Environmental Influences on Quantum Use Efficiency in a Virginia Salt Marsh

Tidal wetlands perform a number of important ecosystem services, such as carbon sequestration, water quality improvement, and nutrient control. However, quantitative relationships between tidal wetland productivity and environmental factors are lacking. In this study, data from a flux tower in a Virginia salt marsh are used to assess the gross primary productivity (GPP), defined as the total amount of carbon dioxide assimilated by vegetation, and investigate the effect of air temperature, inundation level, and photosynthetically active radiation (PAR) on the quantum use efficiency (GPP/PAR) from June to November of 2015. The quantum use efficiency was lowest during the middle of the day, presumably due to temperature and light stress. Quantum use efficiency also declined from summer to fall, with temperature the likely driver of the decline because inundation did not change and PAR decreased. The findings should be helpful in the development of process-based and remote-sensing models of tidal wetland productivity.