1,720,973 research outputs found
The effect of gap openings on soil reinforcement in two conifer stands in northern Italy
No full textGap-oriented forestry is a subject that is gaining interest worldwide as a compromise between economic and operational requirements on the one hand and environmental and safety concerns on the other. In principle, the approach mimics the effects of fine-scale natural disturbance while avoiding the threats of soil degradation and instability associated with large clearcuts, but at the same time, it does not limit the productivity associated with single-tree selection.
Despite this interest, studies of the real effects of gap-oriented forestry are still limited, particularly those dealing with its impact on slope stability. This paper provides quantitative results about the slope stability of two mixed-conifer stands subjected to gap management in the Italian Central Alps that were monitored for five years after felling.
The results showed that root decay, both in strength and density, further reduces additional root cohesion by approximately 60% in the first two years after felling and by another 20% in the third year; it completely vanishes by the fifth year. The observed reduction in root reinforcement values has dramatic consequences for slope stability. In fact:
- In undisturbed conditions, the contribution of forest root systems guarantees a very low probability of instability (approximately 10% for a factor of safety of less than 1 as well as for steep slopes and high levels of saturation).
- After only two years, the probability of instability dramatically increases for gentle slopes and low levels of saturation. We estimated a 50% probability of a factor of safety less than 1 when steepness was greater than 36-38 degrees and soil saturation was 25% and when steepness was greater than 24-26 degrees and soil saturation was 75%.
- The probability of instability is highest five years after felling when the contribution of the root system has vanished. The probability of failure exceeded 50% when steepness was greater than 25-28 degrees and saturation was 25%, and the slopes were practically unstable when saturation was 75%.
- At the point when the contribution of the root system to slope stability was null, the regeneration process was still too undeveloped to contribute to soil reinforcement in any way.
These results suggest that although the gap-oriented approach is, in principle, more conservative than large clearcuts, the pace of natural regeneration could be slower than the process of root decay, so instability could occur, especially where local slopes exceed 25 degrees and soils are frequently saturated
Preliminary phenotypic characterization of Sorbus domestica and S. torminalis under selection for timber production
No full textThe current timber production in Italy covers only 20% of the national demand. The national timber industry has been trying to increase the domestic production of sliced veneer logs from indigenous broadleaved species, which are largely employed by furniture and interior design industry. The present work shows the first results concerning the phenotypic characterization of Sorbus domestica, S. torminalis under selection in the Po Valley (northern Italy) for timber production. Thirty-one S. domestica seedlings from three provenances.
Toscanella (northern Apennines, Italy), Serbia (Research Institute of Serbia) and Oxford (United Kingdom). One hundred and twenty five S. torminalis seedlings from a single mother plant, belonging to the Northern Apennine (Italy), evaluated ,were classified for annual diameter and height increase, according to these results into three groups.. S. domestica seedlings (Ideotypes) were also evaluated for environmental adaptation trait and suitability for timber production, according to a superior phenotypes scoring method. Six S. domestica 'high value' Ideotypes, scoring 20% -42% in respect to the comparison trees, were selecte
Indagine sulle Caratteristiche degli apparati radicali di un abieteto sottoposto a taglio a buche in alta Val Brembana (BG)
No full text
Acclimation to changing light conditions of long-term shade-grown beech (Fagus sylvatica L.) seedlings of different geographic origins
No full textEffects of changing light conditions on the ecophysiological condition behind survival were examined on beech from two different populations. Plants were grown in a greenhouse under simulated understorey and canopy gap light conditions. Upon exposure to high light maximum photosynthesis of shade-acclimated leaves increased followed by a reduction over several days to between high- and low-light control rates. In the reciprocal transfer, the decrease in maximum photosynthesis was rapid during the first 2–3 days and then levelled off to values comparable to low-light controls. Seedlings from Sicily (Madonie) showed generally higher maximum photosynthetic rates than those from Abetone. Leaf conductance varied in the same direction as photosynthesis in high- to low-light seedlings but to a lesser degree. Leaves grown under low light and exposed to high light experienced photoinhibition. The Abetone population was more susceptible to photoinhibitory damage than the seedlings from Sicily. Exposure to high light of shade-acclimated seedlings resulted in intermediate chlorophyll concentrations between levels of the high-light and low-light seedlings. Carotenoid concentration was unaffected by treatments. Seedlings grew more in high light, but had a lower leaf area ratio. Light-limited seedlings showed a shift in carbon allocation to foliage. Leaves formed in the new light regime maintained the same anatomy that had been developed before transfer. Seedlings from Sicily had thicker leaves than those of seedlings from Abetone. Seedlings from Abetone were found to be more susceptible to changing light conditions than seedlings from Sicily. We conclude that small forest gaps may represent a favorable environment for photosynthesis and growth of beech regeneration as a result of the limited ability of seedlings to acclimate to sudden increases in high irradiance and because of the moderate levels of light stress in small gaps
Varibailità delle risposte clima-accrescimento di Pinus cembra L. in cenosi del limite superiore nelle Alpi orientali
No full texta cura di Bucci G., Minotta G., Borghetti M
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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