Management intensity mediates yield responses to rising temperatures in montane grasslands

Understanding responses of temperate grasslands to combined climate and land use changes is needed to secure yields as well as to mitigate future climate change. This study aims to analyse the long-term effects of climate change and grassland management on the water balance, yield, nitrogen uptake and species composition of montane grasslands in S-Germany. We used a space-for-time approach with large intact grassland monoliths (1 m², 1.5 m deep) translocated along an elevation and thus climatic gradient to simulate climate change. The monoliths were operated with four treatments formed by full-factorial combination of climate (current and approx. +2°C warming) and management (high and low frequency of cutting and cattle slurry fertilization events). Measurements of various climate, water balance, and vegetation variables were analysed over a nine-year period (2012–2020). The effect of management on yield was notably higher than the effect of climate change. In general, intensive management led to higher annual yields (mean dry matter of control site: 1020 +/- 160 g m-2, climate change site: 1075 +/- 200 g m-2), than extensive management (control: 784 +/-66 g m-2, climate change: 786 +/- 98 g m-2). Climate change conditions increased grassland yields only under intensive management and during the first 5 years of the experiment (2012-2016), mainly due to higher yields at the first cut. Reduced nitrogen availability, in conjunction with water limitations, emerged as a key constraint on grassland productivity under climate change conditions, explaining the decline in climate change–induced yield responses toward the end of the experiment. The pronounced inter-annual differences and trends illustrated the importance of long-term field experiments. Understanding the drivers of biomass production and forage quality is crucial not only for a better understanding of ecosystem functioning but also for improving grassland management, for instance by adjusting cutting and fertilization practices to future climate conditions.