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Lo stato di salute delle foreste italiane (1997-2017)

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Tree health monitoring provides important information for conservation, management and improvement of forest resources. Such monitoring began in Europe in the '80s, as part of the pan-European ICP-Forests program, to respond to the concerns arising from the impact of pollutants and atmospheric depositions. Currently, forest monitoring has seen its role increasing, and it is also asked to address societal challenges, in relation to the climate crisis and global changes, with reference to the impacts of meteorological factors and alien parasites (fungi and insects). Forest monitoring in Europe consists of two networks of permanent observation areas, one of which is extensive (called Level I) and aims to collect statistical and spatial information on the consistency and distribution of forest damage. The second one is intensive (called Level II) and specific cause-effect studies are carried out. In this volume the authors intend to present the purpose, the structure of the survey and the general results of over 20 years of observations (1997-2017) on Level I in Italy. The survey consists of about 250 observational plots distributed according to the vertices of a 15x18 km network, along the entire national territory. The trees growing inside the plots are assessed annually by teams of operators who have previously participated in an intercalibration course. In the evaluation of the trees a series of vitality parameters is applied, of which the most important is defoliation. About 80% of the plant species examined are broadleaved. Among the main tree species, only beech has an uniform distribution almost on the entire national territory. The other species have instead a geographical and ecological limitation: spruce and larch are widespread only in the Alps; central-southern Italy; holm oak is found exclusively in the Mediterranean region. Defoliation was always greater in broadleaves than conifers. The defoliation also varies over time with trends that are apparently conflicting between the two groups of species. Considering the individual species, in the last years the chestnut crisis has increased. This behaviour can be explained by the infestation of the so-called Asian wasp. The subsequent improvement can probably be attributed to the application of biological control by means and to the improvement of management. The strong increase in defoliation on beech (especially that> 60%) in the years 2016 and 2017 is due to both the late frosts that hit the Apennine beech forests in the spring of both years, and the summer drought of 2017. In conifers, trends they are mainly linked to those of the mountain species (spruce and larch), which together represent the majority of the population, and show a peak of defoliation between 2008 and 2012. Mortality fluctuates year by year, with a tendency to increase. The major impacts found appear to be due to events and / or climatic anomalies, as well as to the action of pests. The discussion provides suggestions and indications to make the system increasingly efficient for monitoring the impacts of climate change on forests.
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