武夷山不同海拔黄山松细根性状季节变化

细根作为植物吸收养分和水分的主要器官,其功能性状对森林生态系统功能具有重要影响。以武夷山黄山松为研究对象,通过对不同季节(春季、夏季、秋季和冬季)和不同海拔(1200、1400、1600、1800 m和2000 m)的黄山松细根的功能性状的测定,分析其细根性状特征随海拔和季节变化的规律。结果表明:(1)黄山松细根比根长(SRL),比根面积(SRA)均随海拔先升高后降低,其均值分别为(9.32±0.35) cm/g与(276.41±68.10) cm~2/g;根组织密度(RTD)随海拔先降低后升高,均值为(0.16±0.05) g/cm~3。根平均直径(AvgDiam)随海拔增加变化不显著,均值为(0.097±0.004) mm。SRL和SRA在海拔1600 m处达到最大,而RTD和AvgDiam的最大值出现在海拔1800 m或2000 m处。(2)SRL和SRA在夏季或秋季达到最大,RTD和AvgDiam最大值则出现在冬季或春季。季节和海拔对各细根性状都有显著影响(P0.01),但季节与海拔对根性状并没有产生显著的交互作用(P0.05)。(3)SRL与SRA间的异速生长指数是1.25,显著大于1.0(P0.01);SRL与RTD存在负等速生长关系,而与AvgDiam存在显著负异速生长关系(P0.01);SRA与RTD,以及RTD与AvgDiam间均存在显著负异速生长关系(P0.01),但SRA与AvgDiam之间不存在异速生长关系。黄山松的细根性状在1600 m处倾向于增加比根长和比根面积,而在海拔1800 m或2000 m处则倾向于增加组织密度与根直径,这与黄山松细根性状从夏秋到冬春的季节变化规律相类似。同时,相对于比根面积来说,黄山松的细根在海拔1600 m处和夏秋季节更倾向于投资比根长来增加养分的吸收。

Seasonal changes of fine root traits in Pinus taiwanensis Hayata at different altitudes in the Wuyi Mountains

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.