Every year, fires destroy large areas in more and more countries.
It seems that this situation will not improve in the next few years – and the increase in temperatures and droughts as a result of climate change will not improve the situation.
But if fire destroys everything, how can plants survive and start rebuilding lost forests?
A study published in the journal Oikos by a Spanish researcher at the Center for the Investigation of Desertification in Valencia, Spain, revealed several strategies that plants adopt to regenerate after a fire.
The first (and most effective) strategy is to avoid having to face fire.
How did they get it? It’s very easy: they grow in places where the fire can never reach. For example, on the walls of a narrow valley, in constantly flooded areas or even under water.
The roots of mangroves are always underwater – Image: Getty Images via BBC
If they must live in a fire-prone habitat, plants can adopt other strategies.
Some shrubs and trees create very thick bark that tries to protect the interior of the plant as much as possible.
In all cases, the leaves are always the most defenseless member of the fire.
Faced with this fragility, many trees (such as some pines) prune themselves, causing their lower branches to fall off. This way, only very high flames would be able to reach its leaves.
Other plants can keep the buds underground (and even protected by other plant tissues) to regenerate if the fire kills the adult plants.
The seeds that are born in the heat of the flame
But fire is not a bad thing for all plants.
There are species that you really need to grow and develop. This is the case, for example, with rocks. It is no coincidence that rock roses were among the first plants to colonize the earth after the fire.
The seeds of the rock rose fall into the ground and remain buried for several years, in a state of dormancy called dormancy.
When a forest fire destroys, the fire causes these seeds to reach high temperatures, which awakens them.
In this way, they germinate quickly and can settle in a new, nutrient-rich habitat (all the ash from the fire) and in the absence of competing plants.
The seeds of crocodile (Cistus ladanifer) fall into the ground and remain buried for several years, in a dormant state – Photo: Science Photo Library via BBC
Despite the strategies mentioned, many plant species are very fire-resistant and are completely eliminated from forests after a fire.
If it is a plant species that easily disperses its seeds, it can reappear in a short time in the same place, coming from other nearby forests.
However, if the fire resistance is poor and their seeds are not easily dispersed, the fire can completely destroy these plants. This causes plant species in the area to disappear for several years or even forever.
Learn to survive fires
All fire survival strategies are the result of evolutionary processes that seek, above all, the survival of the species.
To be able, plants must learn to do this. A research paper published in Proceedings of the Royal Society B by researchers at the University of Sheffield in the UK explains precisely how plants can learn to face fire.
The study was conducted on four different types of herbs. Two types of batches were used: one that has not been burned in 35 years, and another batch that has been burned annually for two years.
In both groups, the four herbaceous species analyzed grew normally. What these researchers did was harvest this weed and plant it in pots in a greenhouse, in order to study its development under controlled conditions.
After a year, they found that plants exposed to annual fires produced more seeds and more biomass underground.
Therefore, these plants focus their efforts on scattering their offspring as much as possible and growing where the fire has the least impact on them (underground).
After that, all the plants were burned and germinated again on their own. In this way, the researchers found that plants exposed to continuous fires grew faster after being burned (than buried plants).
Plants have learned that underground growth is necessary to survive in a place exposed to many fires. A skill not acquired by her comrades, inexperienced with fire.
While there are plants that have learned to survive fires, not many have.
Fire represents an insatiable enemy to humans and all living things in the forest. Therefore, we must do our best to prevent its spread in forests.
Jorge Boveda Arias is Assistant Professor and Physician in Biotechnology and Agriculture at the State University of Navarra, Spain.
This article was originally published on the academic news site The Conversation and is republished here under a Creative Commons license. Read the original (in Spanish) here.
– This text was originally published at https://www.bbc.com/portuguese/geral-62673066
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