Journal Article

Reduced Summer Aboveground Productivity in Temperate C3 Grasslands Under Future Climate Regimes

Ivanov, Martin A., Bendix, Jörg, Luterbacher, Jürg, Obermeier, Wolfgang A., Lehnert, Lukas W.

2018

Overview

Temperate grasslands play globally an important role, for example, for biodiversity conservation, livestock forage production, and carbon storage. The latter two are primarily controlled by biomass production, which is assumed to decrease with lower amounts and higher variability of precipitation, while increasing air temperature might either foster or suppress biomass production. Additionally, a higher atmospheric CO2 concentration ([CO2]) is supposed to increase biomass productivity either by directly stimulating photosynthesis or indirectly by inducing water savings (CO2 fertilization effect). Consequently, future biomass productivity is controlled by the partially contrasting effects of changing climatic conditions and [CO2], which to date are only marginally understood. This results in high uncertainties of future biomass production and carbon storage estimates. Consequently, this study aims at statistically estimating mid‐21st century grassland aboveground biomass (AGB) based on 18 years of data (1998–2015) from a free air carbon enrichment experiment. We found that lower precipitation totals and a higher precipitation variability reduced AGB. Under drier conditions accompanied by increasing air temperature, AGB further decreased. Here AGB under elevated [CO2] was partly even lower compared to AGB under ambient [CO2], probably because elevated [CO2] reduced evaporative cooling of plants, increasing heat stress. This indicates a higher susceptibility of AGB to increased air temperature under future atmospheric [CO2]. Since climate models for Central Europe project increasing air temperature and decreasing total summer precipitation associated with an increasing variability, our results suggest that grassland summer AGB will be reduced in the future, contradicting the widely expected positive yield anomalies from increasing [CO2]. Key Points We link results from an 18‐year FACE experiment with climate forecasts to estimate mid‐21st century C3 grassland productivity Despite increases in atmospheric CO2, the future aboveground biomass under warmer and drier conditions is below today's yield The positive effect of increased CO2 on biomass production cannot compensate for yield losses due to unfavorable climatic conditions

• Publisher: John Wiley & Sons, Inc
• Subject: aboveground biomass / Air temperature / Atmospheric models / Biodiversity / Biomass / Carbon / Carbon dioxide / Carbon dioxide atmospheric concentrations / Carbon dioxide concentration / Carbon sequestration / Climate change / climate extremes / Climate models / Climatic conditions / Evaporative cooling / Fertilization / free air carbon enrichment (FACE) / Future climates / future yields / Grasslands / Heat stress / Heat tolerance / Livestock / Photosynthesis / Precipitation / Precipitation variability / Productivity / Summer / Summer precipitation / temperate grassland / Temperature effects / Wildlife conservation