Plant functional traits provide a valuable tool to improve our understanding of ecological processes at a range of scales. Previous handbooks on plant functional traits have highlighted the importance of standardising measurements of traits to improve our understanding of ecological and evolutionary processes. In open ecosystems (i.e. grasslands, savannas, open woodlands and shrublands), traits related to disturbance (e.g. herbivory, drought, and fire) play a central role in explaining species performance and distributions and are the focus of this handbook. We

There is increasing recognition that plant traits contribute to variations in fire behavior and fire regime. Diversity across species in litter flammability and canopy flammability has been documented in many woody plants. Grasses, however, are often considered homogeneous fuels in which any flammability differences across species are attributable to biomass differences alone and therefore are of less ecological interest, because biomass is hugely plastic. We examined the effect of grass canopy architecture on flammability across eight grass species in short grass steppe of New Mexico and Texas. To characterize grass canopy architecture, we measured biomass density and “biomass-height ratio” (the ratio of canopy biomass above 10 cm to that of biomass below 10 cm). Indoor flammability experiments were performed on air-dried individual plants. As expected, plant biomass influenced all flammability measures. However, biomass-height ratio had additional negative effect on temperature exposure at soil surface (accumulation of mean temperature >100 °C) in well-cured grasses, which is an important fire behavior metric predicting soil heating and meristem survival. This canopy architecture effect, however, needs further investigation to be isolated from biomass density due to correlation of these two traits. This result demonstrates the potential for species-specific variation in architecture to influence local fire effects in grasses.

In ecosystems where trees and grasses coexist, some grass species are found only in open habitats and others persist under trees. The persistence of shade intolerant grasses in ecosystems such as open woodlands and savannas depends on recurrent fires to open the tree canopy. Therefore, grasses that depend on open sites might benefit from high flammability. We tested if shade intolerant grasses are more flammable than shade tolerant grasses and if flammability differences affected post-fire grass growth. We examined the relationship between shade tolerance and flammability by determining individual-level flammability and species shade tolerance of 17 grass species. We also measured grass traits to determine trait effects on flammability and the post-fire response. Grass species varied in flammability, mainly in the amount of heat produced during burning. Shade tolerant species produced less heat at 50 cm above the ground. Biomass and live fuel moisture had the greatest effects on heat release. However, the negative effect of live fuel moisture on heat release at the soil surface was weakened in plants with high specific leaf area. In addition, grass bulk density negatively influenced heat release at 50 cm height. Heat release at the soil surface negatively influenced postfire growth. However, the influences of soil heating and species-specific traits on individual survival were more complex with 2-and 3-way interactions. Shade tolerance was negatively correlated with a major axis of flammability variation: shade tolerant grasses produced less heat where that heat could damage tree boles. Such heterogeneity in grass flammability may help maintain the tree-grass mixture in natural plant communities. If shade tolerant grasses near trees cause less fire damage to woody plants, especially tree saplings, this may weaken positive grass-fire feedbacks and thus aid the long-term coexistence of trees and grasses.

Plant functional traits provide a valuable tool to improve our understanding of ecological processes at a range of scales. Previous handbooks on plant functional traits have highlighted the importance of standardising measurements of traits to improve our understanding of ecological and evolutionary processes. In open ecosystems (i.e. grasslands, savannas, open woodlands and shrublands), traits related to disturbance (e.g. herbivory, drought, and fire) play a central role in explaining species performance and distributions and are the focus of this handbook. We provide brief descriptions of 34 traits and list important environmental filters and their relevance, provide detailed sampling methodologies and outline potential pitfalls for each trait. We have grouped traits according to plant functional type (grasses, forbs and woody plants) and, because demographic stages may experience different selective pressures, we have separated traits according to the different plant life stages (seedlings saplings and adults). We have attempted to not include traits that have been covered in previous handbooks except for where updates or additional information was considered beneficial.