Transpiration and Canopy Stomatal Conductance of 5-Year-Old Loblolly Pine in Response to Intensive Management
The influence of weed control only (W) versus weed control plus irrigation (WI) and weed control plus irrigation and fertigation (WIF) on canopy stomatal conductance (G S) and transpiration expressed on a ground (E) and leaf area (E L) basis was examined over 1 year in 5-year-old loblolly pine (Pinus taeda L.) to determine whether increased leaf area index (L) in response to intensive silviculture resulted in regulation of G S, whole-tree hydraulic conductance per unit sapwood area (G), or the ratio of transpiring leaf area to conducting sapwood area (A L:A S) to minimize the gradient in water potential from soil to leaf (ΔΨ). Values of E were as high as 3.9 mm d−1 and increased from a total of 357 mm in the W treatment to 529 and 565 mm in the WI and WIF treatments, respectively. Values of E L did not vary with treatment and were, on average, 0.8 mm d−1 in summer and 0.4 mm d−1 in winter. Increasing management intensity increased L by as much as 76% and sapwood area up to 68%, but had no influence on ΔΨ, G, G S, or leaf specific hydraulic conductance. High L values realized by intensive management resulted in regulation of A L:A S to maintain ΔΨ with increasing canopy development.
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