27 October 2017

Vital role in carbon sequestration maintained

Plant communities in peat bogs are affected by global change, but their ecological function is robust

Eerste auteur Bjorn Robroek in een van de onderzochte hoogvenen
First author Bjorn Robroek at work in one of the peat bogs

If all peat bogs in the world were to disappear, the amount of CO2 in the atmosphere would increase by two-thirds. A group of European biologists under the leadership of Utrecht University Prof Jos Verhoeven has studied how peat bogs react to climate change and increased levels of sulphur and nitrogen in the air. To their surprise, they discovered that these changes may cause plant species to disappear, but that these are replaced by others with a similar function in the ecosystem. The results of their study are published in Nature Communications on Friday 27th October.

Peat bogs cover only 3 percent of the earth’s surface, but they are estimated to store around 500 billion tonnes of carbon. That is the equivalent of 67 percent of the amount of carbon in the earth’s atmosphere. “We know that the changing climate and increases in nitrogen and sulphur in the atmosphere cause certain plant species to disappear from areas. That may also have strong consequences for certain biological functions in the area, like carbon sequestration by peat bogs”, explains first author Bjorn Robroek.

Previous study confirmed

Recent research, however, has shown that the biodiversity of peat bog plant communities is less affected by climate change than, for example, in grasslands or dune ecosystems. “Our research confirms this, and may also provide an explanation for it”, according to Robroek, who worked on the study for four years.

Entirely dependent on rainwater and airborne minerals

Hoogveen, foto Cornelia Mattiasson
Hoogveen, foto Cornelia Mattiasson

Peat bogs are wet areas with acidic soil and are very poor in plant nutrients. Changes in the climate and in the atmospheric chemistry are expected to immediately affect peat bogs, because they are higher in elevation than the nearby rivers and streams. They are therefore entirely dependent on rainwater and airborne minerals for their nutrients.

End of peat bogs

The plants and animals that live in peat bogs are adapted to these unique conditions. Moreover, they are indispensable for the continued survival of the peat bog ecosystem. That applies especially to peat mosses (Sphagnum spp.), which can hold water like a sponge. If the peat mosses would disappear due to climate change, that would mean the end for peat bogs.

56 Peat bog areas

Overzicht van de onderzochte hoogvenen
Geographical location of the 56 peat bogs in Belgium, Czech Republic, Denmark, Germany, Estonia, Finland, France, Great Britain, Ireland, Italy, Latvia, the Netherlands, Norway, Poland, Slovakia, Slovenia, Sweden and Switzerland

The biologists studied the effects of climate change and the increase in airborne nitrogen and sulphur by comparing 56 peat bogs across Europe. In each peat bog, they inventoried which plant species occurred in the area. They then analysed the relationships between the species composition, the local climatic conditions and the atmospheric deposition of nitrogen and sulphur. This indicated that there are clear differences in vegetation between individual peat bogs, but remarkably they all displayed similar levels of biodiversity - the number of different species in each area.

Opposing preferences

Further analysis showed that two clusters of plants can be identified that usually grow together. The difference between the clusters is that they have opposing preferences for certain conditions. One group thrives under higher temperatures and precipitation, while the other prefers slightly lower temperatures and less precipitation. The data showed that the absence of species with certain functions is compensated by the presence of species from the other cluster with the same functions. In this way, the peat bog can continue to function properly even if the plant species composition shifts as a result of environmental change.

500 billion tonnes of carbon

That is good news, considering the estimated 500 billion tonnes of carbon that lies sequestered in peat bogs around the world. However, the continued existence of peat bogs remains vulnerable. Most European peat bogs have either disappeared or been seriously affected by human activity. “It is therefore vital that the existing peat bogs are not damaged by drainage or other major interventions”, according to research leader Prof Jos Verhoeven from Utrecht University.

This study was financed in part by NWO-ALW and the Netherlands Foundation for the Preservation of Irish Bogs, and is part of the BiodivERsA-PEATBOG project, which is financed as an ERA-net project within the European Union’s 6th Framework Programme for Research. In the final phase, Bjorn Robroek received financing from the Ecole Polytechnique Fédérale de Lausanne, Switzerland and the University of Southampton, United Kingdom.

Publication

Taxonomic and functional turnover are decoupled in European peat bogs
Bjorn J. M. Robroek*, Vincent E. J. Jassey, Richard J. Payne, Magalí Martí, Luca Bragazza, Albert Bleeker, Alexandre Buttler, Simon J. M. Caporn, Nancy B. Dise, Jens Kattge, Katarzyna Zając, Bo H. Svensson, Jasper van Ruijven, Jos T. A. Verhoeven*
Nature Communications, 27th October, DOI 10.1038/s41467-017-01350-5

* Affiliated with Utrecht University; Bjorn Robroek has worked at the University of Southampton since March 2017.

Pathways to sustainability

This study is part of the interdisciplinary research programme Pathways to Sustainability of Utrecht University.