An investigation into the effects of understorey modification on woodland eucalypt recruitment

Widespread tree clearing, grazing, cultivation and fertiliser use have had lasting effects on the understorey of grassy woodlands of south eastern Australia, creating novel systems where resource availability has been altered and ecosystem processes such as tree recruitment may now be impaired. While there is increasing emphasis within management agencies on using natural regeneration to achieve catchment revegetation targets in agricultural landscapes, the effects of understorey modification on woodland eucalypt recruitment are not well known. I compared the potential for tree recruitment in a range of variously modified grassland states based on a state and transition model of woodland vegetation change in agricultural landscapes. Specifically I investigated the effects on seedling germination, growth and survival of changes in species composition of the grass layer, biomass buildup following grazing exclusion, soil nutrient enrichment, and soil compaction in a series of field and laboratory experiments.