Species of Paineira-Barriguda (Ceiba samauma) boboletas318 / iNaturalist When we think of the Amazon, the image that usually arises is that of the treetops forming an immense green carpet. But a decisive part of the survival of the largest tropical forest on the planet happens out of sight: underground. ? Also follow Terra da Gente on Instagram Research carried out by Brazilian scientists showed that Amazonian trees change their nutrient acquisition strategies according to soil conditions. In some cases, they invest in the production and renewal of fine roots. In others, the results suggest that they begin to depend more on the association with microscopic fungi capable of exploring regions of the soil inaccessible to roots. The study monitored, for two years, the behavior of so-called fine roots — structures less than two millimeters in diameter responsible for exploring the soil in search of water and nutrients — in permanent plots of the Amazon Fertilization Experiment (AFEX), one of the largest fertilization experiments ever carried out in a tropical forest. The research simultaneously monitored the stock, productivity and turnover (renewal rate) of these roots, something considered rare in studies carried out in the Amazon due to the difficulty of observing the root system in a natural environment. For forestry engineer Jéssica Schmeisk Rosa, PhD in Tropical Forest Sciences from INPA, one of the authors of the work, plants respond to environmental conditions by adopting different strategies to obtain resources. "The choices will depend on the environment the plant is in. It may be that building new roots is more advantageous and efficient than maintaining older roots, or even that maintaining these roots and investing in mycorrhizae is better in certain conditions. The strategies will depend on the environmental conditions to which these organisms are exposed." See more news from Terra da Gente, on g1: PHOTO: Spotted of an Alta-Floresta zogue-zogue with baby on its back on a canopy bridge BIG DAY: Institute promotes 2nd action to observe great blue macaws in nature SURVIVAL: New species of cloud fish is discovered in the Pantanal A rich forest on poor soil Pará Castanheira (Bertholletia excelsa) in the Amazon hirosho / iNaturalist Although the Amazon is one of the most biodiverse ecosystems on the planet, much of it grows on ancient, highly weathered and nutrient-poor soils. Among the scarcest elements are phosphorus and the so-called basic cations, such as calcium, magnesium and potassium. According to Jéssica, it was precisely this limitation that led Amazonian species to develop different ways of surviving. "The fine roots are extremely plastic. They can expand or reduce their area of ??contact with the soil, increase or decrease their longevity, produce enzymes, stimulate the microbiota or promote associations with fungi and bacteria to obtain nutrients." These roots function as the main interface between the plant and the soil and respond quickly to changes in resource availability. Phosphorus makes a difference The researchers expected that the addition of phosphorus and basic cations would provoke similar responses in roots, as both are naturally scarce in the Central Amazon. But the results showed very different behaviors. When phosphorus was added to the soil, there was an increase in the productivity of fine roots and the rate of renewal of these structures, without changing the total root stock. See what's highlighted in g1:
Do Amazonian trees do 'do math'? See how they can change their strategy to survive
Species of Paineira-Barriguda (Ceiba samauma) boboletas318 / iNaturalist When we think of the Amazon, the image that usually arises is that of the treetops forming an immense green carpet. But a decisive part of the...
In practice, this means that the plants began to produce new roots more frequently. According to the researcher, the explanation lies in the way phosphorus behaves in the soil. "Phosphorus has low mobility in the soil and is extremely scarce in the Central Amazon. Roots need to search intensely for it and younger roots may be particularly more efficient at absorbing water and nutrients." She explains that, under these conditions, producing new roots can represent a more advantageous investment than maintaining old structures. Growing more is not always the best strategy Image of a Brazil nut tree (Bertholletia excelsa) eulucasramus / iNaturalist The behavior was different when the researchers added only basic cations to the soil. In this case, the productivity of the roots remained practically unchanged, while their longevity increased. According to Jéssica, this happens because these nutrients are more mobile and can reach the roots more easily. "The basic cations are present in the soil solution and the roots can access them more easily. Therefore, they do not need to produce as many roots to search the soil." This difference revealed that plants do not respond to all nutrients in the same way. The invisible partnership beneath the forest The results also help explain another important mechanism for the survival of Amazonian trees: the association with arbuscular mycorrhizal fungi. These fungi live attached to the roots and function as an extension of the root system, exploring volumes of soil that the roots alone cannot reach. In exchange for the nutrients captured by the fungi, the plant provides carbon compounds produced during photosynthesis. "Fungi provide greater efficiency in capturing nutrients for the plant. In return, they receive carbon compounds fixed by the photosynthetic process." According to the researcher, depending on environmental conditions, this association may represent a more efficient strategy than continually investing in the production of new roots. The 'bargaining currency' of plants Mycorrhizal fungi seen under a microscope at the AMOLF biophysics institute in Amsterdam. The circular structures are spores; colors have been changed to make viewing easier. Tomás Munita Although it is tempting to say that trees "do math", Jéssica prefers an explanation closer to biological reality. "It's a good analogy, but it's worth highlighting that plants don't do math exactly like we do. Let's say that plants' currency is carbon." She explains that building new roots, maintaining old roots or investing in association with fungi represent different ways of using this energy. Each strategy depends on the conditions found in the environment. What this changes for science The discovery helps to understand how the Amazon manages to maintain its productivity despite growing on soils that are extremely poor in nutrients. In 2022, researchers from the same group published a study in the journal Nature demonstrating, for the first time, that phosphorus is the main nutrient limiting the productivity of the Amazon forest. Now, the new work helps explain how trees manage this limitation by continually adjusting their nutrient acquisition strategies. According to Jéssica, understanding these mechanisms is essential to predict how the forest will respond to climate change. "Understanding how each nutrient affects nutrient acquisition mechanisms and strategies helps to improve climate models and predict more accurately what could happen in these ecosystems in the future." She highlights that this knowledge can also guide public policies aimed at conserving the Amazon. "This better understanding of the processes can result in more accurate climate models and assist in more assertive environmental and social public policy choices, so that climate change impacts the quality of our future as little as possible." VIDEOS: Highlights Terra da Gente See more content about nature on Terra da Gente
