• Energy Research

Climate change is a driver of biodiversity loss, often favouring invasive species such as in the case of Pittosporum undulatum in Eucalyptus forests of south-eastern Australia. We tested whether the invasiveness of P. undulatum is due to the release of secondary metabolites with allelopathic action inhibiting other species germination or to the content of antioxidant secondary metabolites. We compared the germination of P. undulatum and Eucalyptus ovata seeds on different substrates watered with different leachates. Polyphenolic compounds, saponins and tannins of Eucalyptus spp. and P. undulatum leaf extracts were quantified. Biogenic Volatile Organic Compounds were collected in the field and analyzed to compare the emissions in eucalypt forests with and without P. undulatum. Eucalyptus germination rates were not affected by different leachates and no allelopathic compounds were identified in P. undulatum leachate. Flavonoids and tannins characterized Eucalyptus leachates, while P. undulatum leachates showed high hydroxycinnamic acids content. The forests invaded by P. undulatum were characterized by high levels of monoterpenes, whereas the forest lacking P. undulatum were dominated by sesquiterpenes. Our results suggest that the invasiveness of P. undulatum may be due to the high content in secondary metabolites that play a protective role against abiotic stresses rather than the release of allelopathic compounds.

Climate change is impairing tree physiology and growth, causing an increase in tree dieback in many Mediterranean forests. These desiccation phenomena are leading to changes in land cover and plant community composition. Mediterranean plants are capable to emit large amount of Biogenic Volatile Organic Compounds (BVOCs), whose emission and biosynthesis is strongly affected by environmental conditions. This study evaluates the seasonal changes in understory species composition in two forest stands in Southern Tuscany characterized by different levels of Quercus ilex L. crown defoliation (low and high defoliation, LD and HD) and the relationship with BVOCs emissions over three years. We found significant changes in the understory plant community following Q. ilex crown defoliation and mortality, observing an increment in the number of shrubs both in HD and LD stands. The environmental sampling of BVOCs fully reflected the changes in vegetation cover and composition, with a reduction in the amount of monoterpene emissions due to the increasing rates of defoliation and mortality of Q. ilex trees. Our results suggest that terpene emissions from Mediterranean forests would be modified by an increase of Q. ilex dieback, with important consequences for functioning of this forest ecosystem and its atmospheric chemistry.

It is known that the urban environment amplifies the effects of climate change, sometimes with disastrous consequences that put people at risk. These aspects can be affected by urban vegetation and planting design but, while there are thousands of papers related to the effects of climate change, a relatively limited number of them are directly aimed at investigating the role of vegetation as a mitigating factor in the urban context. This paper focuses on reviewing the research on the role of urban vegetation in alleviating the adverse conditions of the urban environment in order to provide some practical guidelines to be applied by city planners. Through an analysis of the documents found in Scopus, Web of Science, and Google Scholar using urban vegetation and climate change-related keywords we selected five major issues related to the urban environment: (1) particulate matter, (2) gaseous pollution, (3) noise pollution, (4) water runoff, (5) urban heat island effect. The analysis of existing knowledge reported here indicates that the roles of urban vegetation on the adverse effect of climate change could not be simply deemed positive or negative, because the role of urban green is also strongly linked to the structure, composition, and distribution of vegetation, as well as to the criteria used for management. Therefore, it could help to better understand the roles of urban green as a complex system and provide the foundation for future studies.

Urban afforestation is increasingly regarded as a key strategy for fostering biodiversity to restore and enhance the ecosystem services needed to counteract the effects of climate change in built-up areas. In Italy, several experimental afforestation projects have been launched as part of the National Recovery and Resilience Plan (NRRP), focusing on cities or metropolitan areas such as Milan, Rome, Pistoia and Campobasso. These projects follow a multidisciplinary approach, integrating botanists, foresters, urban planners, landscape architects and remote sensing specialists. The goal is to address the challenging complexity of urban forest restoration through reforestation and afforestation actions. Key innovations include the integration of transdisciplinary methodologies (landscape analysis, landscape design, forest and plant ecology) with the application of advanced remote sensing technologies and participatory community engagement frameworks to address ecological and social challenges. Experimental plots have been set up across various urban areas, testing a range of planting schemes to maximise climate change resilience and ensure long-term ecological sustainability. Emphasis has been placed on selecting drought-tolerant and thermophilic species that are better adapted to widespread warming and local urban heat islands. ‘Biodiversity strips’ with perennial flowers for insects, shrubs with berries for birds and nests for wild bees and vertebrates have been set up to enhance biodiversity in new afforestation areas. Advanced monitoring tools, such as Light Detection and Ranging (LiDAR) and multi-sensor drones, have been employed alongside field observations to assess forest growth, species survival, structural complexity and biodiversity enhancement over time. Historical analyses of landscape patterns and ecological connectivity over the past 200 years, along with evaluations of afforestation projects from the last 70 years, have provided critical insights into the successes and challenges of previous interventions, serving as a guide for future efforts. By focusing on ecological connectivity, the integration of afforested areas into the urban matrix, and citizen engagement, the current project aims to align urban forestry efforts with sustainable development goals. This comprehensive project framework addresses environmental restoration and the social and aesthetic impacts on local communities, contributing to the overall resilience and well-being of urban and peri-urban ecosystems.

Waste orange peel represents a heavy burden for the orange juice industry, estimated in several million tons per year worldwide; nevertheless, this by-product is endowed with valuable bioactive compounds, such as pectin, polyphenols and terpenes. The potential value of the waste orange peel has stimulated the search for extraction processes, alternative or complementary to landfilling or to the integral energy conversion. This study introduces controlled hydrodynamic cavitation processes, as a new route to the integral valorization of this by-product, based on simple equipment, speed, effectiveness and efficiency, scalability, and compliance with green extraction principles. Waste orange peel, in batches of several kg, was processed in more than 100 L of water, absent any other raw materials, in a device comprising a Venturi-shaped cavitation reactor. The extractions of pectin, endowed with a very low degree of esterification, polyphenols (flavanones and hydroxycinnamic acid derivatives), and terpenes (mainly d-limonene) were effective and fast (high yield, few min of process time), as well as the biomethane generation potential of the process residues was effectively exploited. The achieved results proved the viability of the proposed route to the integral valorization of waste orange peel, though wide margins exist for further improvements.

Mediterranean forest ecosystems are highly vulnerable to climate extremes and anomalies induced by climate change, as evidenced by the increase in forest tree decline and death over the past few decades. Forest dieback may occur with different spatial patterns and in response to many climatic and weather events (i.e., drought spells, heat waves, compound events or hot drought, cold spells, and windstorms). This paper describes the physiological behaviour of Mediterranean tree species (namely evergreen sclerophyllous trees) under extreme climatic events, with a focus on embolism formation and carbon depletion. Additionally, we describe three widely recognised patterns of forest dieback: die-off, patchy dieback, and salt and pepper dieback. Overall, drought spells, heat waves, and compound events have been reported to induce all the mortality patterns described, revealing the great vulnerability of Mediterranean forests to rising air temperature and vapour pressure deficit trends. Many intrinsic factors of plant and structural and contingent factors of the forest can interact, favouring one mortality pattern over another. Patterns of dieback and mortality are the product of the interaction between the complexity of the landscape, the species assemblage, the kind and intensity of the disturbance, and biotic factors. Different patterns have different ecological consequences, and implications for monitoring and management. The combination of terrestrial and remote sensing (RS) is recommended.

This research aims to extend the existing knowledge on air quality improvement by the arboreal–shrub heritage. The PM accumulation (PM10–100, PM2.5–10, and PM0.2–2.5 (µg·cm−2)) was measured with consolidated gravimetric techniques during spring, summer, and fall for 2160 leaf samples belonging to the basal, median, and apical part of the crown of 17 species located in the streets and parks of 2 European cities (Rimini and Krakow). On the same samples, the deposition (PM10 and PM2.5 (µg·cm−2·day−1)) was evaluated according to a model based on the wash-off rain effect. Quercus ilex accumulated more PMx than the other species in Rimini, while in Krakow, the highest accumulators were Pinus nigra for PM10–100, Tilia cordata for PM2.5–10, and Populus nigra for PM0.2–2.5. Only in Krakow was the capture capacity of some species affected by the street or park growing condition. The basal leaves showed greater PM10–100 accumulation than the median and apical ones. In Rimini, the total PM accumulation tended to increase throughout the year, while in Krakow, the opposite occurred. However, as the accumulation increased, the deposition decreased. The PM accumulation was reduced by rainfall and enhanced by the air PM concentration, while the wind speed effect was opposite, depending on the city. These findings are useful for directing decision makers in the design of greener, healthier, and sustainable cities.