基于SCOPE模型的樟子松人工林日光诱导叶绿素荧光及初级生产力模拟与评估

Simulation and Assessment of Sun-induced Chlorophyll Fluorescence and Gross Primary Production in Pinus sylvestris var.mongolica Plantation Based on the SCOPE

【目的】检验SCOPE(Soil Canopy Observation of Photosynthesis and Energy fluxes)模型用于模拟樟子松人工林的日光诱导叶绿素荧光(sun-induced chlorophyll fluorescence,SIF)和植被总初级生产力(gross primary productivity,GPP)动态变化的可能性。【方法】对科尔沁沙地南缘樟子松人工林,基于样地SIF、GPP及气象协同观测数据,利用SCOPE模型模拟SIF与GPP的日变化与季节变化,评估了SCOPE模型在典型晴天、典型多云日、整个观测期的模拟效果。【结果】结果显示,利用气象观测数据及冠层参数(入射短波辐射、气温、大气实际水汽压、CO_(2)浓度及叶面积指数),可驱动SCOPE模型模拟樟子松人工林的SIF与GPP。典型晴天日与多云日的SIF模拟值和实测值的R^(2)分别为0.42与0.52,RMSE分别为0.19与0.18 W·m^(-2)·μm^(-1)·sr^(-1);GPP模拟值和观测值的R^(2)分别为0.78与0.89,RMSE分别为1.87与2.57μmol·m^(-2)·s^(-1)。在季节尺度上,SIF和GPP模拟值和观测值的R^(2)分别为0.50、0.72,RMSE分别为0.19 W·m^(-2)·μm^(-1)·sr^(-1)和2.64μmol·m^(-2)·s^(-1)。在整个观测期,多云日的SIF(R^(2)=0.31,RMSE=0.22 W·m^(-2)·μm^(-1)·sr^(-1))与GPP(R^(2)=0.80,RMSE=2.42μmol·m^(-2)·s^(-1))的模拟效果优于晴天日(SIF:R^(2)=0.30,RMSE=0.26 W·m^(-2)·μm^(-1)·sr^(-1),GPP:R^(2)=0.64,RMSE=3.64μmol·m^(-2)·s^(-1))。SIF模拟值总体高于观测值,当SIF强度较低时易对SIF高估,反之则易低估。GPP的模拟精度较高,模型对较低与较高GPP有所低估,对中间值有所高估。【结论】SCOPE模型可用于日尺度与季节尺度的SIF与GPP模拟,且多云日的模拟精度更高。SCOPE模型对樟子松人工林的GPP模拟结果优于SIF,推测SIF模拟精度较低的原因可能是模型对SIF的模拟是基于阔叶植物的辐射传输过程。未来应发展针对针叶植物的SIF辐射传输模型,为针叶林的辐射传输与荧光遥感监测提供模型基础。

【Objective】To investigate the possibility of using SCOPE(Soil Canopy Observation of Photosynthesis and Energy fluxes)model to simulate the dynamic changes of sun-induced chlorophyll fluorescence(SIF)and gross primary productivity(GPP)in Pinus sylvestris var.mongolica plantation.【Methods】This study focused on a P.sylvestris var.mongolica plantation on the southern edge of the Horqin Sandy Land.Using coordinated observations SIF,GPP,and meteorological data,we simulated the diurnal and seasonal variations of SIF and GPP in the P.sylvestris var.mongolica plantation based on the SCOPE model.The model's performance was evaluated for a typical sunny day,a typical cloudy day,and the entire observation period.【Results】The results showed that using meteorological observation data and canopy parameters(incoming shortwave radiation,air temperature,atmospheric vapor pressure,CO_(2) concentration,and leaf area index),the SCOPE model can be driven to simulate the SIF and GPP in the P.sylvestris var.mongolica plantation.The R^(2) values for SIF simulations on a typical sunny and cloudy day were 0.42 and 0.52,with RMSE values of 0.19 and 0.18 W·m^(-2)·μm^(-1)·sr^(-1),respectively.The R^(2) values for GPP simulations on these days were 0.78 and 0.89,with RMSE values of 1.87 and 2.57μmol·m^(-2)·s^(-1),respectively.At the seasonal scale,the R^(2) values for SIF and GPP were 0.50 and 0.72,with RMSE values of 0.19 W·m^(-2)·μm^(-1)·sr^(-1) and 2.64μmol·m^(-2)·s^(-1),respectively.Throughout the observation period,the simulations of SIF(R^(2)=0.31,RMSE=0.22 W·m^(-2)·μm^(-1)·sr^(-1))and GPP(R^(2)=0.80,RMSE=2.42μmol·m^(-2)·s^(-1))on cloudy days were better than those on sunny days(SIF:R^(2)=0.30,RMSE=0.26 W·m^(-2)·μm^(-1)·sr^(-1);GPP:R^(2)=0.64,RMSE=3.64μmol·m^(-2)·s^(-1)).Overall,the simulated SIF values were higher than the observed values,and the model tended to overestimate SIF at low intensities and underestimate it at high intensities.While GPP simulations demonstrated high accuracy,with slight underestimation for both low and high GPP and slight overestimation for intermediate values.【Conclusion】The SCOPE model is suitable for simulating daily and seasonal variations of SIF and GPP,with higher accuracy in simulations on cloudy days.The model's performance in simulating GPP in the P.sylvestris var.mongolica plantation is better than its performance in simulating SIF.The lower accuracy of SIF simulations is speculated to be due to the model being based on the radiation transfer process of broadleaf plants.Future efforts should focus on developing SIF radiative transfer models specifically for needle forests to establish a modeling foundation for the radiative transfer and fluorescence remote sensing monitoring of needle forests.