Tree growth and wood anatomy along elevational and nutritional gradients in tropical forests in southern Ecuador

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The impact of N and NP fertilization on the intrinsic water use efficiency on selected mountain rainforest tree species shall be studied by means of intra-annual stable carbon isotope analyses along an altitudinal gradient (2000 m asl. and 3000 m asl.). The temporal resolution of the intra-annual isotope variations is about two weeks and thus can be compared to high-resolution measurements of stem diameter variations registered with electronic dendrometers and to quantitative measurements of wood anatomical properties measured by image analyses of wood anatomical microsections. The study will reveal species-specific changes of water use efficiency due to fertilization and its effect on tree growth responses and carbon isotope fractionation levels on short-term drought events. Quantitative wood anatomical characterization of selected tree species along its altitudinal distribution range shall clarify if xylem potential water conductivity poses a potential limit of water supply at the lower distribution limit of the species.