Fitting the revised Gash analytical model of rainfall interception to Mongolian Scots pines in Mu Us Sandy Land, China

A rainfall interception experiment was completed for Pinus sylvestris var. mongolica plots with stand densities ranging from 925 to 2700 plants ha(-1) in Mu Us Sandy Land, China from June to September 2013. The revised Gash analytical model was then applied to the canopy interception of the Mongolian Scots pine plantations. During the experimental process, the incident rainfall (P), throughfall (T-f), and stemflow events (S-f) were collected and measured, and meteorological data were simultaneously obtained on site. The Penman-Monteith equation and Gash regression method were used to estimate the evaporation rate (E) from the saturated canopy. The classical revised Gash calculation procedure and Leyton-constraint method were applied to obtain the canopy storage capacity (S). Parameters such as E, S, stemflow partitioning coefficient (p(t)), and trunk storage capacity (S-t) were scaled to the canopy cover fraction per unit area: E-c, S-c, p(tc), and S-tc in the revised Gash analytical model, which was also used in the simulation of the rainall interception (T-f, S-f, and I). The proportions of the measured T-f, S-f, and I accounted for 62.82%, 1.13%, and 36.05% of P, respectively. The ratios of E-c to rainfall intensity (R), S-c, p(tc), and S-tc were 0.0260 (0.0458), 1.210 mm (2.006 mm), 0.0630, and 0.0486 mm, respectively, during the experimental period. The analytical model with E-c and S-c equal to 0.182 (Penman-Monteith equation) and 1.210 mm (classical revised Gash calculation procedure) accurately simulated the canopy interception of the Mongolian Scots pine plantations, and the canopy interception variation in the analytical model was sensitive to P, S-c, S-tc, c, E-c, and R, but was relatively insensitive to p(tc).