1,721,011 research outputs found
Vegetation at the Limits for Vegetation: Vascular Plants, Bryophytes and Lichens in a Geothermal Field
No full textAbstract The effects of the chemical and physical factors associated with geothermal activity on plant community structure and composition were investigated in one of the largest geothermal fields of central Italy. The study site was located in the geothermal area of Sasso Pisano GÇô Monte Rotondo Marittimo, Southern Tuscany. The percentage cover of all vascular plant, bryophyte and lichen species was estimated within 119 circular plots of 0.25 m2. For each plot the soil pH, soil temperature, slope, aspect, incident radiation, soil nitrogen and carbon contents were also quantified. Two vascular plants, Calluna vulgaris and Agrostis castellana, were found to be the most widespread species tolerating the harshest conditions in terms of low soil pH and high soil temperature. The most widespread cryptogam species was Hypnum cupressiforme. Spatially autoregressive models showed that a proportion of about 41GÇô51% of the variance in species richness of one group of plants (vascular or cryptogamic plants) could be modelled by using three or four uncorrelated environmental factors respectively (soil temperature, soil nitrogen and soil C/N ratio and these three plus incident radiation). For the total number of species (vascular and cryptogamic plants), the variance explained by the same three uncorrelated variables was about 57%. This study evidenced a strong environmental control of community composition and species richness, in a site subjected to extreme soil values of soil pH and temperature. The dominance of vascular over cryptogamic vegetation in this geothermal site can be explained by the combined effects of geothermal stress (low soil pH and high soil temperature) with the summer drought typical of the Mediterranean climat
Vegetation at the Limits for Vegetation: Vascular Plants, Bryophytes and Lichens in a Geothermal Field
No full textAbstract The effects of the chemical and physical factors associated with geothermal activity on plant community structure and composition were investigated in one of the largest geothermal fields of central Italy. The study site was located in the geothermal area of Sasso Pisano GÇô Monte Rotondo Marittimo, Southern Tuscany. The percentage cover of all vascular plant, bryophyte and lichen species was estimated within 119 circular plots of 0.25 m2. For each plot the soil pH, soil temperature, slope, aspect, incident radiation, soil nitrogen and carbon contents were also quantified. Two vascular plants, Calluna vulgaris and Agrostis castellana, were found to be the most widespread species tolerating the harshest conditions in terms of low soil pH and high soil temperature. The most widespread cryptogam species was Hypnum cupressiforme. Spatially autoregressive models showed that a proportion of about 41GÇô51% of the variance in species richness of one group of plants (vascular or cryptogamic plants) could be modelled by using three or four uncorrelated environmental factors respectively (soil temperature, soil nitrogen and soil C/N ratio and these three plus incident radiation). For the total number of species (vascular and cryptogamic plants), the variance explained by the same three uncorrelated variables was about 57%. This study evidenced a strong environmental control of community composition and species richness, in a site subjected to extreme soil values of soil pH and temperature. The dominance of vascular over cryptogamic vegetation in this geothermal site can be explained by the combined effects of geothermal stress (low soil pH and high soil temperature) with the summer drought typical of the Mediterranean climat
Defoliation reconsidered?
No full textSince the 1980s defoliation (often assessed by means of crown transparency) is the most used indicator of tree condition adopted in Europe. It has been criticized for its subjectivity and scarce relation with meaningful endpoints. Here we collated the results of three different studies carried out in France and Italy to investigate the relationship between defoliation/transparency and other measured indicators of tree growth and health.
In a first study, basal area increment (BAI) and mean defoliation of conifers and broadleaves in the French Level II network RENECOFOR were examined for the growing periods 1995-2004 (47 plots, 2008 trees) and 2000-2009 (63 plots, 3116 trees). A second, similar study was carried out on Picea abies (L.) Karts., in Trentino, Northern Italy, on 13 Level I plots and two growing periods, 2001-2005 (136 trees) and 2005-2009 (111 trees). The third study was carried out also in Trentino: nine Picea abies trees were randomly selected along an elevation gradient (900-1500 m asl) and examined for crown transparency, shoot length, needle weight, chlorophyll fluorescence, and stable isotopes in needles (δ 13C and δ 18O).
BAI resulted negatively and significantly related to defoliation at both the French and Italian plots, and growth reduction of 0.73-1.49% per unit increase of defoliation can be expected. The gradient study revealed that the response of trees to elevation is consistently and significantly recorded by the various indicators (e.g. reduced shoot length, needle weight, chlorophyll fluorescence, and increase of crown transparency).
We argue that, despite its “bad” reputation, defoliation can be considered as an effective indicator of forest health and vitality. Its role among the indicators of Sustainable Forest Management is justified, also in view of its long-term documentation in terms of QA/QC procedures at national/international level. These are strong arguments for supporting and promoting forest health monitoring network
Effetti della soluzione nutritiva e del substrato sulla qualità del fiore reciso di Lilium
No full text
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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