Interactions between soil gravel content and neighboring vegetation control management in oak seedling establishment success in Mediterranean environments

Restoration of vegetation in Mediterranean areas is limited by several factors, some of which are poorly understood, such as soil stoniness and competition with natural vegetation. This paper analyzes the interaction between weed management treatments (cultivation, herbicide, mulch and tree shelter) and the profile stoniness in Holm oak (Quercus ilex L. sub. ballota (Desf.) Samp.) seedling establishment in Mediterranean areas. Our experimental trials show that profile gravel content is a key factor in seedling survival, in which optimal reforestation sites would be defined by gravel content <5%; transitional sites by 5% ⩽ gravel content ⩽ 15% and excluded sites by gravel content >15%. The soil profile gravel content caused severe water limitations, especially important in the first year after planting, which influenced the effectiveness of neighboring vegetation control techniques for seedling establishment success. This study also confirms the positive effect of competition management techniques on survival. The treatments tested showed an improvement in the survival rate, but not in growth rate, over the control treatment throughout the monitoring period. We have obtained a vegetation response model in which the beneficial effects of competition control on the success of oak seedling establishment are distorted by soil gravel content.

► Interaction between neighboring vegetation control and soil stoniness is related to survival.
► Relationship between vegetation control and water response must be studied using whole soil profiles.
► Optimal reforestation sites would be defined by gravel content of below 5%.
► Forest plantations on agricultural land will require well-informed vegetation control.