Assestamento forestale, conservazione della biodiversità, Natura 2000: un'intesa per Vaia
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Assestamento forestale, conservazione della biodiversità, Natura 2000: un'intesa per Vaia
- 1. Vaia: un approccio integrato per la gestione post-evento Agripolis, 15 marzo 2019 Assestamento forestale, conservazione della biodiversità, Natura 2000: un’intesa per Vaia Tommaso Sitzia
- 2. Hans von Carlowitz (1713) La tassazione delle foreste, o la determinazione esatta della resa in legno sostenibile presente e futura dei boschi, o l'istituzione di un bilancio forestale naturale affidabile, è senza dubbio uno degli elementi più importanti nella silvicoltura moderna; perché non esiste una silvicoltura sostenibile da pensare e da aspettarsi, se il prelievo del legname dalle foreste non è calcolato sulla sostenibilità
- 3. Dauerwald Perseguire il dauerwald è come seguire un sentiero stretto, roccioso, ripido e spinoso, e ancora pochi ci stanno provando. Ma dà loro un alto obiettivo: l'aumento sostenibile della produzione di legno nazionale (A. Möller, 1920)
- 12. compared to 2000 are about 30% and 50% respectively. Positive effects of climate on wood increment are expected especially for the boreal zone. Schelhaas et al. (2010) show for Finland a growing stock in 2100 that is 65% higher than the estimate in Table 7. 0 1 2 3 4 5 6 7 8 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 PercentageofGSaffected Denmark NL FranceUK Switzerland Germany Sweden Figure 7: Damage as percentage of growing stock for different countries (adapted from Schelhaas, 2008a). Changes in storm climate have to be added on top of the expected changes in growing stock. Table 7 shows that Denmark annually loses 0.551% of their growing stock to wind, much higher than the other countries. With increasing storm intensity, higher damage percentages could occur also in other countries. The decreases in return times of storms with very high intensity according to Della-Marta and Pinto (2009) would lead to a strong increase in damage percentage. However, climate models are still not very reliable in their wind velocity projections and thus confidence in their projections is rather low (Nikulin et al. 2010). Moreover, the forest might acclimate to increased wind Lothar Klaus1981 storm Volume italiano: 1,256,099,493 m3 totale (boschi alti) quindi % del growing stock = 0.7% Gardiner et al. (2013)
- 13. Degron et al. 2000 Les forêts lorraines dans la tempête du 26 décembre 1999 : premier bilan
- 14. Archivi e notizie storiche • Veneto: Cansiglio: 1709, territorio di Farra, sradicati 23.000 faggi e nel 1733 25.000 piante abbattute dal vento; nel Montello oltre 16.000 roveri nel 1689 (Lazzarini, 2006) • Francia: 1580-1640, 1710-1770, 1870-1920 (otto disastri solo dal 1720 al 1760) “la tempesta è un elemento di permanenza storica” e “basandosi sulle fonti archivistiche, il verdetto della storia smentisce le affermazioni di coloro che, all'indomani del disastro del dicembre 1999, hanno insistito sulla natura eccezionale e nuova dei rischi legati al vento” (Garnier, 2004) • Foresta boema (Germania, Austria, Repubblica Ceca): 1710, 1740, 1778, 1810-40 “disturbed large areas of forest, most of them followed by bark beetle outbreaks” (Brůna et al., 2013) • Wisconsin (USA): “presettlement survey records” “413 separate patches (> 1,0 ha) of complete canopy windthrow” (largest: 3785 ha) (circa 1834-1873) (Canham e Loucks 1984)
- 15. Thorn et al. (2017) Čada et al. (2016)
- 16. Stand Height (m) 10.0 12.5 15.0 17.5 20.0 22.5 25.0 27.5 30.0 32.5 %Standwindthrown 0 20 40 60 80 100 Figure 5. Observed windthrow percentage in 612 stands damaged in Denmark in a storm in 1981. Graph redrawn from Lohmander and Helles (1987). The tree height increase for many species in various parts of Europe, resulting from environmental influences, ageing and genetic improvement, will therefore have contributed to the increase in vulnerability of European forests to strong winds. While tree height/tree diameter (H:D) ratio (commonly used as a “stability” indicator) is relevant for most conifers, it is generally not for hardwoods, and many of the commonly used descriptors in silviculture (e.g. density of the stands, basal area) have no clear influence on the level of damage. Brůna et al., 2013 Danimarca (tempesta del 1981) Foresta Boema Gardiner et al. (2013)
- 17. Gardiner et al. (2013)
- 18. Natura 2000 e schianti nel Veneto • 27 siti Natura 2000, circa 5.000 ha • 39 specie il cui habitat è potenzialmente trasformato • 8 tipi di habitat maggiormente interessati • L'ordinanza P.C. n. 558/18 ha derogato per 12 mesi, in 10 regioni e 2 province a statuto speciale, «a quanto disposto dalle misure di conservazione vigenti», per gli «interventi di rimozione degli alberi abbattuti o ammalorati e del materiale vegetale» giudicati necessari
- 21. • Large clearcuts would reduce the length of exposed perimeter for a given area cut (Savill 1983) • In an extensive silviculture context, relying on large clearcuts as the main harvestingmethod, windthrow remains a minor concern (Ruel 1995) • From recent storm damage the success of aiming to always locate the oldest stands in downwind positions by means of long-term “intelligent” cutting regimes appears to be very limited (Gardiner et al. 2013)
Editor's Notes
- Oltre 200 anni di storia. Prime divisioni planimetriche risalgono al 14° secolo (foresta di Erfurt e Reichswald di Norimberga). Federico il Grande: tempo di rotazione. Beckmann, von Wedell e Hennert: divisioni in volumi. Hartig von Carlowitz, Hartig, the Maximum Sustained Yield, the Club of Rome, and the Brundtland Report Rappresentazione schematica di diverse linee di sviluppo dei metodi di gestione forestale Speidel, G., 1972: Planung im Forstbetrieb. Paul Parey. in K. v. Gadow (2005) Forsteinrichtung.
- I piani economici sono dai più considerati delle costose e sterili elucubrazioni matematiche per determinare, sulla carta, una ripresa; degli elaborati le cui prescrizioni all’atto pratico, non sono mai seguite e che, in pari tempo, servono a ben poco per il miglioramento del patrimonio forestale del Paese (frase tratta dall’introduzione alla normativa assestamentale italiana del 1942)
- The Line Storm by John Steuart Curry
- Dying Forest (unfinished) 1852 | August Cappelen | Oil Painting
- These recent paintings by Ringrose are a visual record of the aftermath of Hurricane Ophelia
- Enlil
- Eolo
- Stribog
- Italy: prelievi 6.1-11.1 Mm3 legname da opera (quindi Vaia circa quanto il prelievo annuale) Volume schiantato: 8.5 Mm3 Percentuale del growing stock: 1,256,099,493 m3 totale (boschi alti) quindi % del growing stock = 0.7%
- Fig. 1 : Volumes de bois chablis tombés en France depuis un siècle sous l’effet de grandes tempêtes (en M m3). Lothar: 1999. 140 milioni di m3 in Francia (3 volte il prelievo annuale) nel 1999 Francia, Foreste di Perche-Trappe: sconto del 40-50% rispetto al valore attuale del 1999 Quali sono le specie notevoli la cui conservazione richiede un'attenzione particolare? Le comunità vegetali riflettono una disfunzione dell'ambiente? Annunciano il ritorno della foresta decidua? Piuttosto che focalizzare la sua attenzione sugli effetti puntuali della tempesta, ci sembra più interessante affrontare la questione forestale con la sua propria dimensione, quella del lungo periodo, e metterla nel contesto di un'analisi sociale. e lo spazio globale: i geografi hanno sicuramente un ruolo chiave da svolgere in questa prospettiva. Storms are highly stochastic and relatively rare events. It is thus very dif- cult to prove trends from short time series of meteorological observa- tions.
- Bohemian Forest (Peccete a Calagrostis villosa e Peccete a felci, molto comuni anche da noi e riconducibili a diversi tipi della Pecceta altimontana dei substrati silicatici). The result was a mix of stands differentially impacted by humans, but still a substantial proportion of the landscape developed likely under natural disturbance regime. We limited our sampling to stands that were expected to have developed under natural disturbance regime, i.e., stands that were assumed to be older than 1850. The calculated percentage does not fully correspond to the affected canopy area, because of the different areas occupied by individual trees Fig. 2. (a) Average disturbance chronology and mean age distribution for the study area. The average was calculated from individual plot chronologies (see Appendix B, Fig. B1 in Supplementary material). The height of the column (gap origin + release) indicates the severity of the disturbance (percentage of removed population). (b) Rotation period of disturbances greater than given severity class that is based on distribution of all found disturbance events at all plots (5569 years and 220 events). Whiskers represent 5% and 95% percentiles of plot level values; 95% values are missing for higher severity classes because no such disturbances were detected on some plots. (c) Individual based disturbance chronology and age distribution for the study area. Events from all individuals (including exceptionally old trees outside of the study plots) were summed similarly to plot level chronologies in Appendix B, Fig. B1: we also developed an individual based disturbance chronology that summarizes releases and gap origin events from all the available individual trees, and also exceptionally old trees sampled outside the study plots or historical cross-sections presented as exhibits. The chronology provides insight into a much longer time-scale of 550 years covering more than one tree generation; however, its representativeness is questionable due to lower sample size and distribution. The percentage of trees that were released or originated in an opening correlates to the percentage of trees that died, i.e., to disturbance severity.
- 42 m/s : 150 km h-1 https://doi.org/10.1103/PhysRevE.93.023001 oltre 50% degli alberi schiantati (uragano Klaus, Francia) https://inventaire-forestier.ign.fr/spip.php?rubrique263 In general, vulnerability increases rapidly above a height of 10 m (Busby 1965 ) Large clearcuts would reduce the length of exposed perime- ter for a given area cut (Savill 1983). Such an approach would, however, appear incompatiblewith the public pressure calling for a reduction in clearcut size Cyclone Klaus turbolenza e massima velocità media del vento; • dendrometria: altezza lorey della sottopopolazione del pino marittimo, tasso di copertura assoluta; • stazione: idromorfia, fertilità, livello dell'acqua indicato biologicamente; • paesaggio: effetto riparo. : In general, vulnerability increases rapidly above a height of 10 m (Busby 1965). Smith et al. (1987) recommend that peatland black spruce stands in the Ontario Clay Belt be harvested before they reach 20 or 21 m since, by that height, stands 60% stocked become vulnerable to winds recurring once every 10 years (Fig. 2). The tree height increase for many species in various parts of Europe, resulting from environmental influences, ageing and genetic improvement, will therefore have contributed to the increase in vulnerability of European forests to strong winds (Gantolier for EC) Statistical studies give contradictory results and mechanistic approaches are not yet advanced enough to decipher the opposing influences involved. The practical conclusion is that where thinning is possible, frequent/intensive thinning should commence earlier rather than later during the life span of stands. Stands situated in sheltered situations on the lee side of hills relative to the prevailing wind are somewhat protected. Forests on flat/plateau areas are reported to be more susceptible to damage than those on slopes. More locally, forest edges and any significant unevenness in the forest canopy (open land/forest transitions, recent cuts, stands of different heights) influence the turbulence regime, which strongly influence the spatial distribution of damage (Quine et al, 1995). Reduction of rotation age(and thus mean height). With the recent trends towards close-to-nature forestry and the conversion of coniferous monocultures into mixed stands (e.g. Spiecker et al., 2004), the share of deciduous tree species and mixed stands has substantially increased (Knoke et al., 2008, MCPFE Liaison Unit Warsaw et al., 2007). The declining share of spruce forests may contribute to storm damage abatement because spruce, which tends to grow faster and taller than broadleaves, has statistically been more affected by storm damage (however, see the difficulties in precisely defining species differences in Section 5.3.2). At the same time if there is a continued trend of increasing growing stocks and a larger share of old forests, the vulnerability to storm damage is likely to increase further (Schelhaas et al., 2010). Therefore, the management of European forests will have a distinctive influence on future levels of storm damage. ----- Fig. 2. Disturbance severity significantly increases in older age classes. More of the younger age stands were managed before the disturbance. Width shows proportion of total area. “S” means sparse forests and “R” means areas left intentionally for natural regeneration (20% of standing trees left after logging). Bohemian Forest region Moreover, there is evidence of numerous previous large-scale, high-severity windstorms damaging forests in the region (Elling et al., 1987, Zatloukal, 1998 and Brázdil et al. 2004), including major windstorms in 1710, 1740, 1778, 1810s, 1820s, and 1830s, most of them followed by bark beetle outbreaks. Historical documents state that the windstorms of 1710, 1740, and the 1830s disturbed large areas of forest, which was confirmed by dendrochronological analyses from two localities in the area, Trojmezná and Jezerní Hora
- However, the reports of storm damage are incomplete at the European scale, so it is more likely that the increase in the frequency of storm damage actually reflects the increasing number of reported events rather than a real increase in the number of events (Scheelas et al. 2003). Forest management activities can have noticeable in uence on forest susceptibility to disturbances. Research suggests that forest management may have contributed in the same order of magnitude to the disturbances increase in Europe as climate change. In particular the steady increase of the forest area and growing stock and the increase of the average forest age may have contributed to an increased susceptibility of forests to- wards storm damage (EFI, Fig. sopra)
- Thorn et al. 2018 - https://besjournals.onlinelibrary.wiley.com/doi/10.1111/1365-2664.12945
- Cansiglio ad esempio in Cansiglio nel 1709, quando in territorio di Farra vennero sradicati 23.000 faggi; 23.000 faggi Serenissima 300 / ha circa 80 ha attuale densità in Cansiglio = o nell’aprile del 1729 con lo spianto di un numero imprecisato di abeti e faggi nella parte orientale del bosco; o a fine settembre del 1733, quando furono forse 25.000 le piante abbattute dal vento; altri 80 ha ... Montello oppure nel Montello, con oltre 16.000 roveri svelti dai turbini nel settembre del 1689. 80 ha.... http://www.europeanwindstorms.org/
- In an extensive silviculture context, relying on large clearcuts as the main harvestingmethod, windthrow remains a minor concern (Ruel, 1995). However, with an emphasis on a more refined silvicul- ture, allowing for partial cuts, and with the need for an integrated aproach in forest management, calling for reductions in clearcut size or leaving mature forest reserves or buffer strips, wind-relat- ed damage is becoming an important preoccupation for the sil- viculturist. In general, windthrow losses remain unquantified except for some instances where catastrophic losses have been documented. 4% allowable annual cut in British Columbia For more than one century the optimization of the so-called “spatial order” (the spatial position of different forest stands to each other ac- cording to their age and height) in order to minimize storm damage was a crucial goal of forest management planning in parts of Central Europe. From recent storm damage the success of aiming to always locate the oldest stands in downwind positions by means of long-term “intelligent” cutting regimes appears to be very limited. be taken when interpreting changes in scale of few decades, because the rotation period of extensive disturbances could be much longer but still part of the system ... the lack of disturbance before the peak has no historical precedent. (
- https://www.for.gov.bc.ca/hfp/publications/00179/fnltext.htm Nothing new in Ireland, such violent storms are recorded in the Annals of the Four Masters. Two centuries ago, during “Oiche na Gaoithe Mor”, on 6 January 1839, winds reached over one hundred knots, as they did recently during Hurricane Ophelia, in September 2017. [It is no coincidence that Francis Beaufort, who invented the scale for recording wind speed, was an Irish naval officer, he also trained Robert FitzRoy, who invented a system for weather forecasting]