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Free keywords:
floodplain forest; flood stress; growth strategy; photosynthetic CO₂ assimilation; successional status; várzea
Abstract:
In Central Amazonian floodplain forests, trees are subjected to periodical flooding. The gas exchange behaviour of six tree species with different growth strategies was compared between the non-flooded and flooded period. Photosynthetic assimilation and quantum yields were 20 - 50 % lower in the flooded period in non-pioneers, and 10 - 2 % lower in pioneers. The photosynthetic activities reported here appear to be related to successional status and growth strategy. Stomatal conductance, Ci and Ci/Ca increased in all species when flooded. Leaf age changed from mainly adult leaves at the beginning of flooding, to mainly senescent leaves in the middle of the flooded period and to young leaves towards the end of flooding. The main factor responsible for the reductions of physiological activities in the flooded period is concluded to be leaf age, which indirectly is determined by flooding
