Differences in Plant and Soil Water Relations in and Around a Forest Gap in West Africa during the Dry Season may Influence Seedling Establishment and Survival
Item
Title
Differences in Plant and Soil Water Relations in and Around a Forest Gap in West Africa during the Dry Season may Influence Seedling Establishment and Survival
Date
1996
Language
English
Abstract
1 Soil and plant-water relations were studied in a canopy opening and surrounding
forest shade in a moist tropical forest in Ghana using seedlings of two tree species
with different regeneration strategies, the pioneer Terminalia superba and the non pioneer light demander Entandrophragma utile.
2 During two consecutive dry seasons, soil matric potential varied from -30 kPa at
the end of the rainy season, to below -2.5 MPa in the middle of the dry season. During
part of the first dry season soil matric potential was higher in the gap than in the
surrounding forest. In the second dry season no differences were observed.
3 Leaf water potential varied from about -750 kPa at dawn for unstressed seedlings
of both species to <-2.5 MPa when seedlings were permanently wilted. For both
species, the maximum stomatal conductance of unstressed seedlings varied from 300
to 450 mmol m-2 s-' for those in the gap centre to 150 mmol m-2 s-' for those under
forest shade. Maximum conductance decreased to between 10 and 30 mmol m-2 s-1 in
drought-stressed seedlings during the middle of the dry season. The two species
responded similarly to a drying soil profile but the decrease in leaf water potential
and stomatal conductance was more rapid under forest canopy than in the centre of
the gap.
4 Only 7% of the seedlings of Terminalia superba and 4% of Entandrophragma utile
survived the dry season under forest shade. In contrast, 85% and 78%, respectively,
survived of those growing in the centre of the forest gap. At all positions, seedlings
of T. superba had larger relative height growth rates during the wet season than E.
utile (29.6, 21.4 and 8.4% month-' compared with 5.2, 20.0 and 1.6% month-', for
gap centre, margin and forest shade, respectively).
5 The observed changes in leaf water potential and stomatal conductance indicated
that despite the reduced irradiance, shaded seedlings experienced more drought stress
during the dry season than seedlings growing in the forest gap. The reasons for this
and possible consequences for trees which differ in leaf phenology and regeneration
strategy are discussed
forest shade in a moist tropical forest in Ghana using seedlings of two tree species
with different regeneration strategies, the pioneer Terminalia superba and the non pioneer light demander Entandrophragma utile.
2 During two consecutive dry seasons, soil matric potential varied from -30 kPa at
the end of the rainy season, to below -2.5 MPa in the middle of the dry season. During
part of the first dry season soil matric potential was higher in the gap than in the
surrounding forest. In the second dry season no differences were observed.
3 Leaf water potential varied from about -750 kPa at dawn for unstressed seedlings
of both species to <-2.5 MPa when seedlings were permanently wilted. For both
species, the maximum stomatal conductance of unstressed seedlings varied from 300
to 450 mmol m-2 s-' for those in the gap centre to 150 mmol m-2 s-' for those under
forest shade. Maximum conductance decreased to between 10 and 30 mmol m-2 s-1 in
drought-stressed seedlings during the middle of the dry season. The two species
responded similarly to a drying soil profile but the decrease in leaf water potential
and stomatal conductance was more rapid under forest canopy than in the centre of
the gap.
4 Only 7% of the seedlings of Terminalia superba and 4% of Entandrophragma utile
survived the dry season under forest shade. In contrast, 85% and 78%, respectively,
survived of those growing in the centre of the forest gap. At all positions, seedlings
of T. superba had larger relative height growth rates during the wet season than E.
utile (29.6, 21.4 and 8.4% month-' compared with 5.2, 20.0 and 1.6% month-', for
gap centre, margin and forest shade, respectively).
5 The observed changes in leaf water potential and stomatal conductance indicated
that despite the reduced irradiance, shaded seedlings experienced more drought stress
during the dry season than seedlings growing in the forest gap. The reasons for this
and possible consequences for trees which differ in leaf phenology and regeneration
strategy are discussed
Collection
Citation
“Differences in Plant and Soil Water Relations in and Around a Forest Gap in West Africa during the Dry Season may Influence Seedling Establishment and Survival,” CSIRSpace, accessed September 19, 2024, http://cspace.csirgh.com/items/show/143.