SP6: RhizoHistory

Yield and beyond: Ecosystem services

Introduction:

Agricultural management practices are not only affected by external factors like climate change but also impact the environment and ecosystem services. The choice of crop varieties has a crucial role in these management practices, as the associated rhizosphere traits are important for stable yields and other ecosystem services like carbon sequestration, nutrient retention, and erosion regulation. Therefore, the aim of WP9 is to model the impact of maize varieties and their management on ecosystem services, especially under the influence of climate change.

Main research questions:

• How are the ecosystem services carbon sequestration, nutrient retention, and erosion regulation affected differently by the maize varieties?
• Are mixed cropping approaches or different land cover types suitable to enhance these ecosystem services while maintaining high yields?
• Can a heterogenous landscape buffer the effect of climatic extreme events?

Methods:

In the first phase of the RhizoTraits project, climate change and the resulting extreme events heat and drought were identified as the main drivers for the variability of maize yields. These results are now incorporated in the second project phase, in which the impact of different maize varieties, management practices, and land cover types on ecosystem services are assessed. First, scenarios are built in alignment with the other RhizoTraits subprojects, meaning the separate and combined growing of the two target maize varieties and comparing their effect to different land cover types, like grassland. These scenarios are implemented in the soil and water assessment tool (SWAT+), a spatially distributed hydrological model. In this, their impact not only on yield but on ecosystem services such as carbon sequestration, nutrient retention, and erosion regulation can be modeled (Fig. 1). The first study region is a maize-dominated area in the east of Bavaria, which was in the first project phase discovered as being sensitive to the impact of climatic extreme events. Later, the model can be upscaled to the whole of Bavaria. This matches the spatial resolution of the LandscapeDNDC model, also set up in the RhizoTraits project, and both models will be tested with yield data of maize for the whole of Bavaria analyzed by remote sensing data using the model Light Use Efficiency (LUE).

Expected results and discussion:

We expect an impact of climatic extreme events not only on yields but also on other ecosystem services, especially the nutrient uptake through reduced biomass production and erosion regulation through reduced rhizosphere development. In comparing the two maize varieties, we expect the mixed cropping approach to lead to higher erosion regulation because of the heterogeneous rooting depths. Yet, in areas dominated by the cultivation of maize, we expect a larger positive effect of the incorporation of grassland or small woody features on these ecosystem services. Also, the stability of yields should benefit from this heterogeneity in the landscape, as the first project phase showed a high yield loss due to extreme events, especially in homogeneous areas.

Conclusion:

The results can be used by farmers to incorporate management practices that, on the one hand, lead to stable yields under climate change while, on the other hand, have a positive effect on carbon sequestration, nutrient retention, and erosion regulation.