A research team from the University of Tübingen examined the role of vegetation, precipitation and soil erosion
Plants may stabilize slopes, yet rainfall often intensifies soil erosion. Until now, just how these 2 things interact to form mountain topography was only clear for a few small regions on Earth. In a new study, Professor Todd Ehlers, Dr. Jessica Starke and Dr. Mirjam Schaller of the Geosciences department at the University of Tübingen, Germany investigated how plants and climate shape topography.
They did this in a large study of the 3,500 kilometer long western edge of the Andes Mountains in Peru and Chile and found that the question of how plants influence the landscape and erosion can have different answers, depending on what area is investigated: In the dry Atacama Desert, for example, sparse vegetation is sufficient to hold the soil in place; while higher erosion rates can be seen in the wetter and more temperate regions where plant cover is denser.
The basic is: Plants use their roots to hold the soil onto slopes and slow down water flowing over the surface, thereby stabilizing slopes. But, plants can also enhance erosion by using their roots to break down rocks into soil that is more easily erodible.
However, the situation becomes more complex when rainfall is taken into account. Rain is important for vegetation, but is also a key driver for soil erosion. „You might think that the denser the plant cover, the less erosion there would be. This simple correlation is correct for some regions of the Andes” Ehlers says. „However, other factors such as the rate of rainfall also play an important role. It’s exciting to now see how mountain erosion reflects this interaction between plants and rainfall.”
For example, in the temperate Andean regions there is dense plant cover due to heavy rainfall. This rainfall is high enough that it increases soil erosion, despite the presence of dense vegetation. However, in regions with even denser vegetation than temperate areas, plants are able to outpace the effects of rainfall on erosion and slopes are stabilized, and steeper.
„Our study is an example of a new scientific frontier where the Earth and life sciences meet. We are learning more and more about how strongly the solid and living parts of the Earth interact, and we can observe the effects of these interactions over long time scales of thousands of years,” says Ehlers.
J. Starke, T.A. Ehlers, M. Schaller: Latitudinal effect of vegetation on erosion rates identified along western South America. Science, v. 367, issue 6484, pages 1358-1361, (2020). https://dx.doi.org/10.1126/science.aaz0840
Source: Universität Tübingen
(24.03.2020, USA: 03.24.2020)