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Agricultural land‐use history and restoration impact soil microbial biodiversity
Abstract
Human land uses, such as agriculture, can leave long‐lasting legacies as ecosystems recover. As a consequence, active restoration may be necessary to overcome land‐use legacies; however, few studies have evaluated the joint effects of agricultural history and restoration on ecological communities. Those that have studied this joint effect have largely focused on plants and ignored other communities, such as soil microbes.
We conducted a large‐scale experiment to understand how agricultural history and restoration tree thinning affect soil bacterial and fungal communities within longleaf pine savannas of the southern United States. This experiment contained 64 pairs of remnant (no history of tillage agriculture) and post‐agricultural (reforested following abandonment from tillage agriculture >60 years prior) longleaf pine savanna plots. Plots were each 1 ha and arranged into 27 blocks to minimize land‐use decision‐making biases. We experimentally restored half of the remnant and post‐agricultural plots by thinning trees to reinstate open‐canopy savanna conditions and collected soils from all plots five growing seasons after tree thinning. We then evaluated soil bacterial and fungal communities using metabarcoding.
Agricultural history increased bacterial diversity but decreased fungal diversity, while restoration increased both bacterial and fungal diversity. Both bacterial and fungal richness were correlated with a range of environmental variables including above‐ground variables like leaf litter and plant diversity, and below‐ground variables such as soil nutrients, pH and organic matter, many of which were also impacted by agricultural history and restoration.
Fungal and bacterial community compositions were shaped by restoration and agricultural history resulting in four distinct communities across the four treatment combinations.
Synthesis and applications . Past agricultural land use has left persistent legacies on soil microbial biodiversity, even over half a century after agricultural abandonment and after intensive restoration activities. The impacts of these changes on soil microbe biodiversity could influence native plant establishment, plant productivity and other aspects of ecosystem functioning following agricultural abandonment and during restoration.
... Background Land use conversion leaves enduring legacy effects on soil ecosystems and is considered a dominant threat to biodiversity [56,57]. The impacts on abiotic conditions are well-researched. ...
... The impacts on abiotic conditions are well-researched. Soil pH levels, carbon and nitrogen concentrations are highly related to agricultural practices, but it may take decades to centuries for these to reflect their modern-day land use, following conversion [15,41,57]. Compared to physicochemical analyses, far less focus has been directed towards the impact of land use change on microbial community composition and functioning. ...
Background
Bacterial communities are critical to ecosystem functioning and sensitive to their surrounding physiochemical environment. However, the impact of land use change on microbial communities remains understudied. We used 16S rRNA gene amplicon sequencing and shotgun metagenomics to assess soil microbial communities' taxonomic and functional responses to land use change. We compared data from long-term grassland, exotic forest and horticulture reference sites to data from sites that transitioned from (i) Grassland to exotic forest or horticulture and from (ii) Exotic forest to grassland.
Results
Community taxonomic and functional profiles of the transitional sites significantly differed from those within reference sites representing both their historic and current land uses ( P < 0.001). The bacterial communities in sites that transitioned more recently were compositionally more similar to those representing their historic land uses. In contrast, the composition of communities from sites exposed to older conversion events had shifted towards the compositions at reference sites representing their current land use.
Conclusions
Our study indicates that microbial communities respond in a somewhat predictable way after a land use conversion event by shifting from communities reflecting their former land use towards those reflecting their current land use. Our findings help us to better understand the legacy effects of land use change on soil microbial communities and implications for their role in soil health and ecosystem functioning. Understanding the responsiveness of microbial communities to environmental disturbances will aid us in incorporating biotic variables into soil health monitoring techniques in the future.
... The soil microbes are essential for the transformation and cycling of nutrients in the soil and ecosystems [10]. For instance, the cycling of nutrients, such as carbon, nitrogen and phosphorus, and the decomposition of organic matter are highly dependent on composition and functional structure of soil bacterial community [11][12][13]. Soil bacteria are regarded as the strong indicators of soil fertility [14], as soil physicochemical properties control soil bacterial community composition, diversity, and structural changes [15][16][17], [18], [19], [20], [21][22] by manipulating their metabolic activities [23][24]. Like bacteria, soil fungi interact with other microorganisms, and play key roles in nutrient cycling and energy ow in the soil ecosystem [28][29]. ...
Aims
Continuous cropping is a common cropping practice in northeast China. This practice can positively or negatively impact soil microbial community. However, the response of rhizosphere microbial community structures, specific microbial taxa, and co-occurrence patterns to different continuous cropping systems are rarely tested.
Methods
In this study, soil samples were collected from the rhizosphere of three different continuous cropping systems (Corn, Alfalfa and Sheepgrass) were analyzed for microbial community (bacterial and fungal) composition and structural responses using an Illumina HiSeq high-throughput sequencing technique.
Results
Our results revealed that the α- and β-diversity indices of the fungal communities were significantly different across the three continuous cropping systems. The analysis of the molecular ecological network revealed that Alfalfa communities had the highest number of nodes and edges in the bacterial network while Sheepgrass had the highest number of nodes and edges in the fungal network. To distinguish differences between the co-occurring taxa among the three cropping systems, we compared the number of positive and negative links within and between microbial groups. This highlights that perennial grassland systems had more complex bacterial and inter-domain networks. Our inter-domain networks also revealed the predominant role of fungi as a key taxon in soil microbiome networks across the three land-use types.
Conclusions
Our results demonstrated that continuous cropping of perennial forage crops enhanced soil microbial diversity, network complexity and multifunctionality. Moreover, changes in microbiota characteristics are positively dependent on forage-induced changes in soil multifunctionality.
... We did not establish intra-site variation. Gaining a more robust understanding would require higher replication of sites and soils, and, if possible, the inclusion of additional parameters as potential factors explaining the impact of different pre-treatments, i.e. chemistry of the soil minerals or previous land use history (Morrissey et al., 2015;Foucher et al., 2020;Turley et al., 2020). Most likely the variation of pre-treatment effects detected emerge from a combination of all of these factors. ...
... In addition to the microbial community in sediments, different growth stages of submerged macrophytes also have certain effects on the α diversity of the microbial community in water (Logue et al., 2012). When submerged macrophyte biomass is high, the nutrient level in water is reduced, thus inhibiting the growth and production of microorganisms in water (Turley et al., 2020). ...
Microorganisms play a crucial role in the biogeochemical processes of Dissolved Organic Matter (DOM), and the properties of DOM also significantly influence changes in microbial community characteristics. This interdependent relationship is vital for the flow of matter and energy within aquatic ecosystems. The presence, growth state, and community characteristics of submerged macrophytes determine the susceptibility of lakes to eutrophication, and restoring a healthy submerged macrophyte community is an effective way to address this issue. However, the transition from eutrophic lakes dominated by planktic algae to medium or low trophic lakes dominated by submerged macrophytes involves significant changes. Changes in aquatic vegetation have greatly affected the source, composition, and bioavailability of DOM. The adsorption and fixation functions of submerged macrophytes determine the migration and storage of DOM and other substances from water to sediment. Submerged macrophytes regulate the characteristics and distribution of microbial communities by controlling the distribution of carbon sources and nutrients in the lake. They further affect the characteristics of the microbial community in the lake environment through their unique epiphytic microorganisms. The unique process of submerged macrophyte recession or restoration can alter the DOM-microbial interaction pattern in lakes through its dual effects on DOM and microbial commu-----nities, ultimately changing the stability of carbon and mineralization pathways in lakes, such as the release of methane and other greenhouse gases. This review provides a fresh perspective on the dynamic changes of DOM and the role of the microbiome in the future of lake ecosystems.
... Soil microbiome and extracellular enzyme activities are shaped by land use and agricultural management practices (Díaz-Vallejo et al., 2021) since they dictate pH and the dynamics of C and nutrients in soils (Tian et al., 2017;Turley et al., 2020). Here, distinct land uses conferred higher organic matter, Ca, and Mg contents to the native forest soil, while available P mainly but also K contents were higher in the no-tilled soils. ...
Land use and management changes affect the composition and diversity of soil bacteria and fungi, which in turn may alter soil health and the provision of key ecological functions, such as pesticide degradation and soil detoxification. However, the extent to which these changes affect such services is still poorly understood in tropical agroecosystems. Our main goal was to evaluate how land-use (tilled versus no-tilled soil), soil management (N-fertilization), and microbial diversity depletion [tenfold (D1 = 10−1) and thousandfold (D3 = 10−3) dilutions] impacted soil enzyme activities (β-glycosidase and acid phosphatase) involved in nutrient cycles and glyphosate mineralization. Soils were collected from a long-term experimental area (35 years) and compared to its native forest soil (NF). Glyphosate was selected due to its intensive use in agriculture worldwide and in the study area, as well as its recalcitrance in the environment by forming inner sphere complexes. Bacterial communities played a more important role than the fungi in glyphosate degradation. For this function, the role of microbial diversity was more critical than land use and soil management. Our study also revealed that conservation tillage systems, such as no-tillage, regardless of nitrogen fertilizer use, mitigates the negative effects of microbial diversity depletion, being more efficient and resilient regarding glyphosate degradation than conventional tillage systems. No-tilled soils also presented much higher β-glycosidase and acid phosphatase activities as well as higher bacterial diversity indexes than those under conventional tillage. Consequently, conservation tillage is a key component for sustaining soil health and its functionality, providing critical ecosystem functions, such as soil detoxification in tropical agroecosystems.
... They also concluded that the diversity and composition of microbial community are driven by environmental filters in engineered habitats, versus stochastic processes in nonengineered soils (Gill et al., 2020). However, they did not take management practices into account despite their potential strong influence as drivers of soil microbial diversity Turley et al., 2020;Christel et al., 2021). ...
Soil microbial biodiversity provides many useful services in cities. However, the ecology of microbial communities in urban soils remains poorly documented, and studies are required to better predict the impact of urban land use. We characterized microbial communities (archea/bacteria and fungi) in urban soils in Dijon (Burgundy, France). Three main land uses were considered - public leisure, traffic, and urban agriculture - sub-categorized in sub-land uses according to urban indexes and management practices. Microbial biomass and diversity were determined by quantifying and high-throughput sequencing of soil DNA. Variation partitioning analysis was used to rank soil physicochemical characteristics and land uses according to their relative contribution to the variation of soil microbial communities. Urban soils in Dijon harbored high levels of microbial biomass and diversity that varied according to land uses. Microbial biomass was 1.8 times higher in public leisure and traffic sites than in urban agriculture sites. Fungal richness increased by 25 % in urban agriculture soils, and bacterial richness was lower (by 20 %) in public leisure soils. Partitioning models explained 25.7 %, 46.2 % and 75.6 % of the variance of fungal richness, bacterial richness and microbial biomass, respectively. The organic carbon content and the C/N ratio were the best predictors of microbial biomass, whereas soil bacterial diversity was mainly explained by soil texture and land use. Neither metal trace elements nor polycyclic aromatic hydrocarbons contents explained variations of microbial communities, probably due to their very low concentration in the soils. The microbial composition results highlighted that leisure sites represented a stabilized habitat favoring specialized microbial groups and microbial plant symbionts, as opposed to urban agriculture sites that stimulated opportunistic populations able to face the impact of agricultural practices. Altogether, our results provide evidence that there is scope for urban planners to drive soil microbial diversity through sustainable urban land use and associated management practices.
Anthropogenic habitat fragmentation—the breaking up of natural landscapes—is a pervasive threat to biodiversity and ecosystem function world‐wide. Fragmentation results in a mosaic of remnant native habitat patches embedded in human‐modified habitat known as the ‘matrix’. By introducing novel environmental conditions in matrix habitats and reducing connectivity of native habitats, fragmentation can dramatically change how organisms experience their environment. The effects of fragmentation can be especially important in urban landscapes, which are expanding across the globe. Despite this surging threat and the importance of microbiomes for ecosystem services, we know very little about how fragmentation affects microbiomes and even less about their consequences for plant–microbe interactions in urban landscapes.
By combining field surveys, microbiome sequencing and experimental mesocosms, we (1) investigated how microbial community diversity, composition and functional profiles differed between 15 native pine rockland fragments and the adjacent urban matrix habitat, (2) identified habitat attributes that explained significant variation in microbial diversity of native core habitat compared to urban matrix and (3) tested how changes in urbanized and low connectivity microbiomes affected plant community productivity.
We found urban and native microbiomes differed substantively in diversity, composition and functional profiles, including symbiotic fungi decreasing 81% and pathogens increasing 327% in the urban matrix compared to native habitat. Furthermore, fungal diversity rapidly declined as native habitats became increasingly isolated, with ~50% of variation across the landscape explained by habitat connectivity alone. Interestingly, microbiomes from native habitats increased plant productivity by ~300% while urban matrix microbiomes had no effect, suggesting that urbanization may decouple beneficial plant–microbe interactions. In addition, microbial diversity within native habitats explained significant variation in plant community productivity, with higher productivity linked to more diverse microbiomes from more connected, larger fragments.
Synthesis . Taken together, our study not only documents significant changes in microbial diversity, composition and functions in the urban matrix, but also supports that two aspects of habitat fragmentation—the introduction of a novel urban matrix and reduced habitat connectivity—disrupt microbial effects on plant community productivity, highlighting preservation of native microbiomes as critical for productivity in remnant fragments.
Ecosystem management is integral to the future of soils, yet anthropogenic drivers represent a key source of uncertainty in ecosystem models. First- and new-generation soil models formulate many soil pools using first-order decomposition, which tends to generate simpler yet numerous parameters. Systems or complexity theory, developed across various scientific and social fields, may help improve robustness of soil models, by offering consistent assumptions about system openness, potential dynamic instability and distance from commonly assumed stable equilibria, as well as new analytical tools for formulating more generalized model structures that reduce parameter space and yield a wider array of possible model outcomes, such as quickly shrinking carbon stocks with pulsing or lagged respiration. This paper builds on recent perspectives of soil modeling to ask how various soil functions can be better understood by applying a complex systems lens. We synthesized previous literature reviews with concepts from non-linear dynamical systems in theoretical ecology and soil sciences more broadly to identify areas for further study that may help improve the robustness of soil models under the uncertainty of human activities and management. Three broad dynamical concepts were highlighted: soil variable memory or state-dependence, oscillations, and tipping points or hysteresis. These themes represent less intuitive yet key dynamics that can emerge after assuming nuanced observations, such as reversibility of organo-mineral associations, dynamic aggregate- and pore hierarchies, persistent wet-dry cycles, higher-order microbial community and predator-prey interactions, cumulative legacy land use history, and social management interactions and/or cooperation. We discuss how these aspects may contribute useful analytical tools, metrics, and frameworks that help integrate the uncertainties in future soil states, ranging from micro- to regional scales, including those indirectly affected by human activities and management decisions. Overall, this study highlights the potential benefits of incorporating spatial heterogeneity and dynamic instabilities into future model representations of whole soil processes. Additionally, it advocates for transdisciplinary collaborations between natural and social scientists, extending research into anthropedology and biogeosociochemistry, to better integrate and understand longer-term anthropogenic drivers of soil processes, potentially from soil structural dynamics to microbial community and food web ecology.
1. Anthropogenic habitat fragmentation – the breaking up of natural landscapes – is a pervasive threat to biodiversity and ecosystem function worldwide. Fragmentation results in a mosaic of remnant native habitat patches embedded in human-modified habitat known as the “matrix”. By introducing novel environmental conditions in matrix habitats and reducing connectivity of native habitats, fragmentation can dramatically change how organisms experience their environment. The effects of fragmentation can be especially important in urban landscapes, which are expanding across the globe. Despite this surging threat and the importance of microbiomes for ecosystem services, we know very little about how fragmentation affects microbiomes and even less about their consequences for plant-microbe interactions in urban landscapes. 2. By combining field surveys, microbiome sequencing, and experimental mesocosms, we (1) investigated how microbial community diversity, composition, and functional profiles differed between 15 native pine rockland fragments and the adjacent urban matrix habitat, (2) identified habitat attributes that explained significant variation in microbial diversity of native core habitat compared to urban matrix, and (3) tested how changes in urbanized and low connectivity microbiomes affected plant community productivity. 3. We found urban and native microbiomes differed substantively in diversity, composition, and functional profiles, including symbiotic fungi decreasing 81% and pathogens increasing 327% in the urban matrix compared to native habitat. Further, fungal diversity rapidly declined as native habitats became increasingly isolated, with ~50% of variation across the landscape explained by habitat connectivity alone. Interestingly, microbiomes from native habitats increased plant productivity by ~300% while urban matrix microbiomes had no effect, suggesting that urbanization may decouple beneficial plant-microbe interactions. In addition, microbial diversity within native habitats explained significant variation in plant community productivity, with higher productivity linked to more diverse microbiomes from more connected, larger fragments. 4. Synthesis. Taken together, our study not only documents significant changes in microbial diversity, composition, and functions in the urban matrix, but also supports that two aspects of habitat fragmentation — the introduction of a novel urban matrix and reduced habitat connectivity — disrupt microbial effects on plant community productivity, highlighting preservation of native microbiomes as critical for productivity in remnant fragments.
Soil bacteria and understorey plants interact and drive forest ecosystem functioning. Yet, knowledge about biotic and abiotic factors that affect the composition of the bacterial community in the rhizosphere of understorey plants is largely lacking. Here, we assessed the effects of plant species identity (Milium effusum vs Stachys sylvatica), rhizospheric soil characteristics, large-scale environmental conditions (temperature, precipitation and nitrogen (N) deposition), and land-use history (ancient vs recent forests) on bacterial community composition in rhizosphere soil in temperate forests along a 1700 km latitudinal gradient in Europe. The dominant bacterial phyla in the rhizosphere soil of both plant species were Acidobacteria, Actinobacteria and Proteobacteria. Bacterial community composition differed significantly between the two plant species. Within plant species, soil chemistry was the most important factor determining soil bacterial community composition. More precisely, soil acidity correlated with the presence of multiple phyla, e.g. Acidobacteria (negatively), Chlamydiae (negatively) and Nitrospirae (positively), in both plant species. Large-scale environmental conditions were only important in S. sylvatica and land-use history was not important in either of the plant species. The observed role of understorey plant species identity and rhizosphere soil characteristics in determining soil bacterial community composition extends our understanding of plant-soil bacteria interactions in forest ecosystem functioning.
Agricultural land use is a leading cause of habitat degradation, leaving a legacy of ecological impacts long after agriculture has ceased. Yet the mechanisms for legacy effects, such as altered plant community composition, are not well understood. In particular, whether plant community recovery is limited by an inability of populations to establish within post-agricultural areas, owing to altered environmental conditions within these areas, remains poorly known. We evaluated this hypothesis of post-agricultural establishment limitation through a field experiment within longleaf pine woodlands in South Carolina (USA) and a greenhouse experiment using field-collected soils from these sites. In the field, we sowed seeds of 12 understory plant species associated with remnants (no known history of agriculture) into 27 paired remnant and post-agricultural woodlands. We found that post-agricultural woodlands supported higher establishment, resulting in greater species richness of sown species. These results were context dependent, however, with higher establishment in post-agricultural woodlands only when sites were frequently burned, had less leaf litter, or had less sandy soils. In the greenhouse, we found that agricultural history had no impact on plant growth or survival, suggesting that establishment limitation is unlikely driven by differences in soils associated with agricultural history when environmental conditions are not stressful. Rather, the potential for establishment in post-agricultural habitats can be higher than in remnant habitats, with the strength of this effect determined by fire frequency and soil characteristics.
The soil microbial community is essential for maintaining ecosystem functioning and is intimately linked with the plant community. Yet, little is known on how soil microbial communities in the root zone vary at continental scales within plant species. Here we assess the effects of soil chemistry, large-scale environmental conditions (i.e. temperature, precipitation and nitrogen deposition) and forest land-use history on the soil microbial communities (measured by phospholipid fatty acids) in the root zone of four plant species (Geum urbanum, Milium effusum, Poa nemoralis and Stachys sylvatica) in forests along a 1700 km latitudinal gradient in Europe. Soil microbial communities differed significantly among plant species, and soil chemistry was the main determinant of the microbial community composition within each plant species. Influential soil chemical variables for microbial communities were plant species-specific; soil acidity, however, was often an important factor. Large-scale environmental conditions, together with soil chemistry, only explained the microbial community composition in M. effusum and P. nemoralis. Forest land-use history did not affect the soil microbial community composition. Our results underpin the dominant role of soil chemistry in shaping microbial community composition variation within plant species at the continental scale, and provide insights into the composition and functionality of soil microbial communities in forest ecosystems.
Ecological restoration efforts can increase the diversity and function of degraded areas. However, current restoration practices cannot typically reestablish the full diversity and species composition of remnant plant communities. We present evidence that restoration quality can be improved by reintroducing key organisms from the native plant microbiome. In particular, root symbionts called arbuscular mycorrhizal fungi are crucial in shaping grassland communities, but are sensitive to anthropogenic disturbance, which may pose a problem for grassland restoration. In the present article, we highlight the conceptual motivation and empirical evidence evaluating native mycorrhizal fungi, as opposed to commercial fungi. Reintroduction of the native microbiome and native mycorrhizal fungi improves plant diversity, accelerates succession, and increases the establishment of plants that are often missing from restored communities. The example of mycorrhizal fungi serves to illustrate the value of a more holistic view of plant communities and restoration that embraces the intricacies and dynamics of native microbial communities. © 2018 Published by Oxford University Press on behalf of American Institute of Biological Sciences.
Human land use, including agriculture, is a leading contributor to declining biodiversity worldwide and can leave long‐lasting legacies on ecosystems after cessation. Ecological restoration is an approach to mitigate these impacts. However, little is known about how animal communities and plant–animal interactions respond to the combined effects of land‐use legacies and restoration. We investigated how restoration and agricultural history affect bee (Hymenoptera: Apoidea: Anthophila) communities and pollination function. In 27 paired remnant (no history of agriculture) and post‐agricultural longleaf pine (Pinus palustris Mill.) woodlands, we established 4–10 1‐ha plots (126 total) and experimentally restored half of them, while the other half were left as unrestored controls. Restoration was accomplished through canopy thinning which reinstates open savanna‐like conditions. We collected bees in each plot using a combination of bowl trapping and standardized netting transects. Thinning increased bee abundance by 169% and bee richness by 110%, but agricultural land use had no effect on these variables. Bee community composition was affected by restoration and was marginally affected by agricultural history. To measure pollination function, we conducted a sentinel plant experiment in which potted black mustard (Brassica nigra L.) plants were placed out in a subset of these sites (n = 10) and either bagged to exclude pollinators or left open for pollinator access. Then, we measured fruit and seed set of sentinel plants to compare pollination function among the restoration and land‐use history treatments. Seed set and fruit set of sentinel plants were higher in open than bagged plants, indicating that this model system effectively measured pollination, but we found no differences in pollination based on restoration or agricultural history. These results indicate that although pollinator communities may show clear responses to restoration that are largely independent of prior land‐use impacts, this does not necessarily translate into differences in pollination function after restoration.
Soil microbial communities directly affect soil functionality through their roles in the cycling of soil nutrients and carbon storage. Microbial communities vary substantially in space and time, between soil types and under different land management. The mechanisms that control the spatial distributions of soil microbes are largely unknown as we have not been able to adequately upscale a detailed analysis of the microbiome in a few grams of soil to that of a catchment, region or continent. Here we reveal that soil microbes along a 1000 km transect have unique spatial structures that are governed mainly by soil properties. The soil microbial community assessed using Phospholipid Fatty Acids showed a strong gradient along the latitude gradient across New South Wales, Australia. We found that soil properties contributed the most to the microbial distribution, while other environmental factors (e.g., temperature, elevation) showed lesser impact. Agricultural activities reduced the variation of the microbial communities, however, its influence was local and much less than the overall influence of soil properties. The ability to predict the soil and environmental factors that control microbial distribution will allow us to predict how future soil and environmental change will affect the spatial distribution of microbes.
Background and Aims
Although soil-inhabiting fungi can affect tree health and biomass production in managed and pristine forests, little is known about the sensitivity of the plant-fungal associations to long-term changes in land use. We aimed to investigate how reforestation of farmlands change soil characteristics and affected the recovery of soil fungal functional guilds.
Methods
We examined edaphic conditions and fungal communities (Illumina Sequencing) in three land-use types: primary forests (PF), secondary forests (SF, established over two decades ago) and active farmlands during May, July and September in Wuying, China.
Results
Edaphic conditions and general fungal communities varied with land-use. Interestingly, overall fungal diversity was higher in soils at the farmland than at the forested sites, possibly as a result of recurring disturbances (tilling) allowing competitive release as described by the intermediate disturbance hypothesis. Although ectomycorrhizal fungal diversity and richness were marginally higher in PF than in SF, the latter still hosted surprisingly diverse and abundant ectomycorrhizal fungal communities.
Conclusions
Reforestation largely restored fungal communities that were still in transition, as their composition in SF was distinct from that in PF. Our results highlight the ability of fungi grown in previously strongly managed agricultural land to rapidly respond to reforestation and thus provide support for forest trees.
Rationale:
Pyrogenic savannas with a tree-grassland "matrix" experience frequent fires (i.e. every 1-3 years). Aboveground responses to frequent fires have been well-studied, but responses of fungal litter decomposers, which directly affect fuels, remain poorly known. We hypothesized that each fire reorganizes below-ground communities and slows litter decomposition, thereby influencing savanna fuel dynamics.
Methods:
In a pine savanna, we established patches near and away from pines that were either burned or unburned in that year. Within patches, we assessed fungal communities and microbial decomposition of newly deposited litter. Soil variables and plant communities were also assessed as proximate drivers of fungal communities.
Results:
Fungal communities, but not soil variables or vegetation, differed substantially between burned and unburned patches. Saprotrophic fungi dominated in unburned patches but decreased in richness and relative abundance after fire. Differences in fungal communities with fire were greater in litter than soils, but unaffected by pine proximity. Litter decomposed more slowly in burned than unburned patches.
Conclusions:
Fires drive shifts between fire-adapted and sensitive fungal taxa in pine savannas. Slower fuel decomposition in accordance with saprotroph declines should enhance fuel accumulation and could impact future fire characteristics. Thus, fire-reorganization of fungal communities may enhance persistence of these fire-adapted ecosystems. This article is protected by copyright. All rights reserved.
Although plant-soil interactions are increasingly recognized as an important factor in ecosystem restoration, their effects on community assembly during de novo ecosystem establishment are largely unknown. In a heathland restoration trial after topsoil removal we introduced either only aboveground heathland species with fresh herbage or both above- and belowground heathland species with sods to facilitate community assembly. Sod inoculation increased resemblance of the microbial community to the reference system, with a higher fungal and lower bacterial proportion to the community structure. Also densities of bacteriophagous and phytophagous nematodes, Acari and Collembola increased after sod inoculation. The cover of heathland plant species increased by 49% after sod inoculation. The introduction of solely aboveground heathland species increased the cover of these species by only 13%, and did not affect soil community assembly. Additionally, the increase in cover of heathland species over time was inversely correlated to the cover of mesotrophic grassland species. Inverse correlations were also observed between changes in fungal and bacterial abundances. Simultaneous introduction of key species of both above- and below-ground communities had a critical effect on the establishment of both communities, providing a potential shortcut for successful restoration of target ecosystems on disturbed soils.