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Abstract.The original Gash analytical model and the sparse Gash's model were combined to simulate rainfall interception losses from the top-and sub-canopy layers in Shaoshan evergreen forest located in central-south China in 2003. The total estimated interception loss from the two canopy layers was 334.1 mm with an overestimation of 39.8 mm or 13.5% of the total measured interception (294.3 mm). The simulated interception losses of the top-and sub-canopy suggested that the simulated interception losses in the stages of "during storms" and "after storms" were in good agreement with the published ones. Both the original Gash model and the sparse model overestimated the interception losses, but the sparse model gave more accurate estimates than the original Gash model.

The effects of Weak acids (WA) on the canopy leaching and uptake processes are evaluated by comparing the leached base cations or the absorbed protons while including and excluding WA, e.g. the WA-included method and the WA-excluded method. The seasonal WA throughfall flux is even larger than twice the bulk precipitation flux except summer, which not only partly agrees with the conclusion that the total deposition of WA equals twice the bulk or dry deposition flux in European Intensive Monitoring plots (level II), but also indicates the significant canopy leaching of WA in Shaoshan forest. The seasonal canopy leaching of base cations in association with WA accounts for 6-30% of the total base cations in throughfall, with an annual mean of 23%, which is slightly higher than the 15% at the Speulder forest in The Netherlands. The canopy exchange capacity of H + to NH + 4 is closed to 6.0 while neglecting the WA exchange, which probably supports the assumption that the exchange capacity of H + is six times that of NH + 4 . Simultaneously, we suggest that the WA is competitive to a certain extent with protons to leach base cations of plant tissues during the canopy exchange processes.