Effects of thinning, fertilisation and sheep grazing on the understory vegetation of Pinus pinaster plantations
Review articleOpen access
1995/09/01 Full-length article DOI: 10.1016/0378-1127(95)03545-L
Journal: Forest Ecology and Management
AbstractAfforestation with pines is a common practice in Mediterranean countries but the spacing employed is usually too dense to allow the growth of sufficient understory vegetation for profitable livestock grazing. In a 17-year-old Pinus pinaster Aiton plantation, established at a density of 1200 trees ha−1 in a semi-arid mediterranean environment of Macedonia, Greece, three degrees of thinning (control, 50% and 75% of trees removed), two levels of fertilisation (control and 1000 kg ha−1 of NPK fertiliser), and two grazing intensities (control and 0.8 sheep ha−1 year−1) were applied. All stands were seeded with 30 kg ha−1 of Dactylis glomerata L. seed. Measurements included cover and species composition, herbage production and nutrient content of the understory vegetation for three consecutive growing seasons. It was found that thinning and fertilisation significantly increased vegetative cover and herbage production by favouring the establishment of the seeded grass as well as other spontaneous species while a significant interaction also appeared between them. Grazing, however, significantly reduced understory vegetation. Applied nutrients were reduced by thinning and grazing while other nutrients such as Ca, Mg and Na were not affected by any treatment. It is concluded that thinning of dense P. pinaster stands up to 300 trees ha−1 and seeding palatable range grasses substantially improves grazing conditions for sheep. This improvement becomes impressive with NPK fertilisation, which increases herbage production and ameliorates its nutrient content even under fairly dense pine stands.
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