泰山麻栎人工林降雨截留特征及修正的Gash模型模拟

Canopy interception characteristics of Quercus acutissima plantation forest in Mountain Tai,China and its estimation by the revised Gash model

林冠截留可以调控降雨再分配,对研究森林生态系统的水分平衡和养分循环具有重要意义。通过对山东泰山麻栎人工林2018年生长季的降雨截留进行分析发现,观测期内以中雨和小雨为主,占总降雨场次的64%;林冠截留量为152.24 mm,树干径流量为10.06 mm,穿透雨量为678.8 mm,分别占林外降雨量的18.10%、1.19%和80.70%。利用修正的Gash模型对其进行模拟,结果显示在观测期内,截留过程中的蒸发量和林冠达到饱和状态的截留量占林冠截留总量的大部分,且模拟的林冠截留、穿透雨和树干径流与实测值的误差分别为6%,2%和9%,表明修正的Gash模型能够很好地模拟林冠对降雨的再分配过程,其适用于模拟泰山麻栎人工林的林冠截留。敏感度分析表明:平均雨强(R)、平均蒸发速率(E)、林冠饱和持水量(S)的变化对修正的Gash模型的影响很明显,而郁闭度(c)、树干持水能力(St)和树干径流系数(Pt)的变化对本模型影响不明显。

[Background]Canopy interception can influence the spatial distribution and quantity of precipitation,which is very important for studying the water balance and nutrient cycling of forest ecosystems.[Methods]In a Quercus acutissima plantation forest in Mount Tai,China,25 precipitation events were quantified and analyzed during the 2018 growing season.The revised Gash model was used to estimate the canopy interception and precipitation partitioning,and the suitability of the revised Gash model for estimating the canopy interception and redistribution of precipitation was evaluated.[Results]Precipitation outside the forest was 841.10 mm,of which 152.24 mm(18.10%),10.06 mm(1.19%)and 678.80 mm(80.70%)were canopy interception,stemflow and throughfall,respectively.During the observation period,precipitation events were mainly moderate or light rain,accounting for 64%of the gross precipitation.The results of the precipitation partitioning model estimation using the revised Gash model showed that the majority of canopy interception was the amount of evaporation during the precipitation process and the amount of canopy interception during the canopy humidification stage.The errors between the estimated and observed values for canopy interception,throughfall and stemflow were 6%,2%,and 9%,respectively.[Conculsions]This proves that the revised Gash model estimation for canopy interception and redistribution of precipitation is highly reliable and that the revised Gash model is suitable for estimating the canopy interception of the Q.acutissima plantation forest in Mount Tai,China.The sensitivity analysis indicates that the revised Gash model is strongly sensitive to changes of parameters in the mean precipitation intensity(R),mean evaporation rate(E)and canopy storage capacity(S);however,changes in trunk storage capacity(St),canopy density(c)and the coefficient of rainwater diverted to stemflow(Pt)have little effect on the revised Gash Model.