. The Conservation Atlas of Tropical Forests: the Americas. The History of the Forests and Climate of Tropical South America Loguna de Fuquene (25B0ml . j> . Disploc*menl of Fluciuorioos of veqetolion io«ifs lol<e level Yeort at. Em flemenls"'" 1-3 Subandean forest elemenls exi Figure Pollen record from Laguna de Fuquene (Eastern Cordillera. Colombia. 2580 m elevation) showing the vegetalional and climatic history of the last c. 30,000 years. At the left hand side, a summary diagram shows the downcore contribution of the four main vegetation belts. Records of selected polle
. The Conservation Atlas of Tropical Forests: the Americas. The History of the Forests and Climate of Tropical South America Loguna de Fuquene (25B0ml . j> . Disploc*menl of Fluciuorioos of veqetolion io«ifs lol<e level Yeort at. Em flemenls"'" 1-3 Subandean forest elemenls exi Figure Pollen record from Laguna de Fuquene (Eastern Cordillera. Colombia. 2580 m elevation) showing the vegetalional and climatic history of the last c. 30,000 years. At the left hand side, a summary diagram shows the downcore contribution of the four main vegetation belts. Records of selected pollen are shown. At the right hand side the chronostratigraphy, vertical displacement of vegetation belts, and estimated fluctuations of the lake level, are indicated. Smme: Aflcr Van Gecl and van der Hammen (| Forest History of the Amazon Basin During the wet season, broad belts along the Amazon River and its tributaries become inundated (see Box). The varzea forest that occurs in these belts is adapted to flooding of up to several months duration. The almost permanently inundated sites, such as oxbow lakes and deep backswamps. may support 'floating meadow" vegetation near the shores where the water is rather shallow. The meadows may become more extensive when the mean annual water levels are lower (Van der Hammen, 1986). These more or less permanently flooded sites have vegetation similar to that in the swamps of the Colombian lower Magdalena valley. Analysis of the sediments in Amazonian lakes show that there have been periods of extensive spreading of the "floating meadows", and all evidence points to coincidence with periods of low water levels. In the sediments of the Amazon valley itself, there are also considerable increases in grass pollen. These are often associated with an abundance of Cecropia, a pioneer tree which colonises thicker or "stranded" patches of 'floating meadows". Again, there are striking similarities with developm
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