這對(duì)那些擔(dān)心全球變暖的人來說無疑是一個(gè)好消息——非洲雨林中的樹木正在如饑似渴地吞噬著越來越多的二氧化碳，從而減輕了這種溫室氣體在地球大氣層中的積聚,。研究人員表示，這一發(fā)現(xiàn)強(qiáng)調(diào)了保護(hù)非洲雨林的重要性,。
樹木在生長過程中會(huì)吸收大氣中的二氧化碳,，然而在它們死后，這些植物的腐爛又會(huì)重新將二氧化碳釋放回空氣,。從理論上來說,，這種變化在一座成熟的森林中是能保持平衡的，因此樹木既不單純是溫室氣體的儲(chǔ)藏箱——人們通常會(huì)這么認(rèn)為,，也不完全是大氣中二氧化碳?xì)怏w的發(fā)源地,。然而研究人員在10年前發(fā)現(xiàn)，亞馬遜河流域的雨林正在從大氣中吸收大量的二氧化碳?xì)怏w,。
但沒有人知道在非洲——這里是全球1/3熱帶雨林的家——是否也發(fā)生著類似的事情,。為了找到問題的答案，由英國利茲大學(xué)的生態(tài)學(xué)家Simon Lewis領(lǐng)導(dǎo)的一個(gè)國際研究小組,，對(duì)非洲地區(qū)的二氧化碳?xì)怏w積聚情況進(jìn)行了監(jiān)控,。研究人員使用的數(shù)據(jù)采自遍及10個(gè)非洲國家的79個(gè)地區(qū),，其年代從1968年一直延續(xù)到2007年。他們的測量僅限于那些年老的樹木,，其樹干直徑不小于10厘米,。研究人員對(duì)樹干粗細(xì)隨著時(shí)間的變化進(jìn)行了調(diào)查。最終的結(jié)果顯示,，成熟森林中的樹干正在變粗,，相當(dāng)于每公頃森林每年平均多吸收0.63噸的碳。研究人員在2月19日出版的英國《自然》雜志上報(bào)告了這一研究成果,。
這一變化與亞馬遜雨林的情況大致相同,，意味著遍及熱帶地區(qū)的成熟雨林能夠持久地吸收大氣中的二氧化碳?xì)怏w。將這些來自非洲的第一手?jǐn)?shù)據(jù)考慮在內(nèi),，研究人員最終計(jì)算出全世界的熱帶雨林每年大約能夠吸收12億噸二氧化碳?xì)怏w,，這一數(shù)字相當(dāng)于全球化石燃料燃燒所釋放的溫室氣體的5%。
巴拿馬巴爾博亞市史密森熱帶研究所的生態(tài)學(xué)家Helene Muller-Landau表示,，當(dāng)前熱帶雨林的生長高峰或許多少令人感到費(fèi)解,，但它的復(fù)蘇應(yīng)歸因于幾個(gè)世紀(jì)甚至幾千年來的野火 ，或是人類祖先對(duì)森林的采伐,。然而無論是什么原因造成的,，Muller-Landau認(rèn)為，“毫無疑問,，額外擁有這樣一個(gè)吸收碳的資源,，對(duì)我們來說是相當(dāng)幸運(yùn)的。”然而這種幸運(yùn)究竟 能夠持續(xù)多長時(shí)間尚無法估量,。就像Lewis警告的那樣,，“這些樹木不可能一直越長越大”。（生物谷Bioon.com）
生物谷推薦原始出處：
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.
