Disentangling microplastic degradation effects on soil functionality and plant performance. Consequences for vegetation dynamics in grasslands ecosystems

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Plastic pollution has become a recognized global change threat to terrestrial ecosystems. Once plastics enter the environment, degradation occurs changing the properties of the plastic debris (e.g., sorption capacity, brittleness, flexibility), which may have consequences on plant-soil systems. Photodegradation can be considered one of the most common processes of plastic degradation worldwide. Due to this, plastic becomes brittle and fragmented into small pieces (microplastics), increase its sorption capacity for metal and organic compounds and can potentially increase leachate or hazardous chemicals into the soil. Microplastic degradation may alter not only soil functionality and community structure but also plant performance to the point that the recent research that describes apparent positive effects of microplastics on plant productivity and soil properties might capture only part of the truth, as they only account for the effects of pristine microplastics (before they were degraded) on plant-soil systems. The aim of this project is to understand how degraded microplastics (the real microplastic that actually enters the soil matrix) affects plant-soil functionality using microcosms. Specifically I want to i) disentangle the mechanisms by which microplastic degradation (microplastic, shape, polymer type, size and leachates) may affect plant-soil systems and ii) test the effects that they may have on plant community structure. In order to know this I am going to develop a series of experiment to study this. First, I want to study microplastic degradation as a function of microplastic shape (fibers, films, foams) and polymer type (e.g., polyethylene, polypropylene). Then, I want to disentangle microplastic degradation mechanisms related to microplastic size and chemical leachates, and finally, I want to understand the effects of that microplastic shape, polymer type, size and leachates may have on key life stages of plant development. That is, seed germination, plant growth and plant fitness. In addition, I want to understand the potential effects that all of this may have modulating the competitive ability of plant species.