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ŠUMARSKI LIST 1-2/1971 str. 14     <-- 14 -->        PDF

pijeska i šljunka. Nakon sječe ili odumiranja topola, druge trajnije vrste drveća
bit će toliko razvijene da će i bez topola smanjiti štetne utjecaje voda, vjetrova
i gravitacije.

Distribution, ecological and economic significance

There are almost no data in the domestic and foreign forest literature about the
distribution of Poplars in the Mediterranean region. In the Croatian part of the Yugoslav
seabord we recordet about 100.000 grown-up Poplar trees whose maximum
diameters b. h. range up to 40—80 cm., and even to 150 cm. They are mostly spread
on coastal grounds and on low elevation sites. Found were the following species of
the genus Populus: P. nigra, P. canescens, P. alba, P. tremula, P. euramericana. No
special investigation were performed concerning the ecological adaptability according
to the individula Poplar species and clones.

Ecological characters. Poplars inhabit soils of different composition; they thrive
best on alluvial and diluvial soils, along watercourses and seas and also on skeletal
soils. They stand elevated temperatures rather well; if temperatures did not affect
badly the humidity of the air, warmth would not be a critical factor. The critical
factor for a good growth and increment is lack of water and strong insolation, and
sometimes Poplars shed a part of their foliage. On the sea-shores Poplars benefit
from filtrated sea ater. Older Poplars stand well the adverse mechanical influences
of the winds, in some places even better than Austrian Pine (Fig. 1). They also stand
well the salinity of the soil and air. On drier soils Poplars lengthen much their roots.
Probably the most important problem of the development and growth rate of Poplars
is the summer drought when the Mediterranean tree species pass through a relatively
long period of rest.

Expansion of area. On the basis of the ecological and vegetational relationships
of the recorded Poplars habitats it may be assumed that if adequate clones are
chosen, these broadleaved species can successfully be propagated in the Mediterranean
region: a) by geographical zones — in the Submediterranean area and on better sites
of the Eumediterranean area, b) according to the pedosphere — primarily in deeper
alluvial and deluvial soils, in skeletoidal soils along the shores of watercourses and
seas, exceptionally also elsewhere.

Economic significance. U:p to a certain age Poplars display also on the seaboard
a much higher growth rate than any of the native and foreign coniferous or broad-
leaved species, and they survive relatively well. When there occurs the need for a
rapid establishment of the stands, groups and alleys of forest tree species, Poplars
are irreplaceable, especiallv on fresh sites and deeper soils. This task can be solved
more completely by raising two-storeyed stands of Poplar overstory and Pine understory.
Such a consociation of Poplars and Pines is sometimes very rational and
economically justified. On the best soils of fields Poplar growing can be used for
wood production, and on less good sites for the »production of shade«, for windbreaks,
soil stabilization and protection of harbours. The Poplar planting stock can successfully
be raised also in seaboard nurseries. When establishing the tourist forests,
wide-spread crowns of Poplars (Which also can be expanded by cutting off the tree
tops) and of Pinus brutia make it possible to produce a sufficiently dense shade with
about 500 plants per ha. after 7—10 years of age. Already in the first year of tourist
exploitation camping forests can pay off their cost price. Such a yield is many times
higher than the annual yield given by the forest exploitation of a grown-up forest.