Application of Gash analytical model and parameterized Fan model to estimate canopy interception of a Chinese red pine forest

Loss of precipitation by canopy interception constitutes a substantial portion of the water budget in a forested ecosystem, and accurate models to simulate canopy interception are critical for effective management of forest water resources. We modeled the canopy interception of an evergreen Chinese red pine (Pinus tabulaeformis) forest using the Gash analytical model and the parameterized empirical Fan model and compared the modeled results with directly measured data. Based on 100 rainfall events between 2006 and 2008, the estimated canopy interception ratio was 35.9 % from the Gash model and 53.6 % from the Fan model, compared to 33.2 % from the direct measurement. The differences between measured and modeled values from the Gash model ranged from -0.3 to +7.1 % for different rainfall amounts and from +1.9 to +3.2 % for different years. The Fan model satisfactorily simulated interception for large rainfall events (> 50 mm) with differences from -3.4 to +1.3 %, but substantially overestimated interception loss for smaller rainfall events (+21.2 to +37.2 %). The Gash analytical model adequately simulated the canopy interception of Chinese red pine forest. The parameterized Fan model compared favorably to the Gash model in simplicity but not in precision. The Fan model required only incidental precipitation data to run after parameterization, but substantial improvement in modeling precision is needed before it can be used for this forest.