SusAlps

Grassland in the Alpine region is of great economic interest for milk and meat production. However, the multifunctionality of grassland ecosystems is severely threatened by climate change and changes in management. This affects important ecosystem functions such as productivity, carbon and nitrogen storage, water and nutrient retention, erosion control and biodiversity. The SUSALPS project uses field and laboratory experiments, remote sensing and socio-economic and ecosystem modeling to develop an evidence- and process-based understanding of the impacts of current and future climate and management conditions on grassland soil functions. Sustainable forms of management are derived from this, taking socio-economic framework conditions into account. To this end, science and agriculture are working side by side at numerous locations at altitudes between 1600 and 600 meters. In order to simulate climate change, soil cores from higher altitudes (cooler, more humid) were moved to two different lower altitudes (warmer, drier), resulting in a temperature increase of +2°C and +3°C respectively. In a re-grazing project on an abandoned mountain pasture, the role of grazing for biodiversity, water quality and nutrient stocks in the soil as well as for cultural ecosystem services was also investigated.

Socio-economic analyses show that climate change is already influencing grassland management and farmers' yields. In particular, changes in the political framework require farmers to act quickly (e.g. fertilizer regulations). In addition, a survey shows that the 2018 drought has also greatly increased the perception of climate change in society and that the mixture of forest and grassland as well as biodiversity are important aspects for tourism.

Climate change simulated by soil transplants (+2°C) increased grassland productivity under intensive management. However, this positive effect was reversed under drought stress, especially in 2018 and 2023, or at higher temperatures (+3°C). The increased productivity due to a moderate rise in temperature was accompanied by reduced species diversity. In contrast, extensive management under climate change conditions did not lead to an increase in yield, but to greater resilience to drought. Organic N fertilizer applied to cut meadows initially fertilizes the soil, so that the plants are mainly nourished by mineralization of the soil humus. Together with high fertilizer N losses (primarily NH₃ and N₂), this promotes a net loss of soil N and C stocks, especially under intensive management and climate change. On intensively farmed sites, this can be explained by a reduced diversity and functional diversity of the microbiome, while more nitrate is used for microbial denitrification (with gaseous N losses). Alternative fertilization methods (e.g. solid manure, slurry dilution, near-soil application) and less cutting are effective measures to reduce nutrient losses.

In contrast to fertilized cut meadows, the extensive re-grazing of a revitalized project pasture shows a significant increase in C storage with low NO₃ production and consistently high species diversity. Re-grazing of abandoned mountain pastures is therefore recommended to reduce the greenhouse gas footprint of milk production. The findings of the field studies were used to develop a process-based model for the evaluation of grassland functions. For regional model applications, remote sensing data (cutting frequency) and an agent-based model (distribution of manure) were used to derive location-specific information of grassland management. The simulations confirm yield declines under drought, which lead to increased nitrogen losses (e.g. N₂O and NO₃ ^-) if fertilization practices remain the same. Soils with higher humus content, on the other hand, show greater resilience to drought. Together with stakeholders, the model was used to develop the user-friendly web-based grassland assessment system (dss.susalps.de/), which enables practitioners to assess the impact of management and climate on grassland functions.

SUSALPS was able to develop a better understanding of the effects of management and climate on grassland functions through the interdisciplinary approach with socio-economic studies, field measurements, remote sensing and modeling in close cooperation with farmers and authorities. Due to the long funding period, reliable and practically relevant results were achieved, which could be translated into concrete recommendations for implementation. The resulting network of scientists and practitioners is currently forming the basis for the establishment of a real-world laboratory.

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