Testing interactions between above- and belowground ecosystem services

Agriculture is the predominant form of land management worldwide. During the last fifty years production intensification dramatically impacted the environment and biodiversity harming the ability of ecosystems to provide services essential for human sustenance and well-being. Agricultural ecosystems receive a wide variety of supporting and regulating services crucial for crop production (e.g. soil fertility or pollination). The enhancement of ecosystem services (ecological intensification) has been proposed as a promising solution to meet the growing demand for agricultural goods, decreasing production dependence to external inputs and therefore limiting detrimental effects on environment. However, the implementation of ecological intensification into crop production systems is knowledge-intensive and it requires a comprehensive understanding of the relationships among multiple ecosystems services. The aim of this thesis was to test for potential interactions between above- and belowground ecosystem services for major European crops and to identify innovative management options for ecological intensification in agricultural ecosystems. We explored the relationships between soil-based supporting services and pollination, biological control and an aboveground crop pest (disservice). In Chapter 2, the interactions between pollination and nitrogen input for three different cultivars of oilseed rape (Brassica napus) were explored in a field experiment. Open pollinated cultivar largely depended on pollination, whereas hybrid cultivars did not. However, pollination benefits to yield increased with decreased nitrogen inputs, indicating that nitrogen use efficiency was probably enhanced by pollination. These findings show that the use of hybrid cultivars and the application of fertilizers can compensate degraded pollination service, whereas optimal pollination can potentially replace fertilization. In Chapter 3 we tested potential interactions between soil fertility and pollination in sunflower (Helianthus annuus). To obtain different levels of soil fertility we used soils from a long-term trial with different input management histories. Pollination benefits to yield formation were observable only under good soil fertility conditions whereas they were canceled in more deteriorated soils: limited nutrient availability led to limited yield even at optimal pollination level. In Chapter 4 we performed a greenhouse experiment to test the effects of soil fertility and nitrogen input on herbivore performance (Sitobion avenae) and crop growth (Triticum aestivum) . Increased fertilizer applications strongly enhanced aphid performance. Increased soil organic matter contents had similar but minor effects on pest growth, maintaining similar crop growth. Soil management is known to affect the provision of multiple ecosystem services. In Chapter 5 and 6 the effects of different tillage practices indicated that soil managements that reduce soil disturbance in cereal crops enhance soil fertility, arthropod abundance, biological control and maintain levels of crop production similar to those observable under conventional tillage. This study provides evidence for interactions between above- and belowground ecosystem services, highlighting the role of supporting services in shaping the effects of other services-disservices on crop production. Our results will provide recommendations to correctly valuate ecosystem services and to implement their management in agricultural landscapes. In particular it appears clear that several ecosystem services do interact and that their contribution to yield cannot be considered additive as often assumed in current economic evaluation and mapping exercises.