The ability of forests to absorb carbon from atmosphere depends on nutrients available in the forest soils, according to a recent study.
An international team of researchers found that forests growing in fertile soils with ample nutrients are able to sequester about 30 percent of the carbon that they take up during photosynthesis. In contrast, forests growing in nutrient-poor soils may retain only 6% of that carbon. The rest is returned to the atmosphere as respiration.
"In general, nutrient-poor forests spend a lot of energy -- carbon -- through mechanisms to acquire nutrients from the soil, whereas nutrient-rich forests can use that carbon to enhance biomass production," Marcos Fernandez-Martinez, first author of the paper and researcher at the Center for Ecological Research and Forestry Applications (CREAF) and the Spanish National Research Council (CSIC), said in a statement.
Researchers noted that until now, scientific models to predict forest carbon sequestration on a global scale had only considered the amount of nitrogen in the soil and did not take into account other constraints such as phosphorus or the pH of the soil, which is related to the availability of nutrients.
The new study includes both those factors as well as nitrogen availability, in an analysis synthesizing data from 92 forests in different climate zones on the planet. Tropical rainforests had the poorest nutrient availability, and the lowest efficiency for carbon sequestration, the researchers found.
Researcher said the difference in efficiency of carbon absorption could be due to several factors. For one thing, plants in nutrient-poor soils devote more energy to locating nutrients.
"When plants are in nutrient poor conditions, they send out more roots and produce chemicals that can help dissolve nutrients from the soil. This takes energy, though, and so the plants produce less biomass," Michael Obersteiner, program director of the Ecosystems Services and Management Program Director at the International Institute for Applied Systems Analysis, said in a statement.
Furthermore, the study showed that nutrient-rich ecosystems also generally have more stable ground organic material, which is not easily degraded, and thus retains more carbon.
