Converting coppices into high forests with continuous cover has often been established during the last decades as a management goal in hilly and mountainous Mediterranean areas to attenuate the negative effects that frequent clearcutting may have on soil, landscape and biodiversity conservation. The silvicultural tool usually adopted for this purpose is the gradual thinning of sprouts during the long span of time required to complete the conversion, that also allows the owner to keep harvesting some wood. This research compared the effects of various thinning intensities (three treatments plus control) on the stand growth and structure of a beech coppice with standards. The optimal density after thinning was assessed by expressing mean tree spacing as a function of main stand attributes like stand height and stand dbh. This system was preferred to the empirical evaluation of the percentage of basal area to be removed in order to give forest managers general reference guidelines to adapt to the varying environments of the Mediterranean mountains. Results confirmed that the positive effects of thinning on mean stem volume is due more to the higher diameter increment than to different height growth. The acceleration of crown growth in the thinned plots allowed canopy closure to be achieved 13 years after thinning. This reduced the negative effects of the opening of the stand overlayer and the elimination of most suppressed trees on soil protection. Under the conditions examined, the best thinning intensity proved to be a stand density 20% lower than normal prescribed by the yield tables elaborated for beech high forests in Central and Southern Italy. #

Forests are complex ecological systems, characterised by multiple-scale structural and dynamical patterns which are not inferable from a system description that spans only a narrow window of resolution; this makes their investigation a difficult task using standard field sampling protocols.We segment a QuickBird image covering a beech forest in an initial stage of old-growthnessshowing, accordingly, a good degree of structural complexityinto three segmentation levels. We apply field-based diversity indices of tree size, spacing, species assemblage to quantify structural heterogeneity amongst forest regions delineated by segmentation. The aim of the study is to evaluate, on a statistical basis, the relationships between spectrally delineated image segments and observed spatial heterogeneity in forest structure, including gaps in the outer canopy. Results show that: some 45% of the segments generated at the coarser segmentation scale (level 1) are surrounded by structurally different neighbours; level 2 segments distinguish spatial heterogeneity in forest structure in about 63% of level 1 segments; level 3 image segments detect better canopy gaps, rather than differences in the spatial pattern of the investigated structural indices.Results support also the idea of a mixture of macro and micro structural heterogeneity within the beech forest: large size populations of trees homogeneous for the examined structural indices at the coarser segmentation level, when analysed at a finer scale, are internally heterogeneous; and vice versa.Findings from this study demonstrate that multiresolution segmentation is able to delineate scale-dependent patterns of forest structural heterogeneity, even in an initial stage of old-growth structural differentiation. This tool has therefore a potential to improve the sampling design of field surveys aimed at characterizing forest structural complexity across multiple spatio-temporal scales.

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La rinaturalizzazione è uno degli orientamenti colturali di riferimento della gestione sostenibile di formazioni forestali semplificate nella composizione e nella struttura. La pianificazione degli interventi su area vasta può essere utilmente supportata da informazioni georeferenziate sulle condizioni di suscettività alla rinaturalizzazione dei complessi boscati. Nel presente lavoro si applica un approccio multicriteriale alla mappatura della suscettività a interventi di rinaturalizzazione dei rimboschimenti di pino nero (Pinus nigra Arn.) e soprassuoli di cerro (Quercus cerris L.) presenti in Toscana. La valutazione è basata su un approccio fuzzy, mediante costruzione di funzioni di appartenenza in grado di esprimere il variare delle condizioni di suscettività in rapporto ai seguenti fattori mappati su base raster: i) efficienza ecobiologica del popolamento forestale, stimata mediante un indice guidato da dati telerilevati, e utilizzata per definire il grado di opportunità colturale dell'intervento; ii) fattori di contesto (grado di adiacenza del soprassuolo con altre tipologie forestali e diversità fisionomica della copertura forestale a scala locale) intesi come fattori in grado di rafforzare (o depotenziare) l'opportunità colturale dell'intervento; iii) accessibilità e dimensione del soprassuolo, condizionanti la fattibilità operativa dell'intervento. I valori fuzzy dei singoli fattori sono combinati mediante una funzione moltiplicativa in un indice sintetico di suscettività, per individuare a scala vasta ambiti territoriali a cui accordare priorità di intervento. Su scala comprensoriale o aziendale, la disponibilità di indicatori più puntuali può permettere di collegare in maniera coerente gli indirizzi della pianificazione di area vasta alla concreta programmazione degli interventi.

Parole chiave: immagini telerilevate ad alta risoluzione; classificazione object oriented; indice multitemporale normalizzato; utilizzazioni forestali.