International Institute of Tropical Forestry, USDA Forest Service, Jardín Botánico Sur, Río Piedras, PR, USA.
Biol Rev Camb Philos Soc. 2012 Nov;87(4):912-27. doi: 10.1111/j.1469-185X.2012.00232.x. Epub 2012 May 21.
Tropical forests play a major role in regulating global carbon (C) fluxes and stocks, and even small changes to C cycling in this productive biome could dramatically affect atmospheric carbon dioxide (CO(2) ) concentrations. Temperature is expected to increase over all land surfaces in the future, yet we have a surprisingly poor understanding of how tropical forests will respond to this significant climatic change. Here we present a contemporary synthesis of the existing data and what they suggest about how tropical forests will respond to increasing temperatures. Our goals were to: (i) determine whether there is enough evidence to support the conclusion that increased temperature will affect tropical forest C balance; (ii) if there is sufficient evidence, determine what direction this effect will take; and, (iii) establish what steps should to be taken to resolve the uncertainties surrounding tropical forest responses to increasing temperatures. We approach these questions from a mass-balance perspective and therefore focus primarily on the effects of temperature on inputs and outputs of C, spanning microbial- to ecosystem-scale responses. We found that, while there is the strong potential for temperature to affect processes related to C cycling and storage in tropical forests, a notable lack of data combined with the physical, biological and chemical diversity of the forests themselves make it difficult to resolve this issue with certainty. We suggest a variety of experimental approaches that could help elucidate how tropical forests will respond to warming, including large-scale in situ manipulation experiments, longer term field experiments, the incorporation of a range of scales in the investigation of warming effects (both spatial and temporal), as well as the inclusion of a diversity of tropical forest sites. Finally, we highlight areas of tropical forest research where notably few data are available, including temperature effects on: nutrient cycling, heterotrophic versus autotrophic respiration, thermal acclimation versus substrate limitation of plant and microbial communities, below-ground C allocation, species composition (plant and microbial), and the hydraulic architecture of roots. Whether or not tropical forests will become a source or a sink of C in a warmer world remains highly uncertain. Given the importance of these ecosystems to the global C budget, resolving this uncertainty is a primary research priority.
热带森林在调节全球碳（C）通量和储量方面发挥着重要作用，即使这个生产力生物群系的碳循环发生微小变化，也可能会显著影响大气中的二氧化碳（CO(2) ）浓度。未来所有陆地表面的温度预计都会上升，但我们对热带森林将如何应对这一重大气候变化的了解却令人惊讶地匮乏。在这里，我们对现有数据进行了综合分析，并探讨了它们对热带森林对升温响应的启示。我们的目标是：（i）确定是否有足够的证据支持这样的结论，即升高的温度会影响热带森林的碳平衡；（ii）如果有足够的证据，确定这种影响的方向；以及，（iii）确定应采取哪些措施来解决热带森林对升温响应的不确定性问题。我们从物质平衡的角度来探讨这些问题，因此主要关注温度对碳输入和输出的影响，涵盖从微生物到生态系统尺度的响应。我们发现，尽管温度很有可能影响热带森林的碳循环和储存过程，但由于数据的明显缺乏，以及森林本身的物理、生物和化学多样性，使得我们难以确定这一问题。我们提出了各种实验方法，可以帮助阐明热带森林对变暖的响应，包括大规模的原位操纵实验、更长期的野外实验、在调查变暖效应时纳入各种尺度（空间和时间），以及包括不同的热带森林地点。最后，我们强调了热带森林研究中数据明显缺乏的几个领域，包括温度对以下方面的影响：养分循环、异养呼吸与自养呼吸、植物和微生物群落的热驯化与底物限制、地下碳分配、物种组成（植物和微生物）以及根系的水力结构。在一个更温暖的世界中，热带森林是否将成为碳的源或汇仍高度不确定。鉴于这些生态系统对全球碳预算的重要性，解决这一不确定性是首要的研究重点。
