| Among terrestrial ecosystems,forest ecosystems are the largest organic carbon pool,and are also a decisive factor in the construction of carbon cycles and carbon pools,playing a vital role.As the westernmost region of my country,Tibet has variable climatic conditions and complex geographical factors.Accurately estimating the carbon density and carbon storage of Tibet’s forest ecosystems and exploring their spatial distribution will not only provide a theoretical basis for the composition of my country’s forest ecosystem carbon pools It also helps predict the impact of climate change in forest ecosystems.The study on the dynamic changes of carbon storage in Tibet’s forest ecosystem can not only understand the trend and potential of changes in the carbon storage of Tibet’s forest ecosystem over the years,but also provide a theoretical basis for future forest protection in Tibet.This research mainly conducted field investigations on different forest types in Tibet,collected plant communities and soil samples,and collected a large amount of field investigation data.It was conducted on the basis of the1977-2014 Tibet Resource Inventory and the second scientific expedition of the Qinghai-Tibet Plateau.Inquiry and study the carbon density,carbon storage,distribution characteristics and dynamic changes of the vegetation,litter and soil of Tibet’s forest ecosystem,and analyze the influencing factors based on the selected sample plots,and establish the Tibet forest ecosystem and climate factors,geography The relationship between factors and physical and chemical properties,and analysis of them,the results are as follows:(1)The carbon storage of the forest ecosystem in Tibet is 1137.57Tg,of which the forest vegetation carbon storage is 293.98Tg,accounting for 25.84%of the total carbon storage;the litter carbon storage is 60.88Tg,accounting for 5.35%;the soil organic carbon storage is 782.71Tg,accounting for 68.81%.It shows that the soil in Tibet’s ecosystem is the largest organic carbon pool.The distribution patterns of carbon storage in different forest types are different,with vegetation carbon storage accounting for0.79%to 4.32%;litter carbon storage accounting for 0.33%to 1.43%;soil carbon storage accounting for 50.11%～98.88%.(2)The average carbon density of the forest ecosystem in Tibet is 189.76 t/hm~2,which is mainly divided into three indicators:vegetation,litter and soil.The average carbon density is 62.87 t/hm~2,19.86 t/hm~2,and 107.04 t/hm~2.(3)In this paper,the 20 main forest types of arbor forest,economic forest,sparse forest and shrub forest are classified and statistically studied in this paper.The carbon storage in descending order is:Abies fabri(251.29Tg)>Picea asperata(191.67Tg)>Broad-leaved mixed forest(168.18Tg)>Coniferous and broad-leaved mixed forest(93.20Tg)>Pinus yunnanensis(60.48Tg)>Sparse forest and shrubwood(59.46Tg)>Hard broad-leaved forest(51.85Tg)>Pinus densata(46.55Tg)>Coniferous mixed forest(37.21Tg)>Quercus(30.14Tg)>Pinus griffithii(30.07Tg)>The Economic forest(28.76Tg)>Betula platyphylla(26.34Tg)>Cupressus funebris(17.90Tg)>Pinus armandii(11.81Tg)>Larix gmelinii(11.16Tg)>Populus spp.(4.96Tg)>Taxus chinensis(4.67Tg)>Soft broad-leaved forest(3.75Tg)>Ulmus pumila(3.16Tg)>Salix spp.(2.85Tg)>Tsuga chinensis(2.11Tg).Abies fabri,Picea asperata and Broadleaved mixed forest are the main contributors to the carbon storage of Tibet’s forest ecosystem,which is mainly related to the larger distribution area of forest types and higher carbon density.(4)The main factor affecting the organic carbon content of forest soil in Tibet is climatic factors.The average annual temperature and annual rainfall are significantly related to the organic carbon content of forest soil in Tibet.Topographic factors are also an important indicator that affects the organic carbon content of forest soil in Tibet.The influence of altitude is more obvious,showing significant correlation.Soil organic carbon content is significantly negatively correlated with bulk density and p H,and significantly positively correlated with total nitrogen.(5)From the perspective of the spatial distribution pattern of Tibet,it is mainly divided into geographical spatial distribution and the spatial distribution pattern of vegetation,litter and soil in the ecosystem.In terms of geographical distribution,forests are mainly distributed in Tibet’s Qamdo,Nyingchi,and Shannan regions,and the forest ecosystem has a large carbon storage;the forest ecosystem in Lhasa has a smaller carbon storage than the southeastern region,but it is also greater than the sum of the Ali and Naqu regions.According to research on vegetation and litter,Qamdo,Nyingchi and Shannan account for about 90%of Tibet’s total carbon storage,showing a typical spatial trend of high in the east and low in the south,high in the south and low in the north.The vertical spatial distribution of soil is mainly based on The soil layer is the standard,and the soil organic carbon density in different soil layers(0-10cm,10-20cm,20-30cm,30-50cm)ranges respectively:2.08～4.83kg/m~2,1.42～4.08kg/m~2,2.79～9.46kg/m~2,7.76～19.25 kg/m~2.(6)The forests of the Tibet Autonomous Region are quite different from most areas in my country.The forest area is relatively large,but the proportion of artificial forests is lower among all regions in China.From 1991 to 1997,spruce forest felling was more serious,so the forest carbon storage and spruce forest area decreased in the second and third stages.The main reason for the large differences is that the forests in Tibet are mainly concentrated in specific areas in southeastern Tibet.Near-mature forests and mature forests account for a relatively high proportion of the total area,and the proportion of the total area is the most prominent in the country,and there are fewer human activities in Tibet.The human disturbance caused is less,and the forest protection conditions are relatively well. |
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