How does soil nutrients affect tropical forests?

Tropical forests are one of the most diverse plant populations on earth, and scientists have been studying for decades to identify the evolutionary and ecological processes that have created and maintained them. The main problem is whether all plants use sources - water, light and nutrients - in a similar way or whether each species has its own different living conditions?

A tropical forest on Colorado's Barro Island, Panama, is one of three forests used in the study of soil nutrients and tree distribution.(Photo: Christian Ziegler)

A large-scale study conducted by scientists at the University of Illinois at Urbana - Champaign and eight other scientific institutes clarified this issue. Research has shown that soil nutrients greatly affect the distribution of trees in the rainforest . This finding, published in the multidisciplinary scientific journal of the National Academy of Sciences, rejects the hypothesis that within the local range, the distribution of trees in a forest reflects only the dispersion patterns of the , James W. Dalling, a University of Illinois professor of plant biology and principal researcher, said.

This study was conducted in three areas: two lowland forests, in central Panama and eastern Ecuador, and a mountainous forest in southern Colombia. Scientists chart trees and map the distribution of soil nutrients in these forests with a total area of ​​100 hectares. This study includes 1400 tree species and more than 500,000 plants.

Then, the scientists compared the distribution map of 10 essential nutrients in the soil with the tree map of all trees with a diameter of more than 1 cm. As a result, each area is very different from each other, but in each area, scientists have found evidence that soil composition significantly affects where certain plants grow: The spatial distribution of 36 to 51% of tree species has a great relationship with the distribution of nutrients in the soil.

Before conducting this study, scientists had hoped to see some of the effects of soil nutrients on forest structure, but the results were more pronounced than they thought.

'The fact that up to half of all plants are associated with 1 or more nutrients is really a remarkable result,' Dalling said.

'The difference in nutrient needs between plants can help explain how so many plants can coexist.'

James W. Dalling, professor of University of Illinois Department of Plant Biology, studies tropical forest ecology in Central and South America.(Photo: dost-dongnai)

Although plants in temperate forests affect the soil around them (through the absorption of nutrients, the decomposition of leaf litter on the ground and plant root secretions), in the areas In the tropical forest, the areas in the forest have so many species that the ability of each tree to affect the properties of the soil is very small.

'We think this relationship between plants and soil is the direct response of plants to the changing properties of soil.'

The team also found that certain nutrients in soil that were previously considered important in the development of plants in the rainforest had moderate effects on the distribution of plants.

In the forest in Ecuador, calcium and magnesium have the greatest impact. In Panama's forests, boron and potassium are the most influential nutrients. And in Colombia's mountainous forest, potassium, phosphorus, iron and nitrogen, in order, have the greatest impact on the distribution of plants.

'There are all kinds of minerals in which the minerals that plants seem to be using that we don't think about can be very important.' Mr. Dalling said. He said more research is needed to assess these effects in more detail.

Thanh Van