Impacts of non-vascular vegetation on global biogeochemical cycles from the geological past to the future

Non-vascular vegetation, such as lichens, bryophytes, terrestrial cyanobacteria and algae, have been suggested to contribute significantly to global biogeochemical cycles, e.g. via productivity and nitrogen fixation. They may protect permafrost soil against future warming, and they probably caused global glaciations in the geological past, by enhancing chemical weathering and thereby reducing atmospheric CO2.

However, quantitative knowledge on these effects is still incomplete. In particular, it is unclear how climate change will affect the organisms, and how nutrient limitation may reduce positive effects of higher CO2. Moreover, the large-scale effects of non-vascular vegetation on past climates are highly uncertain.

Here, we estimate the role of these organisms for global biogeochemistry through process-based modeling, establishing a new version of the non-vascular vegetation model LiBry. We examine the limiting effect of nutrient availability on productivity under CO2-fertilisation, and we aim at providing a first global estimate of future productivity under climate change. We will thereby assess the implications for terrestrial nitrogen fixation and permafrost protection by the organisms. In a second project, we explicitly simulate effects of early terrestrial vegetation on biotic enhancement of chemical weathering. By applying our approach to periods in the Paleozoic and the Proterozoic, we will quantify impacts of vegetation on past climate and atmospheric composition.