Aboveground Community Research Articles

Resilience of Collembola communities to extreme drought is moderated by land use at a regional scale

In a world undergoing climate and usage change, soil biodiversity, which accounts to 25 % of the terrestrial biodiversity, is under severe threats. However, scenarios of climate change are based on known sensitivity of aboveground communities while there are differences on the responses to these changes with soil biodiversity. Here, we investigate the effects of an extreme climatic – due to an exceptionally drought year in 2011 - in various land use types (grassland, arable land, forest) through a study conducted at a regional scale (146 sites in Meuse, France) during 5 years. We characterized the responses of Collembola communities to climate change using (i) taxonomic indices and species dynamics, and (ii) species' functional traits and trait-based indices to reveal community assembly mechanisms. Our results demonstrated a total of 98 Collembola species collected during the five year project over the three land uses. Density and species richness were modulated by year, by land use and by their interaction. Three different distribution patterns in response to extreme drought events were demonstrated according to land use. Our findings thus reveal various effects according to land use, with a fast recovery of communities in arable lands, a long term effect for grasslands, and almost no effects observed in forests. These results show that the diversity of Collembola communities may be used as indicators of the resilience of ecosystems facing extreme climatic events.

Plant community richness and foliar fungicides impact soil Streptomyces inhibition, resistance, and resource use phenotypes.

Plants serve as critical links between above- and below-ground microbial communitites, both influencing and being influenced by microbes in these two realms. Below-ground microbial communities are expected to respond to soil resource environments, which are mediated by the roots of plants that can, in turn, be influenced by the above-ground community of foliar endophytes. For instance, diverse plant communities deposit more, and more diverse, nutrients into the soil, and this deposition is often increased when foliar pathogens are removed. Differences in soil resources can alter soil microbial composition and phenotypes, including inhibitory capacity, resource use, and antibiotic resistance. In this work, we consider plots differing in plant richness and application of foliar fungicide, evaluating consequences on soil resource levels and root-associated Streptomyces phenotypes. Soil carbon, nitrogen, phosphorus, potassium, and organic matter were greater in samples from polyculture than monoculture, yet this increase was surprisingly offset when foliar fungal communities were disrupted. We find that Streptomyces phenotypes varied more between richness plots-with the Streptomyces from polyculture showing lower inhibitory capacity, altered resource-use profiles, and greater antibiotic resistance-than between subplots with/without foliar fungicide. Where foliar fungicide affected phenotypes, it did so differently in polyculture than in monoculture, for instance decreasing niche width and overlap in monoculture while increasing them in polyculture. No differences in phenotype were correlated with soil nutrient levels, suggesting the need for further research looking more closely at soil resource diversity and particular compounds that were found to differ between treatments.

Water and nitrogen coupling regulates the present and future restoration trends under Spartina alterniflora invasion in a coastal salt marsh

Global change can easily cause the wetland ecosystem structure and function to be damaged by alien species. Former studies on Spartina alterniflora invasion only focused on the effect of aboveground communities, ignoring the potential regeneration of soil seed banks. Therefore, the study aimed to find the key resources that limit the S. alterniflora invasion and the regulation mechanism for S. alterniflora regeneration. Through investigating the S. alterniflora communities with different invasion stages, we studied the structure and composition of the aboveground communities and the soil seed banks, in response to the soil properties and water and nitrogen addition. The dominant competitive advantage of S. alterniflora was mainly affected by the aboveground biomass, which was regulated by soil NH4+-N and moisture content. Although the richness was same in the soil seed banks under the S. alterniflora communities with different coverage, S. alterniflora seeds maintained its specific competitive dominance. The niche breadth of S. alterniflora and the niche overlap between S. alterniflora and Tripolium pannonicum was the highest under low aboveground coverage. The soil seed bank germination experiments showed that the S. alterniflora density decreased when the soil nitrogen concentration exceeded 1 g/kg, while the density of native species E. crusgalli and T. pannonicum decreased when the water depth above the soil surface exceeded 2 cm. The successful naturalization of S. alterniflora invasion regulated by nitrogen-water coupling is a bet-hedging of the niche and fitness differences between invasive and native species in the coastal salt marsh of eastern China.

Coastal dune management affects above and belowground biotic characteristics.

Dune vegetation mediates dune-building through trapping wind-blown sand and reduces dune erosion by attenuating wave energy via above- and belowground biomass. Despite the role of vegetation in dune functions, the amount and distribution of biomass within a dune remains poorly quantified due to a lack of ample data. Our objectives were to determine the effects of management history and elevation on (1) dune belowground biotic structure and aboveground community composition and (2) to determine best predictors of belowground biomass. We sampled belowground biomass and sedimentology across the dune profile at sites in the Outer Banks, North Carolina, USA. Dunes were classified as either unmanaged (no anthropogenic interventions) or managed (sand fencing, vegetation planting, dune construction). Living belowground biomass was higher in unmanaged dunes and decreased with depth. Non-living belowground biomass was 50% higher than living biomass and with greater abundance in unmanaged dunes. Elevation was a significant covariate of living and non-living belowground biomass, vegetative cover and species richness. Plant community composition varied less in managed dunes and differed significantly from unmanaged dunes. Vegetative cover, species richness, elevation, sedimentology and management history were predictors of belowground biomass. These results underscore the influence of management and geomorphology on dune plant communities, which may influence erosion resistance.

Plasticine models confirm high predator pressure on surfaced earthworms in different ecosystems

Aboveground communities may strongly depend on the detrital subsidy, i.e. the release of energy and nutrients from the soil food webs. Earthworms predated by aboveground animals are seemingly among the most important links connecting belowground and aboveground food webs. Here, we conducted an experiment with plasticine models in alpine tundra, temperate, and monsoon tropical forests to estimate predator pressure on surfaced earthworms compared to aboveground prey (caterpillars). Earthworm models on the ground were attacked several times more often than caterpillar models on the plants. The attack rate was highest in the tropical forest; the most common types of attacks on earthworms were arthropod bites in both forests and mammal bites in tundra.

Plant functional traits modulate the effects of soil acidification on above- and belowground biomass

Abstract. Atmospheric sulfur (S) deposition has been increasingly recognized as a major driver of soil acidification. However, little is known about how soil acidification influences above- and belowground biomass by altering leaf and root traits. We conducted a 3-year S-addition experiment to simulate soil acidification in a meadow. Grass (Leymus chinensis (Trin.) Tzvelev) and sedge (Carex duriuscula C.A.Mey) species were chosen to evaluate the linkage between plant traits and biomass. Sulfur addition led to soil acidification and nutrient imbalances. Soil acidification decreased specific leaf area (SLA) but increased leaf dry-matter content (LDMC) in L. chinensis, showing a conservative strategy and thus suppressing aboveground instead of belowground biomass. However, in C. duriuscula, soil acidification increased plant height and root nutrients (N, P, S, and Mn), favoring competition for natural resources through enhanced above- and belowground biomass, i.e., adoption of an acquisitive strategy. Increased soil acidity resulted in an overall reduction in aboveground community biomass by 3 %–33 %, but it led to an increase in community root biomass by 11 %–22 % due to upregulation as a result of higher soil nutrient availability. Our results demonstrate that both above- and belowground plant biomass is affected by S-induced acidification. Understanding the linkage between plant biomass and functional traits contributes to a better understanding of plant–soil feedback in grassland ecosystems.

Nutrients addition decreases soil fungal diversity and alters fungal guilds and co-occurrence networks in a semi-arid grassland in northern China

Anthropogenic eutrophication is known to impair the diversity and stability of aboveground community, but its effects on the diversity, composition and stability of belowground ecosystems are not yet fully understood. In this study, we conducted a 9-year nitrogen (N) and phosphorus (P) addition experiment in a semi-arid grassland of Northern China to elucidate the impacts of nutrients addition on soil fungal diversity, functional guilds, and co-occurrence networks. The results showed that N addition significantly decreased soil fungal diversity and altered fungal community composition, whereas P addition had no impact on them. The relative abundance of arbuscular mycorrhizal fungi and leaf_saprotroph were reduced by N and P addition, but P addition enhanced the abundance of saprotrophic fungi. Co-occurrence network analysis revealed that N addition destabilized fungal network complexity and stability, while P addition slightly increased the network complexity. Additionally, the network analysis of N × P interaction revealed that P addition mitigated negative effects of N addition on network complexity and stability. Structural equation modeling (SEM) results suggested that nutrients addition directly or indirectly influenced the fungal community structure through the loss of plant richness and the increase of perennial grass biomass. These findings indicate that in comparison to P addition, N addition exhibits a pronounced negative effect on soil fungal communities. Our findings also suggest that changes in plant functional groups under nutrients deposition are pivotal in shaping soil fungal community structure in semi-arid grassland and highlight the need for a better understanding of the belowground ecosystem dynamics.

The plant root economics space in relation to nutrient limitation in Eurasian herbaceous plant communities.

Plant species occupy distinct niches along a nitrogen-to-phosphorus (N:P) gradient, yet there is no general framework for belowground nutrient acquisition traits in relation to N or P limitation. We retrieved several belowground traits from databases, placed them in the "root economics space" framework, and linked these to a dataset of 991 plots in Eurasian herbaceous plant communities, containing plant species composition, aboveground community biomass and tissue N and P concentrations. Our results support that under increasing N:P ratio, belowground nutrient acquisition strategies shift from "fast" to "slow" and from "do-it-yourself" to "outsourcing", with alternative "do-it-yourself" to "outsourcing" strategies at both ends of the spectrum. Species' mycorrhizal capacity patterns conflicted with root economics space predictions based on root diameter, suggesting evolutionary development of alternative strategies under P limitation. Further insight into belowground strategies along nutrient stoichiometry is crucial for understanding the high abundance of threatened plant species under P limitation.

Interaction network rewiring and species' contributions to community-scale flexibility.

The architecture of species interaction networks is a key factor determining the stability of ecological communities. However, the fact that ecological network architecture can change through time is often overlooked in discussions on community-level processes, despite its theoretical importance. By compiling a time-series community dataset involving 50 spider species and 974 Hexapoda prey species/strains, we quantified the extent to which the architecture of predator-prey interaction networks could shift across time points. We then developed a framework for finding species that could increase the flexibility of the interaction network architecture. Those "network coordinator" species are expected to promote the persistence of species-rich ecological communities by buffering perturbations in communities. Although spiders are often considered as generalist predators, their contributions to network flexibility vary greatly among species. We also found that detritivorous prey species can be cores of interaction rewiring, dynamically interlinking below-ground and above-ground community dynamics. We further found that the predator-prey interactions between those network coordinators differed from those highlighted in the standard network-analytical framework assuming static topology. Analyses of network coordinators will add a new dimension to our understanding of species coexistence mechanisms and provide platforms for systematically prioritizing species in terms of their potential contributions in ecosystem conservation and restoration.

Responses of soil seedbank and aboveground weed communities to globe artichoke–cropping systems: an on-farm analysis

AbstractGlobe artichoke [Cynara cardunculus L. var. scolymus (L.) Fiori] is one of the most important crops across the Mediterranean basin, where weeds are an important biotic constraint limiting crop yields. However, the effects of globe artichoke–cropping systems on weeds have been rarely tested. Following the demand for eco-friendly weed management practices, a multi-location trial (13 farms) was carried out, measuring weed seedbanks and aboveground communities within four globe artichoke–cropping systems: globe artichoke monoculture (ART), past cultivation of globe artichoke (8 to 10 yr ago) (past-ART), a globe artichoke–durum wheat (Triticum durum Desf.) rotation (ART-WHEAT), and a control where globe artichoke was never grown. Both below- and aboveground weed communities were dominated by annual therophytes, but a low correspondence was found between both types of communities. Averaged over farms, ART highly reduced both the weed soil seedbank (1,600 seeds m−2 on average) and the aboveground weed biomass (only 3.4 g dry weight m−2) compared with the control, with a decrease of 72% in the soil seedbank and 99% in the aboveground flora. Moreover, on the farms where globe artichoke was previously grown, a very low aboveground weed biomass (77% less than control) was found. In addition, ART contributed to the preservation of high levels of weed diversity (except for aboveground communities) and therefore avoided the creation of a specialized weed flora. In conclusion, we suggest the inclusion of globe artichoke into crop rotation schemes in Mediterranean agroecosystems as a sustainable tool for reducing both the soil weed seedbank and aboveground weeds, thus reducing the requirement of direct weed control methods and preserving the environment.

Land-use legacies affect the composition and distribution of tree species and their belowground functions in a succession from old-field to mature temperate forest

Forests undergoing ecological succession following abandonment from agricultural use (i.e., old fields) are ubiquitous in temperate regions of the U.S. and Europe. Ecological succession in old fields involves changes in vegetation composition influenced by factors such as land-use history, soil conditions, and dispersal limitations. Species’ behavioral, morphological, physiological and life-history attributes influence the outcomes of environmental and biotic filters on distribution and abundance. However, many studies have focused on aboveground attributes, while less attention has been placed on belowground species characteristics that influence community assembly and function. In this study, we used a trait-based approach to examine how aboveground plant composition and distribution vary with plant root functional traits (e.g., mycorrhizal association) that mediate access for nutrients such as nitrogen (N) and phosphorous (P). We inventoried every tree stem (n ​= ​11,551) in a 10-ha forested area containing old-field and historical forests and matched every species with root functional traits (n ​= ​33) from established databases. We found that land-use history influences community composition and distribution in old-field forests, which also varied with belowground root functional traits. Community composition in old-field forests, which were dominated by Acer saccharum and non-native species, were largely associated with arbuscular mycorrhizae (AM) and higher root nutrient concentrations. On the other hand, community composition in historical forests – largely dominated by Tsuga canadensis – were associated with ectomycorrhiza (EcM) and more variation of root length and depth. These results suggest that changes in aboveground communities have implications for belowground ecosystem services (e.g., nutrient cycling) which are important to forest ecosystem development. Trait-based approaches can elucidate mechanisms of community assembly, and understanding how traits influence species coexistence and interactions can inform management decisions related to biodiversity conservation and restoration efforts in disturbed or altered forests.

Light grazing intensity enhances ecosystem services in semi-arid grasslands through plant trait associations

Grasslands provide multiple ecosystem services (ESs) including provisioning, regulating, supporting, and cultural services that are largely affected by livestock grazing. Linking plant functional traits (PFTs) to ecosystem processes and functions has attracted extensive ecological research to explore the responses and inter-relations of ecosystem services to environmental and management changes. However, little information is available on the links between PFTs and ESs in most ecosystems. We conducted a grazing experiment to investigate the response of PFTs at different levels, including in plant organs (leaves and stems), individual plants, and the overall community in a typical steppe region of Inner Mongolia. Additionally, we examined the effect of animal grazing at four intensities (nil, light, moderate, and heavy) and explored the dynamic interconnections between PFTs and ecosystem services in grasslands. Our analysis revealed that the highest total ecosystem service and provisioning service were achieved under light- and moderate-grazing treatments, respectively. Heavy grazing also increased provisioning service but with a large decline in regulating and total ecosystem services. These changes in ESs were closely associated with grazing-induced variations in PFTs. Compared to no grazing, light grazing increased plant size-related functional traits, such as height, leaf length, leaf area, stem length, and the ratio of stem length to diameter. In contrast, heavy grazing decreased these PFTs. Provisioning and regulating services were determined by plant above-ground community function and structural properties, while supporting service was jointly affected by the below-ground community and soil properties. Our results indicate that light grazing should be recommended for the best total ESs, although moderate grazing may lead to high short-term economic benefits. Moreover, PFTs are powerful indicators for provisioning and regulating services. These findings provide a valuable reference for developing effective management practices to achieve targeted ESs using PFTs as indicators.

Plant species and soil depth differentially affect microbial diversity and function in grasslands

AbstractIntroductionGrassland ecosystems are a major store of terrestrial carbon (C), yet little is known about their capacity to cycle and store C in deeper soil horizons. Further, it is unclear how plant community composition within agricultural grasslands mediates this capacity and influences microbial community composition. We investigated whether the aboveground community composition in intensively managed agricultural grasslands influenced belowground microbial community composition, abundance, respiration and enzyme activities with depth.Materials and MethodsSoil was sampled in four soil layers: A (0–15 cm), B (15–30 cm), C (30–60 cm) and D (60–90 cm) in monocultures of six grassland species and a mixture of all six. Functional capacity was measured through enzymatic and substrate‐induced respiration assays, and microbial abundance and diversity were assessed via quantitative polymerase chain reaction and sequencing (16S, Internal transcribed spacer), respectively.ResultsMicrobial abundance and C cycling enzyme activity decreased and community composition changed, along the soil depth gradient, regardless of the plant community. Microbial abundance was not significantly influenced by plant community type across the entire soil depth profile. However, prokaryotic community composition was significantly influenced by plant community in the top 15 cm of soil, and fungal community composition was significantly influenced between 15 and 30 cm in depth. Plant community types mediated the rate at which C cycling enzyme activity decreased along the soil depth gradient, and selected C cycling enzymes were significantly more active at 15–60 cm depth when Cichorium intybus (a deep rooting species) was present.ConclusionThis study provides an improved understanding of how agricultural grassland communities affect the soil microbiome with depth; this has potential implications for the management of these systems for enhanced soil health. Our work indicates the potential for multispecies mixtures with deep rooting species to be a practical strategy to increase C cycling capacity in deeper soil layers within grasslands, which may have implications for policy goals related to C storage.

Changes in the functional and phylogenetic diversity of above- and below-ground plant communities invaded by two alien herbs

Introduced plants can have long-lasting and irreversible effects on the communities and ecosystems they invade. A critical step towards understanding the legacy of plant introductions is the characterisation of changes in the invaded plant communities and how these changes are related to biogeochemical modifications. Here, we addressed this issue by comparing the impacts of two large invasive herbs, Gunnera tinctoria and Impatiens glandulifera, on the compositional, functional, and phylogenetic structure of the standing vegetation (above-ground communities) and the soil seed bank (below-ground communities). The introduction of both invasive species was associated with a significant decrease in above-ground species richness, with subsequent changes in the functional diversity and phylogenetic dispersion of the vegetation. Yet, these invaders differed in their long-term impacts and the reversibility of any modifications they caused. While G. tinctoria invasions resulted in phylogenetically clustered communities (both above- and below-ground) that were clearly distinct from uninvaded ones, seed bank communities invaded by I. glandulifera were indistinguishable from uninvaded ones, despite major compositional changes above-ground. Further, we found alterations in nutrient cycling associated with G. tinctoria invasions that could facilitate its local persistence and exacerbate any negative effects on native diversity. Our findings suggest a high susceptibility of pre-invasion above-ground communities to colonisation by distantly related herbs. However, the seed banks showed a degree of resilience against both invaders, with no major differences in species richness. Ultimately, differences in the impacts of these large invasive herbs suggest that dominance in the vegetation and a large stature are poor predictors of long-term plant community changes, including regeneration potential from seed, which are associated with plant introductions.

Soil seed banks provide a storage effect in post-logging regrowth forests of southeastern Australia

Despite the importance of soil seed banks in diversity maintenance, our understanding of plant response to changes in resource availability is largely limited to above-ground vegetation. We investigated how forest structure and edaphic properties influenced the above-ground vegetation and soil seed banks following logging in montane regrowth forests dominated by Eucalyptus regnans in the Central Highlands of southeastern Australia. We surveyed above-ground vegetation, soil seed banks, forest structure and soil properties across 20 harvest units, aged 16 to 20 years. A total of 80 species were identified in above-ground vegetation with 72 species in the soil seed bank, with only 34% of species co-occurring in both species’ pools. Climate, soil, topography, and light availability shaped plant composition but the relative importance of these properties varied among individual species and pools of diversity (combined, above-ground, soil seed bank, life form). Annual heat moisture index (AHMI) was the most important factor that influenced plant community composition across all species pools with individual species positively associated with AHMI. Acacia, but not Eucalyptus stem density further moderated plant response via effects on both light availability and soil nitrogen at the stem exclusion phase of stand development. Structurally mediated controls on above-ground community composition flow through to the soil seed bank via above-ground diversity effects on below-ground composition. For the combined species pool, individual species were most frequently related to Acacia stem density that on average explained 20% of model variation. Soil nutrients accounted for most of the model variation for individual species in above-ground (26%), soil seed bank (20%) and non-woody (32%) pools of diversity, with AHMI accounting for most of the model variation for woody species (18%). The differential response of individual species and community composition to gradients in resource availability across different pools of species diversity and life forms clearly demonstrates a storage effect in wet temperate forests of southeastern Australia that promotes post-disturbance recruitment and persistence. Our work suggests logging interacts with broad environmental controls to shape species diversity. The key role of Acacia stem density as a biotic filter of plant diversity provides opportunity to shape future plant diversity through management interventions such as thinning in the early stages of stand development. With native forest harvesting of these forests set to end from 2024, our findings provide important information on future patterns of plant diversity as logged forests recover over time, opportunities for management interventions in shaping plant composition, and potential impacts of future wildfire.

Soil bacterial community composition is more stable in kiwifruit orchards relative to phyllosphere communities over time

BackgroundSoil and phyllosphere (leaves and fruit) microbes play critical roles in the productivity and health of crops. However, microbial community dynamics are currently understudied in orchards, with a limited number incorporating temporal monitoring. We used 16S rRNA gene amplicon sequencing to investigate bacterial community temporal dynamics and community assembly processes on the leaves and fruit, and in the soil of 12 kiwifruit orchards across a cropping season in New Zealand.ResultsCommunity composition significantly differed (P < 0.001) among the three sample types. However, the communities in the phyllosphere substrates more closely resembled each other, relative to the communities in the soil. There was more temporal stability in the soil bacterial community composition, relative to the communities residing on the leaves and fruit, and low similarity between the belowground and aboveground communities. Bacteria in the soil were more influenced by deterministic processes, while stochastic processes were more important for community assembly in the phyllosphere.ConclusionsThe higher temporal variability and the stochastic nature of the community assembly processes observed in the phyllosphere communities highlights why predicting the responsiveness of phyllosphere communities to environmental change, or the likelihood of pathogen invasion, can be challenging. The relative temporal stability and the influence of deterministic selection on soil microbial communities suggests a greater potential for their prediction and reliable manipulation.

Plants alter their aboveground and belowground biomass allocation and affect community-level resistance in response to snow cover change in Central Asia, Northwest China

It is important to elucidate the changing distribution pattern of net primary productivity (NPP) to mechanistically understand the changes in aboveground and belowground ecosystem functions. In water-scarce desert environments, snow provides a crucial supply of water for plant development and the spread of herbaceous species. Yet uncertainty persists regarding how herbaceous plants' NPP allocation responds to variation in snow cover. The goal of this study was to investigate how variation in snow cover in a temperate desert influenced the NPP allocation dynamics of herbaceous species and their resistance to environmental change in terms aboveground and belowground productivity. In the Gurbantunggut Desert, wintertime snow cover depth was adjusted in plots by applying four treatments: snow removal (−S), ambient snow, double snow (+S), and triple snow (+2S). We examined their species richness, aboveground NPP (ANPP), belowground NPP (BNPP), and the resistance of ANPP and BNPP. We found that species diversity of the aboveground community increased significantly with increasing snow cover and decreased significantly Pielou evenness in plots. This resulted in greater ANPP with increasing snow cover; meanwhile, BNPP first increased and then decreased with increasing snow cover. However, this productivity in different soil layers responded differently to changed snow cover. In the 0–10 cm soil layer, productivity first rose and then declined, while it declined linearly in both the 10–20 cm and 20–30 cm soil layers, whereas in the 30–40 cm soil layer it showed an increasing trend. Belowground resistance would increase given that greater snow cover improved the BNPP in deeper soil and maintained the resource provisioning for plant growth, thus improving overall belowground stability. These results can serve as a promising research foundation for future work on how the functioning of desert ecosystems becomes altered due to changes in plant community expansion and, in particular, changes in snow cover driven by global climate change.

Effects of warming and nitrogen addition on soil fungal and bacterial community structures in a temperate meadow.

Soil microbial communities have been influenced by global changes, which might negatively regulate aboveground communities and affect nutrient resource cycling. However, the influence of warming and nitrogen (N) addition and their combined effects on soil microbial community composition and structure are still not well understood. To explore the effect of warming and N addition on the composition and structure of soil microbial communities, a five-year field experiment was conducted in a temperate meadow. We examined the responses of soil fungal and bacterial community compositions and structures to warming and N addition using ITS gene and 16S rRNA gene MiSeq sequencing methods, respectively. Warming and N addition not only increased the diversity of soil fungal species but also affected the soil fungal community structure. Warming and N addition caused significant declines in soil bacterial richness but had few impacts on bacterial community structure. The changes in plant species richness affected the soil fungal community structure, while the changes in plant cover also affected the bacterial community structure. The response of the soil bacterial community structure to warming and N addition was lower than that of the fungal community structure. Our results highlight that the influence of global changes on soil fungal and bacterial community structures might be different, and which also might be determined, to some extent, by plant community, soil physicochemical properties, and climate characteristics at the regional scale.

Soil microbial community characteristics and the influencing factors at different elevations on the eastern slope of Helan Mountain, Northwest China.

As an important bridge connecting aboveground communities and belowground biological processes, soil microorganisms play an important role in regulating belowground ecological processes. The altitudinal changes and driving factors of soil microbial community in mountain ecosystem in arid region are still unclear. We measured soil physicochemical properties at seven altitudes in the range of 1300-2800 m in Helan Mountains, and investigated the understory community composition, soil physicochemical properties, and soil microbial community. The driving factor for soil microbial community was explored by variance partitioning analysis and redundancy analysis. The results showed that the total amount of soil microorganisms and bacterial biomass first increased and then decreased with the increases of altitude, fungi, actinomyces, arbuscular mycorrhizal fungi, Gram-positive bacteria, and Gram-negative bacteria groups showed a gradual increase. The variation of fungal-to-bacterial ratio (F/B) along the altitude showed that the cumulative ability of soil bacteria was stronger than that of fungi at low altitudes, while the pattern is opposite at high altitudes. The ratio of Gram-positive bacteria to Gram-negative bacteria (GP/GN) showed an overall decreasing trend with the increases of altitude, indicating that soil bacteria and organic carbon availability changed from "oligotrophic" to "eutrophication" and from "low" to "high" transition as the altitude increased. Vegetation properties, soil physical and chemical properties jointly accounted for 95.7% of the variation in soil microbial community. Soil organic carbon (SOC), soil water content (SWC), and total nitrogen (TN) were significantly correlated with soil microbial community composition. Our results revealed the distribution pattern and driving factors of soil microbial communities at different elevations on the eastern slope of Helan Mountain, which would provide theoretical basis and data support for further understanding the interaction between plant-soil-microorganisms in arid areas.

Temporal dynamics of soil fungi in a pyrodiverse dry-sclerophyll forest.

Fire is a major evolutionary and ecological driver that shapes biodiversity in forests. While above-ground community responses to fire have been well-documented, those below-ground are much less understood. However, below-ground communities, including fungi, play key roles in forests and facilitate the recovery of other organisms after fire. Here, we used internal transcribed spacer (ITS) meta-barcoding data from forests with three different times since fire [short (3 years), medium (13-19 years) and long (>26 years)] to characterize the temporal responses of soil fungal communities across functional groups, ectomycorrhizal exploration strategies and inter-guild associations. Our findings indicate that fire effects on fungal communities are strongest in the short to medium term, with clear distinctions between communities in forests with a short time (3 years) since fire, a medium time (13-19 years) and a long time (>26 years) since fire. Ectomycorrhizal fungi were disproportionately impacted by fire relative to saprotrophs, but the direction of the response varied depending on morphological structures and exploration strategies. For instance, short-distance ectomycorrhizal fungi increased with recent fire, while medium-distance (fringe) ectomycorrhizal fungi decreased. Further, we detected strong, negative inter-guild associations between ectomycorrhizal and saprotrophic fungi but only at medium and long times since fire. Given the functional significance of fungi, the temporal changes in fungal composition, inter-guild associations and functional groups after fire demonstrated in our study may have functional implications that require adaptive management to curtail.