这对那些担心全球变暖的人来说无疑是一个好消息——非洲雨林中的树木正在如饥似渴地吞噬着越来越多的二氧化碳，从而减轻了这种温室气体在地球大气层中的积聚。研究人员表示，这一发现强调了保护非洲雨林的重要性。
树木在生长过程中会吸收大气中的二氧化碳，然而在它们死后，这些植物的腐烂又会重新将二氧化碳释放回空气。从理论上来说，这种变化在一座成熟的森林中是能保持平衡的，因此树木既不单纯是温室气体的储藏箱——人们通常会这么认为，也不完全是大气中二氧化碳气体的发源地。然而研究人员在10年前发现，亚马逊河流域的雨林正在从大气中吸收大量的二氧化碳气体。
但没有人知道在非洲——这里是全球1/3热带雨林的家——是否也发生着类似的事情。为了找到问题的答案，由英国利兹大学的生态学家Simon Lewis领导的一个国际研究小组，对非洲地区的二氧化碳气体积聚情况进行了监控。研究人员使用的数据采自遍及10个非洲国家的79个地区，其年代从1968年一直延续到2007年。他们的测量仅限于那些年老的树木，其树干直径不小于10厘米。研究人员对树干粗细随着时间的变化进行了调查。最终的结果显示，成熟森林中的树干正在变粗，相当于每公顷森林每年平均多吸收0.63吨的碳。研究人员在2月19日出版的英国《自然》杂志上报告了这一研究成果。
这一变化与亚马逊雨林的情况大致相同，意味着遍及热带地区的成熟雨林能够持久地吸收大气中的二氧化碳气体。将这些来自非洲的第一手数据考虑在内，研究人员最终计算出全世界的热带雨林每年大约能够吸收12亿吨二氧化碳气体，这一数字相当于全球化石燃料燃烧所释放的温室气体的5%。
巴拿马巴尔博亚市史密森热带研究所的生态学家Helene Muller-Landau表示，当前热带雨林的生长高峰或许多少令人感到费解，但它的复苏应归因于几个世纪甚至几千年来的野火 ，或是人类祖先对森林的采伐。然而无论是什么原因造成的，Muller-Landau认为，“毫无疑问，额外拥有这样一个吸收碳的资源，对我们来说是相当幸运的。”然而这种幸运究竟 能够持续多长时间尚无法估量。就像Lewis警告的那样，“这些树木不可能一直越长越大”。（生物谷Bioon.com）
生物谷推荐原始出处：
Nature，doi:10.1038/nature07771，Simon L. Lewis，Hannsjörg Wöll
Increasing carbon storage in intact African tropical forests
Simon L. Lewis1, Gabriela Lopez-Gonzalez1, Bonaventure Sonké2, Kofi Affum-Baffoe3, Timothy R. Baker1, Lucas O. Ojo4, Oliver L. Phillips1, Jan M. Reitsma5, Lee White6, James A. Comiskey7,20, Marie-No?l Djuikouo K2, Corneille E. N. Ewango8, Ted R. Feldpausch1, Alan C. Hamilton9, Manuel Gloor1, Terese Hart10, Annette Hladik11, Jon Lloyd1, Jon C. Lovett12, Jean-Remy Makana10, Yadvinder Malhi13, Frank M. Mbago14, Henry J. Ndangalasi14, Julie Peacock1, Kelvin S.-H. Peh1, Douglas Sheil15,20, Terry Sunderland7,20, Michael D. Swaine16, James Taplin12, David Taylor17, Sean C. Thomas18, Raymond Votere3 & Hannsjörg Wöll19
1 Earth and Biosphere Institute, School of Geography, University of Leeds, Leeds LS2 9JT, UK
2 Plant Systematic and Ecology Laboratory, University of Yaounde I, PO Box 047, Yaounde, Cameroon
3 Resource Management Support Centre, Forestry Commission of Ghana, PO Box 1457, Kumasi, Ghana
4 Department of Environmental Management and Toxicology, University of Agriculture, PMB 2240, Abeokuta, Ogun State, Nigeria
5 Bureau Waardenburg bv, PO Box 365, 4100 AJ Culemborg, The Netherlands
6 Institut de Recherche en Ecologie Tropicale (IRET), BP 7847, Libreville, Gabon
7 SI/MAB Biodiversity Program, Smithsonian Institution, Suite 3123, 1100 Jefferson Drive SW, Washington DC 20560, USA
8 Forest Ecology & Management Group, Department of Environmental Sciences, Wageningen University, PO Box 342, NL-6700, The Netherlands
9 Plantlife International, 14 Rollestone Street, Salisbury, Wiltshire SP1 1DX, UK
10 Wildlife Conservation Society–DRC, 1725 Avenue Monjiba, Chanic Building 2nd floor, Ngalinema, BP 240, Kinshasa I, Democratic Republic of Congo
11 Eco-anthropologie et ethnobiologie, Département Hommes, Natures, Sociétés, MNHN, 4 av. du Petit Chateau, 91 800 Brunoy, France
12 Centre for Ecology, Law and Policy, Environment Department, University of York, York YO10 5DD, UK
13Environmental Change Institute, School of Geography and the Environment, Oxford University, Oxford OX1 3QY, UK
14 Department of Botany, University of Dar es Salaam, PO Box 35060, Dar es Salaam, Tanzania
15 Centre for International Forestry Research, PO Box 0113 BOCBD, Bogor 16000, Indonesia
16 Department of Plant & Soil Science, Cruickshank Building, School of Biological Sciences, University of Aberdeen, St Machar Drive, Aberdeen AB24 3UU, UK
17 Department of Geography, Museum Building, School of Natural Sciences, Trinity College, University of Dublin, Dublin 2, Republic of Ireland
18 Faculty of Forestry, University of Toronto, 33 Willcocks Street, Toronto, Ontario M5S 3B3, Canada
19 Sommersbergseestr. 291, A-8990 Bad Aussee, Austria
20 Present addresses: Inventory & Monitoring Program, National Park Service, 120 Chatham Lane, Fredericksburg, Virginia 22405, USA (J.A.C.); Institute of Tropical Forest Conservation, Mbarara University of Science and Technology, PO Box 44, Kabale, Uganda (D.S.); 21 Centre for International Forestry Research, PO Box 6596 JKPWB, Jakata 10065, Indonesia (T.S.).
The response of terrestrial vegetation to a globally changing environment is central to predictions of future levels of atmospheric carbon dioxide1, 2. The role of tropical forests is critical because they are carbon-dense and highly productive3, 4. Inventory plots across Amazonia show that old-growth forests have increased in carbon storage over recent decades5, 6, 7, but the response of one-third of the world's tropical forests in Africa8 is largely unknown owing to an absence of spatially extensive observation networks9, 10. Here we report data from a ten-country network of long-term monitoring plots in African tropical forests. We find that across 79 plots (163 ha) above-ground carbon storage in live trees increased by 0.63 Mg C ha-1 yr-1 between 1968 and 2007 (95% confidence interval (CI), 0.22–0.94; mean interval, 1987–96). Extrapolation to unmeasured forest components (live roots, small trees, necromass) and scaling to the continent implies a total increase in carbon storage in African tropical forest trees of 0.34 Pg C yr-1 (CI, 0.15–0.43). These reported changes in carbon storage are similar to those reported for Amazonian forests per unit area6, 7, providing evidence that increasing carbon storage in old-growth forests is a pan-tropical phenomenon. Indeed, combining all standardized inventory data from this study and from tropical America and Asia5, 6, 11 together yields a comparable figure of 0.49 Mg C ha-1 yr-1 (n = 156; 562 ha; CI, 0.29–0.66; mean interval, 1987–97). This indicates a carbon sink of 1.3 Pg C yr-1 (CI, 0.8–1.6) across all tropical forests during recent decades. Taxon-specific analyses of African inventory and other data12 suggest that widespread changes in resource availability, such as increasing atmospheric carbon dioxide concentrations, may be the cause of the increase in carbon stocks13, as some theory14 and models2, 10, 15 predict.
