Cork influenced by a specific water regime—macro and microstructure characterization: the first approach

Abstract

Cork is the most valuable non-wood product of the cork oak (Quercus suber L.). However, the cork oak sector may be at risk due to climatic and economic pressures on cork oak forests, affecting both the quantity and technological quality of products. At some sites, irrigation may present a solution for stimulating cork growth and thereby increasing production. This study presents an initial approach to characterizing cork grown in a forest stand associated with a specific water regime, by comparing cork growth on two plots—irrigated and a traditional rainfed—over an initial five-year period. Samples of cork tissue were analysed and several parameters were set: cell area, diameter, cell-wall thickness, number of cells, porosity, growth, and density. Irrigation plot samples showed on average: 25.83 ± 3.74 mm thickness, 5.17 ± 1.49 mm cork-ring width, 0.149 ± 0.041 g.cm−3 density, 13 ± 3.4% porosity coefficient in the tangential plane, 407.58 ± 268.22 µm2 cell area in the tangential plane and 887.80 ± 449.14 µm2 in the transverse plane, a total number of cells of 1232 ± 147 per mm2, and 1.03 ± 0.30 µm cell-wall thickness; whereas traditional rainfed plot samples presented: 21.33 ± 5.48 mm thickness, 3.08 ± 1.44 mm cork-ring width, 0.167 ± 0.068 g.cm−3 density, 10 ± 3.5% porosity coefficient in the tangential plane, 304.31 ± 205.83 µm2 cell area in the tangential plane and 752.45 ± 398.94 µm2 in the transverse plane, a total number of cells of 1481 ± 153 per mm2, and 1.204 ± 0.327 µm cell-wall thickness. As regards irrigation, two parameters, ring width and porosity coefficient, proved to be statistically significant, in contrast to density.