基于Gash模型对华北落叶松和油松人工林冠层截留的模拟

Canopy interception simulation of Larix principis-rupprechtii and Pinus tabulaeformis forests in northern China based on Gash model

为验证Gash模型对华北落叶松和油松人工林林冠截留模拟的适用性,分别实测了3块落叶松和油松人工林样地的大气降雨、穿透雨、树干径流以及同步的相关气象环境资料,利用Gash模型,对6块样地的林冠截留分别进行模拟。结果表明:落叶松人工林和油松人工林林冠枝叶持水能力分别为(1.72±0.48)mm和(2.60±0.23)mm,树干持水能力分别为(1.16±0.89)mm和(1.46±0.65)mm,使林冠饱和的平均降雨量分别为(2.50±0.53)mm和(2.98±0.63)mm;由Penman-Monteith公式得到各样地降雨时,饱和林冠的蒸发速率为(1.14×10-1~1.48×10-1)mm/h;Gash模型对各样地截留和蒸发模拟值与实测值的相对误差在0.07%~7.51%之内,模拟值与实测值的方差与均值无显著差异(P>0.1),且相关性很强(R=0.99,P<0.01)。Gash模型能够很好模拟该地区林冠截留特征,为该地区水文循环和水土保持工作提供更为精确的数值模拟和理论依据。

[Background] The interception process of forest canopy is a key of forest hydrology,which directly affects the prediction of hydrological cycle and forest soil and water conservation function. There are many influencing factors which are researched by scholars,and then,how to find a quick and accurate method has become a hot topic recently. One of these methods used widely is Gash model,and this paper verifies the applicability of Gash analytical model in Larix principis-rupprechtii and Pinus tabulaeformis forests in northern China. [Methods] Rainfall outside of stands,throughfall and stemflow of 3 L. principis-rupprechtii forest plots and 3 P. tabulaeformis forests plots in Mulan Forestry ManagementBureau in Weichang County of Hebei Province during trees growing season of 2015 were measured and canopy interception was simulated combined with environmental and meteorological data. The core of the research methodology was to determine the accuracy of the Gash model parameters, including air temperature,temperature of soil depth,relative humidity,saturation vapor pressure,vapor pressure,open wind speed,air pressure,forest area net radiation flux,soil heat flux,psychometric constant and slope of the saturated vapor pressure curve at the temperature of air. In the process of simulation,regression method was used to determine canopy parameters and difference between intercepts of curves,which showed the relationship between stemflow and rainfall outside of stands and water storage capacity of leaves and branches was used as water storage capacity of tree trunks. [Results]Canopy water storage capacity of planted L. principis-rupprechtii forests was（ 1. 72 ± 0. 48） mm for leaves and branches and（ 1. 16 ± 0. 89） mm for tree trunks. Canopy water storage capacity of planted P. tabulaeformis forest was（ 2. 60 ± 0. 23） mm for leaves and branches and（ 1. 46 ± 0. 65） mm for tree trunks. The amounts of rainfall needed to saturate the canopy of L. principis-rupprechtii forests and P. tabulaeformis forest were（ 2. 50 ± 0. 53） mm and（ 2. 98 ± 0. 63） mm respectively. The scope of evaporation rate of plots was from（ 1. 14 × 10-1 to 1. 42 × 10-1） mm/h in rainfall periods. The total values of canopy were 26. 9,38. 34 and 38. 29 mm,respectively,and the simulated values were 27. 95,41. 22,and 38. 32 mm,the relative error range was 0. 07%-7. 51%. The simulated values of canopy total were 54. 37,55. 62,and 33. 03 mm,the simulated values were 51. 37,52. 69, and 35. 23 mm, and the relative error ranged in5. 26%-6. 66%. [Conclusions] There were no significant difference of variances and means between simulated value and measured value（ P 0. 1） while the correlation of them was high（ R = 0. 99,P 0. 01）,indicating the fine simulating effect of Gash analytic model. This study would improve the measurement accuracy of forest canopy interception,rainfall and stemflow of two main tree species,and provide more accurate numerical simulation and theoretical basis for hydrological cycle and soil and water conservation in this area.