Effects of thinning, N fertilization and legume seeding on the understory production of a Pinus brutia plantation in northern Greece

The main purpose of this research was to study the combined effect of thinning of brutia pine (Pinus brutia Ten.) plantations and legume seeding or nitrogen fertilization on productivity of the understory vegetation. The experimental area was located at the Forest Research Institute at Loutra Thermis near Thessaloniki. Three spacings were tested: 2×4, 3×6 and 4×8 m. or 1240, 550 and 310 trees per hectare, respectively, in two replications. In each spacing, three understorey treatments were applied: a) seeding of Trifolium subterraneum and Medicago lupulina, b) nitrogen fertilizer and c) control. Measurements of herbage production of the understory were taken for two years. Open stands had greater biomass of the understory vegetation, than the dense ones. The highest biomass was found in the N fertilized treatment. Moisture had an important role at biomass production in both years.