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Glacial and periglacial landforms as warm-stage refugia for cold-adapted plant and arthropod species:ecological and biogeographical significance of a habitat system
No full textSince 1880 air temperature at global scale rapidly increased of c. 0.85 °C likely due to the increasing amount of anthropogenic greenhouse gas, and is forecast to increase over the 21st century as well. Cold-adapted species of the high latitude/altitude are the first to be threatened by such climate change, due to the progressive reduction of their suitable areas.
Microclimatic heterogeneity at landscape level is supposed to play a key role in this scenario providing warm-stage refugia, sites able to preserve suitable climate conditions for cold-adapted species in spite of the ongoing climate warming. Active rock glaciers and debris-covered glaciers (periglacial and glacial landforms characterized by debris with underlying ice) were proposed as potential warm-stage refugia in mountain regions, due to the microclimate effect of underlying ice and the thermal inertia provided by the debris fraction. Besides microclimate heterogeneity at landscape level, macroclimate heterogeneity at regional scale (e.g. the contrast between continental and oceanic climates of inner and peripheral mountain ranges, respectively) can be important, since drive the distribution of periglacial and glacial landforms as potential warm-stage refugia and the effects of climate change themselves on high mountain landscapes (e.g. temporal pattern of glaciers retreat) and ecosystems (e.g. temporal pattern of primary successions on ice-free glacial landforms).
Aim of this study was to analyze the ecological features of periglacial and glacial landforms (active rock
glaciers and debris-covered glaciers on inner mountain ranges, glacier forelands and recent moraines on
peripheral mountain ranges) to test whether they have the main key-requirements to act as potential warm-stage refugia for cold-adapted species. Concerning active rock glaciers and debris-covered glaciers, we considered as key-requirements a cold microclimate able to support cold-adapted species and the ability to cross the altitudinal zonation of mountain ecosystems, thus supporting cold-adapted species in adverse climate contexts. Concerning glacial landforms on peripheral mountain ranges, we considered as key-requirement a relatively slow colonization pattern able to long-lasting support pioneer cold-adapted species in spite of the primary succession development. The study was carried out in different areas of the Italian Alps (Adamello-Presanella, Ortles-Cevedale, Monte Rosa, Orobian Alps) in which different landforms were analyzed and compared. A multidisciplinary approach was followed, considering both the abiotic (ground surface temperature and humidity, soil physical and chemical parameters) and biotic variables (plant and arthropod communities).
Our results show as active rock glaciers and debris-covered glaciers does not differ from the surrounding debris-featured iceless landforms for soil parameters, but for a cold microclimate likely due to the underlying ice. The microclimate can explain why these landforms differ from the surrounding ones for the occurrence of cold-adapted plant and arthropod species. On the Alps, active rock glaciers are unable to cross the altitudinal zonation of mountain ecosystems, thus can only enhance the occurrence of cold-adapted species within their normal altitudinal distribution. By contrast, debris-covered glaciers can cross the climatic treeline, allowing cold-adapted species to live even below their normal altitudinal distribution. However, the relative altitudinal distribution of active rock glaciers and debris-covered glaciers can be inverted on mountain systems drier than Alps, suggesting a similar ecological role of such landforms in opposite macroclimate conditions.
Moreover, our results suggest that mountain systems characterized by oceanic macroclimate could prevent the extinction risk for pioneer cold-adapted species along a chronosequence of glacier retreat, due to the long-lasting persistence of glaciers at relatively low altitudes (as a consequence of high winter precipitations) and the slow colonization of ice-free glacial landforms (as a consequence of long-lasting snow cover and temperatures around zero). Peripheral mountain ranges in particular outlines as oceanic areas of crucial biogeographical importance during both the opposite climate extremes: in cold-climatic stages they can provide refugia for a lot of species, as a consequence of the relatively low ice-sheet expansion; in warm-climatic stages they may provide refugia for cold-adapted species in particular, as a consequence of their climatic, thus glaciological and ecological features
Serie dinamica del bosco a Rovere: il caso del Parco nazionale Val Grande (VCO)
No full textViene ricostruita la serie dinamica del bosco a rovere nel
Parco Nazionale Val Grande (VCO), quale caso di studio esportabile
a tutta l’area prealpina occidentale suboceanica, per analogia di clima
e substrato. Sono state cartografate, in ambiente GIS, le aree di pertinenza
della serie sulla base delle caratteristiche climatiche e fi siche del
territorio. Entro tali aree sono stati effettuati 48 rilievi fi tosociologici
che hanno compreso tutti gli stadi serali della vegetazione, per poi procedere
con l’analisi delle fi tocenosi individuate e la loro interpretazione
in chiave dinamica. Risultato dello studio è l’individuazione di sei fi -
tocenosi, quattro delle quali (pteridieti, calluneti, betuleti, rovereti) fra
loro collegate da un legame dinamico, suggerito da analisi fl oristiche
quali-quantitative sull’abbondanza delle specie e dall’analisi dei parametri
ecologico-stazionali tramite CCA.Ecological succession of sessile oak woods: Val Grande
National Park (Italian Western Alps) as a case study. We assessed the
ecological succession of sessile oak (Quercus petraea) woods in Val
Grande National Park (Verbano-Cusio-Ossola, Italian Western Alps), as
an example available for all the western prealpine insubric area. With
GIS we have deduced the map of the areas of pertinence of Quercus
petraea, based on climatic and physical characteristics of the territory.
Within these areas we carried out 48 phytosociological relevés according
to Braun-Blanquet method, assessing all stages of the ecological succession.
As a main result the Cluster Analysis individuated 6 phytocenoses
and 4 of the them (Pteridium aquilinum grasslands, Calluna vulgaris
moors, Betula pendula woods, Quercus petraea woods) have a dynamic
link suggested by quali-quantitative analysis about species ecology and
abundance and by several environmental parameters analyzed by CCA
Schede per una Lista Rossa della Flora vascolare e crittogamica Italiana: Androsace brevis (Hegetschw.) Cesati.
No full textVegetation outlines of two active rock glaciers with contrasting lithology
Full text linkRock glaciers are periglacial landforms consisting of coarse debris with interstitial ice or ice core, characterized by creeping due to ice deformation.
These landforms are drawing the attention of plant ecologist as harsh habitats and potential refugia in the global change context. Our aim was to
describe the vegetation outlines of two active rock glaciers of the Ortles-Cevedale Massif (Central Italian Alps) on different substrates (silicate and
carbonate) and compare them with the neighboring stable slopes and scree slopes. Two hypotheses were tested: 1) rock glaciers differ from the surrounding
landforms for the presence of cold-adapted plant communities; 2) rock glacier plant communities indicate similar microclimatic conditions
in spite of the contrasting lithology. Data were collected by phytosociological method performing 80 relevés of 25 m2. Plant communities were
compared by a cluster analysis based on the presence/absence species matrix and species relative frequencies for each landform were calculated. The
cluster analysis separated first for all the two sites; afterwards, the landforms were differently discerned each other depending on the site. Despite
the remarkable floristic differences due to the substrate, the vegetation of both rock glaciers suggest a general adjustment to cold-moist microclimate
and long-lasting snow cover, differentiating more or less evidently from the adjacent scree slopes and enhancing the survival of nival entities at the
elevation of alpine grasslands
Vegetation outlines of a debris-covered glacier descending below the treeline
No full textDebris-covered glaciers are glaciers with the ablation zone covered by a debris layer, which are able to persist below the treeline and to support plant life. These landforms are increasing on many mountain regions of the world as consequence of climate change, providing new habitat for plant colonization, but their vegetation features are still little known. Our aim was to describe the vegetation of an alpine debris-covered glacier descending below the treeline (Belvedere: Western Italian Alps) and compare it with those of the adjacent iceless moraine and stable slope. Our hypothesis was that plant community of the supraglacial debris differs from those of the surrounding landforms for the presence of cold-adapted species. Data were collected by phytosociological method performing 45 relevés of 25 m2. Plant communities were compared by a cluster analysis based on the presence/absence species matrix; species relative frequencies for each landform were calculated. The cluster analysis clearly separated three plant assemblages, each corresponding with one of the investigated landforms. Unlike the iceless moraine, debris-covered glacier stands out for the presence of cold-adapted species typically widespread in the alpine and nival belts (e.g. Poa laxa and Cerastium pedunculatum), allowing them to survive below their normal altitudinal distribution, where the stable slopes host subalpine woodlands and shrublands
Physical and biological features of an active rock glacier in the Italian Alps
No full textWe report on the key physical features of an active rock glacier that influence the distribution of plants and arthropods. We also perform a comparison with neighboring scree slope and alpine grassland to test whether the environmental features of the rock glacier drive the presence of specific species assemblages. Compared with scree slope and grassland, the studied rock glacier provides particular physical features that determine the presence of unique species. Plant distribution is mainly driven by grain size. Arthropod distribution is linked to grain size, with cold-adapted species found on areas with coarse-grained deep debris, which also shows a distinctive temperature regime with very low values throughout the year. On the basis of these findings, we advance the hypothesis that rock glaciers provide specific ecological conditions creating potential refugia for cold-demanding species during warm climatic periods
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
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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