Successional dynamics of soil fungal diversity along a restoration chronosequence post‐coal mining

Soil disruption from open‐cut mining practices can adversely impact microbial communities and the ecosystem services that they mediate. Despite this, assessment of impacts of soil disruption, and the subsequent recovery of microbial communities is rarely studied. Monitoring of ecological restoration success on mine sites has traditionally focused on vegetation; however, most plants rely, at least in part, on associations with soil fungi for enhanced nutrient and water acquisition. Here, we used high‐throughput phylogenetic marker gene sequencing to characterize the diversity of soil fungal communities along a restoration chronosequence ranging from 3 to 23 years at a rehabilitated mine site. We used nonmined analogue sites as a baseline for comparative purposes and examined the associations of soil fungal communities with soil physicochemical and aboveground vegetation variables. Fungal richness on rehabilitated sites was significantly larger than on nonmined sites, suggesting that mixing of topsoil during stockpiling resulted in a composite microbial community. Fungal community composition was significantly influenced by edaphic variables and the length of rehabilitation, with mined sites becoming more similar to nonmined sites over time. Fungal populations associated with ectomycorrhizae were relatively more abundant than those associated with arbuscular mycorrhizae and declined in response to disturbance, but recovered over time on the woody dominated sites indicating a strong coupling of these fungi with aboveground vegetation. Our data indicate that soil fungal diversity is a useful bioindicator of soil restoration in mined sites and may complement more traditional vegetation‐based surveys.     

Summer temperature increase has distinct effects on the ectomycorrhizal fungal communities of moist tussock and dry tundra in Arctic Alaska

Arctic regions are experiencing the greatest rates of climate warming on the planet and marked changes have already been observed in terrestrial arctic ecosystems. While most studies have focused on the effects of warming on arctic vegetation and nutrient cycling, little is known about how belowground communities, such as fungi root‐associated, respond to warming. Here, we investigate how long‐term summer warming affects ectomycorrhizal (ECM) fungal communities. We used Ion Torrent sequencing of the rDNA internal transcribed spacer 2 (ITS2) region to compare ECM fungal communities in plots with and without long‐term experimental warming in both dry and moist tussock tundra. Cortinarius was the most OTU‐rich genus in the moist tundra, while the most diverse genus in the dry tundra was Tomentella. On the diversity level, in the moist tundra we found significant differences in community composition, and a sharp decrease in the richness of ECM fungi due to warming. On the functional level, our results indicate that warming induces shifts in the extramatrical properties of the communities, where the species with medium‐distance exploration type seem to be favored with potential implications for the mobilization of different nutrient pools in the soil. In the dry tundra, neither community richness nor community composition was significantly altered by warming, similar to what had been observed in ECM host plants. There was, however, a marginally significant increase in OTUs identified as ECM fungi with the medium‐distance exploration type in the warmed plots. Linking our findings of decreasing richness with previous results of increasing ECM fungal biomass suggests that certain ECM species are favored by warming and may become more abundant, while many other species may go locally extinct due to direct or indirect effects of warming. Such compositional shifts in the community might affect nutrient cycling and soil organic C storage.     

Temporal variation of Bistorta vivipara‐associated ectomycorrhizal fungal communities in the High Arctic

Ectomycorrhizal (ECM) fungi are important for efficient nutrient uptake of several widespread arctic plant species. Knowledge of temporal variation of ECM fungi, and the relationship of these patterns to environmental variables, is essential to understand energy and nutrient cycling in Arctic ecosystems. We sampled roots of Bistorta vivipara ten times over two years; three times during the growing‐season (June, July and September) and twice during winter (November and April) of both years. We found 668 ECM OTUs belonging to 25 different ECM lineages, whereof 157 OTUs persisted throughout all sampling time‐points. Overall, ECM fungal richness peaked in winter and species belonging to Cortinarius, Serendipita and Sebacina were more frequent in winter than during summer. Structure of ECM fungal communities was primarily affected by spatial factors. However, after accounting for spatial effects, significant seasonal variation was evident revealing correspondence with seasonal changes in environmental conditions. We demonstrate that arctic ECM richness and community structure differ between summer (growing‐season) and winter, possibly due to reduced activity of the core community, and addition of fungi adapted for winter conditions forming a winter‐active fungal community. Significant month × year interactions were observed both for fungal richness and community composition, indicating unpredictable between‐year variation. Our study indicates that addressing seasonal changes requires replication over several years.     

Long‐term increase in snow depth leads to compositional changes in arctic ectomycorrhizal fungal communities

Many arctic ecological processes are regulated by soil temperature that is tightly interconnected with snow cover distribution and persistence. Recently, various climate‐induced changes have been observed in arctic tundra ecosystems, e.g. shrub expansion, resulting in reduction in albedo and greater C fixation in aboveground vegetation as well as increased rates of soil C mobilization by microbes. Importantly, the net effects of these shifts are unknown, in part because our understanding of belowground processes is limited. Here, we focus on the effects of increased snow depth, and as a consequence, increased winter soil temperature on ectomycorrhizal (ECM) fungal communities in dry and moist tundra. We analyzed deep DNA sequence data from soil samples taken at a long‐term snow fence experiment in Northern Alaska. Our results indicate that, in contrast with previously observed responses of plants to increased snow depth at the same experimental site, the ECM fungal community of the dry tundra was more affected by deeper snow than the moist tundra community. In the dry tundra, both community richness and composition were significantly altered while in the moist tundra, only community composition changed significantly while richness did not. We observed a decrease in richness of Tomentella, Inocybe and other taxa adapted to scavenge the soil for labile N forms. On the other hand, richness of Cortinarius, and species with the ability to scavenge the soil for recalcitrant N forms, did not change. We further link ECM fungal traits with C soil pools. If future warmer atmospheric conditions lead to greater winter snow fall, changes in the ECM fungal community will likely influence C emissions and C fixation through altering N plant availability, fungal biomass and soil‐plant C‐N dynamics, ultimately determining important future interactions between the tundra biosphere and atmosphere.     

The rise and fall of arbuscular mycorrhizal fungal diversity during ecosystem retrogression

Ecosystem retrogression following long‐term pedogenesis is attributed to phosphorus (P) limitation of primary productivity. Arbuscular mycorrhizal fungi (AMF) enhance P acquisition for most terrestrial plants, but it has been suggested that this strategy becomes less effective in strongly weathered soils with extremely low P availability. Using next generation sequencing of the large subunit ribosomal RNA gene in roots and soil, we compared the composition and diversity of AMF communities in three contrasting stages of a retrogressive >2‐million‐year dune chronosequence in a global biodiversity hotspot. This chronosequence shows a ~60‐fold decline in total soil P concentration, with the oldest stage representing some of the most severely P‐impoverished soils found in any terrestrial ecosystem. The richness of AMF operational taxonomic units was low on young (1000's of years), moderately P‐rich soils, greatest on relatively old (~120 000 years) low‐P soils, and low again on the oldest (>2 000 000 years) soils that were lowest in P availability. A similar decline in AMF phylogenetic diversity on the oldest soils occurred, despite invariant host plant diversity and only small declines in host cover along the chronosequence. Differences in AMF community composition were greatest between the youngest and the two oldest soils, and this was best explained by differences in soil P concentrations. Our results point to a threshold in soil P availability during ecosystem regression below which AMF diversity declines, suggesting environmental filtering of AMF insufficiently adapted to extremely low P availability.     

Wild bee community change over a 26‐year chronosequence of restored tallgrass prairie

Restoration efforts often focus on plants, but additionally require the establishment and long‐term persistence of diverse groups of nontarget organisms, such as bees, for important ecosystem functions and meeting restoration goals. We investigated long‐term patterns in the response of bees to habitat restoration by sampling bee communities along a 26‐year chronosequence of restored tallgrass prairie in north‐central Illinois, U.S.A. Specifically, we examined how bee communities changed over time since restoration in terms of (1) abundance and richness, (2) community composition, and (3) the two components of beta diversity, one‐to‐one species replacement, and changes in species richness. Bee abundance and raw richness increased with restoration age from the low level of the pre‐restoration (agricultural) sites to the target level of the remnant prairie within the first 2–3 years after restoration, and these high levels were maintained throughout the entire restoration chronosequence. Bee community composition of the youngest restored sites differed from that of prairie remnants, but 5–7 years post‐restoration the community composition of restored prairie converged with that of remnants. Landscape context, particularly nearby wooded land, was found to affect abundance, rarefied richness, and community composition. Partitioning overall beta diversity between sites into species replacement and richness effects revealed that the main driver of community change over time was the gradual accumulation of species, rather than one‐to‐one species replacement. At the spatial and temporal scales we studied, we conclude that prairie restoration efforts targeting plants also successfully restore bee communities.     

Long‐term effects of plant diversity and composition on plant stoichiometry

Plant elemental composition can indicate resource limitation, and changes in key elemental ratios (e.g. plant C:N ratios) can influence rates including herbivory, nutrient recycling, and pathogen infection. Although plant stoichiometry can influence ecosystem‐level processes, very few studies have addressed whether and how plant C:N stoichiometry changes with plant diversity and composition. Here, using two long‐term experimental manipulations of plant diversity (Jena and Cedar Creek), we test whether plant richness (species and functional groups) or composition (functional group proportions) affects temporal trends and variability of community‐wide C:N stoichiometry. Site fertility determined the initial community‐scale C:N ratio. Communities growing on N‐poor soil (Cedar Creek) began with higher C:N ratios than communities growing on N‐rich soil (Jena). However, site‐level plant C:N ratios converged through time, most rapidly in high diversity plots. In Jena, plant community C:N ratios increased. This temporal trend was stronger with increasing richness. However, temporal variability of C:N decreased as plant richness increased. In contrast, C:N decreased over time at Cedar Creek, most strongly at high species and functional richness, whereas the temporal variability of C:N increased with both measures of diversity at this site. Thus, temporal trends in the mean and variability of C:N were underlain by concordant changes among sites in functional group proportions. In particular, the convergence of community‐scale C:N over time at these very different sites was mainly due to increasing proportions of forbs at both sites, replacing high mean C:N (C4 grasses, Cedar Creek) or low C:N (legumes, Jena) species. Diversity amplified this convergence; although temporal trends differed in sign between the sites, these trends increased in magnitude with increasing species richness. Our results suggest a predictive mechanistic link between trends in plant diversity and functional group composition and trends in the many ecosystem rates that depend on aboveground community C:N. Synthesis We compared the effect of plant diversity on the temporal dynamics of community stoichiometry in two long‐term grassland diversity experiments: the Cedar Creek and Jena Experiments. Changes in community C:N ratios were accelerated by increasing diversity at both sites, but in opposite directions depending on soil fertility. Stoichiometry changes were driven by shifts of functional group composition differing in their elemental compositions, the identity of the functional groups depending on the site. Thus, we highlighted that community turnover constrained the effect of diversity on plant stoichiometry at both sites     

Long‐term experimental manipulation of climate alters the ectomycorrhizal community of Betula nana in Arctic tundra

Climate warming is leading to shrub expansion in Arctic tundra. Shrubs form ectomycorrhizal (ECM) associations with soil fungi that are central to ecosystem carbon balance as determinants of plant community structure and as decomposers of soil organic matter. To assess potential climate change impacts on ECM communities, we analysed fungal internal transcribed spacer sequences from ECM root tips of the dominant tundra shrub Betula nana growing in treatments plots that had received long‐term warming by greenhouses and/or fertilization as part of the Arctic Long‐Term Ecological Research experiment at Toolik Lake Alaska, USA. We demonstrate opposing effects of long‐term warming and fertilization treatments on ECM fungal diversity; with warming increasing and fertilization reducing the diversity of ECM communities. We show that warming leads to a significant increase in high biomass fungi with proteolytic capacity, especially Cortinarius spp., and a reduction of fungi with high affinities for labile N, especially Russula spp. In contrast, fertilization treatments led to relatively small changes in the composition of the ECM community, but increased the abundance of saprotrophs. Our data suggest that warming profoundly alters nutrient cycling in tundra, and may facilitate the expansion of B. nana through the formation of mycorrhizal networks of larger size.     

Higher host plant specialization of root‐associated endophytes than mycorrhizal fungi along an arctic elevational gradient

How community‐level specialization differs among groups of organisms, and changes along environmental gradients, is fundamental to understanding the mechanisms influencing ecological communities. In this paper, we investigate the specialization of root‐associated fungi for plant species, asking whether the level of specialization varies with elevation. For this, we applied DNA barcoding based on the ITS region to root samples of five plant species equivalently sampled along an elevational gradient at a high arctic site. To assess whether the level of specialization changed with elevation and whether the observed patterns varied between mycorrhizal and endophytic fungi, we applied a joint species distribution modeling approach. Our results show that host plant specialization is not environmentally constrained in arctic root‐associated fungal communities, since there was no evidence for changing specialization with elevation, even if the composition of root‐associated fungal communities changed substantially. However, the level of specialization for particular plant species differed among fungal groups, root‐associated endophytic fungal communities being highly specialized on particular host species, and mycorrhizal fungi showing almost no signs of specialization. Our results suggest that plant identity affects associated mycorrhizal and endophytic fungi differently, highlighting the need of considering both endophytic and mycorrhizal fungi when studying specialization in root‐associated fungal communities.     

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.     

Scaling up: examining the macroecology of ectomycorrhizal fungi

Ectomycorrhizal (ECM) fungi play major ecological roles in temperate and tropical ecosystems. Although the richness of ECM fungal communities and the factors controlling their structure have been documented at local spatial scales, how they vary at larger spatial scales remains unclear. In this issue of Molecular Ecology, Tedersoo et al. (2012) present the results of a meta‐analysis of ECM fungal community structure that sheds important new light on global‐scale patterns. Using data from 69 study systems and 6021 fungal species, the researchers found that ECM fungal richness does not fit the classic latitudinal diversity gradient in which species richness peaks at lower latitudes. Instead, richness of ECM fungal communities has a unimodal relationship with latitude that peaks in temperate zones. Intriguingly, this conclusion suggests the mechanisms driving ECM fungal community richness may differ from those of many other organisms, including their plant hosts. Future research will be key to determine the robustness of this pattern and to examine the processes that generate and maintain global‐scale gradients of ECM fungal richness.     

Diversity and composition of ectomycorrhizal community on seedling roots: the role of host preference and soil origin

As the main source of inocula, ectomycorrhizal (ECM) fungal propagules are critical for root colonization and seedling survival in deforested areas. It is essential to know factors that may affect the diversity and composition of ECM fungal community on roots of seedlings planted in deforest areas during reforestation. We quantitatively evaluated the effect of host plant and soil origin on ECM fungal propagule community structure established on roots of Castanopsis fargesii, Lithocarpus harlandii, Pinus armandii, and Pinus massoniana growing in soils from local natural forests and from sites deforested by clear-cut logging in the 1950s and 1960s. ECM root tips were sampled in April, July, and October of 2006, and ECM fungal communities were determined using ECM root morphotyping, internal transcribed spacer (ITS)-RFLP, and ITS sequencing. A total of 36 ECM fungal species were observed in our study, and species richness varied with host species and soil origin. Decreased colonization rates were found in all host species except for L. harlandii, and reduced species richness was found in all host species except for P. armandii in soil from the deforested site, which implied the great changes in ECM fungal community composition. Our results showed that 33.3% variance in ECM fungal community composition could be explained by host plant species and 4.6% by soil origin. Results of indicator species analysis demonstrated that 14 out of 19 common ECM fungal species showed significant preference to host plant species, suggesting that the host preference of ECM fungi was one of the most important mechanisms in structuring ECM fungal community. Accordingly, the host plant species should be taken into account in the reforestation of deforested areas due to the strong and commonly existed host preference of ECM fungi.     

Host and tissue variations overshadow the response of boreal moss‐associated fungal communities to increased nitrogen load

Human activity has more than doubled the amount of nitrogen entering the global nitrogen cycle, and the boreal forest biome is a nitrogen‐limited ecosystem sensitive to nitrogen load perturbation. Although bryophyte‐associated microbes contribute significantly to boreal forest ecosystem function, particularly in carbon and nitrogen cycling, little is known about their responses to anthropogenic global change. Amplicon pyrosequencing of the ITS2 region of rDNA was used to investigate how fungal communities associated with three bryophyte species responded to increased nitrogen loads in a long‐term fertilization experiment in a boreal Picea abies forest in southern Norway. Overall, OTU richness, community composition and the relative abundance of specific ecological guilds were primarily influenced by host species identity and tissue type. Although not the primary factor affecting fungal communities, nitrogen addition did impact the abundance of specific guilds of fungi and the resulting overall community composition. Increased nitrogen loads decreased ectomycorrhizal abundance, with Amphinema, Cortinarius, Russula and Tylospora OTUs responding negatively to fertilization. Pathogen abundance increased with fertilization, particularly in the moss pathogen Eocronartium. Saprophytic fungi were both positively and negatively impacted by the nitrogen addition, indicating a complex community level response. The overshadowing of the effects of increased nitrogen loads by variation related to host and tissue type highlights the complexity of bryophyte‐associated microbial communities and the intricate nature of their responses to anthropogenic global change.     

Ectomycorrhizal fungal succession in mixed temperate forests

Ectomycorrhizal (ECM) fungal communities of Douglas-fir (Pseudotsuga menziesii) and paper birch (Betula papyrifera) were studied along a chronosequence of forest development after stand-replacing disturbance. Previous studies of ECM succession did not use molecular techniques for fungal identification or lacked replication, and none examined different host species. Four age classes of mixed forests were sampled: 5-, 26-, 65-, and 100-yr-old, including wildfire-origin stands from all four classes and stands of clearcut origin from the youngest two classes. Morphotyping and DNA sequences were used to identify fungi on ECM root tips. ECM fungal diversities were lower in 5-yr-old than in older stands on Douglas-fir, but were similar among age classes on paper birch. Host-specific fungi dominated in 5-yr-old stands, but host generalists were dominant in the oldest two age classes. ECM fungal community compositions were similar in 65- and 100-yr-old stands but differed among all other pairs of age classes. Within the age range studied, site-level ECM fungal diversity reached a plateau by the 26-yr-old age class, while community composition stabilized by the 65-yr-old class. Simple categories such as 'early stage', 'multi stage', and 'late stage' were insufficient to describe fungal species' successional patterns. Rather, ECM fungal succession may be best described in the context of stand development.     

Arctic root‐associated fungal community composition reflects environmental filtering

There is growing evidence that root‐associated fungi have important roles in Arctic ecosystems. Here, we assess the diversity of fungal communities associated with roots of the ectomycorrhizal perennial herb Bistorta vivipara on the Arctic archipelago of Svalbard and investigate whether spatial separation and bioclimatic variation are important structuring factors of fungal community composition. We sampled 160 plants of B. vivipara from 32 localities across Svalbard. DNA was extracted from entire root systems, and 454 pyrosequencing of ITS1 amplicons was used to profile the fungal communities. The fungal communities were predominantly composed of Basidiomycota (55% of reads) and Ascomycota (35%), with the orders Thelephorales (24%), Agaricales (13.8%), Pezizales (12.6%) and Sebacinales (11.3%) accounting for most of the reads. Plants from the same site or region had more similar fungal communities to one another than plants from other sites or regions, and sites clustered together along a weak latitudinal gradient. Furthermore, a decrease in per‐plant OTU richness with increasing latitude was observed. However, no statistically significant spatial autocorrelation between sites was detected, suggesting that environmental filtering, not dispersal limitation, causes the observed patterns. Our analyses suggest that while latitudinal patterns in community composition and richness might reflect bioclimatic influences at global spatial scales, at the smaller spatial scale of the Svalbard archipelago, these changes more likely reflect varied bedrock composition and associated edaphic factors. The need for further studies focusing on identifying those specific bioclimatic and edaphic factors structuring root‐associated fungal community composition at both global and local scales is emphasized.     

Fungal Community Shifts in Structure and Function across a Boreal Forest Fire Chronosequence

Forest fires are a common natural disturbance in forested ecosystems and have a large impact on the microbial communities in forest soils. The response of soil fungal communities to forest fire is poorly documented. Here, we investigated fungal community structure and function across a 152-year boreal forest fire chronosequence using high-throughput sequencing of the internal transcribed spacer 2 (ITS2) region and a functional gene array (GeoChip). Our results demonstrate that the boreal forest soil fungal community was most diverse soon after a fire disturbance and declined over time. The differences in the fungal communities were explained by changes in the abundance of basidiomycetes and ascomycetes. Ectomycorrhizal (ECM) fungi contributed to the increase in basidiomycete abundance over time, with the operational taxonomic units (OTUs) representing the genera Cortinarius and Piloderma dominating in abundance. Hierarchical cluster analysis by using gene signal intensity revealed that the sites with different fire histories formed separate clusters, suggesting differences in the potential to maintain essential biogeochemical soil processes. The site with the greatest biological diversity had also the most diverse genes. The genes involved in organic matter degradation in the mature forest, in which ECM fungi were the most abundant, were as common in the youngest site, in which saprotrophic fungi had a relatively higher abundance. This study provides insight into the impact of fire disturbance on soil fungal community dynamics.     

Shifts in symbiotic associations in plants capable of forming multiple root symbioses across a long‐term soil chronosequence

Changes in soil nutrient availability during long‐term ecosystem development influence the relative abundances of plant species with different nutrient‐acquisition strategies. These changes in strategies are observed at the community level, but whether they also occur within individual species remains unknown. Plant species forming multiple root symbioses with arbuscular mycorrhizal (AM) fungi, ectomycorrhizal (ECM) fungi, and nitrogen‐(N) fixing microorganisms provide valuable model systems to examine edaphic controls on symbioses related to nutrient acquisition, while simultaneously controlling for plant host identity. We grew two co‐occurring species, Acacia rostellifera (N₂‐fixing and dual AM and ECM symbioses) and Melaleuca systena (AM and ECM dual symbioses), in three soils of contrasting ages (c. 0.1, 1, and 120 ka) collected along a long‐term dune chronosequence in southwestern Australia. The soils differ in the type and strength of nutrient limitation, with primary productivity being limited by N (0.1 ka), co‐limited by N and phosphorus (P) (1 ka), and by P (120 ka). We hypothesized that (i) within‐species root colonization shifts from AM to ECM with increasing soil age, and that (ii) nodulation declines with increasing soil age, reflecting the shift from N to P limitation along the chronosequence. In both species, we observed a shift from AM to ECM root colonization with increasing soil age. In addition, nodulation in A. rostellifera declined with increasing soil age, consistent with a shift from N to P limitation. Shifts from AM to ECM root colonization reflect strengthening P limitation and an increasing proportion of total soil P in organic forms in older soils. This might occur because ECM fungi can access organic P via extracellular phosphatases, while AM fungi do not use organic P. Our results show that plants can shift their resource allocation to different root symbionts depending on nutrient availability during ecosystem development.     

Wildfire severity reduces richness and alters composition of soil fungal communities in boreal forests of western Canada

Wildfire is the dominant disturbance in boreal forests and fire activity is increasing in these regions. Soil fungal communities are important for plant growth and nutrient cycling postfire but there is little understanding of how fires impact fungal communities across landscapes, fire severity gradients, and stand types in boreal forests. Understanding relationships between fungal community composition, particularly mycorrhizas, and understory plant composition is therefore important in predicting how future fire regimes may affect vegetation. We used an extreme wildfire event in boreal forests of Canada's Northwest Territories to test drivers of fungal communities and assess relationships with plant communities. We sampled soils from 39 plots 1 year after fire and 8 unburned plots. High‐throughput sequencing (MiSeq, ITS) revealed 2,034 fungal operational taxonomic units. We found soil pH and fire severity (proportion soil organic layer combusted), and interactions between these drivers were important for fungal community structure (composition, richness, diversity, functional groups). Where fire severity was low, samples with low pH had higher total fungal, mycorrhizal, and saprotroph richness compared to where severity was high. Increased fire severity caused declines in richness of total fungi, mycorrhizas, and saprotrophs, and declines in diversity of total fungi and mycorrhizas. The importance of stand age (a surrogate for fire return interval) for fungal composition suggests we could detect long‐term successional patterns even after fire. Mycorrhizal and plant community composition, richness, and diversity were weakly but significantly correlated. These weak relationships and the distribution of fungi across plots suggest that the underlying driver of fungal community structure is pH, which is modified by fire severity. This study shows the importance of edaphic factors in determining fungal community structure at large scales, but suggests these patterns are mediated by interactions between fire and forest stand composition.     

Links between plant and fungal communities across a deforestation chronosequence in the Amazon rainforest

Understanding the interactions among microbial communities, plant communities and soil properties following deforestation could provide insights into the long-term effects of land-use change on ecosystem functions, and may help identify approaches that promote the recovery of degraded sites. We combined high-throughput sequencing of fungal rDNA and molecular barcoding of plant roots to estimate fungal and plant community composition in soil sampled across a chronosequence of deforestation. We found significant effects of land-use change on fungal community composition, which was more closely correlated to plant community composition than to changes in soil properties or geographic distance, providing evidence for strong links between above- and below-ground communities in tropical forests.     

Differential responses of soil bacteria,fungi, archaea and protists to plant species richness and plant functional group identity

Plants are known to influence belowground microbial community structure along their roots, but the impacts of plant species richness and plant functional group (FG) identity on microbial communities in the bulk soil are still not well understood. Here, we used 454‐pyrosequencing to analyse the soil microbial community composition in a long‐term biodiversity experiment at Jena, Germany. We examined responses of bacteria, fungi, archaea, and protists to plant species richness (communities varying from 1 to 60 sown species) and plant FG identity (grasses, legumes, small herbs, tall herbs) in bulk soil. We hypothesized that plant species richness and FG identity would alter microbial community composition and have a positive impact on microbial species richness. Plant species richness had a marginal positive effect on the richness of fungi, but we observed no such effect on bacteria, archaea and protists. Plant species richness also did not have a large impact on microbial community composition. Rather, abiotic soil properties partially explained the community composition of bacteria, fungi, arbuscular mycorrhizal fungi (AMF), archaea and protists. Plant FG richness did not impact microbial community composition; however, plant FG identity was more effective. Bacterial richness was highest in legume plots and lowest in small herb plots, and AMF and archaeal community composition in legume plant communities was distinct from that in communities composed of other plant FGs. We conclude that soil microbial community composition in bulk soil is influenced more by changes in plant FG composition and abiotic soil properties, than by changes in plant species richness per se.