入侵豚草与本地植物竞争对丛枝菌根真菌多样性的影响

外来植物入侵常引起入侵地丛枝菌根真菌（arbuscular mycorrhizal fungi,AMF）多样性的变化,但AMF多样性的变化与入侵域本地植物种类相关性目前尚不清楚。本研究采用野外同质园试验研究豚草与不同本地植物竞争时对AMF多样性的影响。本试验共设入侵豚草单种、本地植物狗尾草Setaria viridis单种、藜 Chenopodium album单种、黄香草木犀Melilotus officinalis单种、豚草和狗尾草混种、豚草和藜混种、豚草和黄香草木犀混种以及裸土（无任何植物生长）对照8个处理。采集根区土样后分离、鉴定AMF,分析植株生物量和AMF物种多样性变化间的关系。结果表明,对豚草而言,单种处理中生物量均高于混种处理;豚草分别与3种本地植物竞争时,与黄香草木犀混种中豚草竞争能力最强,而与藜混种中竞争能力最弱。豚草分别与3种本地植物混种时土壤中AMF种丰度和香农-威纳指数分别显著高于豚草单种和本地植物单种,其中豚草与藜混种中AMF的种丰度和香农-威纳指数最高,与狗尾草混种中AMF的种丰度和香农-威纳指数最低,而豚草分别与3种本地植物混种处理中孢子密度显著低于本地植物单种（豚草与黄香草木犀混种除外）。豚草单种、狗尾草单种、藜单种、豚草分别与狗尾草和藜混种4个处理中AMF优势种均为网状球囊霉Glomus reticulatum和缩隔球囊霉Septoglomus constrictum;黄香草木犀单种中优势种是网状球囊霉、缩隔球囊霉和根内根孢囊霉Rhizophagus Intraradices,豚草与黄香草木犀混种中优势种是网状球囊霉和根内根孢囊霉;狗尾草单种、豚草与狗尾草混种和豚草与藜混种3个处理的特有种分别是木薯根孢囊霉Rhizoglomus manihotis、近明球囊霉Claroideoglomus claroideum和美丽盾巨孢囊霉Scutellospora calospora。狗尾草单种生物量与孢子密度呈显著正相关,豚草与狗尾草混种中豚草的生物量与均匀度呈显著负相关,豚草与黄香草木犀混种中豚草的生物量与孢子密度呈显著正相关,与香农威纳指数呈显著负相关。综上可知,豚草与本地植物竞争对AMF多样性的影响具有异质性,这与本地植物种类密切相关。     

不同植物(组合)对入侵杂草黄顶菊功能性状的影响

【目的】外来植物的入侵能力与其性状之间的关系是入侵生态学中的基本问题之一。外来植物成功入侵具备哪些植物功能性状,一直是研究的热点问题,研究和把握这些性状对外来植物的入侵机理研究具有重要的现实意义。【方法】利用同质园实验,以入侵植物黄顶菊为研究对象,设置不同的植物(或组合)与黄顶菊竞争处理,研究不同植物(组合)对黄顶菊植物功能性状的影响,从而探究不同植物对黄顶菊的抵御能力。【结果】地肤、苘麻、苏丹草和苏丹草与地肤、黄花草木樨组合对黄顶菊有一定抑制作用,混种处理中黄顶菊的生物量、分枝数、株高显著低于黄顶菊单种处理,且对叶片功能性状、根功能性状、植株的全C和全N量等都有一定程度的影响。而反枝苋、反枝苋和紫花苜蓿组合对黄顶菊的生长有一定的促进作用,混种处理中黄顶菊的生物量与全C、全N含量较单种黄顶菊显著增加。【结论】不同植物与黄顶菊竞争生长对黄顶菊的影响不同,地肤和苘麻可以显著地抑制黄顶菊的主要功能性状生长发育,而反枝苋和紫花苜蓿促进黄顶菊生长发育。     

Bacillus promotes invasiveness of exotic Flaveria bidentis by increasing its nitrogen and phosphorus uptake

芽孢杆菌通过提高黄顶菊对氮和磷的吸收促进外来黄顶菊的入侵 外来植物入侵对土壤芽孢杆菌(Bacillus)多样性的影响及芽孢杆菌在外来植物入侵中的作用目前尚不清楚。黄顶菊(Flaveria bidentis)是入侵中国的有害杂草,狗尾草(Setaria viridis)是黄顶菊入侵地常见的伴生植物种。本研究利用野外大田试验和温室盆栽试验,比较黄顶菊和狗尾草根际土壤芽孢杆菌群落结构的差异,以及黄顶菊和狗尾草根际土壤芽孢杆菌对黄顶菊竞争生长的影响。野外大田试验包括黄顶菊 单种、黄顶菊和狗尾草混种、狗尾草单种3个处理。利用16S rRNA基因测序技术研究了不同处理两种植物 根际土壤芽孢杆菌的多样性,获知黄顶菊根际土壤聚集的优势芽孢杆菌;利用温室盆栽试验探究优势芽孢杆菌对黄顶菊竞争生长的影响。研究结果表明,黄顶菊和狗尾草根际土壤芽孢杆菌多样性差异显著,其中耐寒芽孢杆菌是黄顶菊和狗尾草根际土壤聚集的优势芽孢杆菌,但是黄顶菊根际土壤中耐寒芽孢杆菌相对丰度显著高于狗尾草根际土壤耐寒芽孢杆菌的相对丰度。接菌试验表明,与狗尾草根际土壤中的耐寒芽孢杆菌相比,黄顶菊根际土壤聚集的耐寒芽孢杆菌提高了黄顶菊体内氮和磷的水平。总之,黄顶菊入侵改变了根际土壤芽孢杆菌的群落结构,黄顶菊根际土壤聚集的耐寒芽孢杆菌通过提高黄顶菊植株体内氮、磷水平来促进黄顶菊的生长。     

入侵植物与本地植物互作对丛枝菌根真菌AMF侵染率的影响

外来植物成功入侵与菌根共生体存在着密不可分的关系,丛枝菌根真菌（AMF）侵染率是反映其侵染植物情况的重要指标,影响侵染率的因素很多,但是入侵植物与本地植物互作对AMF侵染率的影响目前还不清楚。因此,本研究以外来入侵植物黄顶菊Flaveria bidentis、豚草Ambrosia artemisiifolia、三叶鬼针草Bidens pilosa和本地植物狗尾草Setaria viridis、黄香草木犀Melilotus officinalis、藜Chenopodium album为研究对象,设置入侵植物单种处理、本地植物单种处理、每种入侵植物分别与本地植物两两混种处理以及每种入侵植物同时与所有本地植物混种处理,观察测定不同处理下入侵植物与本地植物根系丛枝、泡囊、菌丝及总侵染率,比较研究本地植物种类变化对入侵植物和本地植物根系AMF侵染率的影响,以及3种入侵菊科植物对本地植物AMF侵染率的影响规律是否一致。结果表明,与入侵植物单种相比,除豚草与藜、豚草同时与3种本地植物混种两个处理中,豚草根系的AMF菌丝及总侵染率显著增加外,其余所有处理中入侵植物总侵染率均无显著差异;与狗尾草或黄香草木犀单种相比,每种入侵植物同时与所有本地植物混种处理中,本地植物狗尾草和黄香草木犀根系上的AMF菌丝及总侵染率均显著降低,即随本地植物种类数目的增加,对本地植物根系的菌丝及总侵染率存在显著抑制作用,而对入侵植物无显著影响。     

四种牧草植物替代控制对黄顶菊入侵土壤细菌多样性的影响

土壤微生物群落与植物的生长发育密切相关, 入侵植物可以改变入侵地土壤微生物类群, 使土壤理化性质发生变化, 从而促进其入侵过程。该文通过比较高丹草(Sorghum bicolor × S. sudanense)、向日葵(Helianthus annuus)、紫花苜蓿(Medi- cago sativa)和多年生黑麦草(Lolium perenne)4种替代植物与黄顶菊(Flaveria bidentis)混合种植(以下简称混种)后不同时期的土壤细菌多样性的变化, 揭示土壤细菌群落对黄顶菊入侵及替代管理措施的响应规律。结果表明, 单独种植(以下简称单种)黄顶菊的土壤细菌多样性下降, 并且在整个生长期多样性指数多数情况下低于高丹草、向日葵、紫花苜蓿和多年生黑麦草单种或与黄顶菊混种的土壤。当4种替代植物与黄顶菊混种后, 土壤细菌16S rRNA的变性梯度凝胶电泳(DGGE)图谱与它们分别种植时存在明显差异, 且不同生长期各个混种土壤都有特征细菌群落。4种替代植物单种或与黄顶菊混种的土壤细菌Shannon多样性指数变化规律与植物生长发育趋势相同, 7月份达到高峰, 8月份开始降低。总之, 黄顶菊入侵降低了土壤细菌群落多样性, 4种替代植物与黄顶菊混种后, 又可提高土壤细菌群落多样性, 这种变化对黄顶菊成功入侵和替代防控具有重要作用。     

施肥与竞争生长对入侵植物黄顶菊和本地植物光合特性的影响

【背景】黄顶菊具有较强的生态适应性和竞争能力,可压制或排挤本地物种,形成单优势种群,进而导致当地生物多样性下降。【方法】选取黄顶菊入侵域的4种伴生植物益母草、苘麻、马唐、反枝苋为研究对象,采用LI-6400便携式光合仪测定入侵植物黄顶菊与这4种植物竞争生长过程中的光合特性,并研究施肥对不同植物与黄顶菊竞争生长过程中光合速率、蒸腾速率和胞间CO2浓度的影响。【结果】竞争生长对黄顶菊净光合速率的影响与本地植物种类密切相关,施肥促进了黄顶菊的净光合速率;竞争生长显著抑制了益母草、马唐和反枝苋的净光合速率,促进了苘麻的净光合速率,施肥增强了这4种植物的净光合速率。竞争生长对益母草和苘麻蒸腾速率的影响显著,而对其他2种植物的影响较小;与苘麻、益母草和反枝苋竞争生长过程中黄顶菊的蒸腾速率显著降低;施肥显著降低了单种处理中黄顶菊的蒸腾速率。与益母草、苘麻和反枝苋竞争生长过程中黄顶菊的胞间CO2浓度明显降低,施肥处理对黄顶菊的CO2利用率有显著抑制作用。【结论与意义】施肥影响黄顶菊的光合特性,与不同本地植物竞争生长对黄顶菊光合特性的影响不同。本研究结果将为进一步揭示黄顶菊的入侵机制及其综合治理提供理论依据。     

不同植物对黄顶菊根际土壤微生物和土壤养分的影响

[目的] 不同植物对外来入侵植物的抵御能力不同,研究不同植物对入侵植物根际土壤生态的影响可为筛选入侵植物的竞争替代植物提供科学依据。[方法] 利用同质园试验,以入侵植物黄顶菊为研究对象,设置黄顶菊单种、黄顶菊与不同植物（地肤、苘麻、苏丹草、反枝苋）混种处理,采用磷脂脂肪酸分析方法来研究不同植物对黄顶菊根际土壤微生物群落结构的影响,并结合土壤养分的变化探究不同植物对黄顶菊根际土壤生态的影响。[结果] 与黄顶菊单种相比,地肤和苘麻降低了黄顶菊根际微生物的总含量,改变了黄顶菊根际微生物群落结构。地肤、苘麻能竞争性抑制黄顶菊对铵态氮的吸收,从而抑制黄顶菊的生长。[结论] 不同植物的抵御能力与其土壤生态有关,替代植物通过改变黄顶菊根际土壤微生物,抑制黄顶菊对氮的吸收,从而抑制黄顶菊的生长,实现对黄顶菊的替代控制。     

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。     

黄顶菊对入侵地群落动态及植物生长生理特征的影响

为明确黄顶菊对入侵地植物群落和土著植物生理生长的影响机制,采用同质园试验对入侵和非入侵土壤的植物群落开展了整个生育期动态监测,并分析了黄顶菊入侵对狗尾草、羽叶鬼针草、灰绿藜、地肤4种土著植物生长和生理特征的影响规律。结果表明:黄顶菊入侵土壤植物群落多样性指数低于非入侵地,且有季节性差异,随生育期的推进差异逐渐减小;黄顶菊对本地植物的生长指标有显著影响(P0.05),随时间变化显著,但存在物种差异;4种植物的净光合速率(Pn)、气孔导度(Cd)、蒸腾速率(Tr)在非入侵土壤生长显著高于入侵地土壤(P0.05);而4种植物在入侵土壤生长的比叶面积(SLA)、比根长(SRL)、比根面积(SRA)显著高于本地土壤(P0.05)。综上,黄顶菊入侵抑制了本地植物的光合效率,减少了生物量的积累,导致本地植物群落的生物多样性水平降低,但表现出季节差异;不同物种对黄顶菊入侵胁迫的响应表现种间特异性,为理解入侵种对群落结构影响和实现入侵生境恢复提供了理论依据。     

电子废弃物拆解区土壤重金属污染对丛枝菌根真菌多样性的影响

【背景】电子废弃物拆解造成的土壤重金属污染引发的环境问题日益突出,丛枝菌根(arbuscular mycorrhizal,AM)真菌能侵染植物根系并增强植物抵御环境胁迫的能力,具有重要的生态功能和应用潜力。【目的】探究电子废弃物拆解区土壤重金属污染对AM真菌群落结构与多样性的影响,甄别可耐受重金属污染的AM真菌类群。【方法】从浙江台州某典型电子废弃物拆解场地及其周边区域共采集土壤样品12份,针对土壤中AM真菌的18S rRNA基因进行高通量测序以及可操作分类单元(operational taxonomic unit,OTU)相对丰度和多样性指数计算。【结果】该区土壤中AM真菌由原囊霉目(Archaeosporales)、球囊霉目(Glomerales)和多孢囊霉目(Diversisporales)组成,其中球囊霉目占据优势地位。土壤AM真菌多样性指数与重金属的浓度、综合污染指数和潜在生态风险指数间均无显著相关性,但疑似泡囊根生囊霉(Rhizophagus vesiculiferus)的OTU相对丰度与上述重金属污染指标之间均呈显著正相关关系。【结论】R. vesiculiferus可能对重金属污染有极强耐受性,可为今后电子废弃物拆解污染土壤治理提供技术基础。     

Differential host plant performance as a function of soil arbuscular mycorrhizal fungal communities: experimentally manipulating co-occurring Glomus species

In order to evaluate host plant performance relative to different soil arbuscular mycorrhizal fungal (AMF) communities, Andropogon gerardii seedlings were grown with nine different AMF communities. The communities consisted of 0, 10, or 20 spores of Glomus etunicatum and 0, 10, or 20 spores of Glomus intraradices in all possible combinations. Spores were produced by fungal cultures originating on A. gerardii in a serpentine plant community; seeds of A. gerardii were collected at the same site. The experiment was performed in the greenhouse using a mixture of sterilized serpentine soil and sand to which naturally occurring non-mycorrhizal microbes were added. There was no difference in root AMF colonization rates between single species communities of either G. etunicatum or G. intraradices, but G. intraradices enhanced plant growth and G. etunicatum did not. However, plants grew larger with some combinations of G.␣intraradices plus G. etunicatum than with the same quantity of G. intraradices alone. These results suggest the potential for niche complementarity in the mycorrhizal fungi. That G. etunicatum only increased plant growth in the presence of G. intraradices could be illustrative of why AMF that appear to be parasitic or benign when examined in isolation are maintained within multi-species mycorrhizal communities in nature.     

Life history plasticity and fitness in a caddisfly in response to proximate cues of pond-drying

The majority of plants are involved in symbioses with arbuscular mycorrhizal fungi (AMF), and these associations are known to have a strong influence on the performance of both plants and insect herbivores. Little is known about the impact of AMF on complex trophic chains, although such effects are conceivable. In a greenhouse study we examined the effects of two AMF species, Glomus intraradices and G. mosseae on trophic interactions between the grass Phleum pratense, the aphid Rhopalosiphum padi, and the parasitic wasp Aphidius rhopalosiphi. Inoculation with AMF in our study system generally enhanced plant biomass (+5.2%) and decreased aphid population growth (−47%), but there were no fungal species-specific effects. When plants were infested with G. intraradices, the rate of parasitism in aphids increased by 140% relative to the G. mosseae and control treatment. When plants were associated with AMF, the developmental time of the parasitoids decreased by 4.3% and weight at eclosion increased by 23.8%. There were no clear effects of AMF on the concentration of nitrogen and phosphorus in plant foliage. Our study demonstrates that the effects of AMF go beyond a simple amelioration of the plants’ nutritional status and involve rather more complex species-specific cascading effects of AMF in the food chain that have a strong impact not only on the performance of plants but also on higher trophic levels, such as herbivores and parasitoids.     

连作花魔芋软腐病株与健株根域丛枝菌根真菌群落多样性

【目的】解析不同连作年限花魔芋软腐病株、健株根域的丛枝菌根真菌(arbuscular mycorrhizal fungi,AMF)群落多样性。【方法】使用AMF 18S SSU rRNA基因特异引物AMV4.5NF/AMDGR对正茬及连作2年和3年的软腐病株、健株魔芋根系和根际土壤DNA扩增建库,通过高通量测序和生物信息学分析探究魔芋软腐病与其根域AMF群落多样性的关系。【结果】魔芋根系具有明显的AMF菌丝、泡囊和丛枝等结构。在相同连作年限条件下,健株根系AMF总侵染率、侵染强度和孢子密度均显著高于病株(P<0.05);在不同连作年限条件下,病株根系AMF总侵染率和侵染强度随连作年限延长而降低。从所有样品中共鉴定到9属53种AMF,其中有49个已知种和4个新种。球囊霉属(Glomus)和类球囊霉属(Claroideoglomus)是AMF群落的优势属,其AMF种分别占总AMF种数的41.5%和26.4%;丰度最高的Paraglomus sp.VTX00308是所有样品的共有种。连作、软腐病及二者的交互作用显著影响根系AMF群落的Shannon指数和Simpson指数及根际土壤AMF的Chao1指数(P<0.05)。通过丰度差异分析发现6个在连作软腐病发生后丰度差异显著的AMF种(P<0.05);NMDS分析表明,不同连作年限的魔芋软腐病株与健株之间的根域AMF菌种组成、相对丰度和群落结构存在差异。相关性分析表明,软腐病发病率和病情指数与魔芋根系和根际土壤AMF的Shannon指数、根系AMF的Chao1和Simpson指数以及AMF总侵染率、侵染强度和孢子密度极显著负相关(P<0.01)。【结论】比对健株,连作魔芋软腐病株根际土壤AMF孢子密度以及根系AMF侵染率、种数和多样性均降低,其群落结构显著改变。     

Different native arbuscular mycorrhizal fungi influence the coexistence of two plant species in a highly alkaline anthropogenic sediment

Different species of arbuscular mycorrhizal fungi (AMF) can produce different amounts of extraradical mycelium (ERM) with differing architectures. They also have different efficiencies in gathering phosphate from the soil. These differences in phosphate uptake and ERM length or architecture may contribute to differential growth responses of plants and this may be an important contributor to plant species coexistence. The effects of the development of the ERM of AMF on the coexistence of two co-occurring plant species were investigated in root-free hyphal chambers in a rhizobox experimental unit. The dominant shrub (Salix atrocinerea Brot.) and herbaceous (Conyza bilbaoana J. Rémy) plant species found in a highly alkaline anthropogenic sediment were studied in symbiosis with four native AMF species (Glomus intraradices BEG163, Glomus mosseae BEG198, Glomus geosporum BEG199 and Glomus claroideum BEG210) that were the most abundant members of the AMF community found in the sediment. Different AMF species did not influence total plant productivity (sum of the biomass of C. bilbaoana and S. atrocinerea), but had a great impact on the individual biomass of each plant species. The AMF species with greater extracted ERM lengths (G. mosseae BEG198, G. claroideum BEG210 and the four mixed AMF) preferentially benefited the plant species with a high mycorrhizal dependency (C. bilbaoana), while the AMF species with the smallest ERM length (G. geosporum BEG199) benefited the plant species with a low mycorrhizal dependency (S. atrocinerea). Seed production of C. bilbaoana was only observed in plants inoculated with G. mosseae BEG198, G. claroideum BEG210 or the mixture of the four AMF. Our results show that AMF play an important role in the reproduction of C. bilbaoana coexisting with S. atrocinerea in the alkaline sediment and have the potential to stimulate or completely inhibit seed production. The community composition of native AMF and the length of the mycelium they produce spreading from roots into the surrounding soil can be determinant of the coexistence of naturally co-occurring plant species.     

接种AMF对菌根植物和非菌根植物竞争的影响

为了研究丛枝菌根真菌(arbuscular mycorrhizal fungus, AMF)对菌根植物与非菌根植物种间竞争的影响,以玉米(菌根植物)和油菜(非菌根植物)作为供试植物,分别进行间作、尼龙网分隔和单作,模拟这两种植物之间不同的竞争状态,接种丛枝菌根真菌Glomus intraradices和Glomus mosseae,比较菌根植物和非菌根植物的生长和磷营养状况,分析AMF侵染对植物种间竞争作用的影响。结果显示,与单作相比,间作模式下玉米的生物量及磷营养状况有所降低,但其菌根依赖性却有所提高。与不接种相比,接种处理显著降低了间作体系油菜根系的磷含量和磷吸收量,但趋于改善菌根植物玉米的磷营养状况。因此,接种AMF可以降低非菌根植物的磷营养状况及生物量,使得菌根植物的相对竞争能力明显提高,说明AMF在维持物种多样性方面有着重要的作用。     

Diversity and infectivity of arbuscular mycorrhizal fungi in agricultural soils of the Sichuan Province of mainland China

Knowledge about the presence and diversity of arbuscular mycorrhizal fungi (AMF) in a specific area is an essential first step for utilizing these fungi in any application. The community composition of AMF in intensively managed agricultural soil in the Sichuan Province of southwest China currently is unknown. In one set of samples, AMF were trapped in pot cultures from 40 fields growing legumes in the Panxi region, southeast Sichuan. In a second set of samples, the MPN method with four-fold dilutions and maize as host was used to estimate infective propagules in soil from another 50 agricultural sites throughout the province. Soil types were heterogeneous and were classified as purple, yellow, paddy and red. Crops at each site were either maize, wheat or sweet orange. From this set of soil, AMF spores were also extracted and identified. Including all ninety soils, thirty glomeromycotan species in Glomus (20 species), Acaulospora (four species), Scutellospora (three species), Ambispora (one species), Archaeospora (one species) and Paraglomus (one species) were identified. Yellow, red and purple soils yielded similar numbers of AMF species, while AMF species diversity was clearly lower in paddy soil. In trap culture soils, the most frequent species were Glomus aggregatum or Glomus intraradices, Glomus claroideum and Glomus etunicatum. The species Acaulospora capsicula, Acaulospora delicata, G. aggregatum (or intraradices), G. claroideum, Glomus epigaeum, G. etunicatum, Glomus luteum, Glomus monosporum, Glomus mosseae and Glomus proliferum were successfully cultured as single-species pot cultures in Plantago lanceolata. The three most frequent species in field soils were G. mosseae, Glomus caledonium and Glomus constrictum. MPN values varied between 17 and 3334 propagules 100 g soil⁻¹ among the fifty field sites sampled. Regression analysis, including host&soil, log(P) and pH as explanatory variables explained 59% of the variation in log(MPN). The highest MPN estimates were found in purple soil cropped with maize and citrus, 324 and 278 propagules 100 g soil⁻¹, respectively. The lowest MPN value, 54 propagules 100 g soil⁻¹, was measured in wheat in purple and yellow soil. Despite intensive agricultural management that can include often repeated tillage, our examination of 90 agricultural sites revealed that soils of the Sichuan region have moderate to high numbers of infective AMF propagules as well as a high AMF species diversity. This opens possibilities for further studies and utilization of AMF in agriculture and horticulture in the Sichuan province, People’s Republic of China.     

Glomus intraradices dominates arbuscular mycorrhizal communities in a heavy textured agricultural soil

Arbuscular mycorrhizal fungal (AMF) spore communities were surveyed in a long-term field fertilization experiment in Switzerland, where different amounts of phosphorus (P) were applied to soil. Plots receiving no P as well as plots systematically fertilized in excess to plant needs for 31 years were used to test the hypothesis that application of P fertilizer changes the composition and diversity of AMF communities. AMF spores were isolated from the field soil, identified, and counted so as to quantify the effect of P fertilization on AMF spore density, composition, and diversity. Trap cultures were established from field soil with four host plants (sunflower, leek, maize, and Crotalaria grahamiana), and the spore communities were then analyzed in substrate samples from the pots. Altogether, nine AMF species were detected in the soil. No evidence has been acquired for effect of P fertilization on spore density, composition, and diversity of AMF in both the field soil and in trap cultures. On the other hand, we observed strong effect of crop plant species on spore densities in the soil, the values being lowest under rapeseed and highest under Phacelia tanacetifolia covercrop. The identity of plant species in trap pots also significantly affected composition and diversity of associated AMF communities, probably due to preferential establishment of symbiosis between certain plant and AMF species. AMF spore communities under mycorrhizal host plants (wheat and Phacelia in the fields and four host plant species in trap pots) were dominated by a single AMF species, Glomus intraradices. This resulted in exceptionally low AMF spore diversity that seems to be linked to high clay content of the soil.Electronic supplementary material Supplementary material is available for this article at and accessible for authorised users.