探讨豆科树种降香黄檀与桉树间作体系下根瘤与幼苗生长生理对不同施氮处理与pH环境的响应,为探索高效生物固氮的桉树人工林可持续经营模式提供科学依据。采用盆栽可控实验模拟尾巨桉-降香黄檀间作体系;采用双因素完全随机区组设计,氮素及pH分别设置N1,N2,N3,N4及pH4.5,pH5.5,pH7.5,pH9.5各4个浓度梯度处理。结果表明:1)在N2与N3施氮处理下,降香黄檀的结瘤能力被显著抑制(P<0.05),而N1处理幼苗根系结瘤能力与对照组(CK)无显著差异,且均在pH7.5处理下根系结瘤能力最强;2)尾巨桉的生物量与光合指标随施氮量的增加而提高。除pH9.5处理外,降香黄檀的生物量与光合指标随施氮量的增加呈现出先增加后减少的趋势;3)施氮后降香黄檀与尾巨桉的叶片的超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、过氧化物酶(POD)、硝酸还原酶(NR)含量均有提高,而丙二醛(MDA)含量表现相反趋势;4)除N3处理外,降香黄檀与尾巨桉幼苗在pH5.5处理下的生物量均大于pH4.5和pH9.5处理下的;5)冗余分析的结果表明,间作体系下,降香黄檀的结瘤能力会受到降香黄檀生理状况与尾巨桉生物量的限制。综上,适量氮添加与土壤pH处理调节有益于降香黄檀与尾巨桉幼苗在该体系中的共同发育。

In order to provide a scientific basis for exploring sustainable management of Eucalyptus plantations with high-efficiency biological nitrogen fixation,this study explores the response of root nodules,seedling growth and physiology to different nitrogen application and pH environments under the intercropping system of legume species Dalbergia odorifera and Eucalyptus urophylla×E.grandis.Adopting controlled pot experiments to simulate the intercropping system of D.odorifera and E.urophylla×E.grandis.The experiment was carried out by using a two-factor complete randomized block design,nitrogen(N)and pH with four concentration gradients were set to control the experiment:N1,N2,N3,N4 and pH4.5,pH5.5,pH7.5 and pH9.5,respectively.The results indicate that:1)Under N2 and N3 treatments,the nodule formation ability of D.odorifera was significantly inhibited(P<0.05).However,there were no significant differences between the N1 level and the control group(CK)in root nodule formation ability,and the root nodulation ability was strongest at pH7.5.2)The biomass and photosynthetic indexes of E.urophylla×E.grandis increased with the rise of N application.Except for pH9.5 treatment,those of D.odorifera initially increased but then decreased with increasing N application.3)The content of superoxide dismutase(SOD),catalase(CAT),peroxidase(POD),and nitrate reductase(NR)of D.odorifera and E.urophylla×E.grandis.leaves were increased with N application,while the content of malondialdehyde(MDA)showed the opposite trend.4)Except for the N3 treatment,the biomass of E.urophylla×E.grandis and D.odorifera seedlings were significantly higher under pH5.5 treatments than that of pH4.5 and pH9.5 treatments.5)The results of redundancy analysis showed that the nodule ability of D.odorifera in the intercropping system was limited by the physiological condition of D.odorifera and biomass of E.urophylla×E.grandis.In conclusion,moderate nitrogen addition and soil pH regulation are beneficial for the mutual development of D.odorifera and E.grandis seedlings in this system.