Walker - 1967 - A geography of Italy

PART I I : SOME P H YSIC A L GEOGRAPH Y
proved useful for stabilizing unconsolidated slopes and quickly takes possession
o f waste ground. Although the mulberry, which was brought in from the Near
East in the late Middle Ages to support the silk industry, has lost much o f its
economic importance and is probably doomed to disappear with the spread of
mechanization, it still makes a pleasing contribution to the mixed cultivation of
the Piedmont and Venetian plains. The ailanto, a native o f southern Asia imported
for the same purpose in the eighteenth century, is found wild throughout
the length o f Italy. Perhaps the most valuable introduction has been the graceful
and quick-growing eucalypt which provides material for paper-making and is a
useful ally against wind and water erosion. Since the turn of the century, with
the wider appreciation o f the evils o f deforestation, large areas have been replanted
both by private bodies and by the state. The depopulation o f many
mountain areas should provide still greater scope for the restoration of the
original cover.
So all-pervading has been Man’s intervention that to speak o f ‘natural vegetation’
is somewhat imreal, but by making use of such remnants as survive and of
the obvious relationship between the vegetation o f an area and its cUmate, relief
and soil, an approximate picture o f the original cover can be reconstructed. From
the geographer’s viewpoint this is perhaps best described on a threefold basis -
the Alps, the Valle Padana, and the Mediterranean peninsula and islands.
THE ALPS. On a local scale the study o f Alpine vegetation must assess the effects
o f a host o f micro-climatic and edaphic factors but, in the more generalized
picture, altitude, and to a lesser degree, aspect and continentality emerge as the
most important influences. The increasing degree o f continentality towards the
Alpine watershed tends to thin out the beech, which finds its most favourable
habitat on the humid south-facing slopes o f the Pre-Alps, and favours the conifers,
particularly the Pirns sylvestris. The effect o f aspect is to lower the upper
tree limit on north-facing slopes and to create conditions suited to the less
demanding species. For example, on the southern side o f the col between the
Presanella and Brenta groups, the red fir {Picea excelsa) is dominant, but once
over the watershed the hardier larch (Larix decidua) takes its place. The contrast
between the two sides o f valleys trending east and west is well exemplified in the
Graian and Cottian Alps (Val Maira, Val Varaita, Valle del Chisone, Valle di
Susa, etc.) and further east in the Val Venosta, in the Val di Sole, and perhaps
best o f all, in the Valtellina. Here forests o f red fir and larch, briefly interrupted
by pasture, look across to terraced vineyards and chestnut woods above which
hayfields and patches o f arable penetrate the pinewoods almost to the limit of
trees (1850m).
Before generalizing about the main vegetation zones, which are broadly
related to altitude, two facts, neither o f them easily explained, should be noted.
Firstly, the upper limit o f trees is actually higher in the interior Alps than on the
Pre-Alps; and secondly, the vegetational strata, whether nearer the watershed or
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