Water balance in developing leaves of four tropical savanna woody species

AbstractWoody plants in water-limited ecosystems affect their environment on multiple scales: locally, natural stands can create islands of fertility for herb layer communities compared to open habitats, but afforestation has been shown to negatively affect regional water balance and productivity. Despite these contrasting observations, no coherent multiscale framework has been developed for the environmental effects of woody plants in water-limited ecosystems. To link local and regional effects of woody species in a spatially explicit model, we simultaneously measured site conditions (microclimate, nutrient availability and topsoil moisture) and conditions of regional relevance (deeper soil moisture), in forests with different canopy types (long, intermediate and short annual lifetime) and adjacent grasslands in sandy drylands. All types of forests ameliorated site conditions compared to adjacent grasslands, although natural stands did so more effectively than managed ones. At the same time, all forests desiccated deeper soil layers during the vegetation period, and the longer the canopy lifetime, the more severe the desiccation in summer and more delayed the recharge after the active period of the canopy. We conclude that the site-scale environmental amelioration brought about by woody species is bound to co-occur with the desiccation of deeper soil layers, leading to deficient ground water recharge. This means that the cost of creating islands of fertility for sensitive herb layer organisms is an inevitable negative impact on regional water balance. The canopy type or management intensity of the forests affects the magnitude but not the direction of these effects. The outlined framework of the effects of woody species should be considered for the conservation, restoration, or profit-oriented use of forests as well as in forest-based carbon sequestration and soil erosion control projects in water-limited ecosystems.

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LEAF PHENOLOGY OF WOODY SPECIES IN A NORTH AUSTRALIAN TROPICAL SAVANNA

Ecology ◽

10.1890/0012-9658(1997)078[2542:lpowsi]2.0.co;2 ◽

1997 ◽

Vol 78 (8) ◽

pp. 2542-2558 ◽

Cited By ~ 194

Author(s):

R. J. Williams ◽

B. A. Myers ◽

W. J. Muller ◽

G. A. Duff ◽

D. Eamus

Keyword(s):

Woody Species ◽

Leaf Phenology ◽

Tropical Savanna

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Australian Trees for the Rehabilitation of Waterlogged and Salinity-damaged Landscapes

Australian Journal of Botany ◽

10.1071/bt96110 ◽

1999 ◽

Vol 47 (5) ◽

pp. 697 ◽

Cited By ~ 51

Author(s):

David T. Bell

Keyword(s):

Water Balance ◽

Native Species ◽

Salt Water ◽

Economic Value ◽

Woody Species ◽

Agricultural Landscapes ◽

Annual Rainfall ◽

Detailed Knowledge ◽

Australian Species ◽

Excess Water

The revegetation of damaged agricultural landscapes requires a detailed knowledge of appropriate species and their adaptations to cope with the stresses of environments altered by humans. A range of Australian species has a role in the restoration of water and salt balances of catchments and can provide income diversity to agricultural properties damaged by increased frequencies of flooding, rising groundwaters and increased salinities. This review concentrates on the ecologically significant attributes of Australian woody species in waterlogged and saline habitats, and responses of species particularly suited to the restoration of water balance in cleared catchments. Australian catchments yield little water under natural vegetation, the trees and shrubs being especially resourceful in utilising much of the annual rainfall input. Replacing native, deep-rooted perennial species with annual crops always results in a net gain in catchment water. To redress these problems, cleared landscapes must be partially restored to tree and shrub cover to utilise the excess water remaining when crops are harvested or lie dormant over summer. Upland regions of restored landscapes should be planted to tree crops, particularly those that are luxuriant water users, of commercial value to farmers. Tree plantations for paper pulp, soft-wood timber and eucalypt oils are possibilities. Lowland sites in damaged catchments must be revegetated with trees which have waterlogging adaptations, such as aerenchyma, and tolerance to the products of anaerobic respiration. Areas of waterlogging that are additionally affected by excess salts must have exceptional trees. Australia has a number of native species which are well suited to survive these conditions, produce biomass and utilise excess water, while restricting or coping with the uptake of over-abundant salts. Most tolerant Australian species have a range of anatomical, morphological and physiological attributes to contribute to these adaptive qualities. This review highlights some of these features and describes various combinations that are successful. Australia now has a range of genotypes to bring to bear in the battle to rehabilitate landscapes damaged by disruption of the soil–salt–water balance. Only by redressing these problems can we ensure that future generations will have land capable of retaining economic value and producing potable water.

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