Effects of drought stress on growth,nutrient content,and stoichiometry of four native tree species in South China
This study aimed to explore the differences in the responses of four native tree species to different intensities of drought stress to provide a theoretical basis for the physiological mechanisms of acclimation of native tree species to drought in South China.The four selected native tree species of South China were Ormosia pinnata,Dalbergia odorifera,Michelia macclurei,and Castanopsis fissa.Rainfall shelters open-top tanks(OTTs),and automatic watering systems were installed to simulate drought environments.Four treatments were employed:control(100％),low(75％),moderate(50％),and high(25％)drought stress.Variations in tree growth,nutrient content,and stoichiometric responses of the four native tree species to drought treatments were studied.Drought stress inhibited the growth of O.pinnata and D.odorifera;however,it had no significant effect on the growth of M.macclurei and C.fissa.The nitrogen(N)content in the leaves,as well as the N and phosphorus(P)contents in the roots of O.pinnata decreased with increasing drought intensity.In contrast,C:N,C:P,and N:P ratios in the thick roots of O.pinnata increased with drought intensity,whereas C:P and N:P ratios in the fine roots decreased with drought intensity.The stoichiometric ratios of thick roots were significantly affected by drought stress.The leaf soluble sugar content increased with increasing drought stress in all four tree species;the starch and non-structural carbohydrates(NSC)contents in the thick roots of M.macclurei and C.fissa increased under drought stress,whereas the NSC contents of D.odorifera and O.pinnata decreased under drought stress.The collective findings indicate resource-acquiring strategies in O.pinnata and D.odorifera and resource-conserving strategies in M.macclurei and C.fissa.Under high drought stress,M.macclurei maintained normal growth and its nutrient content was not significantly influenced by drought stress.At the same time,it maintained a high soluble sugar content in all organs,indicating that it may have a strong competitive ability in the southern tropical region against the background of the future global climate.
South Chinastoichiometrydrought stressnative tree speciesnon-structural carbohydratenutrient strategy
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