Using plant functional types to predict the influence of fire on species relative abundance

Abstract

Fire influences plant survival, reproduction, and establishment. Consequently, plants exhibit fire-related traits. Grouping species with similar traits into Plant Functional Types (PFTs) enables predictions of fire–related change based on ecological mechanisms. However, if PFTs are to advance conservation decision-making, we must know if predictions are robust. We developed a PFT approach to predict how species relative abundance changes as a function of time since fire, and tested predictions empirically. First, we used trait databases and ecological knowledge to assign species into PFTs based on fire-related mechanisms. Second, we developed graphical predictions of fire-related change in relative abundance. Third, we collected data on species relative abundance at 57 sites, across an 81–year post–fire chronosequence. Finally, we tested predictions using non–linear regression models. Predictions of the direction of changes in relative abundance (increase or decrease from 0 to 81 years since fire) were correct for 18 of 24 species modelled. Predictions of the shape of changes in relative abundance were not as accurate, but still useful: 13 out of 24 species showed ‘excellent’ conformity with shape predictions, 7 ‘good’ conformity, and 4 ‘poor’. Broader functional groupings commonly used in ecology, such as facultative resprouter, inadequately captured changes in relative abundance. An advance of this study is that the direction and trajectory of changes in species relative abundance can be predicted using deductive PFTs that represent population processes. This suggests PFTs can be used to generalize fire responses across species that share similar traits, and thus inform biodiversity conservation and management.