Fog precipitation and rainfall interception in a pure natural oriental beech (Fagus orientalis L.) stand in the Hyrcanian Forests, North of Iran

The Hyrcanian forests are typical deciduous broadleaf forests characterized by an important role in providing moisture to vegetation by fog precipitation (FP). The importance of FP on vegetated surfaces as a source of moisture has been acknowledged for a long time. The aim of this study was to quantify FP and water interception in a natural oriental beech (Fagus orientalis) stand in the Hyrcanian forests. Event-based measurements were carried out on 2016 and 2017 during the full leaf period. The rain-collectors used for measuring throughfall and gross-rainfall were n=122 and 10, respectively. During the measurement period 22 rainfall events occurred (total rainfall = 648 mm). The amount of throughfall and interception were 99.4% and 0.2%, respectively. Due to considerable amount of fog (3.5%) throughfall was found to be greater than 100% of GR in 14 rainfall event with negative interception (total=-22.6 mm) and 8 rainfall event were found with positive interception (total=25.5 mm). Maximum of FP was measured in September of 2016. Results indicated the role of FP on increasing of throughfall and decreasing interception. Because of the various bioclimatic condition in the Hyrcanian forests, interception is extremely different in oriental beech stands. Then, Fagus orientalis would have significant influence on the local hydrological processes of the mountain forests of Hyrcanian and its water demand would supply by FP in dry seasons. So, the maintenance of beech stands would help to increase of FP by capturing of fog droplets which would provide groundwater and water demand supply of these ecosystems.