Faster decomposition of plant litter mixtures can affect climate change

Biodiversity is very important for decomposition, much more than expected, according to new research. This should somehow be taken into account when making CO2 and climate models.

09/25/2020 | 2:56 PM

VU Professor Hans Cornelissen (Department of Ecological Sciences) is one of five authors who published this in a paper in Nature Communications. The paper examines the role of biodiversity for the natural breakdown of plant litter. This process, also called decomposition, is very important for the release of nutrients for plant growth as well as for the release of CO2, the big driver of global temperatures.

Dead leaves of different species help each other
The research team, led by the Japanese scientist Akira Mori, went about to collect experimental data from all over the world where researchers had compared decomposition rates of dead leaves of single species with those of species mixtures. They found that dead leaves of different species tend to “help” each other to rot.

How does that work? Cornelissen: “It is possible, for example, that nutrients are exchanged between dead leaves via fungi. For example, the fungi can export nitrogen from a nitrogen-rich species to a nitrogen-poor species in order to break down the latter more effectively. Or the combination of species can contribute to a more diverse community of fungi and bacteria to ensure more effective decomposition overall. Or one type of leaf can maintain the moisture content of a faster-drying species.” Much is still unknown about these processes and much more research is needed.

Climate models
But it is certain that mixtures of two species generally decompose faster than would be expected from the average decomposition rates of the two individual species separately. The authors showed that these interactions are far from trivial. For instance, the enhancement of decomposition rates due to litter mixing in forests worldwide was even larger than the enhancement of decomposition rates expected from leading, realistic climate warming scenarios for the coming 50 years.

The authors therefore argue that global modellers of CO2 and climate should somehow take these litter interactions into account. Their work also shows how biodiversity, via plant species growing and decomposing together, can be very important for the functioning of ecosystems.