Variable sensitivity of plant communities in Iceland to experimental warming

Facing an increased threat of rapid climate change in cold‐climate regions, it is important to understand the sensitivity of plant communities both in terms of degree and direction of community change. We studied responses to 3–5 years of moderate experimental warming by open‐top chambers in two widespread but contrasting tundra communities in Iceland. In a species‐poor and nutrient‐deficient moss heath, dominated by Racomitrium lanuginosum, mean daily air temperatures at surface were 1–2°C higher in the warmed plots than the controls whereas soil temperatures tended to be lower in the warmed plots throughout the season. In a species‐rich dwarf shrub heath on relatively rich soils at a cooler site, dominated by Betula nana and R. lanuginosum, temperature changes were in the same direction although more moderate. In the moss heath, there were no detectable community changes while significant changes were detected in the dwarf shrub heath: the abundance of deciduous and evergreen dwarf shrubs significantly increased (>50%), bryophytes decreased (18%) and canopy height increased (100%). Contrary to some other studies of tundra communities, we detected no changes in species richness or other diversity measures in either community and the abundance of lichens did not change. It is concluded that the sensitivity of Icelandic tundra communities to climate warming varies greatly depending on initial conditions in terms of species diversity, dominant species, soil and climatic conditions as well as land‐use history.     

Nitrogen deposition enhances moss growth,but leads to an overall decline in habitat condition of mountain moss‐sedge heath

Ecosystems are subject to multiple, natural and anthropogenic environmental influences, including nitrogen (N) deposition, land use and climate. Assessment of the relative importance of these influences on biodiversity and ecosystem functioning is crucial for guiding policy and management decisions to mitigate global change; yet, few studies consider multiple drivers. In the UK, ongoing loss of the internationally important arctic/alpine moss‐sedge community, Racomitrium heath, has been linked to elevated N deposition, high grazing pressures and their combination; however, the relative importance of these drivers remains unclear. We used environmental gradients across the habitat's European distribution (UK, Faroes, Norway and Iceland) to investigate the relative impact of N deposition and grazing pressure, as well as climate, on the condition of the dominant moss species, Racomitrium lanuginosum. Key variables including tissue chemistry, growth and cover were measured at 36 sites, and multiple linear regressions were used to examine the relative importance of the drivers across sites. Our results clearly show that regional variation in the condition of R. lanuginosum across Europe is primarily associated with the impacts of N deposition, with climate (air temperature) and grazing pressure playing secondary roles. In contrast to previous experimental studies, we found moss growth to be stimulated by elevated N deposition; this apparent discrepancy may result from the use of artificially high N concentrations in many experiments. Despite increased growth rates, we found that moss mat depth and cover declined in response to N deposition. Our results suggest that this is due to increased decomposition of material in the moss mat, which ultimately leads to loss of moss cover and habitat degradation. This study clearly demonstrates both the key role of N deposition in degradation of Racomitrium heath and the importance of observational studies along natural gradients for testing predictions from experimental studies in the real world.     

土壤微生物群落对麻栎-刺槐混交林凋落物分解的影响

以麻栎-刺槐混交林和麻栎纯林为研究对象,采用野外定点采样、室内分析与高通量测序的方法,对凋落物分解过程中土壤微生物菌群多样性特征及其对凋落物分解速率的影响进行了研究。结果表明:(1)麻栎-刺槐混交林凋落物的分解速率高于麻栎纯林。两种林分凋落物有机碳(TOC)、全氮(TN)发生释放,全磷(TP)发生积累-释放的过程。(2)两种林分土壤细菌优势类群为放线菌门(Acidobacteria)、变形菌门(Proteobacteria)、酸杆菌门(Actinobacteria)和疣微菌门(Verrucomicrobia),土壤真菌优势类群为担子菌门(Basidiomycota)、子囊菌门(Ascomycota)和被孢霉门(Moritierellomycota)。(3)凋落物分解过程中,麻栎-刺槐混交林土壤微生物菌群丰富度指数和菌群多样性指数变化范围小于麻栎纯林。(4)凋落物分解速率与土壤细菌菌群丰富度指数和菌群多样性指数呈显著正相关,与土壤真菌菌群丰富度指数呈显著正相关。土壤微生物群落对麻栎-刺槐混交林和麻栎纯林凋落物分解速率具有重要影响,研究结果为深入开展混交林土壤微生物多样性对凋落物分解的影响研究提供理论依据。     

Plant species richness, elevated CO2, and atmospheric nitrogen deposition alter soil microbial community composition and function

We determined soil microbial community composition and function in a field experiment in which plant communities of increasing species richness were exposed to factorial elevated CO₂ and nitrogen (N) deposition treatments. Because elevated CO₂ and N deposition increased plant productivity to a greater extent in more diverse plant assemblages, it is plausible that heterotrophic microbial communities would experience greater substrate availability, potentially increasing microbial activity, and accelerating soil carbon (C) and N cycling. We, therefore, hypothesized that the response of microbial communities to elevated CO₂ and N deposition is contingent on the species richness of plant communities. Microbial community composition was determined by phospholipid fatty acid analysis, and function was measured using the activity of key extracellular enzymes involved in litter decomposition. Higher plant species richness, as a main effect, fostered greater microbial biomass, cellulolytic and chitinolytic capacity, as well as the abundance of saprophytic and arbuscular mycorrhizal (AM) fungi. Moreover, the effect of plant species richness on microbial communities was significantly modified by elevated CO₂ and N deposition. For instance, microbial biomass and fungal abundance increased with greater species richness, but only under combinations of elevated CO₂ and ambient N, or ambient CO₂ and N deposition. Cellobiohydrolase activity increased with higher plant species richness, and this trend was amplified by elevated CO₂. In most cases, the effect of plant species richness remained significant even after accounting for the influence of plant biomass. Taken together, our results demonstrate that plant species richness can directly regulate microbial activity and community composition, and that plant species richness is a significant determinant of microbial response to elevated CO₂ and N deposition. The strong positive effect of plant species richness on cellulolytic capacity and microbial biomass indicate that the rates of soil C cycling may decline with decreasing plant species richness.     

Vegetation transition following drainage in a high‐latitude hyper‐oceanic ecosystem

Questions: How does draining affect the composition of vegetation? Are certain functional groups favoured? Can soil parameters explain these differences? Location: Central Faroe Islands, treeless islands in the northern boreal vegetation zone. Since 1987, an area of 21 km² at 100–200 m a.s.l. was drained in order to provide water for hydro‐electric production. Method: Vegetation and soil of a drained area and a control, undrained neighbouring area of approximately the same size were sampled in 2007. Six sites were sampled in each area. The vegetation was classified with cluster analysis. Results: Four plant communities were defined in the area: Calluna vulgaris–Empetrum nigrum–Vaccinium myrtillus heath, Scirpus cespitosus–Eriophorum angustifolium blanket mire, Carex bigelowii–Racomitrium lanuginosum moss‐heath, Narthecium ossifragum–Carex panacea mire. Heath was more extensively distributed within, and was the dominant community of the drained area, whereas moss‐heath was more extensive in the undrained area. Blanket mire and mire had approximately the same distribution in both areas. For the blanket mire, species composition indicated drier conditions in the drained than in the undrained area. The drained area had higher frequencies of woody species and lichens, grasses had finer roots and available soil phosphate was considerably higher, whereas the undrained area had higher frequencies of grasses and sedges. Conclusion: The dominant plant communities were different in the two areas, which indicated that the blanket mire was drying in the drained area. Higher concentration of soil phosphate in the drained area also indicated increased decomposition of organic soils owing to desiccation.     

贝加尔针茅草原土壤真菌群落结构对氮素和水分添加的响应

研究氮沉降和降雨变化对土壤真菌群落结构的互作效应,对未来预测多个气候变化因子对草地生态系统的交互作用具有重要意义。以施氮和灌溉模拟氮沉降和降雨增加,采用裂区设计,应用高通量测序技术,研究8个氮添加水平(0、15、30、50、100、150、200、300 kg N hm~(-2)a~(-1))和2个水分添加水平(不灌溉、模拟夏季增雨100 mm灌溉)对土壤真菌群落结构的影响。结果表明,氮素和水分添加后,土壤真菌群落中占优势的门类分别为接合菌门Zygomycota(22.0%—48.9%)、担子菌门Basidiomycota(7.8%—18.5%)、子囊菌门Ascomycota(9.4%—20.1%)、球囊菌门Glomeromycota(0.7%—3.1%)、壶菌门Chytridiomycota(0.1%—1.3%)。常规降雨条件下,随着氮添加水平升高,接合菌门相对丰度呈现出先升高后降低的趋势,N50处理最高;子囊菌门相对丰度在高氮添加时(N100—N300)呈升高趋势。而在氮素和水分同时添加条件下,随着氮添加水平升高,接合菌门相对丰度呈降低趋势,子囊菌门相对丰度变化则不明显。在相同的氮添加水平下,水分添加使接合菌门相对丰度增加,而担子菌门、子囊菌门、球囊菌门和壶菌门的相对丰度降低。在不同氮素和水分添加条件下,有5个土壤真菌门类11个真菌纲相对丰度变化显著。接合菌门的Mortierella属,担子菌门的Entolomataceae科和Geastrum属相对丰度变化极显著,可作为土壤真菌群落结构变化的指示种。PCo A分析结果也表明氮素和水分添加改变了土壤真菌群落结构。植物-土壤-微生物系统的结构方程模型结果表明,植物群落组成及植物物种丰富度的变化是土壤真菌群落结构发生变化的主要影响因素,土壤无机氮及p H的变化主要通过影响植物群落间接影响真菌群落,其对真菌群落的直接影响则较小。综上,氮素和水分添加改变了土壤真菌群落结构,且两者存在明显的互作效应,水分添加可改变氮添加对土壤真菌群落的影响。     

不同种植年限香榧根际土壤微生物多样性

为探明不同种植年限对香榧根际土壤微生物群落特征的影响,采用高通量测序技术,分析种植5 a、10 a和15 a香榧根际土壤细菌、真菌的群落结构和多样性特征.结果表明: 在种植15 a的香榧土壤中细菌Chao1指数、ACE指数和Shannon指数显著降低,Simpson指数无显著变化.NMDS分析显示,种植年限对细菌群落结构变化有显著影响,而种植5 a和10 a香榧林地土壤具有相似的细菌群落.细菌相对丰度、多样性以及群落结构(基本上由变形菌、放线菌、酸杆菌和绿弯菌组成)的变化与有机质、C/N、全氮呈极显著相关.香榧根际土壤真菌Chao1指数和ACE指数随种植年限的增加显著降低,Shannon指数和Simpson指数在种植10 a香榧林地中较高.真菌NMDS分析显示,相同种植年限土壤真菌群落聚在一起,不同种植年限之间能明显分开.真菌优势菌群主要包括子囊菌门、担子菌门、接合菌门.有机质是影响真菌丰富度、多样性和群落结构变化的主要因子.综上,香榧根际土壤微生物群落随种植年限不同而发生明显变化,种植年限、C/N、土壤全氮和有机质含量是影响香榧根际土壤微生物群落结构的主要因子.     

N2 Fixation in Feather Mosses is a Sensitive Indicator of N Deposition in Boreal Forests

Nitrogen (N) fixation in the feather moss–cyanobacteria association represents a major N source in boreal forests which experience low levels of N deposition; however, little is known about the effects of anthropogenic N inputs on the rate of fixation of atmospheric N₂ in mosses and the succeeding effects on soil nutrient concentrations and microbial community composition. We collected soil samples and moss shoots of Pleurozium schreberi at six distances along busy and remote roads in northern Sweden to assess the influence of road-derived N inputs on N₂ fixation in moss, soil nutrient concentrations and microbial communities. Soil nutrients were similar between busy and remote roads; N₂ fixation was higher in mosses along the remote roads than along the busy roads and increased with increasing distance from busy roads up to rates of N₂ fixation similar to remote roads. Throughfall N was higher in sites adjacent to the busy roads but showed no distance effect. Soil microbial phospholipid fatty acid (PLFA) composition exhibited a weak pattern regarding road type. Concentrations of bacterial and total PLFAs decreased with increasing distance from busy roads, whereas fungal PLFAs showed no distance effect. Our results show that N₂ fixation in feather mosses is highly affected by N deposition, here derived from roads in northern Sweden. Moreover, as other measured factors showed only weak differences between the road types, atmospheric N₂ fixation in feather mosses represents a highly sensitive indicator for increased N loads to natural systems.     

沙坡头地区凋落物分解及其对土壤微生物群落的影响

以腾格里沙漠东南缘沙坡头人工固沙植被区典型植物种凋落物(小画眉草、藓类、油蒿叶片)为对象,运用凋落物分解袋法和高通量测序技术,分析了3种植物凋落物分解特征及其对土壤微生物群落的影响。结果表明: 分解时间和凋落物类型均显著影响分解速率,藓类分解最慢,13个月后质量损失比仅为15.4%,油蒿叶片和小画眉草的平均分解速率分别是藓类的4.9和3.4倍。经过11个月的分解,细菌群落的优势菌门为放线菌门和变形菌门,真菌群落的优势菌门是子囊菌门;藓类分解过程中,拟杆菌门和绿弯菌门的相对丰度显著增加,担子菌门的相对丰度显著降低。凋落物分解后,细菌和真菌群落物种多样性和丰富度显著增加,细菌群落组成在凋落物间变化不显著,真菌群落变化显著。凋落物的分解速率与细菌和真菌群落多样性及丰富度均呈负线性变化。植物多糖、全磷和土壤pH、微生物生物量氮、铵态氮含量是影响微生物群落结构的主要因子。凋落物分解改变了土壤微生物群落物种组成和种间相似性,显著增加了土壤中微生物群落的多样性和丰富度,促进了土壤生境的恢复。     

Fungal community assembly in soils and roots under plant invasion and nitrogen deposition

Fungal community composition in the Anthropocene is driven by rapid changes in environmental conditions caused by human activities. This study examines the relative importance of two global change drivers – atmospheric nitrogen (N) deposition and annual grass invasion – on structuring fungal communities in a California chaparral ecosystem, with emphasis on arbuscular mycorrhizal fungi. We used molecular markers, functional groupings, generalized linear statistics and joint distribution modeling, to examine how environmental variables structure taxonomic and functional composition of fungal communities. Invasive grasses had a lower richness and relative abundance of symbiotic fungi (both AMF and other fungi) compared to native shrubs. We found a higher richness and abundance of rhizophilic (e.g. Glomeraceae) and edaphophilic (e.g. Gigasporaceae) AMF with increasing soil NO₃. Our findings suggest that invasive persistence may decrease the presence of multiple soil symbionts that native species depend on for pathogen protection and increased access to soil resources.     

Responses of subalpine dwarf‐shrub heath to irrigation and fertilization

Question: Our study aimed at testing to what extent water and/or nutrients affect community composition in sub‐alpine heath. We hypothesized that nutrient addition will have an overall positive effect on heath vegetation but water addition will have greater effects and will probably reinforce the effects of fertilization in drier habitat conditions. Location: Monte Rondinaio, northern Apennines, Italy (44°08’ N; 10°35’ E, ca. 1850‐1930 m a.s.l.). Methods: Nutrients and water were added during five growing seasons in two communities (HV community, moister; EV community, drier) and the biomass of all species was estimated non‐destructively by the point‐quadrat method. Results: Total above‐ground biomass increased in both communities with fertilization due to increased graminoid biomass and decreased moss biomass, but was unaffected by irrigation. In the HV community species richness decreased as an effect of fertilization while in the EV community species richness was raised by irrigation. Conclusions: Our study partly supported our hypothesis since water addition had a stronger effect in the drier community. However, this effect was not revealed by changes in above‐ground biomass but rather by differing responses of individual species in the two communities.     

Microbial assimilation of new photosynthate is altered by plant species richness and nitrogen deposition

To determine how plant species richness impacts microbial assimilation of new photosynthate, and how this may be modified by atmospheric N deposition, we analyzed the microbial assimilation of recent photosynthate in a 6-year-long field experiment in which plant species richness, atmospheric N deposition, and atmospheric CO₂ concentration were manipulated in concert. The depleted δ¹³C of fumigation CO₂ enabled us to investigate the effect of plant species richness and atmospheric N deposition on the metabolism of soil microbial communities in the elevated CO₂ treatment. To accomplish this, we determined the δ¹³C of bacterial, actinobacterial, and fungal phospholipid fatty acids (PLFAs). In the elevated CO₂ conditions of this study, the δ¹³C of bacterial PLFAs (i15:0, i16:0, 16:1ω7c, 16:1ω9c, 10Me16:0, and 10Me18:0) and the fungal PLFA 18:1ω9c was significantly lower in species-rich plant communities than in species-poor plant communities, indicating that microbial incorporation of new C increased with plant species richness. Despite an increase in plant production, total PLFA decreased under N deposition. Moreover, N deposition also decreased fungal relative abundance in species-rich plant communities. In our study, plant species richness directly increased microbial incorporation of new photosynthate, providing a mechanistic link between greater plant detritus production in species-rich plant communities and larger and more active soil microbial community.     

Effects of arbuscular mycorrhiza on community composition and seedling recruitment in temperate forest understory

Arbuscular mycorrhizal (AM) fungal communities can influence the species composition of plant communities. This influence may result from effects of AM on seedling recruitment, although the existing evidence is limited to experimental systems. We addressed the impact of AM fungi on the plant community composition and seedling recruitment of two species – Oxalis acetosella and Prunella vulgaris – in a temperate forest understory. We established a field experiment over two years in which soil fertility (using fertilizer to enhance and sucrose to decrease fertility) and the activity of AM fungi (using fungicide) was manipulated in a factorial design. Species richness, diversity and community composition of understory plants were not influenced by soil fertility or AM fungal activity treatments. However, plant community composition was marginally significantly affected by the interaction of these treatments as the effect of AM fungal activity became evident under enhanced soil fertility. Suppression of AM fungal activity combined with decreased soil fertility increased the number of shoots of herbaceous plants. Unchanged activity of AM fungi enhanced the growth of O. acetosella seedlings under decreased soil fertility, but did not influence the growth of P. vulgaris seedlings. We conclude that the role of AM fungi in structuring plant communities depends on soil fertility. AM fungi can have a strong influence on seedling recruitment, especially for those plants that are characteristic of the habitat.     

Insights into fungal communities colonizing the acarosphere in a forest soil habitat

Knowledge on the diversity and ecology of microfungi associated with soil-dwelling mites is rather limited. To get insights into associations between the two highly diverse groups, we studied composition and potential function of mite-associated fungal communities occurring in soil. Two different mite species living in temperate region pine forest soil were screened for associated fungi. The fungal community was assessed by restriction fragment length polymorphism (RFLP) analyses in a predatory (Leptogamasus obesus) and a predominantly saprobic (Oppiella subpectinata) mite species as well as in the organic soil layer. Key fungi were identified by sequencing, and community composition was exemplarily compared between the RFLP and a 454 metabarcoding approach. Composition of the fungal communities differed between mite species and between mites and organic soil layer. The mites were predominantly associated with Zygomycota, less frequently with Ascomycota, and rarely with Basidiomycota. The bulk soil was colonized by roughly equal proportions of the three phyla. Fungal taxa being known to exhibit chitinolytic activity were predominantly restricted to mites. Compositional and functional differences between the communities suggest that mites represent a particular microhabitat for fungi, the “acarosphere.” This mobile habitat may contribute to nutrient cycling by combining fungal and animal decomposition activities and serve as vector for soil-inhabiting fungi.     

Vertical distribution of fungal communities in tallgrass prairie soil

We used 454 sequencing of the internal transcribed spacer region to characterize fungal communities in tallgrass prairie soils subdivided into strata 0-10, 10-20, 30-40 and 50-60 cm deep. The dataset included more than 14000 fungal sequences distributed across Basidiomycota, Ascomycota, basal fungal lineages and Glomeromycota in order of decreasing frequency. As expected the community richness and diversity estimators tended to decrease with increasing depth. Although species richness was significantly reduced for samples from the deeper profiles, even the deepest stratum sampled contained richness of more than a third of that in the topmost stratum. More importantly, nonparametric multidimensional scaling (NMS) ordination analyses indicated that the fungal communities differed across vertical profiles, although only the topmost and deepest strata were significantly different when the NMS axis scores were compared by ANOVA. These results emphasize the importance of considering the fungal communities across the vertical strata because the deeper soil horizons might maintain a distinct community composition and thus contribute greatly to overall richness. The majority of operational taxonomic units (OTUs) declined in frequency with increasing depth, although a linear regression analysis indicated that some increased with increasing depth. The OTUs and BLAST-assigned taxa that showed increasing frequencies were mainly unculturable fungi, but some showed likely affinities to families Nectriaceae and Venturiaceae or to genus Pachnocybe. Although the ecological roles of the fungi in the deeper strata remain uncertain, we hypothesize that the fungi with preferences for deeper soil have adequate access to substrates and possess environmental tolerances that enable their persistence in those environments.     

基于高通量测序的禁牧对土壤微生物群落结构的影响

麋鹿的采食、躺卧和践踏行为均会对栖息地土壤环境造成影响,进而影响土壤微生物群落结构。利用高通量测序技术,分析江苏大丰麋鹿国家级自然保护区禁牧点和补饲点土壤细菌和真菌群落结构差异,并结合土壤理化性质探究禁牧对土壤微生物群落结构的影响。结果表明细菌群落的优势菌门为变形菌门,真菌群落的优势菌门为子囊菌门。禁牧改变了土壤微生物群落结构,在门水平上提高了变形菌门、放线菌门和担子菌门的相对丰度,降低了绿弯菌门、厚壁菌门和子囊菌门的相对丰度,禁牧点与补饲点土壤微生物群落多样性的相似性较低。冗余分析中,细菌受土壤环境因子的影响大于真菌,其中土壤pH是影响细菌和真菌群落最大的土壤环境因子。研究揭示了禁牧对土壤微生物群落结构的影响,为保护区制定麋鹿生境恢复方案提供参考。     

Influence of tree species and soil properties on ground beetle (Coleoptera: Carabidae) communities

Although Carabidae is among the best-studied families of beetles in Europe from the faunistic point of view, there is still a lack of available information on the ecological requirements of the particular carabid species. The habitat preferences that determine the distribution of species are largely influenced by habitat structure and microclimate. In addition to other factors, these habitat parameters are influenced by the nature of the vegetation. Therefore, our study investigated the influence of tree species on carabid beetle communities. We conducted the research at 9 stands in the Borová Hora Arboretum (Zvolen, Central Slovakia). Each studied site represents a monoculture of one of nine tree species. At each site, some soil and leaf litter attributes (pH, conductivity, and content of H, C, N and P) were evaluated. Ground beetles were collected by pitfall trapping during the vegetation periods in 2008–2011. In total, 3012 individuals of 29 species were obtained. Significant differences in the total dynamic activity and species richness of the carabid beetle communities among the compared forest stands were revealed. The results of the research confirmed statistically significant relationships among 1) the soil conductivity and both the richness and Shannon diversity of the ground beetle communities, 2) the litter and soil N content and richness, the Shannon diversity and the species composition of the ground beetle communities. The Shannon diversity and richness were negatively related to the soil conductivity and positively related with the N content. Our research showed that dominant tree species indirectly influence diversity and composition of carabid communities via the soil properties.     

Fungal community composition in neotropical rain forests: the influence of tree diversity and precipitation

Plant diversity is considered one factor structuring soil fungal communities because the diversity of compounds in leaf litter might determine the extent of resource heterogeneity for decomposer communities. Lowland tropical rain forests have the highest plant diversity per area of any biome. Since fungi are responsible for much of the decomposition occurring in forest soils, understanding the factors that structure fungi in tropical forests may provide valuable insight for predicting changes in global carbon and nitrogen fluxes. To test the role of plant diversity in shaping fungal community structure and function, soil (0-20?cm) and leaf litter (O horizons) were collected from six established 1-ha forest census plots across a natural plant diversity gradient on the Isthmus of Panama. We used 454 pyrosequencing and phospholipid fatty acid analysis to evaluate correlations between microbial community composition, precipitation, soil nutrients, and plant richness. In soil, the number of fungal taxa increased significantly with increasing mean annual precipitation, but not with plant richness. There were no correlations between fungal communities in leaf litter and plant diversity or precipitation, and fungal communities were found to be compositionally distinct between soil and leaf litter. To directly test for effects of plant species richness on fungal diversity and function, we experimentally re-created litter diversity gradients in litter bags with 1, 25, and 50 species of litter. After 6?months, we found a significant effect of litter diversity on decomposition rate between one and 25 species of leaf litter. However, fungal richness did not track plant species richness. Although studies in a broader range of sites is required, these results suggest that precipitation may be a more important factor than plant diversity or soil nutrient status in structuring tropical forest soil fungal communities.     

秦岭火地塘真菌群落海拔分布格局

土壤真菌在自然生态系统的养分循环和土壤碳储存方面起重要作用。秦岭火地塘林区在不同海拔分布着不同的优势树种,但其相应的土壤特征及微生物群落的海拔分布格局仍不明晰。本研究分析了5个海拔处(1500、1700、1900、2100和2300 m)的土壤特征变化趋势,并在高通量测序基础上研究了真菌群落格局。结果表明: 土壤有效磷含量、pH值随海拔的增加而显著增加,土壤水分则呈下降趋势。土壤真菌Shannon多样性指数随海拔升高呈下降趋势,而ACE丰度指数相反;真菌优势门为担子菌门(68.2%)、子囊菌门(19.8%)和球囊菌门(1.7%),且随海拔升高整体呈现出“U”型或“单峰”变化格局;真菌优势纲为伞菌纲(64.2%)、粪壳菌纲(5.8%)和锤舌菌纲(4.1%)。冗余分析(RDA)表明,土壤特性解释了土壤真菌群落总变异的89.1%,其中土壤有效磷含量、pH和海拔是土壤真菌群落海拔梯度变化的主要驱动因子。在秦岭火地塘林区,土壤特征在海拔梯度上的差异性影响了土壤真菌群落组成。     

Ectomycorrhizal fungal diversity and saprotrophic fungal diversity are linked to different tree community attributes in a field‐based tree experiment

Exploring the link between above‐ and belowground biodiversity has been a major theme of recent ecological research, due in large part to the increasingly well‐recognized role that soil microorganisms play in driving plant community processes. In this study, we utilized a field‐based tree experiment in Minnesota, USA, to assess the effect of changes in plant species richness and phylogenetic diversity on the richness and composition of both ectomycorrhizal and saprotrophic fungal communities. We found that ectomycorrhizal fungal species richness was significantly positively influenced by increasing plant phylogenetic diversity, while saprotrophic fungal species richness was significantly affected by plant leaf nitrogen content, specific root length and standing biomass. The increasing ectomycorrhizal fungal richness associated with increasing plant phylogenetic diversity was driven by the combined presence of ectomycorrhizal fungal specialists in plots with both gymnosperm and angiosperm hosts. Although the species composition of both the ectomycorrhizal and saprotrophic fungal communities changed significantly in response to changes in plant species composition, the effect was much greater for ectomycorrhizal fungi. In addition, ectomycorrhizal but not saprotrophic fungal species composition was significantly influenced by both plant phylum (angiosperm, gymnosperm, both) and origin (Europe, America, both). The phylum effect was caused by differences in ectomycorrhizal fungal community composition, while the origin effect was attributable to differences in community heterogeneity. Taken together, this study emphasizes that plant‐associated effects on soil fungal communities are largely guild‐specific and provides a mechanistic basis for the positive link between plant phylogenetic diversity and ectomycorrhizal fungal richness.