Environmental Effects on Assimilated Carbon Quantity and Quality in Two Different Wet Grassland Plants

Wetlands are important ecosystems for mitigating climate change impacts on the environment and society. Most studies focus on how single environmental factors affect those ecosystems, although several environmental factors may change simultaneously. This study focused on nutrient – water level interaction effects on two different but associated wet grassland species Carex acuta and Glyceria maxima. Biomass allocation and root exudates were measured in a full-factorial mesocosm experiment. Species identity and water level mostly determined total alive biomass and the biomass allocation pattern. Root weight ratio generally increased in C. acuta whereas increased rhizome biomass was associated with G. maxima. Furthermore, increased water levels increased relative aboveground biomass allocation with C. acuta having more leaf and G. maxima having more stem biomass. Surprisingly, fertilisation had little impact on total biomass, but decreased relative biomass allocation to the roots and also strongly suppressed root exudation. There is an apparent nutrient dependent shift in the realised hydrological niche of both plants towards drier conditions. C. acuta behaves similar under all water levels without fertilisation, but thrives best under dry conditions when fertilised. Without fertilisation, G. maxima thrives best under flooded conditions (water level ~ 15 cm above soil surface), but does equally well in saturated water conditions (water level ~ soil surface) when fertilised.