1. IntroductIon
In Italy since the beginning of the XXI century conifer afforestations, most of them of Pinus sp. species, were established over large areas for soil protection and/or wood production. Today, afterwards insufficient attention to the silvicultural practices, ageing processes, insects and fungi outbreaks lead to an unsteady biological equilibrium in many of these afforestations.
The restoration of conifer afforestations into stands with a more complex structure and composition is a current challenge for the Italian silviculture and an opportunity to provide wood energy.
A silvicultural system aiming to the natural regeneration by means of canopy gaps (gap- based approach, sensu coates and Burton, 1997) has been applied. Gap cutting mimics natural forest evolution and derives from the empirical experience that relates the
– L’Italia Forestale e Montana / Italian Journal of Forest and Mountain Environments 67 (2): 167-172, 2012 © 2012 Accademia Italiana di Scienze Forestali doi: 10.4129/ifm.2012.2.03
The restoration of conifer plantations into stands with a more complex structure and composition is a current challenge for the Italian silviculture and an opportunity to provide wood energy.
A silvicultural system aiming to the natural regeneration by means of canopy gaps (gap-based approach) has been applied in an experimental site in the Calabrian pine (Pinus nigra Arn. ssp. laricio Poiret var.
Calabrica Delamare) stands in the Calabrian Apennine initiated in 2003: small (380 m2), medium (855 m2) and large gaps (1520 m2) were compared.
The main results after 7 years show that the most appropriate gap sizes for regeneration of Calabrian pine (shade-intolerant species) are those of 1500 m2 with a d/h of 2.0. While for late-successional species (silver fir and beech) gaps of 380 m2 with a d/h of 1.0 or slightly larger are recommended. This allows the forest manager to choose whether to maintain the pine or initiate a restoration action with native forest vegetation. The interval between cuttings is 7 years. Whereas any intervention removes the 30% of the forest, the cycle is complete in about 20 years. In this case (stands normally thinned) at the time of the first cutting from 15 up to 70 m3 per gap, or 140 m3 per hectare can be obtained. This gap-based approach is a sustainable silvicultural treatment because of low environmental and aesthetic impact and also meets objectives for timber production.
Key words: forest restoration; gap cutting system; wood energy.
Parole chiave: restauro forestale; sistema di tagli a buche; energia dal legno.
Citation - Bagnato s., MercurIo r., scarfò f., 2012 – Conifer afforestations in Italy: an opportunity for wood energy and forest restoration. L’Italia Forestale e Montana, 67 (2): 167-172. http://dx.doi.
org/10.4129/ifm.2012.2.03
SILVIO BAGNATO (*) (°) - ROBERTO MERCURIO (**) - FRANCESCO SCARFÒ (***)
CONIFER AFFORESTATIONS IN ITALY: AN OPPORTUNITY FOR WOOD ENERGY AND FOREST RESTORATION
(*) Department of Agricultural and Forest Systems Management, Mediterranean University Reggio Calabria, Italy.
(**) Professor of Silviculture and Forest Management - Department of Agricultural and Forest Systems Management, Mediterranean University Reggio Calabria, Italy.
(***) Department of Agricultural and Forest Systems Management, Mediterranean University Reggio Calabria, Italy.
(°) Corresponding author; [email protected]
. . regeneration of natural forests to the accidental
opening of gaps into the forest cover, following the death of one or more individuals, which creates favorable conditions to the establishment and the growth of new trees (Watt, 1947; YaMaMoto, 1992; MccarthY, 2001; schlIeMann and BockheIM, 2011).
2. MethodologIes
The study area was located in a Calabrian pine (Pinus nigra Arn. ssp. laricio Poiret var.
Calabrica Delamare) afforestation in the Calabrian Apennine (38°42’N; 16°20’E) at 900 m asl.
Mean annual precipitations are 1848 mm, summer precipitations are 102 mm, mean annual air temperature is 10.8 °C, mean temperature of the coldest month is 3.1 °C, mean temperature of the warmest month is 21.5 °C. Soils developed from compact gneiss and biotitic scysts (Paleozoic) were depth with a loamy-sand texture and were classified as humic Dystrudept (soIl surveY staff, 1999).
Natural vegetation was beechwoods with Silver fir (Anemono apenninae-Fagetum Brullo 1984 = Aquifolio- Fagetum Gentile 1969) (MercurIo and spaMpInato, 2006) then converted in agricultural lands and afforested in the ’50s with Calabrian pine.
During the spring season 2003 a randomized complete block of six circular gaps: two small (380 m2), two medium (855 m2) and two large (1520 m2) was carried out. Each gap was paired with an adjacent under canopy cover site located 25-30 m from the edge of the gap. The gap diameter to the tree height ratios (D/h) were respectively 1.0, 1.5 and 2.0 (stand height 22 m). After the harvest operations the “Oi”
soil layer was removed.
Thirteen circular sub-plots of 3.14 m2 (radius 100 cm) were established inside each gap. Sub- plots were positioned one in the central part of the gap and the other three at one third of the radius starting from the centre of the gap edge.
All seedlings inside each sub-plot were distinguished by species and measured (total
height and age) at the end of the growing season.
Four soil cores (8 cm diameter x 15 cm depth) were collected in the central part and at the edge of each gap to assess the soil moisture content with gravimetric method. Core samples were also taken below the adjacent stands to the gaps to assess the microclimatic conditions under canopy cover.
Only one depth level of sampling was chosen as seedlings concentrating the greatest part of their root system in the superficial layers of the soil. The soil samples were weighed immedi- ately (wet weight) and later, in the laboratory, soil samples were dried in a drying oven at 105±2°C to constant weight and reweighed (dry weight). Gravimetric soil moisture content was expressed as percentage of dry weight (Eq. 1):
ww dw100 θ= dw− ⋅
Soil temperature was measured in six sub- samples taken at random in four different places in each gap and in its adjacent forest canopy cover site, every month, during the period May-September. Soil temperature thermometer (Elite) was placed at 5 cm depth from the top of the mineral soil. This parameter was measured daily every 60 minutes from 7:00 to 19:00 h. Temperature measurements were summarized into daily averages of the six sub- samples; average for each month is based on all the daily averages.
Measurements of the Photosynthetically Active Radiation (PAR) were collected with a ceptometer (AccuPAR, Degagon Devices Inc., Pullman, WA, USA), at 1 m above the ground, with the instrument held horizontally.
Four instantaneous readings were done at each sampling point, with reference to the cardinal directions.
These measurements were carried out monthly, during growing season (May- September), on bright sunny days, at 12.00 (solar time). Measurements were taken: 1) in a large clearing near the experimental area; 2) under canopy cover; in correspondence of each subplots.
After each measurement cycle, the PAR
transmittance was calculate for each sampling points using the following formula (Eq. 2):
PARsubplot 100 PAR transmittance
PARopen
= ⋅
Data were grouped for analysis according to the position of the subplot inside the gap and the cardinal directions: 1) central subplot CENTRE (C, 1N, 1E, 1S, 1W); 2) edge subplots EDGE (2N, 2E, 2S, 2W, 3N ,3E, 3S, 3W) the four nearest subplots.
Data were subjected to a two-way ANOVA (α=0.05) considering as factors soil moisture and temperature, PAR and seedling density in the different gap sizes and the adjacent under canopy cover site. Treatments were compared using the Student Newman-Keul post hoc test.
3. resultsanddIscussIon
3.1. Soil moisture and temperature
Soil moisture was significantly different among the gaps of different size (in accordance with ochIaI et al., 1994 but not with sarIYIldIz, 2008) showing the highest value in the small gaps (Table 1). Small gaps were generally wetter than the medium and large ones (as observed
by graY et al., 2002 in Douglas-fir forest) and the surrounding forest.
Soil temperature was significantly higher in the large gaps in comparison to small and medium gaps. Under canopy cover sites soil temperature was similar to that detected in small gaps (Table 1).
3.2. Par transmittance
PAR transmittance was higher in large and medium gaps than in small ones (Table 1) with significant difference between gap sizes.
These findings confirm that the amount of solar radiation received on the ground increased with the size of gap opening (canhaM et al., 1900; daI, 1996; Mc guIre et al., 2001; dIacI, 2002; graY et al., 2002). Consequently the micro-environment in large gaps is lighter and warmer than that in smaller gaps which may be favourable for Calabrian pine germination and establishment.
PAR transmittance varied significantly within-gap position, as observed by canhaM
et al., (1990); McguIre et al., (2001); graY et al., 2002; gagnon et al., (2003). high values were recorded in the centre and northern positions in both gap sizes and tended to decline from north to centre to south for all gap sizes (data not reported) as observed by graY et al., (2002).
Table 1 – Soil temperature, soil moisture and PAR values average ± SE (n=40).
Location Year Soil temperature (°C) Soil moisture (%) PAR (%)
A (small gap) 2003 10.1±0.1 31.0±0.7 13
2007 10.8± 0.1 33±0.7 15
B 2003 11.4±0.1 28±0.3 6
2007 11.2±0.1 28± 0.3 5
C (medium gap) 2003 12.7±0.2 26±1.2 36
2007 12.9±0.2 27± 1.2 38
D 2003 11.6±0.1 28±0.3 6
2007 11.1±0.1 28± 0.3 5
E (large gap) 2003 13.0±0.2 25±1.1 61
2007 13.9± .2 26± 1.1 65
F 2003 11.2±0.1 29±0.9 6
2007 11.4±0.1 28± 0.9 5
A = small gap; B = under canopy cover near small gap; C = medium gap; D = under canopy cover near medium gap; E = large gap; F = under canopy cover near large gap.
. . 3.3. Seedling density
Seedling density of Calabrian pine was higher in large gaps than in medium and small ones, evenly distributed, with a prevalence in the central part of the gap, since the first years after the gap opening. In fact in Calabrian pine stands the age at which abundant coning can be expected is generally close to 30-40 years. The mast years occurred at intervals of once every 2 years. Silver fir density was lower and scattered because of the scarcity of seed bearing of the nearby trees and of the abundance of cone production which occurs every three-four years and was more abundant at the gap edge (Figure 1). Sometimes beech regeneration can occur in the gaps (not recorded inside the sub plots).
The main results after 7 years of gap opening confirm what guglIotta et al., (2006) and Muscolo et al., (2007) previously reported and show that the most appropriate gap sizes for regeneration of Calabrian pine (shade- intolerant tree species) are those of 1500 m2 according to the statements of MalcolM et al., (2001) with a D/h of 2. While for late- successional species (silver fir and beech) gap of 380 m2 with a D/h of 1 or slightly larger are recommended. This allows the forest manager
to choose whether to maintain the pine or promote a forest restoration with native species.
The interval between cuttings is 7 years.
Whereas any intervention removes the 30%
of the stand, the cycle is complete in about 20 years.
At the time of the first cutting from 15 up to 70 m3 per gap, or 140 m3 per hectare can be obtained.
In consequence of this experience you can get interesting implications for sustainable forest management. Under the Italian Code of Cultural heritage and Landscape (Codice dei Beni Culturali e del Paesaggio D.L. 42, 22 gennaio 2004), a gap cutting system configures as a sustainable silvicultural treatment because of its low environmental and aesthetic impact, which derives from the possibility of diluting the cuttings over space and time. Therefore, a gap cutting system is particularly suited to the restoration of conifer afforestations growing inside protected areas. For instance, the Management Plans of some Italian protected areas (parco nazIonale delle foreste
casentInesI, Monte falteronae caMpIgna, 2002; parco naturale regIonale delle
serre, 2008) introduce gap cutting for the forest restoration purposes.
Figure 1 – Distribution of seedlings density (2007) according to gap sizes and within-gap position.
aknoWledgMents
This study was supported through funds provided by Regione Calabria within the project
“The re-naturalisation of conifer plantations”
and “Robinwood Plus”- Interreg IV C. We thank Dr. Antonio Poletto from Azienda Agricola S. Maria for logistical support.
RIASSUNTO
Rimboschimenti di conifere in Italia:
un’opportunità per la produzione di energia dal legno e per il restauro forestale
Il restauro di rimboschimenti di conifere in popolamenti con struttura e composizione più complesse è una sfida attuale per la selvicoltura italiana e un’opportunità per la produzione di energia dal legno.
Un sistema selvicolturale finalizzato a favorire la rin- novazione naturale attraverso l’apertura di buche nella copertura arborea (sistema di tagli a buche) è stato adot- tato a partire dal 2003 in un sito sperimentale realizzato in popolamenti di pino laricio (Pinus nigra Arn. ssp.
laricio Poiret var. Calabrica Delamare) situati nell’Ap- pennino calabrese per confrontare gli effetti di buche di piccole (380 m2), medie (855 m2) e grandi (1520 m2) dimensioni. I principali risultati di questa esperienza dimostrano, dopo 7 anni, che la grandezza appropriata delle buche per la rinnovazione del pino laricio (una specie esigente di luce) è quella rappresentata da buche di 1500 m2 con un rapporto d/h di 2.0, mentre per specie tardo-successionali (abete bianco e faggio) sono consigliate buche di 380 m2 con un d/h di 1.0 o legger- mente più grande. Questo consente al gestore forestale di scegliere se mantenere il pino o avviare un’azione di restauro delle formazioni forestali autoctone. L’inter- vallo tra i diversi tagli è di 7 anni. Dato che ad ogni intervento si rimuove il 30% della superficie, il ciclo si completa in circa 20 anni. In questo caso (popolamenti normalmente diradati) al momento del primo taglio si possono ottenere da 15 a 70 m3 di legname per ogni buca o 140 m3 per ettaro. Questo approccio “sistema di tagli a buche” può essere considerato una pratica selvi- colturale sostenibile grazie al basso impatto ambientale ed estetico che produce e grazie alla possibilità che offre di soddisfare anche esigenze di produzione di materiale legnoso da destinare a fini energetici.
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