Response of ecosystem CO2 exchange to biomass productivity in a high yield grassland

We measured the biomass production and ecosystem carbon CO2 exchange in a high yield grassland dominated by Miscanthus sinensis. The experimental grassland is managed by mowing once a year in winter every year and the harvested biomass on the ground is left to become the humus. The maximum aboveground and belowground biomasses were 1117 and 2803 g d.w. m−2 in our grassland. Although the high potential of our grassland for biomass production led to higher carbon uptake than with other types of grassland, the large biomass contributed to a higher respired carbon loss. Biomass increase led to a linear increase in ecosystem respiration. Over the 3 years, RE10 increased with increasing aboveground biomass. The potential gross primary production at a photosynthetic photon flux density of 2000 μmol m2 s−1 logarithmic increased with LAI. These responses of CO2 exchange to biomass production suggest this grassland behaved as weak CO2 sink or near carbon neutral (−78 and 17 g C m−2 year−1) in current management.