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

Abstract

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.