Search

Atmospheric CO2 concentration is increasing, largely due to anthropogenic activities. Previous studies of individual free-air CO2 enrichment (FACE) experimental sites have shown significant impacts of elevated CO2 (eCO2) on soil microbial communities; however, no common microbial response patterns have yet emerged, challenging our ability to predict ecosystem functioning and sustainability in the future eCO2 environment. Here we analyzed 66 soil microbial communities from five FACE sites, and showed common microbial response patterns to eCO2, especially for key functional genes involved in carbon and nitrogen fixation (e.g., pcc/acc for carbon fixation, nifH for nitrogen fixation), carbon decomposition (e.g., amyA and pulA for labile carbon decomposition, mnp and lcc for recalcitrant carbon decomposition), and greenhouse gas emissions (e.g., mcrA for methane production, norB for nitrous oxide production) across five FACE sites. Also, the relative abundance of those key genes was generally increased and directionally associated with increased biomass, soil carbon decomposition, and soil moisture. In addition, a further literature survey of more disparate FACE experimental sites indicated increased biomass, soil carbon decay, nitrogen fixation, methane and nitrous oxide emissions, plant and soil carbon and nitrogen under eCO2. A conceptual framework was developed to link commonly responsive functional genes with ecosystem processes, such as pcc/acc vs. soil carbon storage, amyA/pulA/mnp/lcc vs. soil carbon decomposition, and nifH vs. nitrogen availability, suggesting that such common responses of microbial functional genes may have the potential to predict ecosystem functioning and sustainability in the future eCO2 environment.

Drought may impact plant–soil biotic interactions in ways that modify aboveground herbivore performance, but the outcomes of such biotic interactions under future climate are not yet clear. We performed a growth chamber experiment to assess how long‐term, drought‐driven changes in belowground communities influence plant growth and herbivore performance using a plant–soil feedback experimental framework. We focussed on two common pasture legumes—lucerne, Medicago sativa L., and white clover, Trifolium repens L. (both Fabaceae)—and foliar herbivores—cotton bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae), and two‐spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae). Soil was collected from a field facility where rainfall had been manipulated for 6 years, focussing on treatments representing ambient rainfall and prolonged drought (50% reduction relative to ambient), to consider the effects of biological legacies mediated by the prolonged drought. All soils were sterilized and re‐inoculated to establish the respective home (i.e. where a given plant is cultivated in its own soil) and away (i.e. where a given plant is cultivated in another species' soil) treatments in addition to a sterile control. We found that the relative growth rate (RGR) and relative consumption of larvae were significantly lower on lucerne grown in soil with ambient rainfall legacies conditioned by white clover. Conversely, the RGR of insect larvae was lower on white clover grown in soil with prolonged drought legacies conditioned by lucerne. Two‐spotted spider mite populations and area damage (mm2) were significantly reduced on white clover grown in lucerne‐conditioned soil in drought legacies. The higher number of nodules found on white clover in lucerne‐conditioned soil suggests that root–rhizobia associations may have reduced foliar herbivore performance. Our study provides evidence that foliar herbivores are affected by plant–soil biotic interactions and that prolonged drought may influence aboveground–belowground linkages with potential broader ecosystem impacts. [ABSTRACT FROM AUTHOR]

Innovations in plant and soil sciences are revolutionising our approach to sustainability, offering solutions with broad societal impacts. Discoveries in these fields hold great potential for combatting, mitigating and adapting to climate change; enhancing food security; and revitalising urban environments. By harnessing the power of plants and the soils they grow in, it is possible to cultivate resilience in the face of environmental challenges, informing policy and practice, and thereby guiding us towards a more sustainable future. [ABSTRACT FROM AUTHOR]

The capacity for terrestrial ecosystems to sequester additional carbon (C) with rising CO2 concentrations depends on soil nutrient availability1,2. Previous evidence suggested that mature forests growing on phosphorus (P)-deprived soils had limited capacity to sequester extra biomass under elevated CO2 (refs. 3–6), but uncertainty about ecosystem P cycling and its CO2 response represents a crucial bottleneck for mechanistic prediction of the land C sink under climate change7. Here, by compiling the first comprehensive P budget for a P-limited mature forest exposed to elevated CO2, we show a high likelihood that P captured by soil microorganisms constrains ecosystem P recycling and availability for plant uptake. Trees used P efficiently, but microbial pre-emption of mineralized soil P seemed to limit the capacity of trees for increased P uptake and assimilation under elevated CO2 and, therefore, their capacity to sequester extra C. Plant strategies to stimulate microbial P cycling and plant P uptake, such as increasing rhizosphere C release to soil, will probably be necessary for P-limited forests to increase C capture into new biomass. Our results identify the key mechanisms by which P availability limits CO2 fertilization of tree growth and will guide the development of Earth system models to predict future long-term C storage.Microbial pre-emption of mineralized soil P limits the capacity of trees for increased P uptake and assimilation under elevated CO2 and therefore restricts their capacity to sequester extra C. [ABSTRACT FROM AUTHOR]

While various root-associated fungi could facilitate soil carbon (C) storage and therefore aid climate change mitigation, so far research in this area has largely focused on mycorrhizal fungi, and potential impacts and mechanisms for other fungi are largely unknown. Here, with the aim of identifying novel organisms that could be introduced to crop plants to promote C sequestration, we assessed the soil C storage potential of 12 root-associated, non-mycorrhizal fungal isolates (spanning nine genera and selected from a wide pool based on traits potentially linked to soil C accrual) and investigated fungal, plant and microbial mediators. We grew wheat plants inoculated with individual isolates in chambers allowing continuous 13 C labelling. After harvest, we quantified C storage potential by measuring pools of different origin (plant vs. soil) and different stability with long-term soil incubations and size/density fractionation. We assessed plant and microbial community responses as well as fungal physiological and morphological traits in a parallel in vitro study. While inoculation with 3 of the 12 isolates resulted in significant total soil C increases, soil C stability improved under inoculation with most isolates – as a result of increases in resistant C pools and decreases in labile pools and respired C. Further, these increases in soil C stability were positively associated with various fungal traits and plant growth responses, including greater fungal hyphal density and plant biomass, indicating multiple direct and indirect mechanisms for fungal impacts on soil C storage. We found more evidence for metabolic inhibition of microbial decomposition than for physical limitation under the fungal treatments. Our study provides the first direct experimental evidence in plant–soil systems that inoculation with specific non-mycorrhizal fungal strains can improve soil C storage, primarily by stabilising existing C. By identifying specific fungi and traits that hold promise for enhancing soil C storage, our study highlights the potential of non-mycorrhizal fungi in C sequestration and the need to study the mechanisms underpinning it. [ABSTRACT FROM AUTHOR]

Analyses of diverse aboveground and belowground indicators should underpin assessments of ecosystem recovery, yet monitoring many indicators is costly and their integration is challenging. Our objective was to combine indicators through a Bayesian hierarchical model to provide a comprehensive assessment of ecosystem status and identify a cost‐effective subset of indicators to provide an accurate estimate of ecosystem recovery. We assessed 59 aboveground–belowground indicators, classified into nine components of composition, structure, and function, to estimate the ecosystem status of restored rock spoils and reference forests in south‐eastern Australia. Overall ecosystem status, which integrates across ecosystem components and supporting indicators, was lower within restored forests but positively correlated with forest age. Reference forests had greater aboveground and belowground biotic structure, organic matter supply, and soil carbon stability, and trends were consistent among all of their supporting indicators. A subset of organic matter quality and nutrient cycling indicators were greater within restored forests, suggesting high ecosystem process rates, but that soil carbon may be more vulnerable to loss. Aboveground biotic structure was correlated with organic matter supply and quality, stability of soil carbon, the cycling of nutrients, and belowground biotic structure, providing evidence of aboveground–belowground coupling. A combination of four indicators representing belowground biotic structure, soil carbon stability, organic matter supply, and aboveground composition, provided a good estimate of ecosystem status at a third of the cost. Although ecosystem status can be monitored with a small set of indicators, a diversity of aboveground–belowground indicators provide a robust and comprehensive assessment of recovery. [ABSTRACT FROM AUTHOR]

While various root-associated fungi could facilitate soil carbon (C) storage and therefore aid climate change mitigation, so far research in this area has largely focused on mycorrhizal fungi, and potential impacts and mechanisms for other fungi are largely unknown. Here, we assessed the soil C storage potential of 12 root-associated, non-mycorrhizal fungal isolates (spanning nine genera and selected from a wide pool based on traits potentially linked to soil C accrual) and investigated fungal, plant and microbial mediators. We grew wheat plants inoculated with individual isolates in chambers allowing continuous 13C labelling. After harvest, we quantified C persistence, and pools of different origin (plant vs soil) and of different stability with long-term soil incubations and size/density fractionation. We assessed plant and microbial community responses, as well as fungal physiological and morphological traits in a parallel in vitro study. While inoculation with three of the 12 isolates resulted in significant total soil C increases, soil C stability improved under inoculation with most isolates – as a result of increases in resistant C pools and decreases in labile pools and respired C. Further, these increases in soil C stability were positively associated with various fungal traits and plant growth responses, including greater fungal hyphal density and plant biomass, indicating multiple direct and indirect mechanisms for fungal impacts on soil C storage. We found more evidence for metabolic inhibition of microbial decomposition than for physical limitation under the fungal treatments. Our study provides the first direct experimental evidence in plant-soil systems that inoculation with specific non-mycorrhizal fungal strains can improve soil C storage, primarily by stabilising existing C. By identifying specific fungi and traits that hold promise for enhancing soil C storage, our study highlights the potential of non-mycorrhizal fungi in C sequestration and the need to study the mechanisms underpinning it. [ABSTRACT FROM AUTHOR]