Responses of resilience traits to gradients of temperature, rainfall and fire frequency in fire-prone, Australian forests: potential consequences of climate change
The composition of plant communities may be driven by responses of key plant resilience traits (resprouting R+, non-resprouting R−, persistent P+ and transient P− seedbanks) to either resource competition or disturbance regimes. We explored responses of overall species richness and the richness of herbs and shrubs within the three most common functional types (i.e. facultative resprouters R+P+, obligate resprouters R+P−, obligate seeders R−P+) to orthogonal combinations of temperature (MAT), rainfall (MAP) and fire frequency (FF) in Dry Sclerophyll Forest in the Sydney basin (south-eastern Australia). R+ and P+ species were predominant (>72 % of total species). Overall richness was a significant positive function of MAT, MAP and FF. Positive relationships between species richness and MAP, MAT and FF occurred across all trait and functional type groups, with MAP being the most influential and FF the least. Responses of proportions of species within trait- and functional-type groups were complex. Proportion of R+ species was negatively related to MAT and MAP, but species-rich herb and shrub R+P+ proportions were positively and negatively related to MAT, respectively. The herb R+P+ proportion was negatively related to FF. The results were inconsistent with the disturbance frequency and resource competition models of resilience variation. Rises in MAT under climate change have the potential not only to increase overall species plus richness across all trait groups but also to diminish shrubs relative to herbs in the key R+P+ functional types. Such a scenario is highly uncertain given the variability in future MAP projections for the region.