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18/07/2012 3:58 pm
The Park’s flora and vegetation are greatly influenced by the large number of lakes and small wetlands in the area, as well as abundant outcrops of serpentinite, rocks that result in shallow soils poor in nutrients. In the upper valley of Dondena, in the municipality of Champorcher, extensive outcrops of calc-schist host a very rich and varied flora very different from that found on serpentinite.
The vegetation sceneries of the protected area are unusual for the region, particularly the huge forest of Mountain Pine. This conifer is the tree that best adapts to peaty soils and ophiolite outcrops and, in Val Chalamy, largely replaces the conifers more widely found in the rest of the region (Larch and Spruce).
The Mountain Pine differs from its congener Scots Pine by having entirely grey-brown trunk and branches (and not partially yellow-reddish) and by its cone scales having clearly visible hooks. While present in the Pyrenees and in the central-western Alps, it is not widespread in Italy, but Mont Avic Natural Park is home to the largest Mountain Pine forest in the country (over 1100 ha); the forest of the Serva basin is classified as a “seed wood” and is cultivated by the Valle d’Aosta Forestry Corps. Pinus uncinata comes in two distinct shapes:
- arboreal, where its trunk is erect and straight and is topped by pyramidal crown: it forms dense forests with thick undergrowth of blueberries and rhododendron and manages to sparsely colonise even hillocks of abundant rock outcrops;
- prostrate, with ground-hugging branches that rise upwards only at its apex: it grows in gullies where avalanches take place and tolerates the regular fall of even large masses of snow.
The Mountain Pines rooted in peat bog or in the cracks of the rocks, with their very slow development, can become natural “bonsai”.
In close symbiosis with the roots of the Mountain Pine, numerous fungi develop (at least 100 ectosymbiotic species have been recorded in the Park), organisms that greatly facilitate the tree’s colonisation of poor soils.
The serpentinite flora – adapted to the presence of superficial and nutrient-poor soils that are full of toxic elements such as nickel, chromium and cobalt – consists of a small number of species, frequently cruciferous plants (especially the genera Thlaspi and Cardamine). Cardamine plumieri, Thlaspi sylvium, Alyssum argenteum and Asplenium cuneifolium are among the most interesting.
The rupicolous lichens growing on serpentinite rock are unexpectedly numerous (over 100 species found in the Park), considering the difficult climatic and lithological conditions they have to face. Of considerable interest is the high frequency of “lichenic lichens”, which develop at the expense of other species of lichens previously settled on the rock substratum.
The different levels of environmental humidity between the north facing slope of Val Chalamy and its sunny side can be clearly seen in the progressive replacement of Beech by Scots Pine, a tree better adapted to conditions of environmental aridity.
The interesting flora linked to wetlands can be observed not only next to lake basins, but also in a myriad of peat-marshy areas and resurgent water sources present throughout the protected area. These environments host boreal plants which are now rare or about to become extinct in the Alps; among the rarest and most localised species present in peat bogs are Carex limosa, Carex pauciflora, Eriophorum vaginatum. Also of note is the presence of numerous groups of the insectivorous plant Drosera rotundifolia, as well as a pond with floating islets of sphagnum (including Sphagnum magellanicum, S. squarrosum and S. angustifolium). In high summer on some lakes there is an abundant development of the Water Buttercup, with its showy floating white blooms.
Lastly, the rare or localised flora present in the Park includes Artemisia chamaemelifolia, Asplenium adulterinum, A. cuneifolium, Cortusa matthioli, Diphasiastrum alpinum, Platanthera chlorantha, Sedum villosum and Stemmacantha rhapontica.
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