Abstract: [Objective] This study was to reveal the characteristics and key control mechanism of annual stem cross-section area increment(RAI)longitudinal distribution of Pinus tabulaeformis, to verify the application effects of Cortini et al. (2013) modeling method and model form on developing RAI longitudinal distribution model of Pinus tabulaeformis, and to choose the stem positions whose RAI could represent the RAI at whole stem level and could predict annual volume increment and leaf biomass effectively.[Method] 312 cross-sectional disks were obtained along the stem from 27 destructively sampled trees varying in age from 10 to 98 a in 9 stands,the RAI data obtained from annual ring width measurement on disks was used to analyze the RAI longitudinal distribution patterns of sampled trees,and the patterns were compared with the theoretical patterns to reveal key control mechanism. The RAI longitudinal distribution model of Pinus tabulaeformis was developed according to the method of Cortini et al. (2013), and its application effect was verified and evaluated according to the goodness of fit. The differences between the RAI at different stem positions with that at tree level, and the relationship between RAI at different stem positions with annual volume increment and leaf biomass of single tree was analyzed in the different RAI longitudinal patterns and at the overall level to determine the ideal positions and relationship models.[Result] The RAI longitudinal distribution included two patterns according to the distribution difference in stem middle segments, the RAI distribution in effective crown segment and butt swell segment was close to the theoretical patterns derived from water transport and mechanical support theory respectively, the consistency of distribution in middle stem segment with theoretical patterns varied with sample trees. The model of RAI longitudinal distribution for Pinus tabulaeformis could explain 82.76% of the longitudinal variation of RAI. The difference between the RAI at effective crown base with that at the whole stem level was lower than that at other stem positions, the relationship between the RAI at breast height with the single-tree leaf biomass was better than that at other positions, the relationship between the RAI at breast height with annual volume increment varied with RAI longitudinal distribution pattern, which was better than other locations or slightly worse than that at the ideal location.[Conclusion] The water transport and mechanical support requirements determined the RAI longitudinal distribution of effective canopy and butt swell segment respectively, their relative importance and biological environment factors determined RAI distribution of middle stem segment. Cortini et al. (2013) modeling method and model form was reliable to develop RAI longitudinal distribution model of Pinus tabulaeformis. The RAI at effective crown base was highly representative of that at whole stem level, the RAI at breast height was effective predictive variable, but was defective to represent RAI at whole stem level and to predict annual volume increment.

Key words: Pinus tabulaeformis, annual stem cross-section area increment, annual volume increment, leaf biomass, longitudinal distribution, modelling