Abstract:Fine roots are the main organs for plants to absorb nutrients and water, and there are important effects of their functional traits on forest ecosystem functions. In this study, we collected the fine roots of Pinus taiwanensis Hayata at different altitudes (1200, 1400, 1600, 1800, and 2000 m) in the Wuyi Mountains in different seasons (spring, summer, autumn, and winter), and investigated the altitudinal and seasonal variation in fine root traits. The results showed that:(1) the specific root length (SRL) and specific root area (SRA) of P. taiwanensis firstly increased and then decreased with altitudes, and the average values were (9.32±0.35) cm/g and (276.41±68.10) cm2/g; respectively, root tissue density (RTD) firstly decreased and then increased with altitude with an average value of (0.16±0.05) g/cm3. The root diameter (AvgDiam) did not change significantly among altitudes, and the mean value was (0.097±0.004) cm. Both SRL and SRA reached a maximum at the altitude of 1600 m, while the maximum values of RTD and AvgDiam appeared at altitudes of 1800 or 2000 m, respectively; (2) SRL and SRA reached a maximum in summer or autumn, and RTD and AvgDiam maximum appeared in winter or spring, respectively. Moreover, season and elevation had significant effects on fine root traits(P < 0.01), but not when acting together(P > 0.05); (3) there was a significant allometric relationship between SRL and SRA(P < 0.01), and the exponent was>1. Negative isometric relationships were found between SRL and RTD, but SRL showed a significant negative allometric relationship with AvgDiam(P < 0.01). Significant negative allometric relationships were found between both SRA and RTD, and RTD and AvgDiam(P < 0.01). However, there was no allometric relationship between SRA and AvgDiam. Our research showed that the fine root traits of P. taiwanensis tended to increase the SRL and SRA at an altitude of 1600 m, but tended to increase the RTD and AvgDiam at altitudes of 1800 or 2000 m, respectively, which was similar to the fine root traits of P. taiwanensis from summer and autumn to spring and winter. Moreover, fine roots of P. taiwanensis preferred to invest in SRL than SRA for increasing nutrient absorption at altitudes of 1600 m and in summer or autumn.
