Forecasting land management and extreme weather effects on earthworm populations, soil function and ecosystem services

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Soils form the basic substrate for terrestrial life. They benefit the human population by supporting the production of food, fuel and fiber and regulating the climate, disease and water resources by facilitating essential services such as soil formation and nutrient cycling. Crucial for an exponentially growing human population are the foundations that soils provide for agriculture.The activities of ecosystem engineers are important to the soil functions that underpin the provision of ecosystem services. Earthworms act as ecosystem engineers in soils both directly through digestion and burrowing activities and indirectly by encouraging other beneficial soil organisms. Management practices which optimise soil environmental conditions (e.g. soil organic carbon (SOM) and soil moisture) also stimulate earthworm biomass production. In turn the effects of earthworm activity on soil aggregate stability, nutrient cycling and soil carbon dynamics improve crop yields.Although changes in land management may increase the abundance of soil organisms, these effects depend on specific combinations of management practices and environmental factors. This makes the results of experimental field studies hard to extrapolate for different scenarios, such as in extreme weather. Thus, tools are needed to better forecast how management practices affect the provision of ecosystem services through their effects on important ecosystem engineers. Existing population models of how populations will respond to anthropogenic environmental change ignore the underlying mechanisms. Many focus only on the level of populations or individuals, rather than representing the processes which link both levels of biological organisation. Mechanistic models are needed that capture key biological, physiological and ecological mechanisms underpinning system functioning. Such models will have much better predictive power.In this proposal I show how I will develop and validate mechanistic models of earthworms which deliver important soil functions in a range of habitats. Once the models have demonstrated that they realistically capture earthworm population dynamics in the field, they will be applied to numerous agricultural scenarios, with different combinations of soil and weather conditions, crop management practices (e.g. tillage) and extreme weather (flood and drought) events. Model results will indicate the ecological consequences of the different agricultural systems by forecasting earthworm populations in these different scenarios. Relatively little is known about how earthworms respond to flood and drought. This proposal will identify the underpinning mechanisms by refining the mechanistic models to match new data under these extreme weather conditions. I will relate the role of earthworms as ecosystem engineers to soil functions and ecosystem services such as crop production and yield, by reviewing the relevant scientific literature. This knowledge will be used to provide new methods for quantifying the value of earthworms as ecosystem engineers which will allow better cost-benefit analysis of contrasting land management systems and promote the use of earthworms as a natural resource to land managers.