Spatial and Temporal Variability of Throughfall under a Natural Fagus orientalis Stand in the Hyrcanian Forests, North of Iran

The spatial and temporal heterogeneity of throughfall (TF) have important ecological impacts in forest ecosystems. The aim of this study was to quantify spatio-temporal variability of TF and to evaluate the effects of canopy traits and gross rainfall (GR) characteristics on TF at the event scale. Event-based measurements were carried out from September 2015 to October 2017 during the leafed-out period in a natural uneven-aged beech (Fagus orientalis L.) stand located in the Hyrcanian forest of Iran. Leaf area index (LAI) and canopy openness of the stand were 6 m2 m-2 and 6.2%, respectively. Tree density in the studied plot was 188 tree ha-1 and the basal area (BA) was 51 m2 ha-1. During the measurement period, 25 rainfall events occurred (total rainfall= 784.8 mm). We observed variability of TF under the beech trees canopy in different GR classes (< 15, 15-30, 30-50 and > 50 mm). Increases in rainfall depth and intensity were associated with an increase in TF depth and decrease in TF variability. We found that rainfall depth along with the intensity were the most influential factors on the TF depth, spatial variability as well as time stability. Knowledge of the spatial persistence and variability of TF would help managers to optimize the management of these stands in terms of soil water and nutrition availability.