Forest Soil Microbial Communities Research Articles

Different sexual impacts of dioecious Populus euphratica on microbial communities and nitrogen cycle processes in natural forests

Plant-soil microbe interactions are determined by plant characters. Sexual dimorphism in root development, nitrogen (N) assimilation and resource allocation have been studied in different environments. However, how dioecious plants affect soil microbial communities in natural forests, particularly in low precipitation regions, is still poorly known. In this study, natural Populus euphratica forests were investigated in three arid regions. We hypothesized that males and females impose sex-specific impacts on physiochemical traits of soil, microbial communities and N-cycling processes. We discovered only little sex effect on most physiochemical traits, and bacterial and fungal communities in top soil (0–20 cm) in the three studied forests. However, the sex effect was greater in deep soil. Compared with fungi, the structure and composition of bacterial communities were affected more by plant sex in the rhizosphere and bulk soil. Sex indirectly affected N-cycling processes through a negative impact on the soil water content. Expressions of AOA, AOB, nifH, nirS and nirK in the rhizosphere soil were significantly affected by sex, forest site and their interactions. Proteobacteria, Actinobacteria and Firmicutes in the rhizosphere and bulk soils of P. euphratica males showed more significant effects on ammoxidation, N fixation, denitrification and protease activities when compared to females. The results suggest that sexual differences in shaping bacterial communities and affecting N-cycling processes are greater when the soil becomes drier. Thus, low precipitation causes intense sex differences in the nitrogen uptake and use efficiency. Our study highlights the importance of sexual effects on shaping specific microbial communities and N-cycling processes.

Metagenomic Characterization of Soil Microbial Communities in the Luquillo Experimental Forest (Puerto Rico) and Implications for Nitrogen Cycling

The phylogenetic and functional diversities of microbial communities in tropical rainforests and how these differ from those of temperate communities remain poorly described but are directly related to the increased fluxes of greenhouse gases such as nitrous oxide (N2O) from the tropics. Toward closing these knowledge gaps, we analyzed replicated shotgun metagenomes representing distinct life zones and an elevation gradient from four locations in the Luquillo Experimental Forest (LEF), Puerto Rico. These soils had a distinct microbial community composition and lower species diversity compared to those of temperate grasslands or agricultural soils. In contrast to the overall distinct community composition, the relative abundances and nucleotide sequences of N2O reductases (nosZ) were highly similar between tropical forest and temperate soils. However, respiratory NO reductase (norB) was 2-fold more abundant in the tropical soils, which might be relatable to their greater N2O emissions. Nitrogen fixation (nifH) also showed higher relative abundance in rainforest than in temperate soils, i.e., 20% versus 0.1 to 0.3% of bacterial genomes in each soil type harbored the gene, respectively. Finally, unlike temperate soils, LEF soils showed little stratification with depth in the first 0 to 30 cm, with ∼45% of community composition differences explained solely by location. Collectively, these results advance our understanding of spatial diversity and metabolic repertoire of tropical rainforest soil communities and should facilitate future ecological studies of these ecosystems. IMPORTANCE Tropical rainforests are the largest terrestrial sinks of atmospheric CO2 and the largest natural source of N2O emissions, two greenhouse gases that are critical for the climate. The microbial communities of rainforest soils that directly or indirectly, through affecting plant growth, contribute to these fluxes remain poorly described by cultured-independent methods. To close this knowledge gap, the present study applied shotgun metagenomics to samples selected from three distinct life zones within the Puerto Rico rainforest. The results advance our understanding of microbial community diversity in rainforest soils and should facilitate future studies of natural or manipulated perturbations of these critical ecosystems.

Long‐term restoration altered edaphic properties and soil microbial communities in forests: evidence from four plantations of southern China

Afforestation has been an important approach to mitigate land deterioration and biodiversity reduction. There are increasing interests in understanding the responses of soil microbial communities under long‐term forest restoration, since they play a crucial role in the mediation of ecosystem functions while interacting with plants. Here we examined the effects of four forests (Acacia species [AM], Eucalyptus species [EE], mixed coniferous species [MC], mixed native broadleaf species [NS]) after 35‐year restoration (1986–2015) on soil environmental factors and soil microbial communities. Our results showed that afforestation significantly increased soil organic carbon (SOC) and total N (TN) while decreasing soil pH. Among the four forest types, there were significant differences for TN and TK (total K) but not for pH, sSOC, and TP (total P). Bacterial species richness and phylogenetic diversity in Acacia forest significantly declined more than those of other forests, but those of fungal communities were remarkably higher in the Acacia forest. Both the bacterial and fungal communities' structure of each forest were strongly related to soil TK and TP. Besides, TK and SOC were primary edaphic properties that respectively affected the distribution pattern of bacterial and fungal communities in four forests. Network structures in AM and MC compared with EE and NS were more complex and closely linked, hence more resistant to extrinsic interference. Our results demonstrate that afforestation altered soil properties and microbial communities during long‐term restoration, which may provide insight into ecological restoration practices and biodiversity maintenance.

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。;Forest ecosystems are an important part of the terrestrial ecosystem. In forest ecosystems, the plants transmit carbon, nitrogen, phosphorus and other nutrients to the soil in the form of litter. Soil microorganisms, as the main decomposers of litter, affect the energy flow and material circulation of forest ecosystems. This paper took the mixed Quercus acutissima Carruth. and Robiniapseudoacacia L. forest (QR), as well as pure Quercus acutissima Carruth forest (QAC) as research objects. The field fixed-point sampling, indoor analysis, and high-throughput sequencing methods were used to study the characteristics of soil microbial diversity and their effects on the litter decomposition rate. The results were as follows: (1) The litter decomposition rate of QR was higher than that of QAC, the litter decomposition rate of QR was 0.70, and the litter decomposition rate of QAC was 0.62. During the litter decomposition of the two forest stands (QR and QAC), total organic carbon (TOC) and total nitrogen (TN) were released, but total phosphorus (TP) was accumulated first and then released. (2) The two forest stands had the same dominant soil microbial communities, the dominant soil bacterial communities were Actiobacteria, Proteobacteria, Actinobacteria and Verrucomicrobia, and the dominant soil fungi communities were Basidiomycota, Ascomycota and Mortierierellomycota. (3) During the litter decomposition of the two forest stands, the variation range of the soil microbial community richness index and diversity index of QR was smaller than that of QAC. The bacterial community richness index (Chao1 index and ACE index) and community diversity index (Shannon index and Simpson index) of QR and QAC showed a trend of first increasing and then decreasing. The fungal community richness index of QR showed a trend of first decreasing and then increasing, and the fungal community diversity index showed a gradually decreasing trend. The fungal community richness index of QAC showed a gradually decreasing trend, and the fungal community diversity index showed a trend of first decreasing and then increasing. (4) The litter decomposition rate was significantly positively correlated with the soil bacterial community richness index and diversity index, while significantly positively correlated with the soil fungal community richness index. The soil microbial community had an important influence on the litter decomposition rate of QR and QAC. The research results are helpful to understand the relationship between the litter decomposition rate and soil microbial communities in mixed forests, and provide theoretical basis for the research of the influence of soil microbial diversity on litter decomposition in mixed forests.

Variation of subtropical forest soil microbial biomass and soil microbial community functional characteristics along an urban-rural gradient

Soil microorganisms, which are sensitive to environmental changes, affect soil nutrient cycling and play an important role in the biogeochemical cycling. To understand the changes of soil microorganisms in subtropical forest across the urban-rural environmental gradient, we analyzed the differences in soil microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), and microbial community functional diversitiy in Dashu Mountain National Forest Park (urban forest), Zipeng Mountain National Forest Park (suburban forest) in Hefei and Wanfo Mountain(rural forest) in Luan City. Results showed that soil MBC followed an order of rural natural forest (115.07 mg·kg-1) > suburban forest (101.68 mg·kg-1) > urban forest (82.73 mg·kg-1), soil MBN followed an order of rural natural forest (57.73 mg·kg-1) > urban forest (31.57 mg·kg-1) > suburban forest (29.01 mg·kg-1), soil microbial metabolic activities (AWCD), McIntosh index (U) were shown as rural natural forest > suburban forest > urban forest. The main carbon sources used by soil microbial communities in those forests were carboxylic acids, amino acids and carbohydrates, with weak utilization capacity for polyamines and polyphenols. The utilization capacity of soil microorganisms to amino acids, carboxylic acids, polymers and polyphenols followed the order of rural natural forest > suburban forest > urban forest. There were significant spatial variations in the functional characteristics of soil microbial communities under urban-rural environmental gradient, with Tween 80 and β-methyl-D-Glucoside being the characteristic carbon sources as the influencing factors. Soil pH was significantly positively correlated with the microbial McIntosh index and AWCD value, while soil ammonium nitrogen (NH4+-N) showed a significant positive correlation with microbial Shannon diversity index and AWCD value. There was a negative correlation between the microbial Simpson index and soil nitrate nitrogen (NO3--N). Soil pH, NH4+-N and NO3--N were the main factors affecting diversity index of microbial communities. The results suggested that there were significant differences in microbial community characteristics of forest soil in urban-rural environmental gradient forests, and that the metabolic potential and functional diversity of soil microbial community in urban forests were weaker than that of natural forests.

Fertilization and clear-cutting effects on greenhouse gas emissions of pinewood nematode damaged Masson pine plantation

ABSTRACT Introduction: Management practices are essential for maintaining forest ecological functions under increasing diseases and pest disasters. The effects of nitrogen fertilization (NF) and clear-cutting (CC) on the soil microbial community structure and greenhouse gases emission were investigated of pinewood nematodes (Bursaphelenchus xylophilus)-infected Masson pine (Pinus massoniana) plantations. Outcomes: CC increased the soil microbial biomass carbon (SMBC) and soil microbial biomass nitrogen (SMBN) contents relative to the control (CK). NF increased the SMBN but had no significant effect on the SMBC content. The total fungal and bacterial abundances increased in the CC treatment compared with the CK, but there was no significant difference between the NF and CK. The cumulative soil CO2 emission (2.35 t C·hm−2) was higher than that of CK (1.65 t C·hm−2) in summer, and the cumulative annual N2O emission (16.90 kg N·hm−2 yr−1) of NF was approximately 47 times of CK (0.36 t N·hm−2·yr−1). CC increased the CO2 flux (2.21 t C·hm−2) in summer but have no significantly effects on N2O emission. Conclusion: These results indicated that NF and CC practices changed forest soil microbial community structure and affected soil greenhouse gas emissions in pinewood nematodes -infected Masson pine plantations. The CO2 emission rates increased in the NF and CC treatments, which reduced the carbon sequestration function of forests and had a negative impact on climate change.

Biogeographic Changes in Forest Soil Microbial Communities of Offshore Islands—A Case Study of Remote Islands in Taiwan

Biogeographic separation has been an important cause of faunal and floral distribution; however, little is known about the differences in soil microbial communities across islands. In this study, we determined the structure of soil microbial communities by analyzing phospholipid fatty acid (PLFA) profiles and comparing enzymatic activities as well as soil physio-chemical properties across five subtropical granite-derived and two tropical volcanic (andesite-derived) islands in Taiwan. Among these islands, soil organic matter, pH, urease, and PLFA biomass were higher in the tropical andesite-derived than subtropical granite-derived islands. Principal component analysis of PLFAs separated these islands into three groups. The activities of soil enzymes such as phosphatase, β-glucosidase, and β-glucosaminidase were positively correlated with soil organic matter and total nitrogen. Redundancy analysis of microbial communities and environmental factors showed that soil parent materials and the climatic difference are critical factors affecting soil organic matter and pH, and consequently the microbial community structure.

Influence of Tree Vegetation on Soil Microbial Communities in Temperate Forests and Their Potential as a Proactive Indicator of Vegetation Shift Due to Climate Change

Unexpected vegetation shift is a serious problem caused by climate change, resulting in considerable damage to local communities. It is necessary to be continuously monitored, and the soil microbial community is expected to reflect the pressure on forest ecosystems due to climate change. We investigated soil bacterial and fungal communities in Odaesan at a four-year interval through eDNA meta-barcoding and analyzed the compositional and functional differences between forest types (Mongolian oak (Quercus mongolica) forest with and without Manchurian firs (Abies holophylla)) and sampling years. As a result, denitrifiers predominated in the presence of Manchurian firs, but there was no difference in the influence of climate change by forest type. Although tree vegetation remained stable, the microbial communities significantly changed over four years. This result demonstrates that climate change significantly shifts the microbial communities, even if not enough to trigger a vegetation shift, thus a microbial indicator can be developed to assess the press disturbance accumulated on the forest ecosystem. Through this study, we identified the influence of Manchurian firs and that of climate change on soil microbial communities in temperate forests and demonstrated the potential of the microbial community as a proactive indicator of vegetation shift due to climate change.

Associations between human impacts and forest soil microbial communities

We are living in a new epoch—the Anthropocene, in which human activity is reshaping global biodiversity at an unprecedented rate. Increasing efforts are being made toward a better understanding of the associations between human activity and the geographic patterns in plant and animal communities. However, similar efforts are rarely applied to microbial communities. Here, we collected 472 forest soil samples across eastern China, and the bacterial and fungal communities in those samples were determined by high-throughput sequencing of 16S rRNA gene and internal transcribed spacer region, respectively. By compiling human impact variables as well as climate and soil variables, our goal was to elucidate the association between microbial richness and human activity when climate and soil variables are taken into account. We found that soil microbial richness was associated with human activity. Specifically, human population density was positively associated with the richness of bacteria, nitrifying bacteria and fungal plant pathogens, but it was negatively associated with the richness of cellulolytic bacteria and ectomycorrhizal fungi. Together, these results suggest that the associations between geographic variations of soil microbial richness and human activity still persist when climate and soil variables are taken into account and that these associations vary among different microbial taxonomic and functional groups.

Forest conversion alters the structure and functional processes of tropical forest soil microbial communities

AbstractMany studies have been carried‐out on the effects of forest conversion on soil microbial community composition and diversity. However, impacts on soil microbial functions and how diversity changes across scales are poorly understood. To fill the research gap, we used metagenomic sequencing and 16S rRNA and ITS gene sequences to evaluate the microbial composition, diversity, and function of 260 soil samples collected from tropical rainforest and rubber plantation sites across Hainan Island, South China. The results revealed that: (a) Forest conversion resulted in shifts in microbial composition (from the Proteobacteria to Chloroflexi), archaeal composition (from Thaumarchaeota to Bathyarchaeota), and fungal composition (from Basidiomycota to Ascomycota). (b) Bacterial alpha, beta, and gamma diversity were not reduced by forest conversion. However, fungal beta diversity was lower in the plantations, resulting in a decrease in gamma diversity. Archaeal beta diversity was higher in rainforest versus rubber plantation soils, but archaeal gamma diversity showed the opposite pattern. (c) Soil functional composition and diversity did not differ with forest type; however, genes related to metabolism and degradation processes were significantly more abundant in the tropical rainforest. These changes in gene abundance could alter ecosystem processes. (d) Soil pH and environmental heterogeneity were the main drivers of microbial taxonomic composition and functional gene composition. Land use explained 13.28% of the variation in taxonomic composition but did not explain changes in functional gene composition. We concluded that land use changes can alter soil microbial community structure and have profound effects on ecosystem functions and processes.

Volcanic deposits affect soil nitrogen dynamics and fungal–bacterial dominance in temperate forests

Volcanic deposits increase soil organic carbon storage. However, little is known about the effect of volcanic deposits on forest soil nitrogen (N) dynamics and microbial communities. We explored gross and net N transformation rates and microbial community structure using a phospholipid fatty acid (PLFA) method across eight forests with soils derived from different parent material in Japan. Volcanic mineral soils had approximately three-fold greater total N and inorganic N contents and gross nitrification, ammonium immobilization, and nitrate immobilization rates that were one order of magnitude higher than in non-volcanic soils. Moreover, volcanic mineral soils had a 1.7-fold lower N turnover rate, which was estimated as net N mineralization rate per soil N. This was likely caused by a higher gross N immobilization rate, potentially due to the mineral traits of volcanic soils. Volcanic mineral soils had approximately four- and three-fold greater microbial biomass-N and bacterial PLFA contents, respectively, and the fungal:bacterial PLFA ratio was lower in volcanic mineral soils than in non-volcanic soils. Microbial community structure, analyzed using non-metric multidimensional scaling, was distinct between volcanic and non-volcanic soils, and was significantly affected by soil characteristics. This study demonstrates that aside from soil carbon storage, volcanic deposits are related to increases in soil N immobilization, N content, bacterial biomass, and N transformation rates in forest ecosystems.

Influence of invasive earthworms (Amynthas spp.) on Wisconsin forest soil microbial communities and soil chemistry

The invasion of Amynthas species complex of earthworms from Asia into North American hardwood forests poses a novel threat to these ecosystems. These species can competitively exclude previously-established earthworms, have novel effects on microbial communities, and influence the structural and chemical composition of soils differently than other earthworm species. However, because prior research has found that earthworm species is an important factor for microbial community composition, Amynthas species may also uniquely affect soil microbial community composition. To address this, we took earthworm and soil samples from 0.5-m quadrats along an active invasion front of Amynthas agrestis and A. tokioensis at the University of Wisconsin-Madison Arboretum. We tested all soil samples for basal metabolic rates, total carbon, and total nitrogen. We also extracted microbial DNA from cast samples, dissected worm guts, and soil samples, and we used high-throughput DNA sequencing to characterize Amynthas species-specific differences in bacterial and fungal community composition. We found that plots that had been occupied by Amynthas for longer than a year had higher total nitrogen, lower C/N, and different communities of soil bacteria and fungi when compared to newly-invaded plots. We also found that Amynthas had species-specific differences in bacterial communities adhered to worm guts and in worm casts. These results suggest that Amynthas species introduce novel assemblages of bacteria and fungi through their casts, and these differences are associated with the species-specific community composition of earthworm guts. These results also suggest that Amynthas species are likely affecting the soil microbial community during invasion.

Drought accelerated recalcitrant carbon loss by changing soil aggregation and microbial communities in a subtropical forest

Subtropical forests are considerable carbon (C) sinks in Asia, yet are facing the threat of drought with increased frequency and prolonged duration. Drought may directly and indirectly impact soil C cycling, potentially affecting the fate of the soil organic carbon (SOC) storage. In a subtropical evergreen broad-leaved forest of eastern China, five years of rainfall reduction experiment resulted in an average of 52.6% decrease in soil water content. In this study, the responses of SOC composition, soil aggregate stability, microbial extracellular enzymatic activities, fungal and bacterial community structures under long-term drought were assessed. Our results showed that drought resulted in loss of a third of large macroaggregates, and doubled the proportion of microaggregates. The non-hydrolyzed carbon (NHC) content decreased by over 50% in large macroaggregates, leading to increased sensitivity of SOC to decomposition. Compared with fungi, bacteria were more sensitive to drought. The majority of the affected taxa showed reduced abundances, while that of Actinobacteria, a group commonly associated with recalcitrant C degradation, significantly increased. Drought also increased the overall peroxidase activity typically involved in recalcitrant C turnover, although it reduced hydrolytic enzyme activities in macroaggregates. These findings revealed that drought not only decreased SOC stability through macroaggregate disintegration and changing its chemical characteristics, but also shifted microbial communities in both composition and activities toward enhanced abilities of recalcitrant C conversion. This study highlights the importance of understanding microbially-mediated C turnover processes to better predict the fate of SOC storage in response to long-term drought.

Responses of forest soil microbial communities to drought and nitrogen deposition: A review

Drought and nitrogen input are profoundly influencing most life on Earth and the substance cycling in forest ecosystems in the Anthropocene, with consequences on global carbon balance and feedback on climate changes. Soil microorganisms drive biogeochemical cycling and key ecological processes, with central role and global importance in climate change biology. Here, we reviewed the research in the area of the effects of drought and nitrogen deposition on soil bacteria and mycorrhizal fungi in forest ecosystems. We proposed that future studies should focus on how microbial diversity, activity, and ecological functioning respond to multiple global change factors and their interactions; how subtropical forest ecosystems respond to global changes on the basis of establishment of the long-term field experimental station; the interaction of different soil biological guilds; utilizing microbial big data to construct the relevant mechanistic models. Taken together, based on improved understanding of the responses of soil microbial diversity and community composition to global changes, further research may subsequently focus on manipulating the microbial communities to enhance forest management, ecological resources protection, and environmental sustainability. This review would provide some critical theoretical basis for the microbial strategy in mitigating climate change in future.

Effect of strip harvesting on bacterial diversity of forest soils in the Daxing'an Mountains

AbstractStrip harvesting can improve the management of low‐quality forests, but the practice affects forest soil properties and microbial communities. The effects of different strip widths on the physicochemical properties of the forest soil and the bacterial diversity were determined. The design consisted of four strips with the same length and different widths of 6 m (ZM6), 10 m (ZM10), 14 m (ZM14), and 18 m (ZM18) and an unharvested strip (ZM0) as the control. Illumina high‐throughput sequencing was used to determine the sequence information of the soil microbial community structure in the five strips. The dominant bacterial phyla were Proteobacteria and Acidobacteria, while the dominant bacterial genera were AD101, Rhodoplanes, and Bradyrhizobium. The strip width exhibited a highly significant positive correlation with Proteobacteria and Acidobacteria (p < .001). The order of plots based on soil bacterial diversity (Chao1 and the abundance‐based coverage estimator [ACE]) was ZM18 > ZM10 > ZM6 > ZM14 > ZM0, and there was a highly significant positive correlation between the indices and the strip width (p < .001). Strip harvesting significantly affected soil pH, total nitrogen (TN), total potassium (TK), soil respiration (SR), soil temperature (ST), and soil moisture (SM) (p < .05). The results of a principal component analysis (PCA) showed that strip harvesting explained 23% of the bacterial variation. The 10‐m‐wide strip exhibited the most desirable effects because it had relatively rich bacterial diversity and moderate soil fertility.

Soil Bacterial and Fungal Communities Exhibit Distinct Long-Term Responses to Disturbance in Temperate Forests.

In Appalachian ecosystems, forest disturbance has long-term effects on microbially driven biogeochemical processes such as nitrogen (N) cycling. However, little is known regarding long-term responses of forest soil microbial communities to disturbance in the region. We used 16S and ITS sequencing to characterize soil bacterial (16S) and fungal (ITS) communities across forested watersheds with a range of past disturbance regimes and adjacent reference forests at the Coweeta Hydrologic Laboratory in the Appalachian mountains of North Carolina. Bacterial communities in previously disturbed forests exhibited consistent responses, including increased alpha diversity and increased abundance of copiotrophic (e.g., Proteobacteria) and N-cycling (e.g., Nitrospirae) bacterial phyla. Fungal community composition also showed disturbance effects, particularly in mycorrhizal taxa. However, disturbance did not affect fungal alpha diversity, and disturbance effects were not consistent at the fungal class level. Co-occurrence networks constructed for bacteria and fungi showed that disturbed communities were characterized by more connected and tightly clustered network topologies, indicating that disturbance alters not only community composition but also potential ecological interactions among taxa. Although bacteria and fungi displayed different long-term responses to forest disturbance, our results demonstrate clear responses of important bacterial and fungal functional groups (e.g., nitrifying bacteria and mycorrhizal fungi), and suggest that both microbial groups play key roles in the long-term alterations to biogeochemical processes observed following forest disturbance in the region.

Karst rocky desertification does not erode ectomycorrhizal fungal species richness but alters microbial community structure

There are growing concerns regarding the restoration of karst rocky desertification (KRD) areas. However, the soil conditions and its residing microorganisms, which are essential for the plants, remain largely unclear. We studied soil characteristics and microbial communities in natural forests (non-KRD) and shrubs with eroded soil and surface soil run-off, using Illumina Miseq sequencing. Our results showed that despite KRD reduced soil fertility and altered microbial community structures, microbial diversity did not diminish. Interestingly, bacterial OTU richness and diversity were greater in the KRD areas than in the non-KRD areas, which had relatively greater plant density and diversity. Fungal OTU richness and diversity remained unchanged by KRD. Although the KRD areas had been clear-cut and trees were mostly absent, ectomycorrhizal fungi did not differ in diversity and relative abundance between the two land types, indicating that the KRD shrubs hosted surprisingly diverse and abundant ectomycorrhizal fungi. Our results highlight the highly diverse microbes under environmental and anthropogenic stresses in KRD areas. Despite the fact that degraded soil properties and an altered microbial community structure remain, KRD did not erode ectomycorrhizal fungal species richness, which is crucial in the revegetation of trees in KRD areas.

Community of dark-spored myxomycetes in ground litter and soil of taiga forest (Nizhne-Svirskiy Reserve, Russia) revealed by DNA metabarcoding

Abstract The diversity of dark-spored myxomycetes in forest ground litter and soil from four study plots across a fire chronosequence in Nizhne-Svirskiy Nature Reserve (northwest of Russia) was assessed by a DNA metabarcoding approach. The history of fire disturbances and the season of sampling influenced the composition of myxomycete assemblages. Several species showed substrate preferences different from what is known from fruiting body records. A high abundance of nivicolous species in the majority of the samples suggests that this ecological group constitutes a common element of soil microbial communities in lowland taiga forests. Four species are reported for the Leningrad region for the first time. Our results support the hypothesis that amoebae populations of myxomycetes may have much wider ecological niches than indicated by records of fructifications, and further environmental studies may provide valuable new insights on myxomycete ecology and distribution.

Tree species identity surpasses richness in affecting soil microbial richness and community composition in subtropical forests

Plant interactions and feedbacks with soil microorganisms play an important role in sustaining the functions and stability of terrestrial ecosystems, yet the effects of tree species diversity on soil microbial community in forest ecosystems are still not well understood. Here, we examined the effects of tree species richness (1–12 species) and the presence of certain influential tree species (sampling effect) on soil bacterial and fungal communities in Chinese subtropical forests, using high-throughput Illumina sequencing for microbial identification. We observed that beta rather than alpha diversities of tree species and soil microorganisms were strong coupled. Multivariate regression and redundancy analyses revealed that the effects of tree species identity dominated over tree species richness on the diversity and composition of bacterial and fungal communities in both organic and top mineral soil horizons. Soil pH, nutrients and topography were always identified as significant predictors in the best multivariate models. Tree species have stronger effect on fungi than bacteria in organic soil, and on ectomycorrhizal fungi than saprotrophic fungi in mineral topsoil. Concluding, tree species identity, along with abiotic soil and topographical conditions, were more important factors determining the soil microbial communities in subtropical forests than tree diversity per se.

Spatial scaling of forest soil microbial communities across a temperature gradient.

Temperature is an important correlate of global patterns of biodiversity, yet the mechanisms driving these relationships are not well understood. Taxa-area relationships (TARs) have been intensively examined, but the effects of temperature on TARs, particularly for microbial communities, are largely undocumented. Here we present a continental-scale description of temperature-dependent nested TARs of microbial communities (bacteria and archaea) from soils of six forest sites spanning a temperature gradient from subalpine Colorado to tropical Panama. Our results revealed that spatial scaling rates (z-values) of microbial communities varied with both taxonomic resolutions and phylogenetic groups. Additionally, microbial TAR z-values increased with temperature (r = 0.739, P < 0.05), but were not correlated with other environmental variables tested (P > 0.05), indicating that microbial spatial scaling rate is temperature-dependent. Understanding how temperature affects the spatial scaling of microbial biodiversity is of fundamental importance for preservation of soil biodiversity and management of ecosystems.