Tree-based estimation of canopy water storage capacity and direct throughfall coefficient of Cupressus arizonica Green.

Abstract

The aim of this study was to estimate the individual tree-based 1) canopy water storage capacity (S), 2) ratio of mean evaporation rate from the wet canopy to the mean rainfall intensity () by the Pereira method, and 3) direct throughfall coefficient (p) for Cupressus arizonica trees. The trees wereafforested in the Chitgar forest park in Tehran which is classified as a semiarid region. Measurements were carried out from February 2011 to February 2012. To measure the gross rainfall (GR), six rain-gauges were installed in an open space adjacent to the trees. Throughfall (TF) was measured using a number of twenty rain-gauges located under the crown of five individual trees. Rainfall interception (I) was calculated as the difference between GR and TF. During the measurement period, 55 rainfall events were recorded with a cumulative depth of 234 mm. The C. arizonica trees intercepted 21.8% and 32.1% of the incident rainfall on cumulative-based and event-based (each GR) manner, respectively. Positive and negative power correlations were observed between I and GR (r = 0.89)as well as between(I: GR) % and GR (r = 0.69) for the mean value of five individual trees. Mean values of S,, and p were estimated as 0.38 mm, 0.14, and 0.46, respectively. I and its elements (), S, and p as well as transpiration of trees are, therefore concluded as necessary parameters to be considered when selecting suitable species for afforestation projects in the arid and semiarid zone. In addition and as a key parameter for calculating I, S can be optimally estimated by Pereira method which is exclusively proposed for tree-based measurements.

Keywords

• canopy water storage capacity
• Cupressus arizonica
• Direct throughfall coefficient
• Pereira method
• rainfall interception
• semiarid climate