亚热带4种典型人工林幼树光合特征和生物量对土壤水肥因子的响应

Effects of soil water and nutrient on photosynthetic characteristics and biomass of young trees under four typical plantations in subtropical region

以亚热带4种典型树种(杉木、马尾松、尾巨桉、闽楠)人工林2年生幼树为研究对象,比较不同土壤水分(40%、55%和70%饱和田间持水量)和土壤养分(未施肥和施肥)处理对叶净光合速率、叶绿素荧光特性、总生物量和各器官生物量分配的影响.结果显示,4种典型树种人工林幼树的叶净光合速率、叶绿素荧光特性、总生物量和各器官生物量分配存在显著的树种差异性.土壤水分处理能够显著影响幼树的叶净光合速率、总生物量和分配比例,且存在树种和水分交互性.随土壤水分增加,闽楠、杉木幼树的叶净光合速率呈增加趋势,但尾巨桉和马尾松幼树的叶净光合速率在不同水分处理间差异不显著.幼树总生物量、叶生物量的比例,随土壤水分的增加呈增加趋势,而根生物量所占比例呈下降趋势.回归分析结果表明,树种自身特性是决定植物光合速率、叶绿素荧光的关键因素,土壤水分是幼树总生物量的关键解释因子,而土壤养分因子并不能解释幼树的叶光合速率、叶绿素荧光特征和生物量.研究表明,树种、土壤水分是影响树木叶光合作用和生物量的关键因子,而土壤养分对幼树叶片的光合特性和生物量影响较小.因此,在亚热带人工林培育过程中应重视树种选择,并基于树种差异性进行合理的水肥管理.

In this study,we investigated the effects of soil water(40%,55%and 70%of saturated field water capacity)and nutrient(non-fertilization and fertilization)on leaf net photosynthetic rate,chlorophyll fluorescence and biomass of 2-year old young trees of Cunninghamia lanceolata(Lamb.)Hook.,Pinus massoniana Lamb.,Eucalyptus urophylla×E.grandis and Phoebe bournei(Hemsl.)Yang in subtropical plantations.The results showed that there were significant differences in leaf net photosynthetic rate,chlorophyll fluorescence,total biomass and biomass allocations among the 4 tree species.Soil water treatment exerted a significant effect on leaf net photosynthetic rate,total biomass and ratio,and furthermore there was an interaction between tree species and soil water.Net photosynthetic rates of P.bournei and C.lanceolata enhanced with increasing soil water contents,but not for P.massoniana and E.urophylla×E.grandis.Total biomass and leaf biomass ratio also rose with increasing soil water contents,but root biomass ratio declined.The regression analysis suggested that tree species is the fundamental factor for the patterns of photosynthetic rate and chlorophyll fluorescence,and soil water content plays the determinant factor explaining total biomass,but soil nutrient cannot explain the changes of all the 3 indicators investigated.Our results implied that tree species and soil water rather than soil nutrient are the key influencing factors of leaf photosynthesis and tree biomass.Thus tree species selection should be the priority in plantation breeding,and silvicultural practices of soil water and nutrient management should be tailored to individual tree species.