全球碳循環(huán)_Carbon Sequestration in Forestry_lecture8（英文）

1、Lecture 8: Carbon Sequestration in Forestry 1. The importance of global forests:2. The role of forests as carbon sinks and sources3. Forest carbon conservation, sequestration and management4. Global estimates of the carbon sequestration potential5. Twelve ways to sequester carbon in forests1. The Im

2、portance of Global Forests:1). Global Forests AreaThe worlds forests cover about 3.4 billion ha 26% of total land 43% of forests are distributed at low latitudes, 32% at the highlatitudes, and 25% at mid-latitudesUSA: 246 Mha, 32% of the land areaCanada: 316 Mha, 44% of the land areaChina: 157 Mha,

3、17% of the land areaRussia: 887 Mha, 52% of the land area(referenced year: 1990) 2). The Role of Forests a). Traditional use: as sources of food, shelter, constructionmaterials and fuelb). Other values (service): such as havens for human relaxationand recreation, as wildlife habitats and maintainers

4、 of water suppliesc). Additional value: their ability to sequester atmospheric CO2 - carbon sequestration e.g. at present, mid- and high-latitude forests sequester over0.6Pg C /year (USA, Canada, Russia and China all have largeforest carbon sinks)2. The role of forests as carbon sinks and sources a)

5、 . The worlds forests (in 1990) contain large quantities of carbon 1,146 Pg C (Dixon et al. 1994) - 359 in vegetation (62% in the low-latitude forests) - 787 in soils and peatlands (54% in high-latitude forests)b) In 1990, the estimated net carbon flux from the worlds forests is a sources of 0.90.5

6、Pg per year, or about 16% of the amount produced by the burning fossil fuels and cement manufacture At present, mid- and high- latitude forests sequester over 0.70.2 Pg per yeare.g., USA, Russia and China all have large forests carbon sinks Low-latitude forests (in Brazil, Indonesia, and Zaire) arec

7、urrently shrinking at a rate of 15 Mha per year, and thereby are a carbon sources of about 1.6 0.5 per year Tropical deforestation and land use change are mainly contributing to this carbon source 3. Forest Carbon Conservation, Sequestration and ManagementForest management practices to conserve and

8、sequester C can be grouped intofour major categories: Management for C conservation Management for C storageManagement for creating new C sinksManagement for C substitution Management for C ConservationGoal: mainly to prevent C emissions by conserving existing C pools in forest vegetation and soil a

9、s much as possible Management practice: controlling deforestation protecting forest in reserves e.g. The study projects that cumulative deforestation could be slowed by 138Mha by the end of 2045 from a base line project of 650 Mha under future scenario, thus conserving up to 0.5 Pg C per year changi

10、ng harvesting regimes Protecting forest against fire and insect and pest outbreakse.g. implementation of a fire management system could increase the near- and long-term C sinks in Russia by up to 0.1 to 0.6 Pg C per yeare.g. Peng et al. (2002) suggest that longer rotations and less intensive harvest

11、ingcould increase C sequestration about 36-40% in the boreal forests in central Canada (2) Management for C storageGoal: to expand the storage of C in forest ecosystems by increasingThe area and /or biomass and soil C density of natural and plantation forests,and to increase storage in durable wood

12、products. Management practice: silvicultural treatments as protecting secondary forests and other degraded forests whose biomass and soil C density are less thantheir maximum value and by allowing them to sequester C by natural or artificial regeneration and enrichment of soil C.- practices to expan

13、d or conserve forests also affect soil C, including:a) reduce erosion, b) improve soil fertility, c) removal of marginal lands from agricultural production that is followed by forestation, d) retention of forestLitter and debris after silvicultural and logging activities etc(3) Management for creati

14、ng new C sinksGoal: to increase the C sequestration by expanding tree and forest coverManagement practice: establishment of plantations on non-forested lands (afforestation) increase the tree cover on agricultural or pasture lands (agroforestry)e.g. Nilsson and Schopfhauser (1995) suggested that the

15、 maximum rate of global C sequestration can be achieved about 1.48 Pg C per year after 60 years since the establishment of the plantation Fang et al. (2001) indicated that Chinese forest plantations have sequestered 0.45 Pg C and their average C density increased from 15.3 to 31.1 Mg/ha since the mi

16、d-1970s(4) Management for C substitution Goal: to increase the transfer of forest biomass C into products (e.g. construction materials and biofuels) rather than using fossil-fuel-based energy and products, cement-based products and other building materials.Management practice:The approach involves e

17、xpanding the use of forests for wood products and fuels obtained either from establishing new forests or plantations, or increasing the growth of existing forests through silvicultural treatments.4. Global Estimates of the Carbon Sequestration PotentialGlobal estimates of the potential amount of C t

18、hat could be sequestered andConserved by forest management practices between 1995 and 2050. Latitudinal belt PracticeC Sequestered& conserved (Pg)HighForestation2.4MidForestation11.8Agroforestry0.7LowForestation16.4Agroforestry 6.3Regernaration11.5-28.7Slow deforestation10.8-20.8 Total60-87(Ref. Nilsson and Schopfhauser (1995). Climate Change, 30: 267-293)5. Twelve Ways to Sequester Carbon in ForestsCarbon sequestration strategies logically focus both on increasing the storageper hectare and on increasing