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BG2.5

Constraining global vegetation carbon stocks and fluxes – support for a continuous land sink?
Convener: Martin Thurner  | Co-Conveners: Matthias Forkel , Gitta Lasslop , Thomas Pugh 
The terrestrial vegetation carbon balance is controlled not just by photosynthesis, but by respiration, carbon allocation and turnover (comprising litterfall, background mortality and disturbances) and vegetation dynamics. However, these processes have proved extremely challenging to observe and quantify at regional to global scales and over long time periods. Existing large-scale products of vegetation carbon fluxes and stocks have large uncertainties and integrate over all processes that affect the carbon cycle. This poor empirical basis limits our understanding of the environmental controls on these processes, and in turn their impact on carbon stocks in vegetation biomass and soils. As a result the behaviour of global vegetation models remains underconstrained, giving rise to high uncertainty as to whether the land vegetation will continue to act as a carbon sink under future environmental changes, or whether increases in autotrophic respiration, background mortality or disturbance events (e.g. drought, fire, insect epidemics, pathogens), will counteract this negative feedback to climate change.
We welcome contributions that make use of extensive inventory databases, vegetation models, remote sensing, or model-data integration techniques to advance the understanding on effects of environmental change on processes that control the land carbon sink at regional to global scales and/or on decadal to centennial time scales.

Solicited speaker: David Galbraith, University of Leeds