Development of Quercus ilex plantations is related to soil phosphorus availability on shallow calcareous soils

The objective of this study is to analyse the performance of Quercus ilex plantations established under semiarid conditions on different soils formed on calcareous and gypsiferous parent material. We studied eighteen 300 m2 plots in which 1 year-old seedlings had been planted after subsoiling on the contour. Plots were stratified according to aspect (north and south) and previous land use/parent material: shrubland on limestone (LM-SH), shrubland on gypsum rock (GY-SH), and cropland on colluvium (CO-AG). Soils developed on limestone and colluvium had average rooting depths of 27 and 37 cm, respectively, and mean concentrations of active lime and phosphorus (P) of 130 and 190 mg g−1 and 10 and 19 mg kg−1, respectively. Soils developed on gypsum had a mean rooting depth of 26 cm, and a mean gypsum concentration of 73 %. Height and diameter of trees varied significantly according to parent material/previous land use but not to slope aspect. Mean height and diameter of trees were significantly higher in CO-AG plots than in LM-SH and GY-SH plots. Soil P and depth were the main variables explaining differences in dominant height across all 18 plots. In CO-AG plots mean height was negatively related to soil pH but positively related to soil P concentration. In LM-SH plots, mean diameter and height were negatively related to active lime concentration. This study suggests that soil P is a major determinant of holm oak performance in shallow calcareous soils and highlights the importance of conducting detailed soil studies in order to assess the viability of plantations with this species.