Abstract
Abstract Field and laboratory studies were used to evaluate several water relations characteristics for saplings of three species: hackberry (Celtis occidentalis), a mesic, late successional tree, and bur and chinquapin oak (Quercus macrocarpa and Q. muehlenbergii), more xeric, early successional trees growing in a northeast Kansas gallery forest understory during a dry summer. For all species, maximum stomatal conductance (gwv) (8.9-9.5 mm · s-1) was recorded early in the season when soil moisture was greatest. Seasonally, sunlit leaves generally had significantly higher gwv than shaded leaves. Both gwv and leaf water potential (ψleaf) decreased during the season in each species, with minimum ψleaf values ranging from -2.13 to -2.48 MPa. Seasonally, ψleaf remained consistently higher than the osmotic potential at zero turgor (ψ0π) for each species (minimum values of (ψ0π) ranged from -2.61 to -3.02 MPa). Hackberry, the most mesic species, experienced the largest seasonal decrease in gwv in both shaded and sunlit leaves (69% and 78% reduction, respectively). Moreover, in contrast to the two oaks, a significant seasonal decline in 600 h ψleaf was shown for hackberry. By season's end, hackberry had the lowest gwv and ψleaf values. In contrast, chinquapin oak had the highest late season gwv for sunlit leaves and ψ leaf, suggesting that this species was better able to utilize late season precipitation. Forest Sci. 32:687-696.
Published Version
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