Water relations and growth of loblolly pine seedlings planted under a shelterwood and in a clear-cut

We investigated the influence of shelterwood conditions on water relations and growth of loblolly pine (Pinus taeda L.) seedlings on two harsh sites in eastern Texas. Site I was harvested to provide four overstory density treatments (0, 2.3, 4.6 and 9.2 m2 of residual basal area per ha). To quantify...

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Bibliographic Details
Published in:Tree physiology Vol. 15; no. 1; pp. 19 - 26
Main Authors: Dalton, C.T, Messina, M.G
Format: Journal Article
Language:English
Published: Canada 1995
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Summary:We investigated the influence of shelterwood conditions on water relations and growth of loblolly pine (Pinus taeda L.) seedlings on two harsh sites in eastern Texas. Site I was harvested to provide four overstory density treatments (0, 2.3, 4.6 and 9.2 m2 of residual basal area per ha). To quantify the effects of overstory competition, trenched and nontrenched subplots, each containing 25 one-year-old seedlings, were established within each overstory treatment plot, and predawn and midday water potentials seedling growth and survival were measured during the growing season. Leaf area and seedling biomass partitioning were measured at the end of the growing season. Site II was harvested to provide two overstory density treatments (0 and 6.9 m2 ha-1) and planted with one-year-old loblolly pine seedlings. Seedling water potential, stomatal conductance (gwv), transpiration flux density (E), leaf area, height and survival were determined. On Site I, seedling water potential increased with increasing overstory basal area, whereas trenching only substantially affected water potential of seedlings in the 9.2 m2 ha-1 overstory treatment. Growth was not affected by overstory treatment or trenching. On Site II, water potential and gwv were highest during the morning hours and lowest in the afternoon, whereas E peaked in the afternoon. Vapor pressure deficits and photosynthetic photon flux density were major factors in determining gwv differences between treatments. On individual days, the presence of an overstory increased water potential and reduced both gwv and E. On Site II, leaf area was affected by overstory treatment throughout most of the study. We conclude that the presence of an overstory can have ameliorative effects on harsh sites at the western fringe of the loblolly pine natural range.
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ISSN:0829-318X
1758-4469
DOI:10.1093/treephys/15.1.19