【作者】 山宝琴；

【导师】 贺学礼；

【作者基本信息】 西北农林科技大学 ， 植物学， 2009， 博士

【摘要】 在严酷的荒漠化生境中,植物常通过与丛枝菌根(Arbuscular mycorrhiza,AM)真菌共生来提高对逆境的耐受力。沙生灌木类克隆植物通过其根蘖繁殖抵抗沙埋并占有新的生态位,也为AM真菌提供了特殊的生存环境。本研究以我国西部极端沙地环境为背景,以黑沙蒿(Artemisia ordosica)和白沙蒿(Artemisia sphaerocephala)两种沙生灌木为目标,以荒漠植物与AM真菌共生关系作为切入点,系统研究了黑沙蒿和白沙蒿根围AM真菌多样性及其时空分异规律,AM真菌时空分布与土壤因子的相关性,AM真菌产球囊霉素时空分布等。主要取得如下结果:1.本研究共分离出5属37种AM真菌,其中球囊霉属(Glomus Tul & Tul)占54 %,无梗囊霉属(Acaulospora Gerd & Trappe)占32.4 %,盾巨孢囊霉属(Scutellospora Walker & Sander)占8.1%,多孢囊霉属(Diversispora Walker & Schuessler)和类球囊霉属(Paraglomus Walker & Schuessler)各1种。已鉴定32种,尚有5个未定种,初鉴定为新种。帚状球囊霉(G.coremioides)在沙漠环境中出现为首次报道。2.不同宿主植物根围AM真菌群落组成和丰富度不同,黑沙蒿根围有34种,白沙蒿根围有26种。黑沙蒿根围优势种为双网无梗囊霉(A. bireticulata)、幼套多孢囊霉(D. etunicatum)和地球囊霉(G. geosporum)。白沙蒿根围优势种为双网无梗囊霉(A. bireticulata)、光壁无梗囊霉(A. laevis)、近明球囊霉(G. claroideum)和卷曲球囊霉(G. convolutum)。AM真菌多样性与样地和土层密切相关,最大种群丰度出现在黑沙蒿根围的宁夏盐池沙生灌木园样地,0～20cm土层为优势真菌种群的适生深度。3.不同荒漠环境下,黑沙蒿和白沙蒿在0～50cm土层均有很高的定殖率,黑沙蒿根围总定殖率高达89.94%,白沙蒿根围总定殖率高达94.98%,其根系都有典型的丛枝菌根结构—泡囊和丛枝,菌根类型均为I-型(Intermediate-type),即宿主植物根系同时有疆南星型(Arum-type)和重楼型(Paris-type)两种菌根结构。黑沙蒿和白沙蒿根围菌丝定殖率和泡囊定殖率在0～40cm土层无显著变化;丛枝定殖率随土层加深变化规律与宿主植物须根分布紧密相关。4.AM真菌定殖率受地理环境和土壤因子的影响。土壤养分和土壤酶活性多与丛枝定殖率显著负相关。随着养分增加和水分梯度升高,丛枝定殖率下降,孢子密度增加;贫瘠土壤条件伴随着较高的丛枝定殖率和较低的孢子密度。5.黑沙蒿和白沙蒿根围孢子密度在不同采样深度差异明显,峰值大多出现在0～10cm土层,并随土壤剖面深度增加而显著降低。土壤酶活性在土壤垂直剖面显示与孢子密度同样的规律。孢子密度在不同样地间差异显著,黑沙蒿根围最大值出现在7月的陕西榆林北部沙区样地,白沙蒿根围最大值出现在7月的鄂尔多斯沙地草地生态研究站样地。孢子密度季节性明显,大都在4～7月显著增加,7～10月降低或持平。孢子密度与土壤养分含量都呈一定正相关关系,同时还与土壤脲酶、酸性磷酸酶、碱性磷酸酶和蛋白酶活性均有显著正相关关系。6.黑沙蒿根围0～50cm土层总球囊霉素含量为0.35～4.40mg/g,易提取球囊霉素含量为0.29～0.92mg/g,两者都是在0～20cm土层较大,随土层深度增加而递减。总球囊霉素和易提取球囊霉素有明显季节变化,春季含量最高,夏秋逐渐降低。土壤总球囊霉素含量与土壤总微生物活性显著正相关,与土壤养分、土壤酶活性、孢子密度均表现出显著相关关系,可作为土壤生产力和微生物活力评价的新指标。荒漠土壤球囊霉素含量的测定及季节变化分析,填补了我国这一领域的空白。研究表明,不同荒漠环境下,黑沙蒿和白沙蒿与AM真菌都有良好的共生性,这是其适应极端环境的主要生态对策之一。研究成果丰富了荒漠恢复生态学的基础理论,为菌根生物技术在荒漠植被恢复和生态重建中的应用提供了科学依据和种质资源。更多还原

【Abstract】 In a rigorous desert ecosystem, the symbiosis between arbuscular mycorrhizal (AM) fungi and plants plays a vital role in improving plant drought tolerance and mineral nutrients uptake. Clonal plants occupy new ecological niche by root-sucker reproduction surviving sand burying, which also provide special environment for AM fungi. As fine semi-shrubs for sand fixation in northern China desert, Artemisia ordosica and Artemisia sphaerocephala are typical phalanx clonal plants. Despite their own physiological characters, their endurance capability for the atrocious circumstance also rest with their symbiosis with AM fungi. In this research, soil samples in the rhizosphere of A.ordosic and A.sphaerocephala were collected to isolate arbuscular mycorrhizal (AM) fungi. The spatial and temporal variation and diversity of AM fungi were determined; correlations between distribution of AM fungi and soil factors, soil glomalin concentration were systemically analyzed. Results were shown as follows:An abundant diversity of AM fungi was found in sandland. 37 AM fungi taxa in five genera were isolated and identified, of which 54% belong to the genus Glomus, 32.4 % to Acaulospora, 8.1 % to Scutellospora,others to Diversispora and Paraglomus. Five uncertain species were identified as unrecorded species. It is the first time to report G.coremioides existing in desert.Dominant species of AM fungi in the rhizosphere of different host plants were different, A.bireticulata, D.etunicatum and G.geosporum were the dominant species in the rhizosphere of A. ordosica. A.bireticulata, A. laevis, G. claroideum and G. convolutum were the dominant species in the rhizosphere of A.sphaerocephala.The community members and species richness of AM fungi were also different among sampling sites and soil depths due to soil properties and microenvironment. The most species was found in Yanchi site, while dominant community of AM fungi mainly distributed in 0-20cm soil profile.Both two host plants can form well symbionts with AM fungi in desert. The total colonization of AM fungi of A. ordosica was 89.94%, and that of A.sphaerocephala was 94.98%, both of them formed the intermediate type mycorrhizas.The colonization of hyphae and vesicles were higher in 0-40cm soil layer than that in 40-50cm. The arbuscular colonization was higher only in 10-40cm soil layer.Geographical and environmental factors affected the diversity of AM fungi and colonization of arbuscular mycorrhiza. Both soil fertility and soil enzyme activities were negatively correlated with arbuscular colonization.On the flowing dunes where soil was infertile and serious drought, the spore density was lower but arbuscular colonization were higher.The maximal value of spore density was observed at the 0-10cm layer, and then gradually decreased with soil depth. The soil enzyme activities showed the same trend with the spore distribution. Seasonal variation of spore density in the rhizosphere of phalanx clonal plants was found; the highest value appeared in summer. The spore density was different among sites, and was significantly and positively correlated with soil available P, N, organic matter contents and soil enzyme activities.Total Glomalin concentrations in the rhizosphere of A.ordosica ranged from 0.35 to 4.40mg/g, Easily Extractable Glomalin concentrations ranged from 0.29 to 0.92mg/g. glomalin concentrations showed a clear pattern of decrease from 0 to 50cm soil layer in every site and decline trend with season change, the maximal value was in spring. Glomalin concentrations were significantly positively correlated with soil fertility, microbial activity and spore density, suggesting that glomalin can be used as a new indicator to monitor desertification and soil degradation. We have determined the Glomalin concentrations in desert, which has not been reported yet by the national peers before.The results showed that both Artemisia ordosica and Artemisia sphaerocephala could establish well symbiosis with AM fungi, which was the main reason for maintaining integrity and stability of the desert ecosystem, elucidated the ecologic function of AM fungi and interaction between host plants and AM fungi, provided the scientific basis for the applications of AM biotechnology in vegetation restoration and ecology reconstruction of desert.更多还原