Measuring throughfall and interception loss in Horizontal cypress and Turkish pine afforestations and a natural stand of chestnut-leaved oak at Kohmian of Azadshahr, Iran

The amounts of throughfall and interception loss are as significant as habitat suitability regarding to the tree selection for afforestation. Horizontal cypress (Cupressus horizontalis Mill.), Turkish pine (Pinus brutia Ten.), and chestnut-leaved oak (Quercus castaneifolia C.A. Mey.) have been mainly used in afforestation projects in the East of the Hyrcanian region. How these afforestations affect the precipitation components and water balance of the region, however, is obscure. The main objective of this study was to measure throughfall and interception loss of Horizontal cypress and Turkish pine afforestation as well as of a natural stand of chestnut-leaved oak, over a period of 12 months starting from May 2012. One rain gauge and four rain collectors were placed in an open area adjacent to the study area in order to measure precipitation. To measure throughfall, thirty five throughfall collectors were randomly installed under the canopy of each stand. The amount of gross precipitation was 1135 mm over the study period. Throughfall measurements for planted Horizontal cypress and Turkish pine, and for natural stand of chestnut-leaved oak, were 439.4, 642.7, and 614.7 mm, respectively. Interception loss estimated to be about 61%, 43%, and 46% of gross precipitation in the above mentioned species, respectively. The positive and statistically significant relationships were found between throughfall and gross precipitation for the investigated stands, and then were parameterized with the power regression model. The identical procedure was applied as well for interception loss and gross precipitation for the stands. The analysis showed that considerable amounts of gross precipitation were intercepted by the canopy cover of the study stands and subsequently evaporated into the atmosphere. Since the species used for afforestation has significant influences on the amount of water reached to the ground, throughfall and interception loss should be considered in the process of choosing the species.