Longleaf pine (Pins palustris Mill.) forests are thought to be drought tolerant and if so, planting longleaf pine presents a forest management strategy for climate change adaptation in the southeastern United States (U.S.). To better understand how longleaf pine copes with drought, leaf water relations, sap flow, canopy stomatal conductance (Gs), and growth were studied over three growing seasons in response to ambient throughfall (ambient treatment) versus an approximate 40% reduction in throughfall (drought treatment) in a 13-year-old plantation. An exceptional drought occurred the first year of the study and decreased mean predawn (Psi(PD)) and midday (Psi(MD)) leaf water potential to -2.9 MPa and -3.6 MPa, respectively, and decreased average monthly midday Gs to near zero for at least one month in both treatments. Stomatal closure occurred at a Psi(MD) of -3.0 MPa in both treatments. Leaf water potentials and transpiration recovered quickly following significant rain events that terminated the drought and mortality was similar among years and treatments (2.8%). Longleaf pine responded to drought treatment with greater stomatal control of plant water loss rather than adjustments in leaf area, the sapwood to leaf area ratio, or leaf water potential at the turgor loss point (Psi(TLP)). Annual transpiration per unit leaf area was reduced 16% by drought treatment, but greater stomatal control of water loss in response to drought treatment was associated with decreases in growth efficiency and volume, and no improvement in water use efficiency.
Samuelson, LJ; Stokes, TA; Ramirez, MR; Mendonca, CC
Drought tolerance of a Pinus palustris plantation
Forest Ecology And Management