Response of fungal communities to afforestation and its indication for forest restoration

Soil fungi in forest ecosystems have great potential to enhance host plant growth and systemic ecological functions and services.Reforestation at Saihanba Mechanized Forest Farm,the world's largest artificial plantation,has been integral to global forest ecosystem preservation since the 1950s.To better assess the ecological effects of soil microbiology after afforestation,fungal diversity and community structure(using Illumina sequencing)from forests dominated by Larix gmelinii var.principis-rupprechtii,Pinus sylvestris var.mongolica and Picea asperata,and from grassland were surveyed.In total,4,540 operational taxonomic units(OTUs)were identified,with Mortierella and Solicoccozyma being the dominant genera of grassland soil and Inocybe,Cortinarius,Piloderma,Tomentella,Sebacina,Hygrophorus and Saitozyma dominating the plantation soil.Principle coordinate analysis(PCoA)and co-occurrence networks revealed differences in fungal structure after afforestation.Significantly,more symbiotroph guilds were dominated by ectomycorrhizal fungi in plantations under the prediction of FUNGuild.The community composition and diversity of soil fungi were significantly influenced by pH via redundancy analysis(RDA)and the Mantel test(p<0.01).This finding emphasizes that soil pH has a strong effect on the transition of fungal communities and functional taxa from grassland to plantation,providing a novel indicator for forest restoration.

天山北部不同生境苜蓿根际土壤真菌分布特征及驱动因子

在农业生态系统中,根际微生物群落是土壤中养分和有机物质成功循环和转化的动力,对作物的生长、健康和营养状况起着重要的影响作用。为了探究天山北部不同生境苜蓿根际土壤真菌多样性以及形成差异的驱动因子。利用高通量测序技术对天山北部山地和平原2个生境的苜蓿根际土壤与非根际土壤中真菌多样性、结构、功能以及驱动因子进行分析。结果表明:(1)山地苜蓿根际土中土壤氮、钾、有机质和酶活性均显著大于平原苜蓿根际土,而电导率和pH显著小于平原苜蓿根际土。(2)山地和平原的真菌群落存在显著差异,平原苜蓿根际土壤的可操作分类单元(OTUs)、Chao1和ACE指数均显著大于山地苜蓿根际土壤,并且OTUs、Chao1、ACE和香农指数(Shannon指数)均表现为根际土壤显著大于非根际土壤。(3)该区域的优势真菌门为子囊菌门(Ascomycota)、被孢霉菌门(Mortierellomycota)、担子菌门(Basidiomycota)和芽枝菌门(Blastocladiomycota),并且在不同生境存在显著差异。(4)基于FUNGuild真菌功能预测,山地中植物的致病真菌显著高于平原而外生菌根显著低于平原地区。(5)通过冗余分析(RDA)和Mantel检验发现土壤pH、全氮、全钾和速效钾是真菌群落结构差异分布的主要驱动因子。

The “neighbor avoidance effect” of microplastics on bacterial and fungal diversity and communities in different soil horizons

Microplastics are a new type of environmental pollutant,and pose a serious threat to soil ecosystems.It is important to study microplastics effects on soil microorganisms to better understand their effects on terrestrial ecosystems.Therefore,we collected soil and microplastic samples from corn,pepper,peanut and cucumber fields in Shunyi District,Beijing,China,and used Illumina MiSeq high-throughput sequencing technology to analyze bacterial and fungal community composition and diversity.We focused on microplastic surface and its surrounding“rhizosphere-like”soil in the 0e10 cm(humus)and 10e20 cm(eluvial)deep horizons.Microbial richness and diversity on microplastic surface were significantly lower than those in surrounding“rhizosphere-like”soil,and microbial richness and diversity were reduced to a greater extent in the humus horizon than in the eluvial horizon.Microplastics likely enriched the microbes involved in their biodegradation.The relative abundance levels of Cyanobacteria and Basidiomycota on microplastic surfaces were significantly higher than those in surrounding“rhizosphere-like”soil,while the relative abundance levels of Acidobacteria,Chloreflexi,and Mortierellomycota were higher in“rhizosphere-like”soil.Furthermore,the relative abundance levels of pathways related to human diseases,animal pathogen,and fungal parasites were significantly higher on microplastic surfaces than in“rhizosphere-like”soil.These results show that the microbial diversity,richness,community structure and function between microplastic surfaces and surrounding“rhizosphere-like”soil are significantly different,leading to a“rhizosphere-like neighbor avoidance effect”between microplastic surfaces and the surrounding soil.

小麦与蚕豆间作对根际真菌代谢功能多样性的影响

通过田间小区试验，采用Biolog FF微平板培养方法，研究小麦与蚕豆间作对小麦和蚕豆根际真菌代谢功能多样性的影响。结果表明：与单作相比，间作明显提高了小麦和蚕豆根际真菌的碳源平均利用率（AWCD），且问作提高蚕豆根际真菌活性的幅度大于小麦。与单作相比，间作显著提高了蚕豆和小麦根际真菌对Biolog FF板中聚合物、糖类、羧酸类、氨基酸类和胺类碳源的利用；同时间作使小麦和蚕豆根际真菌对碳源的总利用强度比单作分别显著提高63．30％和52．02％，小麦和蚕豆根际真菌对Biolog FF板中6类碳源的利用强度百分比以糖类、羧酸类和氨基酸最高，分别为36．66％～45．99％、25．65％～27．70％和16．37％～20．67％。小麦与蚕豆间作显著提高了小麦和蚕豆根际真菌的香农多样性指数（H）和丰富度指数（S）。主成分分析表明，间作明显改变了小麦和蚕豆根际真菌的群落结构。小麦与间作蚕豆明显促进了小麦和蚕豆根际土壤真菌的碳源代谢强度，显著提高了根际真菌的多样性和丰富度，改变了根际真菌的群落结构，因而是一种有利于改善蚕豆连作栽培根际微生态环境的有效措施。

转基因高蛋氨酸大豆对根际真菌群落碳代谢功能的影响

尽管转基因作物在农业上的推广为人们提供了许多好处,但其对生态环境的影响也越来越引起人们的广泛关注。本研究采用Biolog FF微平板法,调查了转基因高蛋氨酸大豆ZD91对根际真菌群落碳代谢功能的影响。结果表明,转基因大豆ZD91与其受体大豆ZD的根际真菌群落功能没有显著差异。本研究为转基因作物的环境安全性评价提供了基础。

Plant-associated fungal communities in the light of meta’omics

Approaches for the cultivation-independent analysis of microbial communities are summarized as meta’omics,which predominantly includes metagenomic,-transcriptomic,-proteomic and-metabolomic studies.These have shown that endophytic,root-associated and soil fungal communities are strongly shaped by associated plant species.The impact of plant identity on the composition of its litterssociated fungal community remains to be disentangled from the impact of litter chemistry.The composition of the plant community also shapes the fungal community.Most strikingly,adjacent plant species may share mycorrhizal symbionts even if the plants usually have different types of mycorrhizal fungi associated with them(ectomycorrhizal,ericoid and arbuscular mycorrhizal fungi).Environmental parameters weakly explain fungal community composition globally,and their effect is inconsistent at local and regional scales.Decrease in similarity among communities with increasing distance(i.e.distance decay)has been reported from local to global scales.This pattern is only exceptionally caused by spatial dispersal limitation of fungal propagules,but mostly due to the inability of the fungi to establish at the particular locality(i.e.environmental filtering or competitive exclusion).Fungal communities usually undergo pronounced seasonal changes and also differ between consecutive years.This indicates that development of the communities is usually not solely cyclic.Meta’omic studies challenge the classical view of plant litter decomposition.They show that mycorrhizal and(previously)endophytic fungi may be involved in plant litter decomposition and only partly support the idea of a succession from an Ascomycota to a Basidiomycota-dominated community.Furthermore,vertical separation of saprotrophic and mycorrhizal species in soil and sequential degradation from easily accessible to‘recalcitrant’plant compounds,such as lignin,can probably not be generalized.The current models of litter decomposition may therefore have to be eventually refined for certain ecosystems and environmental conditions.To gain deeper insights into fungal ecology,a meta’omic study design is outlined which focuses on environmental processes,because fungal communities are usually taxonomically diverse,but functionally redundant.This approach would initially identify dynamics of chemical shifts in the host and/or substrate by metametabolomics.Detected shifts would be subsequently linked to microbial activity by correlation with metatranscriptomic and/or metaproteomic data.A holistic trait-based approach might finally identify factors shaping taxonomic composition in communities against the dynamics of the environmental process(es)they are involved in.

5种植物根际真菌群落结构与多样性

根际真菌在植物生长和健康方面具有非常重要的作用,然而由于分离和培养技术的限制,对根际真菌群落、多样性及功能仍缺乏认识.为明确不同植物根际真菌群落的结构与差异,揭示其潜在的生态功能,采用Illumina MiSeq技术对马蔺、葡萄、大豆、玉米等5种植物根际真菌ITS rRNA基因的ITS2区进行高通量测序,并利用FUNGuild对其功能进行预测分析.结果显示,5种植物根际中80%以上的真菌序列划分到17-45个OTUs中,优势菌门为子囊菌门,优势菌纲为座囊菌纲和粪壳菌纲等;这5种植物根际真菌群落各自聚群,其香农指数(Shannon)和丰富度(Chao1)从大到小依次为木瓜、马蔺、葡萄、大豆、玉米;在获得的1 290个OTUs中,49.76%的OTUs归属于8个功能类群,其中腐生菌约占总OTUs数的25.89%,是主要功能类群,其次是病原菌/腐生/共生过渡型、植物病原体等,葡萄、木瓜和马蔺根际中腐生菌显著高于大豆和玉米.本研究表明木瓜、马蔺和常见植物根际真菌的群落结构和多样性不同,一年生作物的根际真菌多样性小于多年生植物,进而也表明根际真菌群落及其生态功能受到植物的生活周期或类型的影响.(图4表1参30)