New research reveals that living plant roots are as important as dead leaves to sustain tropical soil animal biodiversity

A research team led by the University of Göttingen has shed new light on the importance of plant roots for belowground life, particularly in the tropics.

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.

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.

See also: Microbes could be used as natural fertiliser for poor soil


Animal abundance


The researchers isolated plots within natural ecosystems and separated the plots from accessing plant roots with a plastic barrier (a technique known as ‘root trenching’).

Their study included rainforest, as well as both rubber and oil palm plantations in Sumatra, Indonesia. As a comparison, they removed all dead leaves, the main resource of decomposer animals, from other experimental plots.

They found that without living roots, animal abundance in the rainforest plots decreases by 42% and in plantations by 30%.

By contrast, 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% in rainforest and rubber plantations due to physical litter removal.

However, the effects of plant litter removal were not observed in oil palm plantations, where litter is very scarce in any case.


Smaller soil animals


The study also revealed that living roots are especially important for the smaller soil animals, such as mites and springtails. Interestingly, after adding artificial plastic leaves in oil palm plantations, abundance of some animal groups – such as prostigmata – increased, highlighting that improving habitat structure, for instance by mulching, can promote soil food networks and the services they provide.

Professor Stefan Scheu, head of the Animal Ecology Working Group at the University of Göttingen, said: “The study provides novel perspectives for the management of the resources provided by plant litter in tropical plantations, fostering soil animal biodiversity.

“This is important to develop sustainable agricultural landscapes in the tropics.”

Dr Anton Potapov, who studies soil biodiversity and functions at the German Centre for Integrative Biodiversity Research (iDiv), Halle-Jena-Leipzig, added: “This study’s findings 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.

“We need a better understanding of the complex ecological systems that support life on Earth.”

The results are published in Ecology Letters.

Image: The researchers compared the effects of living roots or leaf-litter in small experimental plots in rainforest (left hand side) with oil palm plantation (right hand side) © Ananggadipa R.