Journal Article

Water relations of several hardwood species in response to throughfall manipulation in an upland oak forest during a wet year

G. Michael Gebre, Timothy J. Tschaplinski and Terri L. Shirshac

in Tree Physiology

Volume 18, issue 5, pages 299-305
Published in print May 1998 | ISSN: 0829-318X
Published online May 1998 | e-ISSN: 1758-4469 | DOI: http://dx.doi.org/10.1093/treephys/18.5.299
Water relations of several hardwood species in response to throughfall manipulation in an upland oak forest during a wet year

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We investigated the effects of altered precipitation on leaf osmotic potential at full turgor (Ψπo) of several species in an upland oak forest during the 1994 growing season as part of a Throughfall Displacement Experiment at the Walker Branch Watershed near Oak Ridge, Tennessee. The main species sampled included overstory chestnut oak (Quercus prinus L.), white oak (Q. alba L.), red maple (Acer rubrum L.); intermediates sugar maple (A. saccharum L.) and blackgum (Nyssa sylvatica Marsh.); and understory dogwood (Cornus florida L.) and red maple. The precipitation treatments were: ambient precipitation; ambient minus 33% of throughfall (dry); and ambient plus 33% of throughfall (wet). Except in late September, midday leaf water potentials (Ψl) were generally high in all species in all treatments, ranging from –0.31 to –1.34 MPa for C. florida, –0.58 to –1.51 MPa for A. rubrum, and –0.78 to –1.86 MPa for Q. prinus. Both treatment and species differences in Ψπo were evident, with oak species generally exhibiting lower Ψπo than A. saccharum, A. rubrum, C. florida, and N. sylvatica. The Ψπo of C. florida saplings declined in the dry treatment, and Q. prinus, Q. alba, and A. saccharum all exhibited a declining trend of Ψπo in the dry treatment, although Ψπo of Q. prinus leaves increased in late August, corresponding to a recovery in soil water potential. Cornus florida exhibited osmotic adjustment with the largest adjustment coinciding with the period of lowest soil water potential in June. The only other species to exhibit osmotic adjustment was Q. prinus, which also maintained a lower baseline Ψπo than the other species. We conclude that a 33% reduction of throughfall is sufficient both to alter the water relations of some species in the upland oak forest and to enable the identification of those species capable of osmotic adjustment to a short-term drought during a wet year.

Keywords: Acer rubrum; Acer saccharum; blackgum; chestnut oak; Cornus florida; dogwood; drought tolerance; Nyssa sylvatica; oak; osmotic adjustment; osmotic potential; Quercus alba; Quercus prinus; red maple; sugar maple; white oak

Journal Article.  0 words. 

Subjects: Plant Sciences and Forestry

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