MoLiCarb - Impacts of mosses and lichens on permafrost soil carbon dynamics since the last glacial

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This project will investigate the importance of vegetation, in particular mosses and lichens, for soil carbon (C) content at high latitudes. Permafrost soil C in these regions is of great relevance for future climate, since thawing of this soil will likely lead to strong emissions of CO2 and a positive feedback on global warming. The prediction of these emissions by Earth system models is uncertain, however, since the effects of vegetation at high latitudes, especially of mosses and lichens, on the ecosystem C balance are currently poorly constrained. This is due to the lack of respective proxy-data time-series for model output validation and also because mosses and lichens have so far rarely been taken into account in vegetation models. As a new solution to this problem, we will use sedimentary ancient DNA (sedaDNA) in our planned project to quantify the long-term relationships between vegetation, climate and soil C in permafrost areas on the glacial-interglacial time-scale. Advances in analytical methods (applicant U. Herzschuh) have made it possible to determine the taxonomic composition of vegetation, including mosses and lichens, in sedaDNA and its relationship to soil C content. We will apply these findings to create and validate a new version of the process-based LiBry vegetation model which was developed by applicant P. Porada. The LiBry model is able to calculate the physiological properties and diversity of moss and lichen communities and their effects on the C balance of ecosystems on the basis of climate and other environmental data. The work will be organized into two complementary sub-projects (A, B), each divided into three work packages (WP), which will be concluded with a synthesis WP. Subproject A aims at the adaptation and evaluation of cutting-edge sedaDNA methods (including metabarcoding, shotgun sequencing and capture approaches) for identification of vegetation taxa, including mosses and lichens, in modern permafrost soils; and their application to permafrost soil sections in eastern Siberia reaching back to the last glacial and beyond in concert with traditional palaeoecologcial methods. All material was collected during previous field works. In subproject B, the LiBry model will be extended by the most relevant soil processes of permafrost regions and updated vascular vegetation, creating a new version LiBry-PERM. The simulated soil C content and the proportions of mosses and lichens will be validated using the proxy data collected in WP A. With the new LiBry-PERM, it will be possible to reconstruct the dynamics of permafrost soil C at high latitudes since the last glacial. In the synthesis WP we will, finally, use LiBry-PERM to predict permafrost soil C for the next decades, taking into account the effects of mosses and lichens. Thus, we will make a substantial contribution to the improvement of future Earth system models, which estimate the role of permafrost soil C for global warming.