Advancing grassland process representation in the dynamic vegetation model LPJ-GUESS to evaluate management impacts

Grassland ecosystems dominated by herbaceous plants provide essential ecosystem services, most prominently food provision, and play a key role in the global carbon cycle and in sustaining biodiversity. They are therefore central to both human well-being, and Earth system functioning. Despite their ecological importance, grassland ecosystems and herbaceous species are insufficiently represented in dynamic global vegetation models, limiting our ability to project their responses to climate and land-use change. For example, a realistic representation of phenology of grassland ecosystems is needed for analysing management practices including grazing, cutting and ploughing. However, many vegetation models lack key grass-specific processes that determine vegetation persistence and regrowth both in unmanaged and managed grasslands. As a consequence, it remains difficult to analyse feedbacks between grassland vegetation, soils and the atmosphere and the effect management has on them.

   In this study, we address these limitations by advancing the representation of herbaceous species in the dynamic global vegetation model LPJ-GUESS. We implemented a daily carbon allocation scheme, grass-specific traits for i.e. allometry and life-cycle dynamics to better capture growth and seasonal development of grassland vegetation. Model performance was assessed using European grassland FLUXNET sites. We evaluated the effects of the new model representation on biomass accumulation, carbon stocks and fluxes, both in absence of management and under different management scenarios.  These developments allow for a more mechanistic simulation of grassland responses to different management regimes.