塞北荒漠草原柠条锦鸡儿AM真菌的空间分布

为了探明塞北荒漠草原AM真菌生态分布规律,于2013年6月选取河北沽源县二牛点、内蒙古上都镇和青格勒图嘎查3个样地,按照0—10 cm、10—20 cm、20—30 cm、30—40 cm、40—50 cm 5个土层分别采集柠条锦鸡儿(Caragana korshinskii)根围土壤样品,研究了AM真菌空间分布特征及其与土壤因子的相关性。结果表明,柠条锦鸡儿根系能与AM真菌共生形成疆南星型丛枝菌根,AM真菌孢子密度和定殖率与样地和采样深度密切相关。二牛点孢子密度最大,3个样地孢子密度最大值均在0—10 cm土层,并随土层加深而减少;3个样地菌丝定殖率依次为上都镇青格勒图嘎查二牛点,峰值均在0—10 cm土层;泡囊定殖率青格勒图嘎查显著低于其他样地,但土层间无规律性变化;丛枝样地间定殖状况差异明显,变化趋势为青格勒图嘎查上都镇二牛点;AM真菌总定殖率和定殖强度最大值在上都镇。孢子密度与土壤有机C、全N、易提取球囊霉素和总球囊霉素极显著正相关,与p H值显著正相关,与速效P显著负相关;菌丝定殖率与土壤p H值、速效P、全N和酸性磷酸酶显著负相关;泡囊和丛枝定殖率与土壤碱解N和碱性磷酸酶具有极显著相关性;总球囊霉素和易提取球囊霉素与脲酶显著正相关,与碱解N、全N、碱性磷酸酶和酸性磷酸酶极显著正相关。主成分分析表明,酸性磷酸酶、总球囊霉素、全N、碱性磷酸酶、有机C是影响荒漠土壤营养状况的主要因子。总球囊霉素和易提取球囊霉素平均含量分别为3.19 mg/g和1.17 mg/g,占土壤有机C平均含量比为7.77%和3.83%,占土壤全N平均含量比为20.81%和9.57%。多元线性回归表明,总球囊霉素和易提取球囊霉素与土壤有机C和全N具有显著线性相关关系。研究球囊霉素与土壤有机C和N的比例关系可进一步明确AM真菌的生态功能,对荒漠土壤C库和N库研究具有重要意义。     

硬化地表对油松和白蜡树下非根围及根围土壤微生物量碳氮的影响

硬化地表是城市化发展的重要特征,为了明确硬化地表下土壤环境的变化,以北京典型绿化树油松和白蜡为试验材料,设置透水硬化地表(PP)、不透水硬化地表(IPP)和自然地表(Ctr)3个水平的地表类型,探讨硬化地表对非根围和根围土壤微生物量碳(MBC)、氮(MBN)的影响。结果表明,与对照(Ctr)相比,PP和IPP显著降低了油松和白蜡树下非根围土壤MBC、MBN、MBC/OC(微生物量碳/有机碳)和MBN/TN(微生物量氮/全氮)(P<0.05),并显著降低了油松树下根围土壤MBN/TN(P<0.05);PP显著降低了白蜡树下根围土壤MBN、MBC/OC、MBN/TN和油松树下根围土壤MBC(P<0.05)。硬化地表引起的土壤MBC、MBN的变化与土壤全碳、全氮、有机碳的变化显著正相关(P<0.05),MBN的变化与含水量呈显著负相关(P<0.05)。可见,硬化地表不利于土壤微生物的生长,并且在非根围土壤中表现更为明显,这种不利影响将可能进一步影响城市绿地的养分循环、树木生境和生态系统服务功能。     

Arbuscular mycorrhizal contribution to heavy metal uptake by maize (Zea mays L.) in pot culture with contaminated soil

In two pot-culture experiments with maize in a silty loam (P2 soil) contaminated by atmospheric deposition from a metal smelter, root colonization with indigenous or introduced arbuscular mycorrhizal (AM) fungi and their influence on plant metal uptake (Cd, Zn, Cu, Pb, Mn) were investigated. Soil was -irradiated for the nonmycorrhizal control. In experiment 1, nonirradiated soil provided the mycorrhizal treatment, whereas in experiment 2 the irradiated soil was inoculated with spores of a fungal culture from P2 soil or a laboratory reference culture, Glomus mosseae. Light intensity was considerably higher in experiment 2 and resulted in a fourfold higher shoot and tenfold higher root biomass. Under the conditions of experiment 1, biomass was significantly higher and Cd, Cu, Zn and Mn concentrations significantly lower in the mycorrhizal plants than in the nonmycorrhizal plants, suggesting a protection against metal toxicity. In contrast, in experiment 2, biomass did not differ between treatments and only Cu root concentration was decreased with G. mosseae-inoculated plants, whereas Cu shoot concentration was significantly increased with the indigenous P2 fungal culture. The latter achieved a significantly higher root colonization than G. mosseae (31.7 and 19.1%, respectively) suggesting its higher metal tolerance. Zn shoot concentration was higher in both mycorrhizal treatments and Pb concentrations, particularly in the roots, also tended to increase with mycorrhizal colonization. Cd concentrations were not altered between treatments. Cu and Zn, but not Pb and Cd root-shoot translocation increased with mycorrhizal colonization. The results show that the influence of AM on plant metal uptake depends on plant growth conditions, on the fungal partner and on the metal, and cannot be generalized. It is suggested that metal-tolerant mycorrhizal inoculants might be considered for soil reclamation, since under adverse conditions AM may be more important for plant metal resistance. Under the optimized conditions of normal agricultural practice, however, AM colonization even may increase plant metal absorption from polluted soils.     

Influence of Arbuscular Mycorrhizal (AM) Symbiosis on Phosphorus Leaching through Soil Cores

Two experiments with soil cores were carried out to investigate the effects of arbuscular mycorrhizal (AM) fungal colonization on mobility of phosphorus (P) during leaching of repacked columns of a soil with a loamy sand texture. Trifolium subterraneum plants inoculated with an AM fungus or not inoculated were grown in cores with low or high P concentrations for 8 or 10 weeks in the glasshouse. Cores were then irrigated with 2500 mL water and the leachate collected. Plant growth and the amounts of P removed by plants, remaining in soil as available P and removed dissolved in leachate were measured. Mycorrhizal fungal colonization and development of external hyphae were also determined. Inoculation and/or P application significantly increased plant growth and plant P removal and decreased P leaching. In low P soils AM fungal colonization significantly increased plant P uptake and decreased soil available P and total dissolved P in leachates. Lower P leaching from cores with AM plants under low P conditions was related to enhancement of plant growth and to scavenging and removal of P from the soil by roots and/or external hyphae. When P was applied AM effects were not observed and available P remaining in the soil after leaching was much higher, regardless of AM fungal colonization.     

General microflora,arbuscular mycorrhizal colonization and occurrence of endophytes in the rhizosphere of two age groups of <Emphasis Type="Italic">Ginkgo biloba</Emphasis> L.of Indian Central Himalaya

The populations of the general microflora (bacteria, actinomycetes and fungi) in the rhizosphere and their corresponding non-rhizosphere soil samples of Ginkgo biloba L. of two age groups (Group A, <25 years-young trees; Group B, >60 years-old trees) growing under a temperate location of Indian Himalayan Region (IHR) have been determined. Observations were also made for the diversity, distribution and colonization of arbuscular mycorrhizal (AM) fungi and occurrence of endophytes in roots of G. biloba. The population of general microflora was found to be higher in the rhizosphere of Group B trees, more clearly reflected in terms of rhizosphere: soil (R:S) ratios. Contrary to this, per cent colonization and spore densities of AM fungi were higher in the rhizosphere of Group A trees as compared to the rhizosphere of Group B. AM fungal colonization was observed mostly in form of loose coils. All the spores detected, belonged to the genus Glomus with five different types. Presence of endophytes (both bacteria and fungi) was observed in the cortical cells of G. biloba roots, more profound in case of Group B trees. Data suggest that, while the species of Glomus dominated the rhizosphere of G. biloba, an inverse correlation exist between the colonization of general microflora and the colonization of AM fungi including endophytes.     

Effect of arbuscular mycorrhiza on inter- and intraspecific competition of two grassland species

We were interested in the role of arbuscular mycorrhiza (AM) in the competition between plants of different sizes. A pot experiment of factorial design was established, in which AM root colonization and competition were used as treatments. Five-week-old Prunella vulgaris seedlings were chosen as target plants (i.e. plants whose response to competition was studied) and the following (13 replicates of each) were used as neighbours: (1) a large, 10-week-old P. vulgaris, (2) two P. vulgaris seedlings, and (3) a large, 10-week-old Fragaria vesca. In the experiment where small neighbours were grown together with small target plants, competition did not reduce target plant weight significantly, compared to the other two treatments. The competitive effects of large neighbours were significant, regardless of species (both older neighbours reduced the weights of target plants similarly), but there was a clear difference between intra- and interspecific competition when plants were mycorrhizal. In intraspecific competition with a large neighbour, the target plant shoot weight was reduced 24% when inoculated with AM. Thus, AM amplified rather than balanced intraspecific competition. In interspecific competition with old F. vesca, the shoot weights of target plants were 22% greater when inoculated with AM than when non-mycorrhizal. The results showed that, for given soil condition, AM might increase species diversity by increasing competitive intraspecific suppression and decreasing the interspecific suppression of small plants by larger neighbours.     

荒漠植物油蒿根围AM真菌的时空分布

 2006年5、8和10月分别从陕西榆林沙生植物园样地油蒿(Artemisia ordosica)根围分0～10、10～20、20～30、30～40和40～50 cm 5个土层采集土壤样品, 系统研究了AM真菌的时空分布。结果表明, AM真菌孢子密度和丛枝定殖率随时间呈递减趋势; 泡囊定殖率随时间变化先降后升, 在10月出现最高值; 菌丝定殖率随时间变化先升后降, 8月出现最高值; AM真菌孢子密度和定殖率的最大值分别出现在5月的0～10和20～30 cm土层。实验站中土壤因子对AM真菌时空分布有显著影响, 土壤速效N、速效P和有机质与孢子密度呈极显著正相关, 土壤速效K与菌丝定殖率呈极显著正相关, 和总定殖率成显著正相关。     

The role of seed depth,litter, and fire in the seedling establishment of amphicarpic peanutgrass (Amphicarpum purshii)

Summary Amphicarpum purshii is an annual grass which mostly grows in disturbed areas of the New Jersey Pine Barrens, USA. It is amphicarpic, producing spikelets (and seeds) both above and below the soil surface. Previous research has shown that subterranean seed production ensures reproduction in the event of a major disturbance such as fire and results in rapid post-burn colonization of these sandy habitats. The effects of fire, litter, and seed depth were further examined by planting subterranean seeds at four depths in 16 litter-covered flats buried at ground level and comparing plants arising from burned flats with those in undisturbed litter-covered flats. At 0 and 1 cm depth, rates of seedling emergence were lowest in burned flats. Surface-sown seeds produced seedlings more likely to desiccate. Sowing depth had a greater influence on most measured characters than burning treatments. The mean depth of subterranean seed placement by Amphicarpum is 3.5 cm and this coincides with the seed depth from which plants showed the greatest height growth, shoot biomass, and reproductive output. In a second experiment, subterranean seeds on the bare soil surface in clay pots were more likely to lose viability and less likely to germinate than seeds protected by litter or burial in soil. In addition to providing protection from fire, placement of seeds below ground in the sandy habitat of peanutgrass provides conditions more suitable for seed survival and subsequent seedling establishment.     

深松对乌拉尔甘草根际土壤养分以及微生物群落功能多样性的影响

通过大田试验和室内分析相结合,研究了深松对乌拉尔甘草根际土壤养分和微生物群落功能多样性的影响,以期为乌拉尔甘草人工种植地土壤耕作措施优化和土壤环境改良提供依据。结果表明,与未深松(常规耕作)处理相比,深松处理对乌拉尔甘草根际土壤0—20 cm耕层土壤养分含量无显著性影响,可显著提高乌拉尔甘草根际土壤20—40 cm耕层有机质、全氮、全磷和全钾的含量,分别提高了60.8%、65.3%、48.9%和86.8%;明显增加了0—20 cm和20—40 cm耕层细菌、真菌和放线菌的数量(P0.05),3种类型的微生物数量均呈现出上层大于下层,深松大于未深松的变化趋势。在156 h的微生物温育期内,深松处理下不同土层的平均颜色变化率(AWCD)均显著高于未深松处理,并显著提高了AWCD的利用率(72 h,P0.05),较未深松分别提高了35.5%和130.8%。与未深松处理相比,深松处理显著提高了土壤微生物的多样性指数(H、S、D)。主成分分析(PCA)表明,深松优化了乌拉尔甘草根际土壤微生物的群落组成;聚合物、羧酸类化合物、氨基酸和碳水化合物是深松处理下根际土壤微生物利用的主要碳源。总而言之,深松处理显著提高乌拉尔甘草根际土壤养分含量、微生物数量和微生物多样性指数,改变了微生物群落功能多样性,造成这种差异的主要原因可能是深松改变了土壤耕层结构,改善了微生物的生存环境。因此,深松对乌拉尔甘草人工种植地土壤质量的改良有积极作用。     

Effects of AM colonization on “wild tobacco” plants grown in zinc-contaminated soil

This greenhouse study aimed to determine the effect of colonization by the arbuscular mycorrhizal (AM) fungus (Glomus intraradices Schenck & Smith) on the “wild” tobacco (Nicotiana rustica L. var. Azteca), under soil–zinc (Zn) conditions. Plants of N. rustica were grown in AM or non-AM inoculated substrate and subjected to four soil–[Zn] concentrations (0, 50, 100, and 250 mg Zn kg⁻¹ dry soil). The AM root colonization increased markedly from 14 to 81% with the increasing soil–[Zn] and the mycorrhizal structures were significantly more abundant at the highest soil–[Zn], suggesting that Zn may be involved directly or indirectly in AM root colonization. In addition, total Zn content or Zn concentrations in shoots and roots were shown to increase as soil–[Zn] increased in both AM and non-AM plants. As for the growth parameters studied, there were no significant differences between treatments despite the increase in Zn content or concentration. The AM roots subjected to the highest soil–[Zn] had a significant reduction by about 50% of total Zn content and Zn concentration compared to non-AM roots. Still, the relative extracted Zn percentage decreased dramatically as soil–[Zn] increased. Soil pH was significantly lower in non-AM than AM treatments at the highest soil–[Zn]. In summary, AM plants (particularly roots) showed lower Zn content and concentration than non-AM plants. In this regard, the AM fungi have a protective role for the host plant, thus playing an important role in soil-contaminant immobilization processes; and, therefore, are of value in phytoremediation, especially when heavy metals approach toxic levels in the soil.     

荒漠植物根际AM真菌的空间分布和定殖

 通过分析以色列荒漠地区Zygophyllum dumosum, Hammada scoparia, Artemisia herba-alba 和 Atriplex halimus 等4种灌木根际AM真菌的空间分布和定殖程度,研究了AM真菌分布和定殖与植物种类和土壤因子间的相关性。样品分别从0～10 cm,10～20 cm,20～30 cm,30～40 cm和40～50 cm等5个土层中采取,土样过2 mm筛。收集的根样切成1 cm根段,经染色后,根据感染长度确定AM真菌不同结构的定殖率;用湿筛倾析法和蔗     

Arbuscular mycorrhizae respond to plants exposed to elevated atmospheric CO2 as a function of soil depth

The importance of arbuscular mycorrhizae (AM) in plant and ecosystem responses to global changes, e.g. elevated atmospheric CO₂, is widely acknowledged. Frequently, increases in AM root colonization occur in response to increased CO₂, but also the lack of significant changes has been reported. The goal of this study was to test whether arbuscular mycorrhizae (root colonization and composition of root colonization) respond to plants grown in elevated CO₂ as a function of soil depth. We grew Bromus hordeaceus L. and Lotus wrangelianus Fischer & C. Meyer monocultures in large pots with a synthetic serpentine soil profile for 4 yr in an experiment, in which CO₂ concentration was crossed factorially with NPK fertilization. When analyzing root infection separately for topsoil (0–15 cm) and subsoil (15–45 cm), we found large (e.g., about 5-fold) increases of AM fungal root colonization in the subsoil in response to CO₂, but no significant changes in the corresponding topsoil of Bromus. Only the coarse endophyte AM fungi, not the fine endophyte AM fungi, were responsible for the observed increase in the bottom soil layer, indicating a depth-dependent shift in the AM community colonizing the roots, even at this coarse morphological level. Other response variables also had significant soil layer ^* CO₂ interaction terms. The subsoil response would have been hidden in an unstratified assessment of the total root system, since most of the root length was concentrated in the top soil layer. The increased presence of mycorrhizae in roots deeper in the soil should be considered in sampling protocols, as it may be indicative of changed patterns of nutrient acquisition and carbon sequestration.     

氮肥添加对高寒藏嵩草(Kobresia tibetica)沼泽化草甸和土壤微生物群落的影响

以藏嵩草沼泽化草甸为研究对象,利用磷脂脂肪酸(PLFA)技术,研究连续6年N素添加对地上植被群落数量特征、土壤微生物群落结构的影响。结果表明:①藏嵩草沼泽化草甸群落生物量、枯枝落叶对施肥处理无明显响应,且莎草科植物对土壤氮素的吸收和利用率较低。②施肥增加了0-10 cm土壤微生物类群PLFAs丰富度尤其细菌和革兰氏阳性菌PLFAs,降低了10-20 cm PLFAs丰富度;③磷脂脂肪酸饱和脂肪酸/单烯不饱和脂肪酸、细菌PLFAs/真菌PLFAs的比值随土壤层次增加而增加;④0-10 cm土层革兰氏阳性菌、真菌PLFAs含量与pH、土壤速效磷、速效氮、土壤有机质显著正相关(P0.05或P0.01);10-20 cm土层,细菌、革兰氏阳性菌、真菌和总PLFAs含量与土壤有机质含量显著正相关(P0.05或P0.01)。表明藏嵩草沼泽化草甸微生物PLFAs含量和丰富度对施肥的响应存在明显的土层梯度效应,土壤微生物PLFAs含量和丰富度主要受表层土壤初始养分含量的影响。     

AM真菌影响入侵植物黄顶菊与本土物种狗尾草竞争生长的机理研究

该研究以入侵植物黄顶菊[Flaveria bidentis(L.)Kunt]和本土伴生植物狗尾草为材料,通过筛选出黄顶菊单一优势群落AM真菌,于温室盆栽条件下,采用2物种单播、混播以及接种AM真菌和不接种共6个处理,分析AM真菌对黄顶菊和狗尾草的根系侵染率、相对竞争强度、植株氮磷钾光合利用率、以及丙二醛含量和保护酶活性的影响,探讨AM真菌对黄顶菊与狗尾草竞争生长的机理。结果显示:(1)黄顶菊根际土壤AM真菌共包括4属10种,其中优势种为Glomus constrictum、Glomus perpusillum、Glomus reticulatum;盆栽接种AM真菌后,黄顶菊的根系侵染率显著高于本土伴生植物狗尾草,但接种AM真菌后黄顶菊相对竞争强度显著降低了29.57%,却对狗尾草相对竞争强度无显著影响。(2)接种AM真菌使黄顶菊植株光合氮、磷、钾利用率显著升高,但对伴生植物狗尾草的光合氮、磷、钾利用率均无显著影响。(3)接种AM真菌对黄顶菊植株POD和CAT活性以及MDA含量无显著影响,但显著增加了SOD和APX活性,而伴对生植物狗尾草的POD、CAT和APX活性均显著降低,MDA含量显著提高。研究表明,AM真菌对黄顶菊和狗尾草具有不同的选择性,AM真菌的定植促进了黄顶菊的竞争生长,增加了植株N、P含量、光合养分利用率以及抗氧化酶活性;但显著降低了本土伴生植物狗尾草的N、P吸收以及抗氧化酶活性。因此,AM真菌在竞争生长中对黄顶菊产生了偏利反馈,有助于黄顶菊的入侵。     

Vertical distribution of soil nematodes in an age sequence of <Emphasis Type="Italic">Caragana microphylla</Emphasis> plantations in the Horqin Sandy Land,Northeast China

The vertical distribution of soil nematodes down to a depth of 50 cm was studied in an age sequence of 0-, 5-, 10-, and 22-year-old Caragana microphylla plantations (treatments) in the Horqin Sandy Land, Northeast China. The abundances and generic compositions of nematode fauna in five soil layers (0–10, 10–20, 20–30, 30–40, and 40–50 cm) were analyzed. 42 genera were observed in the nematode suspensions, and Acrobeles was the dominant genus in all treatments. The results showed that the total number of nematodes and the generic diversity in an age sequence of C. microphylla plantations decreased with increasing soil depth. Significant differences in the numbers of total nematodes, bacterivores (BF), plant parasites (PP), and omnivores–predators (OP) were observed between treatments and depths. BF was the most abundant trophic group in our study, followed by OP. The numbers of OP showed an obviously increasing trend with increasing age of C. microphylla plantation. The vertical distribution of the soil nematode communities was related to gradual changes in soil chemical properties, and it indicated that C. microphylla plantations have played positive roles in improving soil environmental conditions and restoring desertified ecosystems in the Horqin Sandy Land. The ecological indices selected were influenced by plantation chronosequence but not by soil depth.     

荒漠沙蒿根围AM真菌和DSE的空间分布

2009年7月在内蒙古黑城子北、多伦县城东和正蓝旗元上都遗址3个样地分别从0-10 cm、10-20 cm、20-30cm、30-40 cm和40-50 cm 5个土层采集沙蒿(Artemisia sphaerocephala)根围土壤和根样,系统研究了沙蒿根围AM真菌和DSE(Dark septate endophytes)的空间分布及与土壤因子的相关性。结果表明,沙蒿根系能被AM真菌高度侵染形成典型的I-型(Intermediate type)丛枝菌根,并发育形成泡囊和丛枝结构, 并与DSE形成良好的共生关系,样地生态条件和采样深度对AM真菌分布和活动有显著影响。黑城子样地孢子密度最高,元上都样地泡囊定殖率最高,不同样地间丛枝、菌丝、总定殖率和DSE定殖率无显著差异。孢子密度峰值出现在0-10cm表层土,并随土壤剖面深度增加而降低;泡囊定殖率峰值出现在10-20cm土层;AM真菌其他结构定殖率及DSE定殖率在各土层间差异不显著或变化无规律。孢子密度与AM真菌不同结构定殖率无显著相关性,与各土壤因子极显著正相关。泡囊定殖率与脲酶和碱性磷酸酶极显著负相关,与酸性磷酸酶显著负相关。菌丝定殖率、总定殖率及DSE定殖率与各土壤因子均无显著相关性。土壤碱解N和有机C与脲酶、酸性磷酸酶和碱性磷酸酶极显著正相关;土壤速效P与碱性磷酸酶极显著正相关,与脲酶显著正相关。对沙蒿根系AM真菌和DSE真菌分布和定殖规律的研究,可进一步明确AM真菌和DSE的生态功能,为利用菌根生物技术促进荒漠植被恢复和生态重建提供依据。     

Arbuscular mycorrhizal colonization of the dominant plant species in primary successional volcanic deserts on the Southeast slope of Mount Fuji

Arbuscular mycorrhizal (AM) colonization was observed on four plant species in primary successional volcanic deserts on the Southeast slope of Mount Fuji. The AM colonization of the dominant species, Polygonum cuspidatum, contradicts the conclusion that Polygonaceae are often regarded as being non-mycorrhizal species. The secondary dominant species, Polygonum weyrichii var. alpinum, formed no mycorrhizas. The roots of Cirsium purpuratum, Clematis stans and Campanula punctata ssp. hondoensis, showed a higher percentage of AM colonization than P. cuspidatum. AM colonization and spore density in the rhizosphere soil of P. cuspidatum significantly decreased as elevation increased. AM colonization in roots of Cirsium purpuratum and Clematis stans also tended to decrease with increased altitudes. Cirsium purpuratum and Campanula punctata ssp. hondoensis formed single structural types of Arum- and Paris-type, respectively, whereas P. cuspidatum and Clematis stans formed both Arum- and Paris-type morphologies.     

不同生境下川麦冬根围土壤丛枝菌根真菌多样性北大核心CSCD

采用高通量(Illumina Miseq)测序技术对栽培和野生2种生境下川麦冬根围的丛枝菌根(AM)真菌多样性和群落结构进行测定,并结合土壤理化因子进行相关性分析,以明确两种生境下川麦冬根围土壤AM真菌多样性和优势群落的分布特点,探讨AM真菌群落分布差异的驱动因子,为AM真菌应用于麦冬生产提供理论依据和技术支持。结果表明:(1)不同生境下川麦冬根围土壤中共鉴定出AM真菌3属10种,其中野生川麦冬根围土壤鉴定出的AM真菌3属7种,分别隶属于无梗囊霉属(Acaulospora)、多孢囊霉属(Diversispora)和球囊霉属(Glomus),而栽培环境下鉴定出AM真菌1属6种,隶属于球囊霉属。2个生境优势属均为球囊霉属。(2)不同生境下川麦冬根围AM真菌之间存在显著差异,野生生境下川麦冬根围土壤AM真菌多样性指数ACE和Shannon均显著高于人工栽培生境,而Simpson指数则相反。(3)相关性分析表明,AM真菌多样性指数及群落组成结构均与土壤理化因子存在相关性,其中全钾(TK)、全磷(TP)、全氮(TN)对AM真菌多样性指数和群落结构组成均存在显著影响。研究认为,不同生境下川麦冬根围AM真菌群落存在显著差异,球囊霉属为川麦冬互利共生的关键属,TK、TP、TN是不同生境川麦冬根围AM真菌群落差异的主要驱动因子。     

柠条人工林细根不同分枝根序寿命估计

植物细根在发育结构上表现的形态特征和生理功能异质性影响细根寿命的准确估计,因此了解分枝根序细根寿命差异对于深入认识细根的周转过程和陆地生态系统碳分配具有重要意义。采用微根管(Minirhizotron)技术对晋西北黄土区的五年生柠条(Caragana Korshinskii Kom.)人工林细根的生长过程进行了为期3a(2007—2009年)的追踪观测,分析了不同因素(土层深度、季节变化、空间位置)对一级根和高级根寿命的影响。结果表明:(1)在各土层深度处,一级根的中值寿命均低于高级根中值寿命,其中一级根中值寿命表现随土层深度增加而增加趋势,而高级根除表层0—20 cm中值寿命较短外,各土层间变化趋势不明显,40—60 cm、80—100 cm土层高级根在观测期结束时其累积存活率仍在50%以上;(2)不同季节出生一级根和高级根的中值寿命季节性表现为:秋季夏季春季,并且在各个季节均表现,高级根寿命显著大于一级根寿命(P0.01);一级根仅夏季与秋季差异性不显著(P0.05),而高级根仅春季与秋季存在极显著差异(P0.01);(3)一级根和高级根距树干基部0 cm处细根中值寿命均大于50 cm处一级根和高级根细根的中值寿命。同一位置处高级根寿命要大于一级根寿命。在距树干基部0 cm处和50 cm处,一级根和高级根的寿命均存在极显著差异(P0.01),但高级根却在距树干基部0 cm和50 cm处差异不明显,而一级根却表现极显著差异(P0.01)。     

荒漠油蒿（Artemisia ordosica）根围AM真菌分布与土壤酶活性

于2007年10月在油蒿(Artemisia ordosica)集中分布区选取4个典型样地,分别从0～10cm、10～20cm、20～30cm、30～40cm和40～50cm土层采集根围土样,分离其丛枝菌根(arbuscular mycorrhiza,AM)真菌并测定了3种土壤酶活性.结果表明,在各样地0～50cm土层中油蒿根系AM真菌菌丝定殖率均很高,有典型的泡囊与丛枝结构.菌丝定殖率与泡囊定殖率呈显著正相关,但菌丝、泡囊和丛枝定殖率与AM真菌孢子密度和土壤酶活性之间都无相关性;孢子密度在不同样地及采样深度间差异明显,与土壤有机质、速效磷和速效氮含量都呈一定正相关关系.孢子密度与脲酶和酸性磷酸酶活性有显著或极显著相关关系,与碱性磷酸酶活性之间的相关性受到土壤pH的显著影响.孢子密度的峰值出现在0～10cm表层土,并随土壤剖面深度增加而降低.土壤酶活性在土壤垂直剖面显示与孢子密度同样的规律.不同样地间AM真菌分布及油蒿根系定殖率的差异表明,油蒿与AM真菌之间有良好共生性,对维护荒漠生态环境系统结构的完整性具有重要意义.