A simplified method for forest water storage capacity measurement

A simplification of direct methods to measure canopy storage capacity is presented. It is based on measurement of water retained by vegetal entities (needles, stems and branches) and the up-scaling of these measurements using the determination of the surface of canopy elements from common vertical photographs taken from the ground. The specific water retention capacities of Pinus sylvestris pine needles ranged between 0.104 and 0.043 mm, depending on the simulation of still air or windy conditions. These values are low when compared with the specific water retention capacity of branches and stems, 0.62 mm. The water retained in branches and stems, therefore, plays a key role in rainfall interception. The canopy storage results obtained are consistent with the spatial distribution of throughfall measured in five experimental plots located in a heterogeneous 40-year-old Pinus sylvestris stand in a Mediterranean mountain area of the South Eastern Pyrenees (Catalonia, Spain), and are 30% higher than the values estimated through indirect methods.