Soil Gypsum and Increased Penetration Resistance Restrict Early Growth of Quercus ilex Plantations

The objective of this study is to analyze the influence of soil characteristics on the early growth of Quercus ilex in order to support planning of future plantations. We studied 31 200-m2-plots on 10-year-old plantations in fields that were set-aside from agriculture in a semiarid area in northeast Spain. Tree height and diameter, slope, geomorphic position, and various soil characteristics were measured. On north-facing slopes height and diameter of trees were significantly greater (150?200%) in soils without gypsum than in soils with gypsum. In soils without gypsum, increased penetration resistance in the upper 50 cm of soil (from 4.4 MPa to more than 7.0 MPa) decreased dominant height of trees to 40% of the maximum. While plantations of Quercus ilex can achieve satisfactory growth in semiarid conditions, detailed field studies of soil and site conditions are required for successful plantation establishment. The actual need for soil preparation treatments should be carefully evaluated considering species response and soil penetration resistance.