Clear-Cutting Forestland Of Chinese Fir Under Different Regeneration Approaches

In recent years,deforestation has become the second largest greenhouse gas emission sources of human activities.It leads to changes in greenhouse gas concentrations in the atmosphere,and thus affects the global climate change.China has a large number of excessive logging of the degraded forest that caused by improper activities,the regeneration of these degraded forest land will significantly improve the carbon storage of forest ecosystems in China.At present,the domestic research on the carbon storage in the process of forest regeneration has just started,and the effects of different forest regeneration approaches on carbon storage of degraded forest land are not very clear.In this thesis,the author takes two Chinese fir plantations restored 20 years under two regeneration approaches(natural regeneration approach and artificial regeneration approach)of Huitong Experimental Station of Forest Ecology,Hunan province.The study analyz the difference of carbon storage in each forest layer and the difference of carbon storage of each species in tree layer of Chinese fir plantations under two regeneration approaches through field investigation of woodland,laboratory determinations combing with the main tree species Allometric equation.On the one hand,a general understanding of carbon storage dominant tree species in tree layer under two regeneration approaches provides a scientific basis for the selection of tree species for the restoration of forest land,even for afforestation,forest management,etc.On the other hand,understanding the differences of carbon storage natural regeneration approach and artificial regeneration approach provides a theoretical basis for the choice of carbon sink restoration approach for Chinese Fir Plantation in the future.And the result showed that:(1)There were some differences between forest species composition under the two regeneration approaches.The tree species of tree layer,shrub layer and herb layer under artificial regeneration approach were fewer than those under natural regeneration approach.And the dominant tree species of each forest layer under the two regeneration approaches weresignificantly different.There were no significant difference in the carbon content of the same tree species under the two regeneration approaches.The carbon content of different tree species under the same regeneration approach in the tree layer was almost the same,except that the carbon content of Cunninghamia lanceolata was significantly higher than other tree species;in shrub layer,the carbon content of Rubus rosaefolius was significantly higher than other tree species and the carbon content of Itea chinensis was significantly lower than other tree species.There were some differences between the carbon content of different organs of the same tree species but different tree species showed different rules.(2)There were significant differences between carbon storage distribution of each forest layer among different species under the two regeneration approaches(natural regeneration approach and artificial regeneration approach).Under the natural regeneration approach,the top three of the carbon storage content in the tree layer were Cunninghamia lanceolata,Machilus pauhoi and Cyclobalanopsis glauca.However,the top three of the carbon storage content in the tree layer were Machilus pauhoi,Sapium discolor and Cunninghamia lanceolata under the artificial regeneration approach.The dominant species of carbon storage content of shrub layer,herb layer were significantly different under the two regeneration approaches.In the shrub layer,the top three of the carbon storage content were Mussaenda esquirolii,Michelia macclurei and Oreocnide frutescens under the artificial regeneration approach.However,the top three of the carbon storage content in the shrub layer were Cunninghamia lanceolata,Camellia oleifera and Eurya japonica under the natural regeneration approach.And in the herb layer,the top three of the carbon storage content were Lophatherum gracile,Parathelypteris japonica and Athyrium delicatulum under the artificial regeneration approach.However,the top three of the carbon storage content in the herb layer were Neolepisorus ovatus,Alpinia japonica and Pronephrium penangianum under the natural regeneration approach.(3)Compared with those under artificial regeneration approach,the carbon storage under natural regeneration approach was significantly higher in vegetation layer,specifically,with22.56% higher in tree layer.Under the natural regeneration approach,the distribution pattern ofcarbon storage in each organ showed in an order of stem(47.49%)> branch(18.03%)> root(16.76%)> leaf(9.63%)> bark(7.30%),while that under the artificial regeneration approach showed in an order of stem(50.43%)> root(12.75%)> branch(7.24%)> bark(6.86%)>leaf(3.67%).The proportion of carbon storage of vegetation layer under canopy and litter layer were very small.Still,the carbon storage of shrub? layer,herb layer and litter layer under natural regeneration approach were greater than those under artificial regeneration approach,respectively 3.99,5.94 and 1.14 times.Soil carbon storage in a Chinese fir plantation ecosystem restored 20 years under natural regeneration approach was lower than that under artificial regeneration.The soil carbon content and carbon storage in the surface layer(0-10cm)under the natural regeneration approach was higher than that under artificial regeneration,while the other layers were opposite.Under both regeneration approaches,the soil carbon content and soil carbon storage in the same unit(10cm per layer)were all decreased with the increase of soil depth,and the distribution ratio of each layer was significantly different in terms of soil carbon content and soil carbon storage.(4)From the view of the entire ecosystem,the carbon sequestration capacity of Chinese fir plantation ecosystem under natural regeneration approach was higher than that under artificial regeneration approach.The distribution pattern of carbon storage of the plantation ecosystem under natural regeneration approach was in the order of tree layer(56.13%)> soil layer(41.50%)> litter layer(1.83%)> shrub layer(0.56%)> herb layer(0.06%),and that under artificial regeneration approach was in the order of soil layer(49.49%)> tree layer(48.64%)>litter layer(1.71%)> shrub layer(0.15%)> herb layer(0.01%).