Mayle Francis E, Beerling David J, Gosling William D, Bush Mark B
Department of Geography, University of Leicester, Leicester LE1 7RH, UK.
Philos Trans R Soc Lond B Biol Sci. 2004 Mar 29;359(1443):499-514. doi: 10.1098/rstb.2003.1434.
The aims of this paper are to review previously published palaeovegetation and independent palaeoclimatic datasets together with new results we present from dynamic vegetation model simulations and modern pollen rain studies to: (i) determine the responses of Amazonian ecosystems to changes in temperature, precipitation and atmospheric CO2 concentrations that occurred since the last glacial maximum (LGM), ca. 21 000 years ago; and (ii) use this long-term perspective to predict the likely vegetation responses to future climate change. Amazonia remained predominantly forested at the LGM, although the combination of reduced temperatures, precipitation and atmospheric CO2 concentrations resulted in forests structurally and floristically quite different from those of today. Cold-adapted Andean taxa mixed with rainforest taxa in central areas, while dry forest species and lianas probably became important in the more seasonal southern Amazon forests and savannahs expanded at forest-savannah ecotones. Net primary productivity (NPP) and canopy density were significantly lower than today. Evergreen rainforest distribution and NPP increased during the glacial-Holocene transition owing to ameliorating climatic and CO2 conditions. However, reduced precipitation in the Early-Mid-Holocene (ca. 8000-3600 years ago) caused widespread, frequent fires in seasonal southern Amazonia, causing increased abundance of drought-tolerant dry forest taxa and savannahs in ecotonal areas. Rainforests expanded once more in the Late Holocene owing to increased precipitation caused by greater austral summer insolation, although some of this forest expansion (e.g. in parts of the Bolivian Beni) is clearly caused by palaeo Indian landscape modification. The plant communities that existed during the Early-Mid-Holocene may provide insights into the kinds of vegetation response expected from similar increases in temperature and aridity predicted for the twenty-first century. We infer that ecotonal areas near the margins of the Amazon Basin are liable to be most sensitive to future environmental change and should therefore be targeted with conservation strategies that allow 'natural' species movements and plant community re-assortments to occur.
本文的目的是回顾先前发表的古植被和独立古气候数据集，以及我们通过动态植被模型模拟和现代花粉雨研究得出的新结果，以：（i）确定自末次盛冰期（LGM）以来，约21000年前，亚马逊生态系统对温度、降水和大气二氧化碳浓度变化的响应；（ii）利用这一长期视角预测未来气候变化可能对植被产生的影响。在末次盛冰期时，亚马逊地区仍以森林为主，尽管温度、降水和大气二氧化碳浓度的降低导致森林在结构和植物种类上与现在大不相同。在中部地区，适应寒冷的安第斯类群与雨林类群混合生长，而干燥森林物种和藤本植物可能在季节性更强的亚马逊南部森林中变得更为重要，稀树草原在森林 - 稀树草原生态交错带扩张。净初级生产力（NPP）和冠层密度显著低于现在。在冰期 - 全新世过渡期间，由于气候和二氧化碳条件的改善，常绿雨林分布和净初级生产力增加。然而，全新世早期至中期（约8000 - 3600年前）降水减少，导致季节性较强的亚马逊南部地区广泛频繁发生火灾，使得生态交错带地区耐旱的干燥森林类群和稀树草原的数量增加。由于南半球夏季日照增加导致降水增多，雨林在全新世晚期再次扩张，尽管部分森林扩张（如玻利维亚贝尼部分地区）显然是由古印第安人的景观改造造成的。全新世早期至中期存在的植物群落可能为21世纪预计的类似温度升高和干旱加剧情况下的植被反应类型提供见解。我们推断，亚马逊河流域边缘的生态交错带地区可能对未来环境变化最为敏感，因此应采取保护策略，允许“自然”的物种迁移和植物群落重新组合。
