Sustainable use of alpine and pre-alpine grassland soils in a changing climate
Project number: 031B1067A
Contact: PD Dr. Ralf Kiese, Karlsruhe Institute of Technology
Project team: Technische Universität München, Universität Bayreuth, Helmholtz Zentrum München, WWL Umweltplanung und Geoinformatik GbR, Bayrische Landesanstalt für Landwirtschaft, Karlsruhe Institute of Technology IMK-IFU, Deutsches Zentrum für Luft- und Raumfahrt (DLR), Bayrische Landesanstalt für Landwirtschaft (LfL)
SUSALPS experimental work quantifies impacts of climate and land management changes on plant and microbial diversity, nutrient use efficiencies, biomass production and quality, soil carbon and nitrogen storage and turnover, greenhouse gas emissions and nutrient leaching at several sites covering different elevations and thus, climatic conditions. Results will be used to
1. develop early warning systems (agri-ecological indicators) indicating potential negative impacts on grassland ecosystems and
2. inform and validate biogeochemical models which will be used in scenario studies to evaluate best management options for sustainable use of grassland ecosystems.
To allow the assessment of joint socio-economic impacts of current and climate smart grassland management practices the biogeochemical model will be coupled to a socio-economic model. This decision support system will represent a practical tool which will help stakeholders and farmers to understand consequences of grassland management on soil functions and other ecosystem services.
Project results from phase 1
The holistic SUSALPS approach improved the understanding of pre-alpine/ alpine grasslands carbon and nitrogen cycling, importance of plant and microbial diversity and activities for nutrient cycling and ecosystem resilience and an assessment of the socio-economic role of grasslands in the study region. Key findings are that grassland plant nitrogen (N) uptake is high and grassland N losses are dominated by N2 and by NH3 emissions after manure application, leading to overall small losses and low environmental risks for nitrate leaching and N2O emissions. Plant N export and ecosystem N losses are higher than N inputs, which indicates that plant growth is also promoted by release of N from soil organic matter mineralization. On the long term this can lead to decreasing soil C and N stocks with negative effects on e.g. soil fertility.
Project esults from phase2
Results from Phase II show that climate change (+2°C) significantly increases grassland productivity under intensive management, but this effect reverses under prolonged dry conditions, as in 2018, or under translocations with higher temperatures (+3°C) and higher drought stress. Productivity increases are less pronounced in extensively managed, more species-rich plant communities. However, these systems show significantly higher drought resilience. The general increase in grassland productivity under climate change is supported by high gross N mineralization rates that correlate with SOC and the abundance/activity of N-mineralizing bacteria. Therefore, maintaining SOC/SON stocks in grasslands through improved grassland management is of paramount importance; especially in light of the fact that current grassland C and N balances are equally negative (intensive more negative than extensive). Socio-economic analyses show that climate change is already affecting grassland management and farmer yields. In addition, farmers need to respond quickly to changing policy conditions, such as recent adjustments to fertilizer regulations, making decision making even more complex. As a result, there is a growing need among practitioners for model- and remote sensing-based tools and products for assessment and decision making to respond appropriately to these challenges.
Expected results from phase III
In Phase III (synthesis), SUSALPS identifies and quantifies the key climatic and socio-economic factors influencing the functioning of grassland systems in southern Germany. In addition, SUSALPS is developing indicator systems and practical tools and solutions to support sustainable grassland management with the aim of increasing the resilience of these systems to ongoing climatic and socio-economic change, or to enable adaptation. Combining a biogeochemical and a socio-economic model, the project aims to provide a bio-economic assessment approach that can be applied at field, farm and regional scales. Concurrently and together with remote sensing products (e.g., cutting calendars, yield maps), the modeling tools can be transferred to other regions or applied at larger scales.
The overall goals for Phase III are:
- Evaluate the effects of climate and management on grasslands- (i) plant diversity, productivity, and forage value, (ii) soil carbon/nitrogen (C/N) stocks and organic matter quality, (iii) greenhouse gas (GHG) exchange and nutrient leaching.
- Evaluate grassland vegetation and soil management options to optimize nutrient use efficiency, grassland productivity, and biodiversity while minimizing environmental impacts due to nutrient losses along gaseous and hydrologic pathways under current and future climatic conditions.
- Evaluate benefits and costs of farmers' current grassland management options and intentions to adopt alternative grassland management options.
- Develop agri-environmental indicators as proxies for the status of soil functions, biodiversity, and ESS of grasslands.
- Develop, test, and disseminate decision support products at the field, farm, and regional levels for various audiences