10 April 2024

When restoring ecosystems, biodiversity is the key

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Brazilian study highlights how the use of increased biodiversity of reintroduced species in restoration areas limits the colonization of invasive species

by Matteo Cavallito

 

Biodiversity of species and functional traits promotes successful regeneration practices in deforested areas. This is suggested by a survey conducted by the Campinas State University, Brazil. The findings are particularly useful in providing guidance to experts engaged in the reforestation of the Cerrado, the savanna located in the center of the country and known for its rich biodiversity.

“Statistics made available in January 2024 show that while deforestation in the Amazon fell by half in 2023, it increased 43% in the Cerrado, the Brazilian savanna,” explains a statement released by FAPESP, a public research foundation based in São Paulo. Previous studies “already highlighted the urgency of combating destruction of the biome. However, it is not enough to defend what remains: restoration is also needed.”

The problem with invasive species

The problem, however, is that regenerating what existed is not an easy task given that areas subjected to this type of intervention typically experience constant colonization by exotic plants, i.e., those invasive species that are not native to that biome.

“Many ongoing restoration projects aim to produce rapid plant cover in the area concerned, but in our study, we showed this isn’t always the best strategy,” Ana C. C. Oliveira, a researcher at the University of Sao Paulo and co-author of the study, explained, quoted by FAPESP.

“Any restoration initiative ,” she added, “must be based on a profound understanding of the ecology of the ecosystem to be restored. Unfortunately, that’s not usually the case.”

The role of biodiversity

According to Oliveira, greater biodiversity would promote resistance to invasion by non-native plants, “probably owing to competition for resources in the nutrient-poor, acidic soil of the Cerrado.” As previous studies highlight, communities with greater diversity tend to have lower levels of available resources.

This penalizes exotic species that typically need large amounts of resources to sustain their rapid growth.

“Plants in any environment survive and grow by means of a range of ecological strategies associated with the anatomy and morphology of their leaves, stems and roots: these characteristics are known as functional attributes,” explained Guilherme G. Mazzochini, a researcher at the University of Campinas and co-author of the study. And it is precisely these characteristics that the authors focused on.

The study

In the research, conducted in an abandoned pasture area now included in Chapada dos Veados National Park in west-central Brazil, the researchers sought to understand “how native grass communities composed by species with different ecological strategies affect the invasion success,” the study explains.

“Specifically, we tested the hypothesis that greater above- and below-ground functional diversity reduces exotic species invasion,” they explain. “We also evaluated whether the isolated effects of native species on invasion were positive or negative.”

The researchers then installed 302 two-by-two-meter plots where they sowed eight different native species in combination to create composite communities with different ecological strategies. They then quantified the above-ground biomass of exotic plants that regularly recurred as a measure of invasion.

Greater diversity means fewer invasive species

Plots sown with only one native species had 3.6 times more exotic biomass than their counterparts with eight species, the researchers say. Determinant, they explain, were some elements such as greater functional diversity in terms of plant height and specific root length. The height diversity of the native species, in particular, appears to limit the amount of sunlight that reaches the invasive species.

Roots, in any case, also play an essential role. According to the researchers, monoculture plots had, on average, 4.7 times more exotic biomass than plots with greater length diversity at the root level. In light of all this, the study notes, the research findings “highlight the need for careful selection of the species to be used in restoration programmes.”