Agro-ecosystem diversification: digging deeper

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Mounting evidence suggests that biological diversity is of pivotal importance for ecosystems. Most studies have focused on the importance of above ground diversity for ecosystem functioning. However, a large part of biodiversity is literally hidden below ground. It is still poorly understood whether below ground biodiversity loss impacts ecosystem functioning. It is important to investigate this because a number of recent studies have shown reductions in soil biodiversity upon land use intensification. Here we explore whether agro-ecosystem diversification can promote soil biodiversity and the delivery of ecosystem services, testing four hypotheses:H1: Agro-ecosystem diversification enhances ecosystem multifunctionality.H2: Soil biodiversity and soil community composition is more important for ecosystem multifunctionality and soil functioning when diversity is low.H3: The relative importance of soil biodiversity and soil community composition vs. other abiotic and management drivers is ecosystem-service dependent.H4: Diverse soil communities enhance ecosystem resilience to climate change (e.g. warming and altered precipitationWe will establish a European network of 250 agricultural fields (50 per country) that vary in above ground diversity. This network includes sites with low above ground diversity to high agricultural diversity. We will assess below-ground diversity (using high throughput sequencing) and a number of ecosystem functions (plant yield, soil fertility, soil aggregation, soil carbon) in these fields. Subsequently, we will use advanced statistical tools (e.g. structural equation modelling) to assess the impact of above ground diversity, below ground diversity and management on ecosystem multifunctionality and on individual ecosystem services. We will use different ecosystem multifunctionality indexes, including a production, a biodiversity and an environmental sustainability oriented index. In a next set of experiments we take a more mechanistic approach. We will collect soil cores from field sites with low, medium and high soil biodiversity. These soil cores will be brought to the greenhouse where nutrient losses through leaching and denitrification will be assessed. We will then manipulate soil biodiversity of those soils by filtering organisms according to size and using these soils as inoculum for an experimental system in which we manipulate soil biodiversity. We will test whether changes in soil biodiversity influence ecosystem multifunctionality. We will also test if soils managed under higher levels of above ground diversity enhance soil ecosystem functions. Finally, we will collect soils from selected field sites and subject them to different climate change scenarios. Together with stakeholders and policy makers we will develop a theoretical and applied framework for agro-ecosystem diversification and will identify the impact of various agricultural practices on productivity, biodiversity and sustainability.