Irrigating Cork Oaks Trees – First Insights on Growth and Stripping

Abstract

Cork oak (Quercus suber L.) trees have a high environmental value already well documented in the literature. Also, its socio-economical value is recognized due to their ability to produce cork, which is renewable every 9 years. However, high cork oak mortality rates are being observed since last decades in all Mediterranean basis. The lack of regeneration and well-structured forest stands with trees of different ages are compromising the cork production in the short term future. Since cork is the most profitable forest product in Portugal, a closer involvement of applied research with producers is important. Our studies regarding irrigation and fertigation application in cork oak trees intend to evaluate different treatments for a faster tree growth, reducing the time until the first cork stripping. Our intention with this presentation is to show the first pointers from irrigated cork oaks with 16 years old (irrigated since plantation). Comparable measurements and parameters will be presented between cork oak growing in irrigated and non-irrigated plots, including some cork formation analysis. Our studies also include cork quality laboratory analysis which are being processed. Irrigated cork oaks annual increment growth is significantly higher than control. Also, some indicators from eco-physiology show the effect of irrigation on transpiration rates of the trees, allowing a continuous growth even during dry seasons. First results are promising regarding tree growth performance leading to a shorter first time stripping period. Non irrigated cork oaks only in their 20’s reach 70 cm at breast height (CAP). Due to their water availability since plantation, 130 monitored irrigated trees of 16 years old presented more than 70 cm of CAP and were stripped for the first time this year. Also, some irrigated adult trees from the same plot were stripped. Continuous structural and functional data were acquired during this process and some results will also be presented.