Potential impact of climatic changes on floristic evolution of phytocoenoses in mediterranean agroecosystems

In order to predict the potential agronomic scenarios of the future, the probable involvements of climatic changes on weed dynamics were analyzed. In this perspective the several climatic parameters were examined and overlapped to the biological characteristics of the different species to predict both: weed evolution and the sustainability of the relative management. Thermal and CO2 increasing favour the weed ruderality in terms of seed quantity and velocity of seed set. In addition the increasing of stress factors (thermal, drought, UV-B, etc.) favour the de-specialization trend as typically occurs in the most persistent weeds. Adverse climatic dynamics, even due to events of opposite biological action (for example drought and flooding), appears to have a synergistic impact with the agronomic disturbances. Indeed these additive disturbances increase the selective pressure of the phytocoenoses and play a crucial role in the allowing survival only to the “segetal” weeds as well it occurs from the origin of agriculture. Consequently, the different degree of resilience induces a decreasing of the phytocoenoses complexity. This biodiversity reduction appears to increase the risk of exotic weed invasion overall regards to species from warmer and more arid environments (potentially even parasite species). Their invasivity could be increased by biotic or abiotic stress factors that are not present in their native environment. The fate of rare weeds appears to go to their extinction, overall if their dynamics is linked to fragile mutualistic interaction as it occurs in the case of entomogamous species. Indeed such simultaneous presence (flora and pollinator fauna) is mined by the progressive differences between photoperiod and thermoperiod and the consequent de-synchronization of their phenological phases. This virtual weed evolution through the increasing of the richness of self- and wind-pollinated weeds will involve both: 1) the agricultural landscape degradation; 2) a worse human health because of atmosphere rich of allergenic pollen. In conclusion, weed phytocoenoses appear to be less vulnerable of the relative crops to the climatic injuries. This higher crop vulnerability will increase the pesticides use as well as already predicted regards to entomologic and phytopatologic aspects. Finally, an agronomic strategy of the future was hypothized. This is based on the germplasm utilization of the wild types in order to increase the environmental crop plasticity in the predicted climatic scenarios.