4 April 2023

Plant roots are crucial for soil animals


In tropical soils plant roots affect biodiversity no less than leaf litter, a German research explains. A significant finding for the development of sustainable solutions capable of balancing agriculture and land conservation

by Matteo Cavallito


Live plant roots are as important as dead leaves in sustaining tropical soil biodiversity. This is the main conclusion of a study carried out by a team of researchers at the initiative of the University of Göttingen, Germany, and published in the journal Ecology Letters.

“Millions of small creatures toiling in a single hectare of soil including earthworms, springtails, mites, insects, and other arthropods are crucial for decomposition and soil health,” a statement from the German university explains. “For a long time, it was believed that leaf litter is the primary resource for these animals. However, this recent study is the first to provide proof that resources derived from plant roots drive soil animal communities in the tropics.”

The study

The investigation took place in rainforest and palm oil plantations in Sumatra, Indonesia. Here researchers isolated portions of the soil inside by separating them from access to plant roots with a plastic barrier. Other sections of soil, at the same time, were stripped of all dead leaves present, i.e., the main resource used by decomposing organisms. This made it possible to compare the effects of the different deprivations.

“Without living roots, animal abundance in the rainforest plots decreases by 42 percent and in plantations by 30 percent”. While “removing the dead leaves has almost no effect on the animals in the underlying soil, but decreased the total animal abundance (in the soil and dead leaves) by 60 percent in rainforest and rubber plantations due to physical litter removal.

Roots are essential for smaller organisms

Indeed, the researchers note that the effects of lack of access to roots vary with different land uses. This isolation, in particular, “prevents water uptake by roots and this resulted in increased soil moisture in rainforest and rubber plantations, but not in oil palm plantations, which may have been due to lower biomass and production of roots in the latter.”

Variation in soil moisture levels, in any case, “did not affect faunal abundance, which likely reflects high soil moisture throughout the year in the studied tropical ecosystems.” Finally, the study also revealed that live roots are particularly important for smaller living organisms, such as mites and springtails.

Protecting tropical soil biodiversity

The results thus showed how both litter-derived and root-derived resources contribute to the underground food web in tropical ecosystems. The investigation, in particular, “sheds light on principle carbon pathways in tropical soil animal food webs and how they change with anthropogenic land use,” the study states. Moreover, “This knowledge is crucial to build mechanistic animal-inclusive models on the functioning of tropical soils.”

According to Stefan Scheu, head of the animal ecology working group at the University of Göttingen, the information gained can be used “to develop sustainable agricultural landscapes in the tropics.”

The data collected, adds his colleague Anton Potapov, of the German Centre for Integrative Biodiversity Research, a study center with offices in Halle, Jena and Leipzig, “are significant not only for the conservation of tropical soil biodiversity, but also for the development of global ecosystem models describing carbon cycling in the tropics.” Moreover, they can contribute to the understanding and protection of soil animal biodiversity in the context of agricultural expansion in the tropics, the research concludes.