Clark Deborah A
Department of Biology, University of Missouri-St Louis, St Louis, MO 63121, USA.
Philos Trans R Soc Lond B Biol Sci. 2004 Mar 29;359(1443):477-91. doi: 10.1098/rstb.2003.1426.
How tropical rainforests are responding to the ongoing global changes in atmospheric composition and climate is little studied and poorly understood. Although rising atmospheric carbon dioxide (CO2) could enhance forest productivity, increased temperatures and drought are likely to diminish it. The limited field data have produced conflicting views of the net impacts of these changes so far. One set of studies has seemed to point to enhanced carbon uptake; however, questions have arisen about these findings, and recent experiments with tropical forest trees indicate carbon saturation of canopy leaves and no biomass increase under enhanced CO2. Other field observations indicate decreased forest productivity and increased tree mortality in recent years of peak temperatures and drought (strong El Niño episodes). To determine current climatic responses of forests around the world tropics will require careful annual monitoring of ecosystem performance in representative forests. To develop the necessary process-level understanding of these responses will require intensified experimentation at the whole-tree and stand levels. Finally, a more complete understanding of tropical rainforest carbon cycling is needed for determining whether these ecosystems are carbon sinks or sources now, and how this status might change during the next century.
热带雨林如何应对当前大气成分和气候的全球变化，这方面的研究很少，人们对此了解也很有限。尽管大气中二氧化碳（CO₂）浓度上升可能会提高森林生产力，但气温升高和干旱可能会使其降低。目前有限的实地数据对这些变化的净影响产生了相互矛盾的观点。一组研究似乎表明碳吸收增加；然而，这些发现引发了一些问题，最近对热带森林树木的实验表明，冠层叶片出现碳饱和，在二氧化碳浓度升高的情况下生物量并未增加。其他实地观察表明，在近年来气温峰值和干旱（强烈厄尔尼诺事件）期间，森林生产力下降，树木死亡率上升。为了确定全球热带地区森林当前对气候的响应，需要对代表性森林的生态系统性能进行仔细的年度监测。为了对这些响应形成必要的过程层面的理解，需要在整树和林分层面加强实验。最后，要确定这些生态系统目前是碳汇还是碳源，以及在下个世纪这种状况可能如何变化，就需要对热带雨林碳循环有更全面的了解。
