MODELLING THE INTERACTION BETWEEN WILD AND CULTIVATED SPECIES.

Yield losses due to wild species are relevant for a variety of cropping systems worldwide, e.g., in the case of rice weeds they can reach 60%. However, in the broader sense, wild species may also have positive effects on cropping systems for their capability to provide environmental benefits. In fact, they are fundamental to maintain high levels of biodiversity and, in the context of grassland communities, they are crucial for the provision of ecosystem services like those involved with pollination and recreational experiences. A quantitative understanding of the complex and dynamic interactions among species within agro-environmental systems is thus crucial to better analyze, for instance, the possible effects of climate change on community dynamics and to timely define effective adaptation strategies. In this context, the aim of this thesis was the development of new models for the simulation of the interaction between cultivated and wild species. Biophysical models are powerful tools to analyze the interactions between plants and environmental variables as well as to optimize crop management. However, one of their main weakness is the lack of algorithms for simulating the interactions between cultivated and wild species. The few examples available that consider these interactions are mainly related to fungal pathogens, whereas approaches considering weeds, insects and multi-species plant communities are extremely rare and insufficiently validated. To fill this gap, this PhD Thesis focused on the modelling of three categories of communities of increasing complexity: crop-weed (two plant species), grasslands (multi-species plant communities) and crop-insect-insect predators (different kingdoms). For the three categories, agroecosystems of worldwide importance were identified as case studies: paddy rice (chapter 2), grasslands (chapter 3 and 4) and olive trees (chapter 5). In particular, in chapter 2 a new model was developed for simulating the interaction between rice and two weeds (barnyardgrass and red rice); chapter 3 and 4 are focused on the extension of a model for the simulation of plant community dynamics in the context of mountain grassland systems, with case studies in temporary grasslands in the Apennine and in natural pastures in the Alps. The third chapter, in particular, focuses on the definition of strategies for adapting 9 grasslands management to climate change by explicitly considering their floristic composition, whereas the fourth chapter presents initial results on the effects of grazing and climate change on the productivity and floristic composition of pasture communities. Chapter 5 shows a new model of interactions among olive trees, the olive fruit fly (Bactrocera oleae (Rossi, 1790)) and its predators, whereas chapter 6 refers to the general conclusions of the researches carried out in this PhD Thesis. Although the new models developed in this work are process-based to reflect the complexity of interactions occurring in agroecosystems, they assume simplified descriptions of biophysical processes through a limited number of parameters to make them usable in operational contexts.