Trees in savanna areas of Cerrado produce three times more bark than species in forest areas

Tropical regions of the world often exhibit the coexistence of savannas and forests within the same geographic area, which are subject to similar climatic conditions. The Cerrado biome in Brazil is a prime example of such coexistence, encompassing a diverse range of vegetation types ranging from dense woodland or shrubland with broad-leaved and sclerophyllous vegetation (cerrado sensu stricto), to closed-canopy semi-evergreen forests (cerradão), grasslands with scattered shrubs (campo sujo), and even semi-deciduous seasonal forests.

Areas of cerradão develop in the absence of fire, in both poor and moderately fertile soil (dystrophic to mesotrophic).

Botanists and ecologists find the coexistence of savannas and forests intriguing due to their distinct species composition, dynamics, and functions. Savannas, characterized by dense and highly flammable grasslands, frequently experience fires that have a direct impact on other forms of vegetation.

Forests, on the other hand, have a broad, mostly continuous canopy that provides shade for undergrowth, bushes and smaller trees, and prevents the growth of flammable grass.

Savanna species have undergone millions of years of evolution in the presence of fire, which has led to the development of thick bark to protect them. Following a fire, they have the ability to regenerate new branches and leaves from asexual buds called gemmae.

The Annals of Botany recently published an article on a study carried out at the Santa Bárbara Ecological Station, an environmental protection unit situated in São Paulo state. The study aimed to determine the bark production of savanna and forest species in the Cerrado region, investigate if savanna species producing more bark offer better protection to their gemmae, and examine whether generalist species growing in distinct environments produce varying amounts of bark.

The principal investigator for the study was Alessandra Fidelis, a professor in the Department of Biodiversity at São Paulo State University’s Rio Claro Institute of Biosciences (IBRC-UNESP). 

The first author of the article is Marco Antonio Chiminazzo, a PhD candidate at IBRC-UNESP. 

The other co-authors are Aline Bombo, a postdoctoral fellow at IBRC-UNESP, and Tristan Charles-Dominique, a researcher at the Sorbonne in Paris and the University of Montpellier, both in France. 

According to Chiminazzo, it was observed that savanna species produce approximately three times the amount of bark compared to forest species. However, generalist species demonstrate an intermediate trend, producing more bark in savanna areas than forest areas. This adaptation of bark production in response to the environment is referred to as phenotypic plasticity, which could be a deliberate strategy. Furthermore, it was discovered that species with higher bark production tend to offer better protection to their gemmae and internal tissues. Chiminazzo shared this information with Agência FAPESP.

The research conducted demonstrates the significance of fire as a crucial factor for savanna-type vegetation in the Cerrado region. The presence of fire helps to encourage the growth of woody species that possess the ability to withstand this form of disturbance, which would otherwise not thrive in shaded forested areas.

The findings of the study provide compelling evidence in favor of those who advocate for the cautious and controlled use of fire as a means of managing the savanna regions of the Cerrado. Effective management of fire involves the establishment of zoning and a carefully designed timetable. The process of zoning creates a framework that enables designated areas to be burnt in a rotational manner, in accordance with the predetermined timetable.

As stated by Fidelis, who is Chiminazzo’s thesis advisor, plant species that are native to the Cerrado region have undergone adaptations to deal with fire incidents, which includes the development of thick bark and effective protection mechanisms for their gemmae. These attributes, which are the outcome of a lengthy evolutionary process, are essential for their survival in the event of fires and for successful regeneration post-burning.

Remainder

The study was conducted in an ecological station located in the municipality of Águas de Santa Bárbara, which is a crucial remaining area of native Cerrado in São Paulo state. This location contains all the various types of savanna and forest that are found within the biome. The research team sampled shrub and tree species from four different types of vegetation, each with varying frequencies of burning and light availability. The team investigated the amount of bark produced during development and how the species protected their gemmae from the effects of fire. Based on the preferred environment of each species, they were grouped into three categories: savanna specialists, forest specialists, and generalists, which have the ability to grow in both habitats. Chiminazzo provided this information.

Chiminazzo also suggested that future research should focus on understanding the mechanisms that enable some species to adjust their bark production while others cannot. According to him, this is crucial, especially in the context of climate change and changes in fire patterns. A better understanding of these species will provide valuable insights into predicting which organisms are more susceptible to endangerment or have a higher likelihood of adapting to varying environmental conditions. Therefore, it presents a significant opportunity for further research.

The study was supported by FAPESP via a Young Investigator Grant awarded to Fidelis. In addition, Chiminazzo received a master’s scholarship and a doctoral scholarship. 

About São Paulo Research Foundation (FAPESP)

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