关键词: 地上生物量, 地下生物量, 哑变量, 误差变量, 联立方程组

Abstract: [Objective] Climate change has increased the need of information on amount of forest biomass.The purpose of this study is to develop compatible individual tree biomass and volume equations,providing a quantitative basis on accurate estimation of forest biomass.[Method] Based on the mensuration data of above-and belowground biomass from 301 and 104 destructive sample trees of Masson pine (Pinus massoniana) in southern China,respectively,one-and two-variable systems,which combined aboveground biomass and stem volume equations with belowground biomass equation,and ensured them compatible with biomass conversion factor and root-to-shoot ratio equations,were developed using dummy variable modeling approach and error-in-variable simultaneous equations approach,and effects of region and origin on estimation of biomass and volume were analyzed.[Result] The coefficients of determination (R²) of one-and two-variable compatible individual tree biomass and volume equations for Masson pine developed in this study were more than 0.92,whereas the mean prediction errors (MPEs) of above-and belowground biomass equations were less than 4% and 8%,respectively.For estimation of aboveground biomass and stem volume of Masson pine,two-variable equations were significantly better than one-variable equations,for the F-statistics between one-and two-variable aboveground biomass and stem volume equations were greatly larger than the critical F value.But for estimation of belowground biomass,one-variable were even better than two-variable ones.Effects of region and origin on estimation of both one-and two-variable aboveground biomass equations were not significant,indicating that aboveground biomass equations of Masson pine were generalized on national level.Furthermore,the general allometric biomass model M=0.3ρD^7/3presented by Zeng et al.(2012) was proved to be applicable in practice.For estimation of belowground biomass of Masson pine,models in different regions were significantly different.For trees with the same diameter,estimate of belowground biomass in the region of modeling population 1(south-eastern part of Yangtze River basin) was larger than that in the region of modeling population 2(central-western part of Yangtze River basin).For estimation of stem volume of Masson pine,two-variable model was not affected by region and origin,whereas one-variable model was affected by origin.For trees with the same diameter,estimate of stem volume in a planted stand was larger than that in a natural stand.[Conclusion] Integrating dummy variable into error-in-variable simultaneous equations is a practical approach,which not only can ensure the compatibility among several target variables,but also can develop simultaneously a system even though numbers of above-and belowground biomass observations are very different.The biomass equations,volume equations,and compatible biomass conversion factor equations and root-to-shoot ratio equations developed for Masson pine in this study meet the need of precision requirements to relevant regulation,and can be used in application.

Key words: aboveground biomass, belowground biomass, dummy variable, error-in-variable, simultaneous equations