Needle-leaved trees impacts on rainfall interception and canopy storage capacity in an arid environment

In semiarid and arid areas, it is important to understand the amount of rainfall reaching the ground in order to develop effective water plan strategies for the selection of the tree species for afforestation goals. We measured the rainfall interception and canopy storage capacity of individual trees of Pinus eldarica and Cupressus arizonica growing in an afforested Park located in an arid region of Iran. Correlations between percent relative interception and gross rainfall, mean daily wind speed, mean daily air temperature, and mean daily relative humidity were examined both for the wet and dry seasons. Canopy storage capacity was estimated by indirect methods: the Pereira, mean, minimum, and Gash and Morton. The cumulative mean values of percent relative interception and gross rainfall for P. eldarica and C. arizonica trees averaged 66 and 53 %, respectively. Combining meteorological parameters with rainfall depth only slightly improved the correlation with the percent of gross rainfall lost to interception loss in the dry season for P. eldarica (from 0.87 to 0.90) and C. arizonica (from 0.90 to 0.92). For P. eldarica, the mean estimate of canopy storage capacity was 1.31 versus 1.00 mm in C. arizonica trees. Because the storms in this region are small, the large canopy water storage of P. eldarica will result in greater interception losses relative to C. arizonica. Therefore, afforestation efforts would be better served planting C. arizonica over P. eldarica, if maximizing water inputs is a main management goal.