The effect of soil compaction at different depths on cork oak seedling growth

Abstract

Soil compaction promoted either by inadequate management (pressure of livestock and machinery) or by soil natural conditions (podzolisation) can influence the growth of cork oak seedlings. We hypothesized that compaction could be related with the lack of natural regeneration and decline on cork oak stands. In this paper, we evaluated the response of cork oak seedlings growth in terms of area and biomass production for above and belowground parts at different compaction depths tested for a sandy-loam soil. This study was done in a greenhouse, with germinated seedlings. Three treatments were applied. One no-compaction treatment (control, C0) and two with a soil compacted layer at 60 cm (C1) and 30 cm depth (C2). The level of compacted layer was 1.37 MPa of mechanical resistance. Results show that tap root length is negatively affected by compaction at 60 and 30 cm depth. Below and aboveground biomass are affected by compaction at 30 cm depth. In addition, the leaf area results demonstrate that compaction is a sensitive factor for this parameter. In this 1-year stage, plants spend more energy in roots production. Due to soil formation and bad management of cork oak stands, soil compaction at depth could be a cause for the observed lack of natural regeneration, affecting the growth at earlier stages and probably for the decline of cork oak populations.