Biomass Growth Prediction And Spatialization Of Larix Olgensis Based On 3-PG Model

To predict the spatial distribution of Larix olgensis biomass based on 3-PG model and provide the basis for studying 3-PG space model.Determination of physiological parameters of 3-PG model by plot scale,the data used in this article was obtained from 5 plots of experimental forests observed for 28 years and 24 plots with 3 re-measurements.The stem density,DBH(diameter at breast height),volume and biomass of each plot were calculated using the biomass calculation formulas for each component(leaf,stem,and root).The physiological parameters of the 3-PG model of Larix olgensis were determined,using the parameters calibrated by density experiment forest,soil survey data and meteorological data,combined with parameter calibration,iterative fitting and sensitivity analysis.Then the biomass growth of 24 plots was predicted using the parameterized 3-PG model.The regression model and the relevant statistics were compared between the predicted data and the plot data.The results were evaluated by calculating coefficient of determination(R2),mean error(ME),mean absolute error(MAE),mean relative error(MRE),and mean square error(RMSE).Sensitivity analysis was performed on the results of canopy quantum efficiency(alpha)and minimum biomass fraction of NPP to roots(pRn).Then,the biomass growth of Larix olgensis was calculated when the fertility ratings(FR)was 0.2,0.4 and 0:6.Based on the determined model physiological parameters,combined with spatialized climate and soil data,quantify the monthly growth effects of temperature,frost and vapor pressure deficit on Larix olgensis,the distribution of stem,root,above ground,and total biomiss in 2018 in Mengjiagang forest farm were predicted.Research indicates:(1)The comparison of predicted data and measured data indicated that the prediction results were reliable and the coefficient of determination(R2)was above 0.77.Except for the foliage and stem biomass ratio with value of 25.6%,the absolute value of MRE of all other indicators was within 10.97%.(2)The sensitivity analysis showed that alpha and pRn were the key parameters of the model with high sensitivities.(3)The predicted biomass growth in this study was consistent with the growth mechanism of plants under different FR.At the same time,the biomass of larch increased with the growth of FR.(4)Larix olgensis was most affected by the difference of water vapor pressure during the growing season,and the frost was the most affected during the non-growth season.(5)Based on the parameter calibration by field data,the 3-PG model could simulate the biomass growth of Larix olgensis well.Combined with spatialized data,the model enabled spatialized prediction of biomass changes.