【作者】 庞丽；

【导师】 周志春；

【作者基本信息】 中国林业科学研究院 ， 林木遗传育种， 2014， 博士

【摘要】 马尾松(Pinus massoniana)是我国南方重要的用材树种之一，其天然林和人工林分布面积居南方造林树种前列，支撑着我国造纸、木材加工、林产化工等产业。然而，我国南方森林土壤有效P严重匮乏且呈高度异质性分布，限制了马尾松的生长和生产力。当前研究已揭示了马尾松适应低P胁迫的生物学机制。近年来我国南方地区大气N沉降日趋严重，导致土壤有效N含量增加、N/P发生改变，这将会对低P下马尾松生长和P效率产生影响，然而相关研究较少有报道。本论文以马尾松优良家系作为试验材料，设置了模拟N沉降与同质低P、异质低P耦合的模拟盆栽试验，系统研究了模拟N沉降对不同类型低P胁迫下马尾松家系根系形态、根系分泌、光合作用、菌根共生以及P效率的影响，阐明马尾松、杉木和木荷幼苗对低P下土壤N素增加感知、响应的种间差异，为在大气N沉降背景下开展林木P效率的遗传改良提供更全面的理论基础和科学指导。主要研究结果如下：1.模拟N沉降对低P下马尾松根系形态参数、根系分泌以及P效率的影响同质低P下，模拟N沉降对马尾松生长、生物量和P效率的影响较小，但存在显著的N×家系互作效应。异质低P下，模拟N沉降显著促进了马尾松生长和生物量积累，其原因是促进了根系的生长和表层土壤中根系分布比例的增加，从而增加了马尾松对土壤P的吸收。不同P环境下模拟N沉降对马尾松生长性状的影响，与植株N/P有关。同质低P环境下，马尾松植株N/P为13.8，植株生长受P素限制，模拟N沉降处理未改善马尾松生长状况。在异质低P环境中，植株N/P为9.7，马尾松对N素增加敏感，模拟N沉降显著增加了苗木生物量和P吸收效率。同质低P和异质低P下，模拟N沉降均提高了植株N/P化学计量比、增加了P素的相对匮乏程度，从而诱导根系增加了APase和有机酸的分泌，同质低P较异质低P下增加幅度更大，其中有机酸分泌与马尾松生长呈正相关关系，而APase活性与磷效率相关性较小。同质低P下，N沉降虽然增加了根系分泌，但未提高马尾松P吸收效率和生长量，其原因在于，同质低P下植株N/P过高，马尾松生长受P的限制，虽然N素的增加促进了根系分泌，可以活化一定量的固定态P，但不足以满足植物生长对P的需要。另外，马尾松根系分泌对模拟N沉降的响应存在较大的家系差异。同质低P下，模拟N沉降显著增加了马尾松针叶N含量和N/P，叶净光合速率随着叶N含量和N/P的增加而增加。模拟N沉降虽然增加了针叶净光合速率，但并没有明显改善植株生物量。咎其原因，模拟N沉降虽然增加了土壤N的含量，但却造成土壤和植株体内P更加的相对匮缺，马尾松P吸收效率降低。另外，模拟N沉降抑制了根系的生长，减少了养分的吸收，而光合作用的增加，又进一步加重了植株养分的亏缺。异质低P下，马尾松针叶P含量显著增加，N/P降低，净光合速率增加幅度较同质低磷下模拟N沉降小。马尾松根冠比增大，植株N、P吸收和生物量增加，为光合作用提供了所需的营养元素。2.模拟N沉降对低P下马尾松菌根共生和P效率的影响不同P素环境下，模拟N沉降对马尾松菌根土养分含量的影响不同。同质低P下，模拟N沉降增加了菌根土水解N，有效P和速效K的含量，降低了有效Al含量，未引起马尾松菌根土明显的酸化，改善了土壤理化性质。异质低P下，模拟N沉降增加了菌根土水解N和有效P含量，但N/P和pH值降低，土壤速效K和有效Al含量增加。同质低P下，模拟N沉降增加了土壤N的有效性，然而降低了1年和2年生苗木菌根侵染率和侵染程度，形成的菌根根毛数量减少，但菌丝厚且紧密。异质低P较同质低P菌根侵染率和侵染程度小，但模拟N沉降分别增加了1年生和2年生苗木菌根侵染率，菌根根毛数量多，表面菌丝厚密。同质低P下，模拟N沉降显著降低了马尾松1年生菌根苗根系的生长，但增加了根系分泌，尤其是有机酸分泌量增加了近3倍。相关性分析表明，有机酸分泌对菌根化苗生长的贡献显著高于APase。异质低P下，模拟N沉降显著降低了马尾松1年生菌根化苗表层根系的生长，增加了深层根的生长，根系干物质积累量和有机酸分泌量增加。同质低P下，接种菌根菌显著改善了马尾松苗木的生长状况，促进了生物量的积累。模拟N沉降促进了1年生菌根化苗的生长和生物量积累，增加了P和N的吸收，植株N/P比增加为11.70。但减少了2年生菌根化苗生物量的增加，N的吸收增加，P的吸收减少，植株N/P比显著增加为14.99。异质低P下，模拟N沉降促进了马尾松1年生和2年生菌根化苗的生长和生物量积累，增加了N和P的吸收。3.低P胁迫下马尾松、杉木和木荷响应模拟N沉降的种间差异及机制同质低磷下，模拟N沉降增加了3种树苗土壤水解N含量，增加幅度大小顺序为马尾松＞杉木＞木荷。马尾松、木荷表层土壤酸化程度较杉木大。另外，马尾松、木荷土壤有效P和速效K含量降低幅度较杉木大，3种树苗土壤有效铝含量均增加。异质低磷处理下，杉木和木荷土壤酸化程度较马尾松大。木荷土壤有效P和水解N含量降低，马尾松和杉木土壤有效P和水解N含量增加。3种树苗有效铝含量均增加。同质低磷下，模拟N沉降增加了3种树苗根系分泌物总量，增加幅度大小顺序为木荷＞马尾松＞杉木，这可能是木荷和马尾松较杉木生物量高的原因之一。异质低P处理下，3种树苗根系酸性磷酸酶活性和有机酸总量均减少。同质低磷下，3种树苗叶N/P比均增加，杉木对N沉降较敏感，叶N/P较马尾松和木荷增加幅度大，但其叶净光合速率却降低。马尾松较木荷净光合速率增加幅度大，马尾松对氮素增加的调节和适应能力较强。异质低P下，马尾松和木荷叶N/P均降低，杉木N/P比增加。3种树苗净光合速率增加幅度大小顺序为马尾松＞杉木＞木荷。模拟N沉降对马尾松苗木根系生长的影响较杉木和木荷相比较小。木荷地上部分生长增加，但根系生长受到抑制，整株生物量降低。N素的增加严重抑制了杉木幼苗根系生长和生物量积累。模拟N沉降抑制了马尾松和杉木P的吸收，促进了木荷P的吸收，同时促进了马尾松和木荷N的吸收，抑制了杉木N的吸收。异质低P处理增加了3种树苗的生物量和根冠比，生物量增加幅度大小顺序为木荷＞杉木＞马尾松。更多还原

【Abstract】 Pinus massoniana is one of the important timber species in southern China. Thedistribution areas of its natural forests and plantations are forefront of the southern plantationspecies, and it widely used in the pulp and paper, construction, rosin ect. However, forest soilin southern China are acidic red soil, mostly severe scarcity of phosphorus(P) and phosphorushighly heterogeneous distribution. The limited availability of P in forest soils is thus one of themost important factors causing a decline in growth and productivity of Pinus massonianaplantations. The current study had revealed Pinus massoniana biological mechanisms ofadapting to different types of low P stress. Atmospheric nitrogen(N) deposition dramaticallyraised in recent decades, resulting in increases of soil N availability and N/P ratio, whichwould impact Pinus massoniana P efficiencyand biological mechanisms of adapting to low Pstress. Taking different excellent families of Pinus massoniana as test materials, a potexperiment was conducted to simulate two P conditions, i.e., homogeneous low P vs.heterogeneous low P among soil layers, in combination with two N deposition levels on rootmorphology, root exudates, photosynthetic, mycorrhizal symbiosis and P efficiency. The studyillustrated the differentes perception and response of Pinus massoniana、Cunninghamialanceolata and Schima superba to soil N content increased. The objectives of this study wereto provide theoretical foundation and scientific guidance for genetic improvement of treesphosphorus efficiency in the context of atmospheric N deposition. The main results obtainedfrom experiments are as follows:1. Effects of simulated N deposition on root and phosphorus efficiency of Pinusmassoniana under low P conditionUnder the homogeneous low phosphorus condition, growth traits of seedling height,diameter, biomass etc and P efficiency of Pinus massoniana were not significantly improvedby simulated N deposition, but significant N×family interaction effect was detected. Under the heterogeneous low P condition, significant N effects on the seedling height, biomass and Pabsorption efficiency were observed, due to promoted root length and root distribution ratio oftopsoil. In addition, the effects of simulated N deposition on growth and P efficiency of Pinusmassoniana were relevant to the N/P ratio. Under the homogeneous low P condition, the N/Pratio of Pinus massoniana plant was13.8, plants exhibited a low sensitivity to simulated Ndeposition, root secreted APase activity was increased but the plant growth was not promoted.In comparison, the plant N/P ratio was9.7under the heterogeneous low P condition, and theplant growth and P efficiency were significantly promoted, while no obvious change occurredin root secreted APase activity.Under both the homogeneous and heterogeneous low P conditions, N/P stoichiometricratio in Pinus massoniana seedlings was significantly increased by simulated N deposition,which stimulated the amount of root acid phosphatase and organic acid secretion. The amountof root exudates was higher under the homogeneous low P condition than under theheterogeneous low P condition. The level of root secreted organic acids was significantlycorrelated with the growth in Pinus massoniana seedlings. Under the homogeneous low Pcondition, P acquisition efficiency and biomass in Pinus massoniana seedlings were notaffected by simulated N deposition, mainly due to the high N/P ratios and low sensitivity to Naddition. Significant variations among families in root exudates to the simulated N depositionwere observed.Simulated N deposition significantly increased the N content and N/P ratio of Pinusmassoniana needles under the homogeneous low P condition, meanwhile net photosyntheticrate improveded. Under the heterogeneous low P treatment, P content of Pinus massoniananeedles increased but N/P decreased. The increasing degree of net photosynthetic rate wassmaller than simulated N deposition. Under homogeneous low P, simulated N depositiondespite increased in the plant net photosynthetic rate, but did not significantly improve plantbiomass.The reasons was that simulated N deposition increased the N content of soil, yetCausing the P content of soil and plant was relative scarcity, and reduced the P absorption efficiency ofPinus massonianaplant. In addition, the simulated N deposition inhibited rootgrowth, reducing the absorption of nutrients, and photosynthesis increases, further aggravatingthe plant nutrient deficiency. Under heterogeneous low P conditions, the root-shoot ratioofPinus massoniana was increased, meanwhile N, P uptake and biomass were increased, whichprovided necessary nutrients for the photosynthesis.2. Effects of simulated N deposition on mycorrhizal symbiosis and P efficiency underlow P stressUnder different P contitions, the effects of simulated N deposition on nutrient content inmycorrhizal soil of Pinus massoniana is different. Simulated N deposition increased thecontent of available N, available phosphorus and potassium in mycorrhizal soil underhomogeneous low P treatment, and reduced the effective aluminum content, but soilacidification did not cause obvious. The results showed that inoculation mycorrhiza fungicould improve the effects of simulated N deposition on nutrient content in mycorrhizal soil ofPinus massoniana and adjust N/P ratio and soil physicochemical properties. Underheterogeneous low P treatment, Simulated N deposition increased the content of available N,available phosphorus, K and effective aluminum, but N/P ratio and pH significantly decreased.Under different P conditions, the effects of simulated N deposition on mycorrhizalinfection of Pinus massoniana was different.The colonization ratio and infection degree ofmycorrhizal fungi under homogeneous low P was larger than under heterogeneous low P.Under homogeneous low P condition, simulated N deposition increased the effectiveness ofsoil N, but reduced the1-year and2-year-old seedlings mycorrhizal infection rate andinfection degree. The number of mycorrhizal hairs was decreased, but hyphae of mycorrhizaewere thick and dense. Under heterogeneous low P treatment,simulated N deposition increasedthe1-year and2-year-old seedlings mycorrhizal infection rate. The number of mycorrhizalhairs were increased, and surface hyphae of mycorrhizae was dense.Under homogeneous low P condition, simulated N deposition treatment significantlyreduced the mycorrhizal growth of1-year-old Pinus massoniana seedlings, but increased the root APase activity and the secretion of organic acids, organic acid secretion particularlyincreased by nearly three times. Correlation analysis showed that root biomass and APaseactivity was significantly negatively under homogeneous low P, but it was significantlypositive with organic acid secretion. The contribution of organic acids secreted to the growthof mycorrhizal seedlings was significantly higher than APase. Under heterogeneous low Ptreatment, simulated N deposition treatment significantly reduced the surface root growth of1-year-old Pinus massoniana mycorrhizal seedlings, but increased the growth of deep roots.Meanwhile, root dry matter accumulation and organic acid secretion increased, while APaseactivity decreased.Under homogeneous low P condition, inoculation mycorrhiza fungi significantlyimproved the growth status and promoted the biomass accumulation of Pinus massonianaseedlings. Simulated N deposition treatment improved the growth and biomass accumulationof1-year-old Pinus massoniana mycorrhizal seedlings. Although increased the height growthof2-year-old Pinus massoniana mycorrhizal seedlings, but reduced its biomass accumulation.Under heterogeneous low P treatment, simulated N deposition improved the growth andbiomass accumulation of Pinus massoniana1-year and2-year-old mycorrhizal seedlings.Under different soil P condition, the simulated N deposition level of this study had allpromoted the growth of Pinus massoniana mycorrhizal seedlings, but the dry matteraccumulation of heterogeneous low P was larger than that of homogeneous low P.Correlation analysis showed that the absorption efficiency of N and P were significantlypositive correlation with the growth and biomass accumulation of Pinus massonianamycorrhizal seedlings. Under homogeneous low P condition, simulated N deposition increasedthe absorption efficiency of N and P of Pinus massoniana1-year-old mycorrhizal seedlings,and plant N/P increased to11.70. The N absorption of Pinus massoniana2-year-oldmycorrhizal seedlings was increased, but the P absorption was decreased. Plant N/Psignificantly increased to14.99. Under heterogeneous low P treatment, simulated N depositionincreased the absorption efficiency of N and P of Pinus massoniana1-year and2-year-old mycorrhizal seedlings. Plant N/P of1-year-old mycorrhizal seedlings increased to10.96, andthat of2-year-old mycorrhizal seedlings decreased to5.56.3. The differences of growth and P efficency responses ofPinus massoniana,Cunninghamia lanceolata and Schima superba to simulated N deposition under low P stressBecause of three species have different biological characteristics, significant differencesin nutrient content of potting soil to the simulated N deposition were observed. The order ofincreasing extent of potting soil hydrolysis N content was Pinus massoniana, Cunninghamialanceolata and Schima superba. The degree of surface soil acidification of Pinus massonianaand Schima superba was large than Cunninghamia lanceolata, due to Schima superba strongerabsorption and eluviation of surface soil N, and N eluviation of surface soil of Pinusmassoniana was larger than Cunninghamia lanceolata. In addition, the decreasing degree ofpotting soil P and K content of Pinus massoniana and Schima superba were larger thanCunninghamia lanceolata. The increasing of soil Al content of three species may be related tothe reducing of soil P content.The order of increasing degree of leaf N/P ratio was Cunninghamia lanceolata,Schimasuperba.and Pinus massoniana. Cunninghamia lanceolata was sensitive to N deposition, itsleaf N/P ratio largely increased. Pinus massoniana had stronge ability of regulation andadaptability to increased N. The study on photosynthesis of three species showed that theincreasing degree of net photosynthetic rate of Pinus massoniana was large than Schimasuperba,.leaf net photosynthetic rate of Cunninghamia lanceolata decreased. Leaf endogenousacid phosphatase activity of three species were decreased, and the order of reducing extentwas Cunninghamia lanceolata,Schima superba.and Pinus massoniana. The result may beassociated with changes of leaf enzymes metabolism.due to increased leaf N content. Underthe heterogeneous low P conditions, leaf N/P ratio of Pinus massoniana.and Schima superbawere lower, but that of Cunninghamia lanceolata was increased. The heterogeneous low Ptreatment can promoted the photosynthesis of three species, and the order of increasing extentof leaf N/P ratio was Cunninghamia lanceolata,Schima superba.and Pinus massoniana.. The increased activity of leaf endogenous acid phosphatase of Cunninghamia lanceolata, andPinus massonian promoted the recycling of phosphorus in leaves.Under the simulated N deposition treatment, the order of increasing extent of rootexudates was Schima superba, Pinus massoniana and Cunninghamia lanceolata. This may beone of reasons for the high biomass of Schima superba, Pinus massoniana compared toCunninghamia lanceolata. Under the heterogeneous low P condition, acid phosphataseactivity and total organic acids of three species were significantly reduced. The influences ofsimulated N deposition on root growth of Pinus massoniana was less than Schima superba,and Cunninghamia lanceolata. Aboveground growth of Schima superba increased, but rootgrowth was inhibited, while the biomass of whole plant decreased. Increased N depositionseverely inhibited root growth and biomass accumulation of Cunninghamia lanceolata.Correlation analysis showed that growth index of height, ground stems and biomass of threespecies had significant correlation with plant N, phosphorus efficiency. Simulated Ndeposition inhibited the P absorption of Pinus massoniana and Cunninghamia lanceolata, butpromoted the P absorption of Schima superba. Simultaneously, the N absorption of Pinusmassoniana and Schima superba were increased by simulated N deposition, but that ofCunninghamia lanceolata was reduced. The biomass and root-shoot ratio were increased ofthree species under the heterogeneous low P condition. The order of increasing extent ofbiomass was Schima superba, Cunninghamia lanceolata and Pinus massoniana.更多还原