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| Titel |
Water-use dynamics of a peat swamp forest and a dune forest in Maputaland, South Africa |
| VerfasserIn |
A. D. Clulow, C. S. Everson, J. S. Price, G. P. W. Jewitt, B. C. Scott-Shaw |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1027-5606
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| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 17, no. 5 ; Nr. 17, no. 5 (2013-05-31), S.2053-2067 |
| Datensatznummer |
250018888
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| Publikation (Nr.) |
 copernicus.org/hess-17-2053-2013.pdf |
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| Zusammenfassung |
Peat swamp forests are the second rarest forest type found in South Africa
while dune forests have been under severe threat through mining and
agriculture. Both forest types exist in the conservation area, and World
Heritage site, known as the iSimangaliso Wetland Park on the East coast of
South Africa. The area is prone to severe droughts (Taylor et al., 2006) and
recent attempts to understand the local water balance revealed that there
was insufficient information on the water use of the indigenous forests of
the area. The peat swamp forest and dune forest sites studied in this
research were located within close proximity to each other, yet, are
characterised by different landscape positions in terms of water
availability. The coastal dune forest soil profile was generally dry and
sandy and the tree roots did not have access to the water table. In
contrast the peat swamp forest is located in an interdunal wetland where the
trees have permanent access to water. The climate at both sites is
subtropical with a mean annual precipitation of 1200 mm yr−1.
However, over 20 months of measurement, the first summer (October 2009 to
March 2010) was drier (424 versus 735 mm) than the second summer (October
2010 to March 2011) emphasising the variability of the rainfall in the area
and providing a wide range of conditions measured.
The sap flow of an evergreen, overstory Syzygium cordatum and a semi-deciduous, understory
Shirakiopsis elliptica were measured in the peat swamp forest using the heat ratio method. The
Syzygium cordatum water use was not highly seasonal and the daily maximum water use ranged
from approximately 30 L d−1 in winter to 45 L d−1 in summer
whereas the \textit{Shirakiopsis elliptica} water use was more seasonal at
2 L d−1 in winter and 12 L d−1 in summer. The water use of the Syzygium cordatum was not influenced by seasonal
rainfall variations and was actually higher in the drier summer (October 2009
to March 2010). Three trees of different heights were monitored in the
same way in the dune forest and the water use found to be highly seasonal.
Over the entire measurement period, the water use was highest for an emergent
Mimusops caffra (5 to 45 L d−1), whereas the water use
of the Eugenia natalitia (2 to 28 L d−1) and
Drypetes natalensis (1 to 4 L d−1) was lower. At the
dune forest, the water use was highest in the wetter summer due to the
reliance of the trees on rainfall to recharge the soil water. A split-line
regression showed that on average, soil water limited tree water use 64%
of the time over the measurement period at the dune forest. For modelling tree
water use at the dune forest, it was concluded that a two-stage model, taking
soil water content into account (from multiple sampling points), would be
necessary. |
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