Application of the ecosystem mimic concept to the species-rich Banksia woodlands of Western Australia

Abstract

This article describes the structure and functioning of a natural Banksia woodland at Moora, Western Australia. Species are first grouped in terms of growth form, root morphology, phenology and nutrient acquisition strategy. Above- and belowground standing biomass of a woodland is measured and its net annual primary production per unit rainfall compared with that of adjacent crops and plantings of the tree tagasaste. Information on seasonal water use and nutrient cycling in the dominant tree species Banksia prionotes is used to highlight the pivotal role of deep rooted summer growing trees in the maintenance of sustainability of the system. The article then addresses how one might select species mixtures as functionally effective analogues of the woodland. Assuming the mimic system replaces cleared virgin woodland not previously subject to runoff of water and nutrients from agriculture, a selection procedure would incorporate native flora representing (a) summer-growing deep- rooted and winter-growing shallow-rooted trees and shrubs, (b) herbaceous ground cover species, (c) fire resistant and fire sensitive species, and (d) a range of complementary nutrient uptake strategies. Assuming the mimic is designed to rehabilitate agricultural land experiencing rising water tables and nitrate pollution of ground water, incorporation of fast growing deep rooted exotic trees or herbaceous perennials is recommended alongside conventional annual crops or pastures, with appropriate nutrient stripping through removal of biomass. Difficulties in this context are scale of planting required and current lack of profitable incentives for planting and maintenance of perennials.