MYCOMOSS · Mosses as a gateway of nitrogen into northern ecosystems

Mosses as a gateway of nitrogen into northern ecosystems

Climate change is one of the major challenges of our time and the socio-economic consequences are alarming. High latitude ecosystems experience especially drastic changes in temperatures. In cold ecosystems organic matter decomposition is slow, which restricts recycling of nitrogen (N), which here is the primary limiting nutrient for plant growth . However, new N can enter ecosystems via biological N2 fixation taking place in e.g. mosses or through atmospheric deposition. N2 fixation is highly temperature dependent and increased N input via N2 fixation could therefore be a consequence of climate warming. Input of N via atmospheric N deposition is also increasing as a result of increased anthropogenic use of synthetic fertilisers. Increased N availability has large effects on plant production, community composition , and plant and soil carbon stocks, which can ultimately feedback to the global carbon cycle and thus influence climate change. Understanding N cycling in northern latitude ecosystems is therefore essential for understanding consequences of climate change. Mosses are primitive plant and are a major component of high latitude and high elevation ecosystems where they often cover most of the ground. Mosses are known to be important contributors to primary production and through their insulation and water retention capacity they control soil biogeochemical processes such as decomposition of soil organic matter. However, mosses are also key players for N input to terrestrial ecosystems as they readily take up nutrients entering the ecosystem from deposition through the cell walls of their thin leaves and through their association with bacteria fixing atmospheric N2. In this way, mosses work as a gateway and conduit for new N to enter these N-limited ecosystems. Mosses are considered efficient in holding on to newly incorporated N in the short term and old moss tissue is highly recalcitrant and therefore decomposing slowly. However, mosses may loose N via leakage e.g. upon drying and re-wetting , while old parts of the moss shoot eventually die and turn into litter, which then becomes subject to decomposition. Mosses thus likely play a two-faced role in the cycling of N but the mechanisms of and extent to which N bound in mosses becomes available to the decomposer sub-system and to vascular plants is largely unknown, despite the crucial role of N in these ecosystems. The overall objective of MYCOMOSS was to develop mechanistic and quantitative understanding of the role of mosses as providers of new nitrogen to nitrogen-limited ecosystems under climate change.

Data: CORDIS, © European Union