Understanding How Fire-Adapted Plants Face Climate Change Through the Concept of “Modularity”

A recent research paper by Chiminazzo and colleagues, published in AoB PLANTS, looks at how woody plant species can survive and even thrive amidst frequent fire events. With climate change predicted to alter fire regimes, understanding these survival strategies becomes crucial for preserving biodiversity and predicting future ecosystem shifts.

Plants in fire-prone ecosystems have evolved to weather fire events using a strategy known as resprouting – the ability to grow new branches after a fire disturbance. Chiminazzo’s team highlights a factor less explored so far in such research – woody plant “modularity,” the concept that plants are composed of different parts or modules that interact with their environment in unique ways.

The researchers argue that as woody plants grow, each module (new growth unit) experiences its environment differently, impacting overall survival and adaptation to fire. This includes how quickly these modules can protect themselves from fire and contribute to the plant’s survival. Understanding this could help predict which species will endure changing fire regimes.

The researchers present an intriguing concept, the ‘firetrap,’ a phenomenon explaining the abundance of shorter plants like sub-shrubs and forbs in frequently burned savannas. These plants store most of their biomass underground, safe from fire, and their survival hinges on their ability to transition from seedlings to adults, elevating their canopies above flames. Yet, due to frequent fires, many species are often killed before reaching this height. Understanding how these fire-prone ecosystems work can inform fire management strategies and aid in predicting the effects of climate change.

The authors then apply their ideas to the Cerrado, the tropical savannah of eastern Brazil. They concentrate on Miconia albicans, a plant that can grow as a tree or a shrub. In their article, the authors write:

The aerial buds of M. albicans are protected differently when this species grows as a shrub or a tree. When growing in an open savanna as a shrub, its buds are not protected by the bark layer (Chiminazzo et al. 2021). However, when growing as a tree in a woody savanna, the buds are well protected (De Antonio et al. 2020), being located at the base of depressions in the bark layer (Fig. 1). This difference could be due to either phenotypic plasticity or the stage of development of the sampled growth modules. Charles-Dominique et al (2017) found a positive relationship between bark production and aerial bud protection aboveground, meaning that species producing more bark were also able to better protect their buds aboveground. We note here that for most species, the bud location in relation to the bark surface is maintained through time, meaning that buds are growing at the same pace as the bark surface and that their location is actively maintained by a balance between bark production and bud growth (Fig. 1; Chiminazzo et al. 2023). The shift in bud protection in M. albicans, associated with its development into alternative growth forms, influences its post-fire responses: when growing as a shrub, it resprouts from basal parts after fire events (from the root crown; Pilon et al. 2021b); when growing as a tree, it can also resprout from aboveground buds (Chiminazzo and Rossatto, pers. obs.).

Chiminazzo et al. 2023.

Chiminazzo and colleagues conclude:

Woody species present a wide diversity of traits and strategies allowing them to survive fire, reflecting the high diversity of fire regimes. Therefore, there is a need to investigate in more detail the diversity of fire persistence traits to predict which species will prevail when fire regimes become altered by climate and land uses and why. Thus, we urgently need to study plant responses at the module level, because these responses are sensitive to the modules position relative to the flame height, and they are determined by ontogenetic patterns that translate into plants being protected fast or slow, depending on the ability of plants to cope their development with the environment. Studying fire persistence traits of woody plants and their inclusion in intermediate strategies should be considered priority tasks, since the structure of open ecosystems is strongly affected by changes in woody plant density worldwide, as a result of altered fire regimes.

Chiminazzo et al. 2023.

READ THE ARTICLE
Chiminazzo, M.A., Charles-Dominique, T., Rossatto, D.R., Bombo, A.B. and Fidelis, A. (2023) “Why woody plant modularity through time and space must be integrated in fire research?,” AoB PLANTS, 15(3), p. lad029. Available at: https://doi.org/10.1093/aobpla/plad029.