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Question: Can vegetation changes that occur following cessation of cultivation for cereal crop production in semi-arid native grasslands be described using a conceptual model that explains plant community dynamics following disturbance?

Location: Eighteen native grasslands with varying time-since-last cultivation across northern Victoria, Australia.

Methods: We examined recovery of native grasslands after cessation of cultivation along a space for-time chronosequence. By documenting floristic composition and soil properties of grasslands with known cultivation histories, we established a conceptual model of the vegetation states that occur following cessation of cultivation and inferred transition pathways for community recovery.

Results: Succession from an exotic-dominated grassland to native grassland followed a linear trajectory. These changes represent an increase in richness and cover of native forbs, a decrease in cover of exotic annual species and little change in native perennial graminoids and exotic perennial forbs. Using a state-and-transition model, two distinct vegetation states were evident: (1) an unstable, recently cultivated state, dominated by exotic annuals, and (2) a more diverse, stable state. The last-mentioned state can be divided into two further states based on species composition: (1) a never-cultivated state dominated by native perennial shrubs and grasses, and (2) a long-uncultivated state dominated by a small number of native perennial and native and exotic annual species that is best described as a subset of the never-cultivated state. Transitions between these states are hypothesized to be dependent upon landscape context, seed availability and soil recovery.

Conclusions: Legacies of past land use on soils and vegetation of semi-arid grasslands are not as persistent as in other Australian communities. Recovery appears to follow a linear, directional model of post-disturbance regeneration which may be advanced by overcoming dispersal barriers hypothesised to restrict recovery.