Urban forests provide important ecosystem services, such as urban air quality improvement by removing pollutants. While robust evidence exists that plant physiology, abundance, and distribution within cities are basic parameters affecting the magnitude and efficiency of air pollution removal, little is known about effects of plant diversity on the stability of this ecosystem service. Here, by means of a spatial analysis integrating system dynamic modeling and geostatistics, we assessed the effects of tree diversity on the removal of tropospheric ozone (O3) in Rome, Italy, in two years (2003 and 2004) that were very different for climatic conditions and ozone levels. Different tree functional groups showed complementary uptake patterns, related to tree physiology and phenology, maintaining a stable community function across different climatic conditions. Our results, although depending on the city-specific conditions of the studied area, suggest a higher function stability at increasing diversity levels in urban ecosystems. In Rome, such ecosystem services, based on published unitary costs of externalities and of mortality associated with O3, can be prudently valued to roughly US$2 and $3 million/year, respectively.
Hypothalamus–pituitaryadrenal (HPA) axis activity was monitored in 20 women with chronic migraine (CM), previously affected by medication overuse headache (MOH), in comparison to healthy women (20 subjects) by measuring salivary cortisol, testosterone, dehydroepiandrosterone–sulphate (DHEA–S) levels, and their ratios, one week after the end of the MOH rehabilitation procedure. The participants were instructed how to collect saliva samples at home, a procedure that was performed twice a day (08:00 a.m. and 8:00 p.m.). Morning and evening levels of cortisol were significantly increased in CM patients with respect to controls. With regard to the cortisol/DHEA–S ratio, an inverse marker of psycho–physical wellbeing, CM women showed significantly higher values than controls. Moreover, testosterone/cortisol ratios (anabolic/catabolic index of physical performance) were significantly lower in CM patients than in controls. In the present study, CM appears not to be associated with an impairment of cortisol and DHEAS circadian fluctuation; however, CM patients present alterations in HPA axis function that might contribute to metabolic and psychological alterations that have also been associated with CM.
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