Ecological response syndromes in the flora of southwestern Western Australia: Fire resprouters versus reseeders

Two fire-response syndromes can be described for species of the vegetation of Mediterranean-climate, southwestern Western Australia. Resprouters survive fires as individuals. Reseeders are killed by fire and must reestablish through germination and establishment of seedlings. Of the Western Australian plant families analyzed for fire-response strategies, 50% of the Proteaceae, 50% of the Restionaceae, 45% of the Orchidaceae, and 25% of the Epacridaceae are resprouter species. Within genera of the Proteaceae, the proportions of resprouters include Adenanthos (56%), Hakea (52%), Dryandra (35%), and Grevillea (31%). Within Banksia, 49% are resprouters, and it appears that the reseeding syndrome is the derived character in this genus. The proportion of resprouters within southwestern Western Australian plant communities ranges from 66% to 80%. These percentages are generally higher than in more and parts of Western Australia and in comparable plant communities from other Mediterranean-type climates of the world. The relatively high proportion of resprouters within plant families and within plant communities probably indicates that the Western Australian vegetation experiences a harsher fire stress regime than do other Mediterranean-type climate areas. Western Australian plant communities have their highest diversity in the early years after fire, when the vegetation contains a higher number of reseeding species and individuals. Seed banks are dominated by the seeds of reseeders. There are no basic differences in mean seed mass, viability, or germinability of seeds between resprouting species and reseeding species, but reseeders tend to have narrower optimum germination temperature regimes. Establishment success is related more to seed mass, seedling size, and leaf ecophysiology and morphology than to fire-response strategy. Reseeder seedlings tend to grow faster than do resprouter seedlings. Basic shrub morphology differs, with reseeders generally being umbrella shaped and resprouters urn shaped. Reseeding species most commonly have a shallow, fibrous root system. Resprouters have a massive, deeply penetrating root system. Shoot:root ratios of first-year seedlings and mature plants are higher for reseeders. Resprouter seedlings store starch in root tissue at a much greater rate than do reseeder seedlings. Although the concentrations of essential nutrients in seedlings are not different between fire-response types, reseeders tend to conserve nutrients to a greater extent through leaf retention. Reseeders tend to produce greater numbers of flowers and greater amounts of floral rewards, but the breeding systems, which lead to the higher seed set in reseeders, can vary between strict outcrossing and considerable selfing. Reseeding species are not likely to be wind pollinated. Species survival in a fire-prone environment can involve a wide range of combinations of attributes. It appears that in Western Australian reseeder species the lack of an ability to resprout is compensated for by a number of other structural and functional features. Knowledge of the fire-response strategies of species of southwestern Western Australia can influence fire-regime management, conservation of rare species, and restoration of vegetation after disturbance. Further knowledge of the fire-response strategies of species of the southwestern Western Australian flora should result in better management of natural and restored plant communities of the region.