Performance di recenti imboschimenti con quercia da sughero in ex-coltivi

Growth performance of cork oak plantations recently established on farmlands in Sardinia, Italy. Recently,
significant forestry activities have taken place in Sardinia thanks to EU Regulation 2080/92 funds. Some 80%
of the afforestated surface has been planted with holm oak and cork oak. The latter also characterizes 89% of
the reforestation area. Given the funding source, plantations have been established on farmlands. Growth
performances of these recent cork oak stands have been quantitatively evaluated and compared with the performances
of two experimental plots. In Gallura (north-east of Sardinia), that is the traditional cork production
area and still is economically the most important cork district of the island, these new cork oak plantations
have an average size of 28 ha. They have been established on lands that, before plantation, were either
pastures (30%) or arable lands (70%). Plantation failures are limited to 8.8% of the total (in term of mass) and
seem independent of environmental factors or plantations species composition (conifers have been frequently
used as secondary species). Average growth of the stem, measured above cork at collar height, is in the
range 4 to 8mm/year with a mean value of 5.5mm/year. No correlation appears with either environmental
conditions or species composition of the plantations. In the first experimental plot, soil management practices
(natural vegetation removal vs its cutting and mulching) does not differentiate young plants growth
trends. In the control subplots (no removal) stem collar diameter is 20% smaller. Localized manual hoeing
around trunk base increased the diameters by 13% but reduced cork thickness by 21%. The second experimental
plot allows comparisons among 27 Mediterranean proveniences of cork oak. The trial exhibits reduced
genetic influence: diameters and heights growth are significantly different only among extreme groups.
In conclusion, reduced growth performances of the plantations established in farmlands is due, to some extent,
to the limitations inherent with private land management (constrained to costs minimization) and, on
the other hand, to the generally very limited thickness of Gallura soils. Demand for good quality commercial
cork is steadily raising. To sustain the request, in the short term, it would be necessary to extend financial
support for plantations care, from 5 to 10 years, or even up to the first stripping (virgin cork).