Canopy interception loss in a pure oriental beech (Fagus orientalis Lipsky) stand during the summer season

At forest ecosystems, gross rainfall (GR) is partitioned into throughfall (TF), stemflow (SF) and results in canopy interception loss (CIL). In the present research, CIL, which is considered a major component of the water balance, was measured at the midland of the central Caspian forests, Kheyrud forest research station of University of Tehran. Measurements were carried out in a sample plot of pure oriental beech (Fagus orientalis Lipsky) stand with an area of 5625 m2. GR was collected using three manual collectors in an open area approximately 160 m apart from the study plot. Thirty six TF manual gauges were randomly placed beneath the beech canopies and SF was collected from six beech trees with different diameters by means of the spiral type SF collection collars installed at diameter at breast height. GR, TF and SF were collected on an event basis using a graduated cylinder during the summer season of 2008. The amount of cumulative GR depth of 19 events was 206.8 mm allocated to TF, SF and CIL, 135.5, 4.2 and 67.1 mm, respectively. At the event scale, the mean values of TF, SF and CIL were accounted 64.7, 1.6 and 33.7% of GR, respectively. Regression analysis suggested a strong positive relationship between CIL and GR. There was also observed a fairly weak negative relationship between CIL/GR and GR. We concluded that CIL contributes a remarkable amount of incident rainfall in the pure oriental beech forest of the study site and therefore should be considered in assessment of water balance.