Plant morphological traits and leaf nutrient concentration are associated with flammability and phylogenetic relationships in sub-alpine vegetation, New Zealand

Background Understanding relationships among leaf nutrient concentrations, morphological traits and plant flammability aids predictions of plant flammability. Few studies have simultaneously examined these relationships in a phylogenetic context. Aim Quantify relationships among plant flammability, leaf nutrient concentrations, morphological traits and phylogenetic pattern. Methods We measured shoot and whole plant flammability (for small-sized species), shoot and leaf morphological traits, and leaf nutrient concentrations for 29 vascular plant taxa. Shared and unique plant flammability variation explained by nutrient traits, leaf morphology and shoot traits was estimated, incorporating phylogenetic relationships among species via variance partitioning. Key results Flammability had a substantial phylogenetic proportion; 28% of variation in flammability was explained either independently by phylogenetic relatedness or as shared variation with morphology and shoot traits (49%), or nutrient concentrations (20%). Twig dry matter content and retained dead material were positively and moisture content and most nutrient traits were negatively correlated with plant flammability. Conclusions Variation in leaf nutrient concentrations and plant morphology showed a strong phylogenetic pattern, suggesting that features of plants that determine their flammability are strongly underpinned by evolution. Implications The substantial shared variation between leaf nutrient concentrations, morphological traits and phylogenetic relationships suggests that morphological traits will be more useful than nutrient traits when predicting flammability.