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Abstract

tNewly created forest edges have significant ecophysiological effects on bordering trees. We studied edgeeffects on microclimate and tree transpiration rates during wet and dry seasons along a 250 m transectspanning the edge of an unpaved road into an old growth tropical lowland forest in the Central BrazilianAmazon. Canopy openness decreased only minimal from the road (3.68%) towards the forest interior(1.69%). Vapor pressure deficit (measured at 2.2 m height above ground) was lower in the forest inte-rior. The edge effect on microclimate penetrated deeper into the forest (>100 m) during the dry seasoncompared to the wet season (<100 m). Overall, sap flux, and therefore transpiration rate, was 54% higherin trees adjacent to the road compared to forest interior trees. Higher transpiration rates at the forestedge can be explained by higher turbulences and energy exchange of the canopy boundary layer andby a shift in species composition to high water using secondary forest species 25 years after the roadconstruction. Similar changes might be expected for other disturbances affecting local relative humidityand in situations that favor plants with water use traits differing from those found in the forest interior.