Canopy gap edge effects on overstory sap flux in a temperate mixed-hardwood forest

Abstract

Canopy openings create gradients in microclimate and can increase transpiration of individual trees bordering the gaps. This study evaluates overstory tree water use in a mature, temperate, upland hardwood forest three and four years after the establishment of 0.1 and 1 ha experimental gaps. Sap flux density (Js) was measured using thermal dissipation probes in 63 trees of dominant species groups, red maple (Acer rubrum), hickory (Carya spp.), tulip-poplar (Liriodendron tulipifera), and white oak and red oak groups (Quercus spp.), with increasing distance from experimental canopy gap edge (0 – 30 m). Diurnal, daily, and seasonal patterns of Js showed no change with distance from gap edge and no difference between gap sizes, despite increased edge tree diameter growth. High tree-to-tree variability in Js was prevalent within species, potentially intensified by steep slopes and rocky soils. There were clear differences in summer Js between species with mesic species 43 % higher than oak and hickory species on average. As such, short-term effects of gap creation on local-scale water availability and stand-scale water use in mixed-hardwood forests will be largely driven by interactions between microclimate and vegetation dynamics within the gap, but not by canopy trees at the edge of the gap.

Citation

Arteman, M.L., Forrester, J.A., Oishi, A.C., Keyser, T.L. 2025. Canopy gap edge effects on overstory sap flux in a temperate mixed-hardwood forest. Agricultural and Forest Meteorology 373: 110754