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Free keywords:
waterlogging; water stress; transpiring surface; xylem sap flux; water potential; water availability
Abstract:
Trees of the Amazon River floodplain (várzea) are subjected to regular periods of waterlogging which last up to seven
months every year. The present study shows the importance of stem water storage for buffering root water uptake
restrictions during water logging in different tree species which are common in this environment. With the method of
Granier, total water fluxes were measured in five individuals of each of six species (Crateva benthami, Laetia corymbulosa, Nectandra amazonum, Pseudobombax munguba, Tabebuia barbata and Vitex cymosa) with different phenologies, located in a várzea inundation forest near Manaus, Brazil. Xylem sap flux density was positively correlated with the above stand or upper canopy diurnal variation of vapour pressure deficit in all tree species under study. Increasing above stand or upper canopy vapor pressure deficit lead to an increasing sap flux density and total sap flow, and vice versa. Reduced water availability during day time was buffered by stem water which was filled up during night time. The severe physiological stress caused by anoxic conditions in the root zone was indicated by a reduction of the transpiring surfaces via leaf shedding. Stem water store could buffer water shortage during day time
