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Scientia Silvae Sinicae ›› 2018, Vol. 54 ›› Issue (8): 1-12.doi: 10.11707/j.1001-7488.20180801

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Simulation of CO2 Flux and Controlling Factors in Moso Bamboo Forest Using Random Forest Algorithm

Chen Liang, Zhou Guomo, Du Huaqiang, Liu Yuli, Mao Fangjie, Xu Xiaojun, Li Xuejian, Cui Lu, Li Yangguang, Zhu Di   

  1. Zhejiang Province Key Laboratory of Carbon Cycling in Forest Ecosystems and Carbon Sequestration School of Environmental and Resources Science, Zhejiang A & F University Lin'an 311300
  • Received:2016-09-25 Revised:2018-06-14 Online:2018-08-25 Published:2018-08-18

Abstract: [Objective]This paper aims to investigate the influence of environmental factors on the CO2 flux of moso bamboo forest and to provide technical and theoretical support for carbon cycle simulation of typical subtropical forests.[Method]The CO2 flux of moso bamboo forest was simulated using random forest model based on eddy covariance flux data collected from 2011 to 2014, and the accuracy of model was evaluated using the mean squared root error (RMSE), the coefficient of determination (R2) and the lin's concordance correlation coefficient (LCCC). The contribution of each environmental factor to CO2 flux was analyzed based on importance score calculated using the random forest algorithm.[Result]The random forest model accuracy of testing data (R2=0.845 5, RMSE=0.437 7 mg·m-2s-1; LCCC=0.914 1) was lower than that of training data (R2=0.961 5; RMSE=0.005 4 mg·m-2s-1; LCCC=0.980 1), because the model was hard to accurately depict this kind of short, intense interference to CO2 flux during the extreme drought occurred in July and August in 2013. The accuracy was stable for different training data based on 10-fold cross-validation method and the parameters of the model were appropriately set. The error in the model was mainly caused by the input data. The importance score of each environmental factor was decreased in the following order:PAR (63.332) > TS (29.932) > RH (25.839) > TA (25.581) > CCO2 (25.095) > VPD (24.123) > WS(23.504) > AE (19.323) > QS(18.502). PAR was the dominant factor for explaining the change of CO2 flux in moso bamboo forest. Based on the significance test, monthly CO2 flux was significantly influenced by PAR, TS, and VPD (P<0.05).[Conclusion]The random forest model can simulate the CO2 flux of moso bamboo with a high accuracy; PAR, TS, and VPD remarkably affect the CO2 flux at the 0.05 significance level, according to their importance score, indicating that PAR, TS, and VPD play an important role in controlling the CO2 flux of moso bamboo forest at a monthly time scale.

Key words: moso bamboo forest, eddy covariance, flux tower, CO2 flux, random forest model, environmental factors, Anji County

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