Classifying the fire-responses of plants: How reliable are species-level classifications?

Abstract

Plant species in fire-prone environments possess specific traits which allow them to survive fire. Species are commonly classified according to whether they survive fire and resprout or whether they are killed by fire and regenerate from seed. However, different populations of the same species have been shown to vary in their responses. Therefore, the classification of a species into a single category based on fire-response traits may not necessarily be representative of every population under every circumstance. This study examined the extent of within-species variation in fire-response traits of woody plants in south-eastern Australia after the 2003 fires. Species were then classified using two approaches: (i) using data from a field survey of fire-response traits, taking into account within-species variation; and (ii) using species' fire responses listed in a pre-existing fire-response database compiled from a variety of primary sources. Field data showed that the majority of species in the study area resprouted after fire with around one in 10 species variable in their resprouting response. Almost half of all species varied from site to site according to whether they regenerated from seed, either solely or in addition to resprouting. The numbers of species classified as resprouters and seed regenerators varied according to the classification method used. Differences were also found between the classification method when calculating the mean proportion of resprouters and seed regenerators across sites. The fire-response traits for some species from the database were found to differ from the observed field responses. This study demonstrated that the application of a fire-response trait, reported in a trait database, to an entire species, may not adequately represent the actual fire responses of the populations of interest. Rather than considering the fire-response traits of a species, accurate prediction may be better achieved by considering how different populations of plants will respond to fire.