1,720,981 research outputs found
Dalla dendrocronologia all’anatomia quantitativa intra-annuale. Verso una maggiore risoluzione temporale nello studio delle relazioni clima-accrescimento.
No full textHost preference and growth patterns of ivy (Hedera helix L.) in a temperate alluvial forest
Full text linkRecent studies have highlighted the role of lianas in shaping stand dynamics both in tropical and temperate forests. However, English ivy (Hedera helix L.), one of the most widespread lianas in Europe, has received little attention. We conducted a study in the Siro Negri alluvial forest (NW Italy) to determine what factors most affected ivy distribution and investigate its interactions with the trees in the stand. We evaluated the influence of tree size, age, species, and neighborhood crowding on ivy occurrence. In addition, growth ring widths were used to explore the development pattern of climbing stems. Fifty-two percent of trees in our study plots carried ivy, a value comparable to liana incidence found in mature tropical forests. Tree characteristics and their spatial pattern significantly influenced ivy distribution. Preferred hosts were large, isolated trees, while the effect of tree age and species on ivy occurrence was marginal. Growth pattern analysis revealed that radial growth was positively related to the available space on the tree trunk for each ivy stem. We conclude that neighborhood crowding around trees and competition among climbing stems relying on the same trunk may reduce the colonization rate of ivy
Growth decline or periodic fluctuations? Evidence from Fagus sylvatica in the forest of Lom, Bosnia-Herzegovina
No full textDrought impact on beech (Fagus sylvatica L.) forests in the North-West of Italy. A driver of future forest growth reduction?
No full textRisposta al clima e agli eventi estremi di Cedrus deodara nel parco Bolasco, Castelfranco Veneto (TV)
No full textTemporal variability of size–growth relationships in a Norway spruce forest: the influences of stand structure, logging, and climate
No full textIn a forest stand, competition plays a central role, affecting individual growth. The size–growth relationship (SGR) indicates whether large trees grow proportionally more than (asymmetric SGR), equal to (symmetric), or less than (inversely asymmetric) smaller trees. SGR is thus an indicator of the growth partitioning and competition intensity within a stand. Using tree-ring analysis, we investigated long-term trends and interannual variability of SGR in several Norway spruce (Picea abies (L.) Karst.) stands in the Paneveggio Forest (eastern Italian Alps) over a 100-year period. The study plots were characterized by different stand structures (one multilayered and two monolayered) and disturbance histories (different dates of logging). Logging conducted until the 1940s induced an inversely asymmetric SGR in all the plots. During the successive five decades, in the monolayered plots, it shifted to direct asymmetric (plot 1) and to symmetric (plot 2). In the multilayered plot (plot 3), SGR remained inversely asymmetric. A direct effect of climate on SGR interannual variability was not found. However, fast-growing trees had a stronger climatic signal than slow-growing trees, indicating that growth rate affects tree response to climate. Moreover, we observed that sensitivity to climate was reduced in the monolayered plots over the study period, possibly as a consequence of increased competition
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
Summer climate variability over the last 250years differently affected tree species radial growth in a mesic Fagus–Abies–Picea old-growth forest
No full textSustainable forest management has to consider the long-term effects of climate change on species growth to develop adaptation measures. In this perspective, dendrochronology provides valuable information on climate-growth relationships over long time periods. Tree-ring analyses in mixed stands can elucidate how different species respond to climate change within the same environmental conditions. However, few studies have investigated such stands, especially in South-Eastern Europe. In the forest reserve of Lom, in Bosnia and Herzegovina, we had the opportunity to study three co-occurring species (silver fir, Norway spruce, European beech) in an old-growth forest characterized by reduced human and natural disturbances, and a climate favourable to the tree species. We evaluated tree growth response to climate on inter-annual and decadal time scales over about 250 years. Response to inter-annual climate variability changed over the study period. Climate signal in beech was generally low, with a negative correlation to April temperature in the last decades. In fir and spruce, the positive effect of current year's spring temperature decreased, while the negative effect of the previous summer temperature considerably increased over the last century. At the decadal scale, different responses have been detected among species: spruce was mostly negatively affected by summer temperature whereas summer precipitation benefited fir growth, probably balancing high evapotranspiration. Beech showed a peculiar delayed response, and protracted drought periods led to severe growth reductions. Despite a temperature increase over the last three decades, fir did not experience any growth reduction, while a strong decline was evident in spruce and beech productivity. Mesic sites are commonly underrepresented in tree-ring research. In our analysis, covering about 250 years, we observed that climate also affects species-specific growth patterns in these areas. Within a global change perspective, specific divergent responses are likely to occur even where current environmental conditions appear to be not limiting for tree species. Future management strategies should consider these outcomes. (C) 2014 Elsevier B.V. All rights reserved
Growth responses to decadal climate variations over the last 250 years pose issues on future performance of Norway spruce, silver fir and European beech. Evidences from a mixed old-growth forest in Bosnia and Herzegovina
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