We lack strong empirical evidence for links between plant attributes (plant community attributes and functional traits) and the distribution of soil microbial communities at large spatial scales.
...Using datasets from two contrasting regions and ecosystem types in Australia and England, we report that aboveground plant community attributes, such as diversity (species richness) and cover, and functional traits can predict a unique portion of the variation in the diversity (number of phylotypes) and community composition of soil bacteria and fungi that cannot be explained by soil abiotic properties and climate. We further identify the relative importance and evaluate the potential direct and indirect effects of climate, soil properties and plant attributes in regulating the diversity and community composition of soil microbial communities.
Finally, we deliver a list of examples of common taxa from Australia and England that are strongly related to specific plant traits, such as specific leaf area index, leaf nitrogen and nitrogen fixation.
Together, our work provides new evidence that plant attributes, especially plant functional traits, can predict the distribution of soil microbial communities at the regional scale and across two hemispheres.
The study of feedbacks between plants and soils (plant–soil feedbacks; PSFs) is receiving increased attention. However, PSFs have been mostly studied in isolation of abiotic and biotic drivers that ...could affect their strength and direction. This is problematic because it has led to limited predictive power of PSFs in “the real world,” leaving large knowledge gaps in our ability to predict how PSFs contribute to ecosystem processes and functions.
Here, we present a synthetic framework to elucidate how abiotic and biotic drivers affect PSFs. We focus on two key abiotic drivers (temperature and soil moisture) and two key biotic drivers (above‐ground plant consumers and below‐ground top‐down control of pathogens and mutualists). We focus on these factors because they are known drivers of plants and soil organisms and the ecosystem processes they control, and hence would be expected to strongly influence PSFs.
Our framework describes the proposed mechanisms behind these drivers and explores their effects on PSFs. We demonstrate the impacts of these drivers using the fast‐ to slow‐growing plant economics spectrum. We use this well‐established paradigm because plants on opposite ends of this spectrum differ in their relationships with soil biota and have developed contrasting strategies to cope with abiotic and biotic environmental conditions.
Finally, we present suggestions for improved experimental designs and scientific inference that will capture and elucidate the influence of above‐ and belowground drivers on PSFs. By establishing the role of abiotic and biotic drivers of PSFs, we will be able to make more robust predictions of how PSFs impact on ecosystem function.
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Plain Language Summary
Overgrazing generally induces dwarfism in grassland plants, and these phenotypic traits could be transmitted to clonal offspring even when overgrazing is excluded. However, the dwarfism-transmitted ...mechanism remains largely unknown, despite generally thought to be enabled by epigenetic modification. To clarify the potential role of DNA methylation on clonal transgenerational effects, we conducted a greenhouse experiment with Leymus chinensis clonal offspring from different cattle/sheep overgrazing histories via the demethylating agent 5-azacytidine. The results showed that clonal offspring from overgrazed (by cattle or sheep) parents were dwarfed and the auxin content of leaves significantly decreased compared to offspring from no-grazed parents'. The 5-azaC application generally increased the auxin content and promoted the growth of overgrazed offspring while inhibited no-grazed offspring growth. Meanwhile, there were similar trends in the expression level of genes related to auxin-responsive target genes (ARF7, ARF19), and signal transduction gene (AZF2). These results suggest that DNA methylation leads to overgrazing-induced plant transgenerational dwarfism via inhibiting auxin signal pathway.
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•Overgrazing generally induces dwarfism in grassland plants.•Alteration of DNA methylation removes the overgrazing-induced dwarfism.•Demethylation activated auxin signal pathway in overgrazed offspring.•DNA methylation mediates overgrazing-induced transgenerational dwarfism.
Temperate grassland ecosystems face a future of precipitation change, which can alter community composition and ecosystem functions through reduced soil moisture and waterlogging. There is evidence ...that functionally diverse plant communities contain a wider range of water use and resource capture strategies, resulting in greater resistance of ecosystem function to precipitation change. To investigate this interaction between composition and precipitation change we performed a field experiment for three years in successional grassland in southern England. This consisted of two treatments. The first, precipitation change, simulated end of century predictions, and consisted of a summer drought phase alongside winter rainfall addition. The second, functional group identity, divided the plant community into three groups based on their functional traits- broadly described as perennials, caespitose grasses and annuals- and removed these groups in a factorial design. Ecosystem functions related to C, N and water cycling were measured regularly. Effects of functional groupidentity were apparent, with the dominant trend being that process rates were higher under control conditions where a range of perennial species were present. E.g. litter decomposition rates were significantly higher in plots containing several perennial species, the group with the highest average leaf N content. Process rates were also very strongly affected by the precipitation change treatmentwhen perennial plant species were dominant, but not where the community contained a high abundance of annual species and caespitose grasses. This contrasting response could be attributable to differing rooting patterns (shallower structures under annual plants, and deeper roots under perennials) and faster nutrient uptake in annuals compared to perennials. Our results indicate that precipitation change will have a smaller effect on key process rates in grasslandscontaining a range of perennial and annual species, and that maintaining the presence of key functional groups should be a crucial consideration in future grassland management.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Drought reduces floral resources for pollinators Phillips, Benjamin B.; Shaw, Rosalind F.; Holland, Matthew J. ...
Global change biology,
July 2018, 2018-07-00, 20180701, Letnik:
24, Številka:
7
Journal Article
Recenzirano
Odprti dostop
Climate change is predicted to result in increased occurrence and intensity of drought in many regions worldwide. By increasing plant physiological stress, drought is likely to affect the floral ...resources (flowers, nectar and pollen) that are available to pollinators. However, little is known about impacts of drought at the community level, nor whether plant community functional composition influences these impacts. To address these knowledge gaps, we investigated the impacts of drought on floral resources in calcareous grassland. Drought was simulated using rain shelters and the impacts were explored at multiple scales and on four different experimental plant communities varying in functional trait composition. First, we investigated the effects of drought on nectar production of three common wildflower species (Lathyrus pratensis, Onobrychis viciifolia and Prunella vulgaris). In the drought treatment, L. pratensis and P. vulgaris had a lower proportion of flowers containing nectar and O. viciifolia had fewer flowers per raceme. Second, we measured the effects of drought on the diversity and abundance of floral resources across plant communities. Drought reduced the abundance of floral units for all plant communities, irrespective of functional composition, and reduced floral species richness for two of the communities. Functional diversity did not confer greater resistance to drought in terms of maintaining floral resources, probably because the effects of drought were ubiquitous across component plant communities. The findings indicate that drought has a substantial impact on the availability of floral resources in calcareous grassland, which will have consequences for pollinator behaviour and populations.
Climate change is predicted to result in increased occurrence and intensity of drought in many regions worldwide. We simulated drought using a field experiment and measured the impacts on the availability of flowers and nectar for different plant species and plant communities. Drought consistently reduced the number of flowers available which will have consequences for pollinator behaviour and populations.
Aims Root characteristics are important for predicting plant and ecosystem responses to resource scarcity. Simple, categorical traits for roots could be broadly applied to ecosystem function and ...restoration experiments, but they need to be evaluated for their role and behaviour under various stresses, including water limitation. We hypothesised that more complex root architectures allow more plastic responses to limited water than do tap roots. Methods We carried out two greenhouse experiments: one with a range of grassland plant species; the other with only species of Asteraceae to test the responsiveness of root architectural classes to location of limited water in the soil column. Using trait screening techniques and X-ray tomography, we measured the plasticity of the roots in response to water location. Results Plasticity of root biomass was lowest in tap rooted species, while fibrous and rhizomatous roots allocated biomass preferentially to where the soil was wettest. X-ray tomography indicated that root morphology was least plastic in rhizomatous species. Conclusions Our results provide a starting point to effective categorisation of plants in terms of rooting architecture that could aid in understanding drought tolerance of grassland species. They also demonstrate the utility of X-ray tomography in root analyses.
Most studies focusing on plant-soil feedbacks (PSFs) have considered direct interactions between plants, abiotic conditions (e.g., soil nutrients) and rhizosphere communities (e.g., pathogens, ...mutualists). However, few studies have addressed the role of indirect interactions mediated by plant litter inputs. This has left a major gap in our understanding of PSFs in natural ecosystems, where plant litter is a key component of feedback effects. Here, we propose a framework that integrates rhizosphere- and litter-mediated PSF effects to provide insights into the relative contribution of direct effects mediated by interactions between plants and soil rhizosphere organisms, and indirect effects between plants and decomposer organisms mediated by plant root and shoot litter. We examine three pathways via which litter-mediated PSFs can operate (1) physical effects of litter (layer) traits on seed germination, soil structure, and plant growth; (2) chemical effects of litter on concentrations of soil nutrients and secondary metabolites (e.g., allelopathic chemicals); and (3) biotic effects of saprotrophic soil communities. We assess the role of litter in PSF effects via physical, chemical and biotic pathways to address how litter-mediated feedbacks may play out and we identify critical research gaps that need to be filled in order to understand their relative contribution to PSF effects. We also present one of the first experimental studies to show the occurrence and species-specificity of litter-mediated feedbacks. Formally incorporating the plant-litter feedback pathway into PSF experiments will further our understanding of PSFs under natural conditions.
Background
Plants condition the soil in which they grow, thereby altering the performance of subsequent plants growing in this soil. This phenomenon, known as plant-soil feedback (PSF), has garnered ...increasing interest. Experiments are moving from single species soil pairings in the glasshouse to community-level field trials. Consequently, our knowledge of the role PSF plays in shaping ecosystem functions has advanced. However, knowledge gaps remain.
Scope
Here, we explore intrinsic and extrinsic abiotic and biotic drivers of PSF such as maternal effects, plant functional traits, self-DNA, plant-plant competition, herbivory, interactions between soil organisms, temperature, drought, flooding, greenhouse gases, (micro)nutrients, plant-litter-soil feedback and priority effects. These drivers have begun to feature in experiments, thereby increasing our mechanistic understanding of PSF. Nonetheless, many of these topics have received insufficient coverage to determine general principles across larger temporal and spatial scales. Further, conflicting terminology has excluded PSF studies from reviews and meta-analyses. We review terms such as soil sickness, Janzen-Connell hypothesis, soil-related invasive species work, soil legacies, allelopathy and soil-related succession that overlap with PSF but are generally not named as such.
Conclusion
Holistic experimental designs that consider the continual reciprocal feedback between the extrinsic environment, plants and soil, as well as the unification of terminologies are necessary if we are to realise the full potential of PSF for understanding and steering ecosystem processes. Here, we compile outstanding questions related to PSF research that emphasis the aforementioned topics and suggest ways to incorporate them into future research in order to advance plant-soil ecology.
Overgrazing directly and indirectly affects soil microorganisms, which can have feedback effects on plant growth. Little is known about the root metabolites plants produce and whether they recruit ...beneficial microbes in response to overgrazing. Here, we used the dominant grassland species Leymus chinensis to explore correlations between root metabolites and the rhizosphere microbiome shaped by long-term overgrazing, which was determined by using LC-MS technology and high-throughput sequencing. In total, 839 metabolites were detected, with 41 significantly higher and 3 significantly lower in overgrazing versus grazing exclusion plots. The rhizosphere bacterial community was changed, but the fungal community was not altered. Moreover, 11 bacterial orders were found only in the overgrazed samples, and these showed close relationships to root metabolites and certain soil properties. Of these, Latescibacterales, B10-SB3A, and Nitrosococcales are known to be involved in growth promotion, C and N metabolism, respectively. In addition, root metabolites play an important role in mediating root-fungi interactions. The beneficial fungal orders Agaricales and Sordariales have a tread to be higher maybe due to root metabolites, mainly facilitate nutrient absorption and protect organic carbon in the soil, respectively. Our results indicate that grassland plants send metabolic signals to recruit key beneficial bacteria and stabilize fungal communities to alleviate grazing-induced stress in typical grassland ecosystems.
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•Plant roots significantly changed their metabolites under Long-term overgrazing.•Bacteria showed a stronger response to changes in root metabolites compared to fungi.•Grassland plants send metabolic signals to recruit key beneficial bacteria.•Beneficial rhizosphere microorganisms help host alleviate grazing stress.
Plant–soil feedbacks (PSFs) describe the effect of a plant species on soil properties, which affect the performance of future generations. Here we test the hypothesis that drought alters PSFs by ...reducing plant–microbe associations and nutrient uptake. We chose two grassland forb species, previously shown to respond differently to soil conditioning and drought, to test our hypothesis. We conditioned unsterilised grassland soil with one generation of each species, and left a third soil unconditioned. We grew a second generation consisting of each combination of plant species, soil, and drought in a full factorial design, and measured soil microbial community and nutrient availability. Scabiosa columbaria displayed negative PSF (smaller plants) under non-droughted conditions, but neutral under drought, suggesting that drought disrupts plant–soil interactions and can advantage the plant. Photosynthetic efficiency of S. columbaria was reduced under drought, but recovered on rewetting regardless of soil conditioning, indicating that PSFs do not impede resilience of this species. Sanguisorba minor showed positive PSFs (larger plants), probably due to an increase in soil N in conspecific soil, but neutral PSF under drought. PSF neutralisation appeared to occur through drought-induced change in the soil microbial community for this species. When S. minor was planted in conspecific soil, photosynthetic efficiency declined to almost zero, with no recovery following rewetting. We attributed this to increased demand for water through higher demand for nutrients with positive PSF. Here we show that drought neutralises PSFs of two grassland forbs, which could have implications for plant communities under climate change.
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