6.2.1 Site

This study was carried out in February 2003 in two Pinus radiata D. Don planta­tions, aged 13 and 15 years (Table 6.1), in the province of Lugo (northwest Spain) (43° 13′ N, 7°39′ W and 43°07′ N, 749′ W respectively). Shrubs predominated in the understory vegetation (Calluna vulgaris, Cytisus scoparius, Erica umbellata, Halimium lasianthum subsp. alyssoides, Ulex europaeus, etc.).

The average annual precipitation during the study period (2003-2006) was 1,135 mm, and the average monthly minimum and maximum temperatures were

15.1 and 5.0°C, respectively.

6.2.2 Soil

The plots (Table 6.2) were established on different soils developed on migmatites and lutites both classified as Humic Umbrisol (FAO-UNESCO 1998) (Fig. 6.1). The soil in the first plot contained a high percentage of coarse particles (which create a sandy loam soil that favors good drainage), had a low pH (4.7), and had a C-to-N ratio of 19.3. In contrast, the soil in the second plot was of fine texture, with moderate permeability, was low hydraulic conductivity, had a high percentage of organic matter (C-to-N ratio 31.2), and had acid pH (4.8).