Quantifying the biodiversity threshold for peatland carbon service delivery

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Sphagnum moss peatlands sequester carbon, providing a vital climate regulation service. The carbon that is used in the growth of these bog plants can come from two main sources. The first is atmospheric carbon dioxide. The other is from methane released by the decomposition of plant material in the sub-surface layers. Methane itself can not be used for photosynthesis. However, certain species of methane-feeding bacteria have been found to exist in peatland surfaces when those surfaces become particularly wet. They have been found to live in the tissues of Sphagnum mosses. These "methanotrophic" bacteria feed on the methane released from the peatland. As they do so, they create carbon dioxide as a bi-product. As they live in the Sphagnum tissues, the carbon dioxide that they create provides an additional source for Sphagnum photosynthesis. What is still unclear is how much of the carbon that becomes Sphnagum moss is drawn-down from the atmosphere and how much is recycled from methane released from anoxic decay in the sub-surface layers of the peatlands. Furthermore, it is vitally important to understand whether there is a certain threshold of surface wetness beyond which the methanotrophic bacteria start or stop doing their work.This project will demonstrate the relative importance of recycled methane and atmospheric CO2 in peatland carbon sequestration using a novel combination of four types of geochemical and physical sediment analyses. We will test whether past changes in peatland surface wetness, themselves linked to climate change, created conditions favourable for populations of methane-feeding bacteria. We will test whether the presence of those bacteria led to changes in carbon sequestration in the past, thereby helping understanding of how they might respond to changes in present.The work will have direct implications on just how far peatlands should be re-wetted. We hope, then, to answer the question of whether to wet or not to wet?!