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1.
Damage to residual stand after partial harvesting or thinning may lead to serious economic losses in terms of both timber quality at the final harvest, and tree growth reduction. Logging damages and their effect on tree growth were studied in a long term experiment on Corsican pine in central Italy. Damage frequency, agent (felling, skidding), position (root damage, stem base, between 0.3 and 1 m a.g.l., >1 m a.g.l.) and severity (light, severe) and tree growth were measured after selective thinning from below and at 10 years after the treatment. In detail, we aimed at: monitoring mechanical damages to trees at the end of thinning and after 10 years; and assessing stand stability, growing stock, ring width and basal area at 10 years after the thinning. The thinning removed about 20% of volume, 38% of trees and 26% of basal area. The basal area decreased from 56 m2 ha−1 to 42 m2 ha−1 but after 10 years it increased again to 56 m2 ha−1. Immediately after thinning, 13.6% of the standing trees was damaged, out of these 36.17% showed severe injuries. Damages to standing trees were mainly due to skidding. Ten years after thinning, the percentage of damaged trees was about 17%, out of which 86.67% showed severe wounds. An increase of damaged trees and of trees with severe wounds was observed suggesting that a deeper knowledge on long-term effect of logging damages is needed. This study did not highlight any effect of logging damage on tree growth. In fact, no difference in ring width was recorded between damaged and undamaged trees.  相似文献   
2.
Snow damage on natural stands is an important problem concerning mountainous forest management.In the present research,the frequency and intensity of heavy snow damage on natural stands and the relationship of damages with characteristics of trees,stand and topography were studied in mountainous forests of northern Iran.A systematic sampling design was applied to the study area(140 ha),with 122 circular plots.The grid dimension was100 m and each plot area was 1000 m^2.The four types of snow damage to trees include:crown damage(8.6%),stem breakage(5.4%),uprooting(3.2%),and bending(1.4%).The frequency of crown damage grew with an increase inthe diameter at breast height(DBH),while the frequency of stem breakage,uprooting and bending decreased with an increase the DBH.The frequency of crown damage,stem breakage,and total damages was related to tree species(p<0.01).Not all tree species were equally susceptible to snow damage.The amount of damage grew with increasing elevation and slope angle and decreased with increasing soil depth.Young trees(DBH<25 cm)were more susceptible to snow damage than other trees.Snow damage decreased by as the trees in the stand became more mixed in age.The susceptibility of trees to snow damage increased by height and slenderness coefficient.With adequate silvicultural operation,snow damage can be reduced to a minimum level in these natural forests.  相似文献   
3.
This study aims to investigate wood density at different levels of moisture, basic density and shrinkage of timber from Turkey oak (Quercus cerris L.) coppice forests growing in Central Italy. We also studied the variability in density in the trees within and among sites. Density shows no significant statistical differences in the tested population. A higher variability in the shrinkage than in the density was found. Wood moisture is referred to as dry mass and fresh mass, which is related to many performance characteristics of wood, i.e., energy production. Trends in moisture and water content were studied because these physical parameters play an important role in the specific area of firewood which requires an accurate estimation of mass, volume and energy content. This work is a contribution to improve xylo-energy estimates of small and medium forestry issues.  相似文献   
4.

One of the basic requirements for sustainable forest management in mixed broadleaved stands is to provide suitable conditions for natural regeneration of trees. These conditions include, but are not limited to, the frequency, quality and the composition of seedling species. Compacted soil layers caused by forest machinery traffic are the most common problem affecting seedling establishment and growth after skidding operations. In this study, we evaluated the frequency, quality, diversity of seedling species and physicochemical properties of soil on 10-, 20- and 30-year-old abandoned skid trails. Further comparison to the values of the mentioned above parameters in control areas allowed for the evaluation in terms of natural recovery processes, under varying traffic intensity and the longitudinal slope of the skid trails in a mixed broadleaved forest. Results showed that there is a significant positive trend of recovery for soil physicochemical properties and ecological characteristics (density and quality) of seedling growing on the skid trails. The time required to recover soil properties and ecological attributes of seedlings increased with increasing traffic intensity and slope of the skid trail. Our results showed that it takes 20 and 30 years to fully recover the chemical and physical properties of the soil, respectively. On the 30-year-old skid trails, density and species diversity indices were fully recovered, but the quality of the seedlings was not restored to the control conditions. The results suggest the importance of a proper planning of the skid trail network, avoiding in particular skid trails with a slope gradient higher than 20%.

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5.
This study aims to analyze the factors affecting the costs of different logging systems, in particular considering three different bunching-extraction methods. Moreover the stumpage value of each plot was calculated, and a comparison analysis of the results is presented. The work was carried out in Central Italy, in an aged Quercus cerris L. coppice in hill zones, with a 45% average slope. Short wood system harvesting was applied. Felling and processing were performed by chainsaw, while extraction with three different methods: plot No. 1 with mules, plot No. 2 with a tractor with winch, plot No. 3 with polyethylene chute line. Transport of firewood from the forest track to the landing was made by a tractor loaded as a mule. In the plot No. 1 the costs per unit mass (30.76 ? 33% -1 ) were higher despite having the lower cost per hour (39.99 ? -1 ). The reason was the lower productivity (1.3 t 33% ·h -1 ). The plot No. 2 had the highest cost per hour (66.79 ? -1 ). However, productivity was the highest (2.7 t 33% ·h -1 ). This aspect was notable from the financial point of view (24.74 ? 33% -1 ). Plot No. 3 was the less expensive (23.92 ? 33% -1 ). Comparing the three methods, a reduction of the costs through more appropriate extraction systems may increase the stumpage value from 8.3 to 9.65 ? 33% -1 .  相似文献   
6.
Forest harvesting operations may have a significant impact on soil physical properties by reducing its porosity and organic functions. Soil variations, in particular bulk density and total porosity, caused by external perturbations as soil becomes compacted due to machinery passes, can lead to changes in biogeochemical cycles that have consequences on soil ecosystems. This study investigated how the impact of forest operations and the elapsed time from harvest can influence: (1) the physical–chemical characteristics of soil and (2) the nitrogen-fixing and nitrifying microbial communities. The study area is located inside the Regional Park of Migliarino, San Rossore, Massaciuccoli (Pisa, Italy). In the study area, the soil has been classified as recent sands with sandy loam texture and slightly calcareous (USDA Soil Taxonomy classification). Soil samples were collected in patchy cut areas (strip cut) of Pinus pinea stand that was harvested in two steps: half area in 2006 and the rest in 2011. Soil samples were collected also in a control area (not harvested) with similar stand and soil characteristics. Statistical analysis was preceded by a test of normality (Kolmogorov–Smirnov test) and a variance homogeneity test (Levene’s test). Considering the dependence of the variables studied (physical and chemical soil characteristics), a MANOVA test and a post hoc Tukey HSD test were applied to determine statistical difference among the three treatments: harvested 2006, harvested 2011 and not harvested. The results did not indicate significant variations to the parameters of shear and penetration resistance, though soil bulk density and total porosity were significantly altered in the short period since forestry operations occurred. These physical changes induced qualitative (presence/absence and number of species) and quantitative (abundance and spatial evenness of the species) variations in the nitrogen-fixing and nitrifying microbial communities.  相似文献   
7.
Short-rotation coppice (SRC) represents an important source of wood biomass. Many uncertainties create barriers to farmers establishing SRC plantations, especially under Mediterranean climate conditions. In this study, five species and respective genotypes were analyzed. The five species were Fraxinus angustifolia, Robinia pseudoacacia, Salix alba, Populus nigra (Limatola), and Populus × euroamericana, with the genotypes of the latter being Grimminge, Vesten, Hoogvorst, Muur. For the plantations studied, two different harvesting systems were replicated: the single machine pass, or cut-and-chip (CC); and the double machine pass, for which the tree are cut first, then chipped later (chip of stored trees CS). In the CC, fresh trees were harvested and chipped by Claas Jaguar 880. In the CS, dry trees were chipped by Farmi Forest CH 260. Within the same site, in climatic conditions and low-input management, the best result in terms of biomass yield was obtained from the black poplar Limatola. Both wood typologies and harvesting systems affected the chip quality. The disk chipper, when working on dried biomass, produced lower quality chips than the other chipping device in terms of particle size. In the chips obtained, there was an increase in the number of chips classified as being “larger size” and “oversized”, and a decrease in the percentage of those classified as “accept” (45–3 mm fraction). The chips obtained from dried trees were of better energy quality compared with the same biomass obtained from the fresh trees in terms of heating value and ash content.  相似文献   
8.
Lime-trees (Tilia begonifolia Stev.) have countless ecological and economical values in the northern forests of Iran. Bole wounds on residual trees are commonly caused by logging. The healing ability of bole wounds and the effect of bole wounds on diameter growth in lime-trees were assessed in a natural mixed uneven-age stand. The susceptibility to decay in relation to the wound severity was also evaluated. Condition and location of lime-trees before and after selective logging were determined through systematic plot sampling. The position of each lime-tree was identified on a topographical map using the global positioning system. After 10 years from wound occurrence, tree and wound characteristics were also re-measured. Overall, 68 stems (9.7 stem ha?1) of lime-trees were found in the sampled area, 25 stems (36.8%) were damaged in the form of bole wound, and 43 stems (63.2%) were undamaged. Statistical differences between wounded or non-wounded lime-trees in terms of diameter and height were not found. Most of the wounds occurred at the height of < 1 m; the average wound size was 370.5 cm2. Wound severity was related to wound size and wound position. Wound width healing rate was 6.2 mm year?1. The wound shape was found to be a healing factor as the healing rate by width was higher than that by length. Healed wounds were only 12, 60% of bole wounds resulted in decay. Diameter growth of wounded trees was 43.5% lower than undamaged trees. The average annual diameter growth decreased by increasing wound severity. The results indicated the lime-tree is a very sensitive species to damage caused by logging (bole wound). Single-tree selection cutting needs more careful logging operations to reduce damage on residual lime-trees in order to safeguard this species, valuable in ecologic and economic terms.  相似文献   
9.
The focus of this study was to investigate the chemical and colour changes occurring at different exposure times on artificially photo-irradiated surfaces of normal and red heartwood in beech in order to understand the mechanisms that cause the changes and to evaluate the possibility of usages of beech not only for energy production purposes. In this sense, surface colour modifications are of crucial importance to define the commercial value of beech wood. The artificial photo-irradiation of the wood samples was performed in a Solar Box, equipped with an ultraviolet filter that cuts off the spectrum at 280 nm. Reflectance spectrophotometry and Fourier transform infrared (FTIR) spectroscopy were used to assess artificial sunlight influence. The experimental data were statistically treated to evaluate their significance. Colour monitoring revealed that wood surface colour undergoes an important variation due to photo-irradiation, occurring within the first 24–48 h. Moreover, it was found that the chromatic coordinates (L*a*b*) in normal wood and in red heartwood tended to similar values after 504 h. FTIR spectroscopy allowed for investigating the rate of photodegradation of wood surface due to oxidation reactions of wood components. The results were validated by statistical analysis applied both to the colorimetric and spectroscopic data.  相似文献   
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