Fire persistence traits of plants along a productivity and disturbance gradient in mediterranean shrublands of south-east Australia

Aim To understand changes in fire persistence traits of plants along a latitudinal gradient, considering the interactions between productivity, community (fuel) structure and fire regime. Location A gradient in the south of Australia (latitude 33-37 degrees S; longitude 140-143 degrees E), including: Little Desert National Park (VIC), Big Desert Wilderness Park (VIC), Murray-Sunset National Park (VIC), Danggali Conservation Park (SA) and Tarawi Nature Reserve (NSW). Methods We selected four areas along a latitudinal gradient for which information on fire history and vegetation was available. Then, we tested to what extent the four selected areas have different climate and different fire regimes. Plant cover values of different life forms provided an indication of the plant community structure and flammability, and the proportion of species with different fire persistence traits (resprouting, seedbank persistence) informed us on the trait selection. Results Precipitation decreases and temperature increases from south to north. Thus the selected sites represent a gradient from high productivity (low aridity) in the south to low productivity (high aridity) in the north. Fire statistics suggest that fire frequency parallels productivity. There is a tendency for life form dominance and community structure to shift in such a way that fuel connectivity is reduced towards the north. Resprouting species increase and obligate seeders decrease along the fire-productivity gradient. Main conclusions Changes in plant traits are difficult to understand without simultaneous consideration of both the disturbance and the productivity gradients. In our study area, fire regime and productivity interact in such a way that decreases in productivity imply changes in fuel structure that produce a reduction in fire frequency. Resprouting species are better represented at the high fire-productivity part of the gradient, while obligate seeders are better represented at the opposite end of the gradient. The results also emphasize the importance of considering not only climate changes but also changes in fuel structure to predict future fire regimes.