| 1. |
- Abs, Elsa, et al.
(författare)
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Microbial evolution—An under-appreciated driver of soil carbon cycling
- 2024
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Ingår i: Global Change Biology. - 1354-1013 .- 1365-2486. ; 30:4
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Tidskriftsartikel (refereegranskat)abstract
- Although substantial advances in predicting the ecological impacts of global change have been made, predictions of the evolutionary impacts have lagged behind. In soil ecosystems, microbes act as the primary energetic drivers of carbon cycling; however, microbes are also capable of evolving on timescales comparable to rates of global change. Given the importance of soil ecosystems in global carbon cycling, we assess the potential impact of microbial evolution on carbon-climate feedbacks in this system. We begin by reviewing the current state of knowledge concerning microbial evolution in response to global change and its specific effect on soil carbon dynamics. Through this integration, we synthesize a roadmap detailing how to integrate microbial evolution into ecosystem biogeochemical models. Specifically, we highlight the importance of microscale mechanistic soil carbon models, including choosing an appropriate evolutionary model (e.g., adaptive dynamics, quantitative genetics), validating model predictions with ‘omics’ and experimental data, scaling microbial adaptations to ecosystem level processes, and validating with ecosystem-scale measurements. The proposed steps will require significant investment of scientific resources and might require 10–20 years to be fully implemented. However, through the application of multi-scale integrated approaches, we will advance the integration of microbial evolution into predictive understanding of ecosystems, providing clarity on its role and impact within the broader context of environmental change.
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| 2. |
- Bassiouni, Maoya, et al.
(författare)
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Optimal plant water use strategies explain soil moisture variability
- 2023
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Ingår i: Advances in Water Resources. - : Elsevier BV. - 0309-1708 .- 1872-9657. ; 173
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Tidskriftsartikel (refereegranskat)abstract
- Plant responses to water stress influence water and carbon cycles and can lead to feedbacks on climate yet characterizing these responses at ecosystem levels remains uncertain. Quantifying ecosystem-level water use strategies is complex due to challenges of upscaling plant traits and disentangling confounding environmental factors, ultimately limiting our ability to understand and anticipate global change in ecosystem dynamics and ecohydrological fluxes. We reduce the dimensionality of this problem and quantify plant water use strategies by combining plant traits with soil and climate variables into parameter groups that synthesize key eco-physiological tradeoffs. Using a parsimonious soil water balance framework, we explore variations in plant water uptake capacity, water stress responses, and water use performance via these non-dimensional parameter groups. The group characterizing the synchronization of plant water transport and atmospheric water demand emerges as the primary axis of variation in water use strategies and interacts with the group representing plant hydraulic risk tolerance, especially in arid conditions when plant water transport is limiting. Next, we show that specific plant water use strategies maximize plant water uptake (leading to carbon gain benefits) weighted by risks of water stress (leading to higher costs of water use). A model-data comparison demonstrates that these ecohydrologically optimal parameter groups capture observed soil moisture variability in 40 ecosystems and beyond aridity, rainfall frequency is an important environmental control for plant water use strategies. The emerging parsimonious link between ecohydrological performance and non-dimensional parameters provides a tractable representation of plant water use strategies, relevant to parameterize global models while accounting for ecological and evolutionary constraints on the water cycle.
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| 3. |
- Butler, Orpheus M., et al.
(författare)
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Community composition and physiological plasticity control microbial carbon storage across natural and experimental soil fertility gradients
- 2023
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Ingår i: The ISME Journal. - 1751-7362 .- 1751-7370. ; 17:12, s. 2259-2269
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Tidskriftsartikel (refereegranskat)abstract
- Many microorganisms synthesise carbon (C)-rich compounds under resource deprivation. Such compounds likely serve as intracellular C-storage pools that sustain the activities of microorganisms growing on stoichiometrically imbalanced substrates, making them potentially vital to the function of ecosystems on infertile soils. We examined the dynamics and drivers of three putative C-storage compounds (neutral lipid fatty acids [NLFAs], polyhydroxybutyrate [PHB], and trehalose) across a natural gradient of soil fertility in eastern Australia. Together, NLFAs, PHB, and trehalose corresponded to 8.5–40% of microbial C and 0.06–0.6% of soil organic C. When scaled to “structural” microbial biomass (indexed by polar lipid fatty acids; PLFAs), NLFA and PHB allocation was 2–3-times greater in infertile soils derived from ironstone and sandstone than in comparatively fertile basalt- and shale-derived soils. PHB allocation was positively correlated with belowground biological phosphorus (P)-demand, while NLFA allocation was positively correlated with fungal PLFA : bacterial PLFA ratios. A complementary incubation revealed positive responses of respiration, storage, and fungal PLFAs to glucose, while bacterial PLFAs responded positively to PO43-. By comparing these results to a model of microbial C-allocation, we reason that NLFA primarily served the “reserve” storage mode for C-limited taxa (i.e., fungi), while the variable portion of PHB likely served as “surplus” C-storage for P-limited bacteria. Thus, our findings reveal a convergence of community-level processes (i.e., changes in taxonomic composition that underpin reserve-mode storage dynamics) and intracellular mechanisms (e.g., physiological plasticity of surplus-mode storage) that drives strong, predictable community-level microbial C-storage dynamics across gradients of soil fertility and substrate stoichiometry.
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| 4. |
- Chakrawal, Arjun, 1992-, et al.
(författare)
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Modelling optimal ligninolytic activity during plant litter decomposition
- 2024
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Ingår i: New Phytologist. - 0028-646X .- 1469-8137.
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Tidskriftsartikel (refereegranskat)abstract
- A large fraction of plant litter comprises recalcitrant aromatic compounds (lignin and other phenolics). Quantifying the fate of aromatic compounds is difficult, because oxidative degradation of aromatic carbon (C) is a costly but necessary endeavor for microorganisms, and we do not know when gains from the decomposition of aromatic C outweigh energetic costs.To evaluate these tradeoffs, we developed a litter decomposition model in which the aromatic C decomposition rate is optimized dynamically to maximize microbial growth for the given costs of maintaining ligninolytic activity. We tested model performance against > 200 litter decomposition datasets collected from published literature and assessed the effects of climate and litter chemistry on litter decomposition.The model predicted a time-varying ligninolytic oxidation rate, which was used to calculate the lag time before the decomposition of aromatic C is initiated. Warmer conditions increased decomposition rates, shortened the lag time of aromatic C oxidation, and improved microbial C-use efficiency by decreasing the costs of oxidation. Moreover, a higher initial content of aromatic C promoted an earlier start of aromatic C decomposition under any climate.With this contribution, we highlight the application of eco-evolutionary approaches based on optimized microbial life strategies as an alternative parametrization scheme for litter decomposition models.
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| 5. |
- Clemenzi, Ilaria, et al.
(författare)
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Annual water balance and hydrological trends in the glacierised Tarfala Catchment, Sweden
- 2023
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Ingår i: Journal of Hydrology. - 0022-1694 .- 1879-2707. ; 626
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Tidskriftsartikel (refereegranskat)abstract
- Quantifying components of the hydrological cycle in glacierised catchments is important for the assessment of the temporal distribution, quantity and quality of water resources available to downstream regions, especially under a changing climate. However, this assessment requires long time series of observations, which are typically unavailable for remote catchments, such as those in mountainous areas. In this study, we leverage a unique ∼40 year time series of hydrological data recorded in the subarctic glacierised Tarfala catchment (Sweden) to explore temporal trends in the components of the catchment water balance (precipitation, runoff, change in storage, and evaporation), and to assess if water balance residuals are associated with specific hydro-climatic conditions. No significant temporal trends were found in precipitation and storage changes of the glacierised area, but significant increases were found in evaporation and summer discharge (in part attributed to glacier volume losses). The annual water balance could not be perfectly closed, and water losses were on average 112 mm y−1 larger than the water inputs over the study period. Among the water balance components, discharge contributed most to the total water balance uncertainty, and storage surplus due to antecedent meteorological conditions could explain why water losses in specific years exceeded the uncertainty bounds. It is therefore essential to consider legacy effects from previous years when applying water balance calculations in mountainous and/or glacierised catchments.
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| 6. |
- Guasconi, Daniela, 1992-, et al.
(författare)
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Climate-dependent responses of root and shoot biomass to drought duration and intensity in grasslands–a meta-analysis
- 2023
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Ingår i: Science of the Total Environment. - 0048-9697 .- 1879-1026. ; 903
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Tidskriftsartikel (refereegranskat)abstract
- Understanding the effects of altered precipitation regimes on root biomass in grasslands is crucial for predicting grassland responses to climate change. Nonetheless, studies investigating the effects of drought on belowground vegetation have produced mixed results. In particular, root biomass under reduced precipitation may increase, decrease or show a delayed response compared to shoot biomass, highlighting a knowledge gap in the relationship between belowground net primary production and drought. To address this gap, we conducted a meta-analysis of nearly 100 field observations of grassland root and shoot biomass changes under experimental rainfall reduction to disentangle the main drivers behind grassland responses to drought. Using a response-ratio approach we tested the hypothesis that water scarcity would induce a decrease in total biomass, but an increase in belowground biomass allocation with increased drought length and intensity, and that climate (as defined by the aridity index of the study location) would be an additional predictor. As expected, meteorological drought decreased root and shoot biomass, but aboveground and belowground biomass exhibited contrasting responses to drought duration and intensity, and their interaction with climate. In particular, drought duration had negative effects on root biomass only in wet climates while more intense drought had negative effects on root biomass only in dry climates. Shoot biomass responded negatively to drought duration regardless of climate. These results show that long-term climate is an important modulator of belowground vegetation responses to drought, which might be a consequence of different drought tolerance and adaptation strategies. This variability in vegetation responses to drought suggests that physiological plasticity and community composition shifts may mediate how climate affects carbon allocation in grasslands, and thus ultimately carbon storage in soil.
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| 7. |
- Guasconi, Daniela, 1992-, et al.
(författare)
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Spatial and temporal variability in soil and vegetation carbon dynamics under experimental drought and soil amendments
- 2023
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Soils are the largest carbon (C) pool on the planet, and grassland soils have a particularly large C sequestration potential. Appropriate land management strategies, such as organic matter additions, can improve soil health, increase soil C stocks, and increase grassland resilience to drought by improving soil moisture retention. However, soil C dynamics are deeply linked to vegetation response to changes in both management and climate, which may also be manifested differently in roots and shoots. This study presents findings from a three-year experiment that assessed the impact of a compost amendment and of reduced precipitation on soil and vegetation C pools. Compost addition increased aboveground biomass and soil C content (%C), but because bulk density decreased, there was no significant effect on soil C stocks. Drought decreased aboveground biomass, but did not significantly affect root biomass. Overall, the soil amendment shifted C allocation to aboveground plant organs, and drought to belowground organs. We also observed significant spatial and temporal variability in vegetation biomass and soil C over the study period. These results highlight the need to consider multiple biotic and abiotic factors driving ecosystem C dynamics across spatial scales when upscaling results from field trials.
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| 8. |
- Guasconi, Daniela, 1992-
(författare)
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The hidden half of the meadow : Interactions between drought, soil carbon, roots and soil microbial communities
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Soil is a hidden ecosystem which harbours plant roots and countless microorganisms, vital for sustaining life aboveground. These belowground communities provide essential ecosystem services like soil stabilisation and organic matter decomposition. Soil is also one of the largest terrestrial carbon repositories, and land management strategies aimed at increasing organic matter inputs from plants, such as compost additions, can promote further soil carbon accumulation. Because organic carbon is important for soil water retention, this management may also help to increase resilience against more frequent and intense droughts. Although roots and microbial communities are largely acknowledged to play a key role in regulating the carbon cycle, there are still many open questions regarding the link between above- and belowground processes and ecosystem functions. Observing climate- and management-driven changes in the soil habitat is fundamental for understanding how ecosystems respond to environmental change.The aim of this thesis is to explore the relationship between soil properties, plant communities, and soil microbial communities in response to environmental changes. The research builds on a meta-analysis of drought effects on grasslands, and a multifactorial field experiment which combined three years of precipitation reduction and a compost treatment in two Swedish grasslands. We analysed the response of roots and soil microbial communities to drought and compost amendments, and identified environmental factors behind their large spatial variability. Finally, we tested the effects of compost additions on soil carbon storage and its interactions with drought.The results of the meta-analysis indicate that, on a global scale, grassland roots and shoots have diverging responses to drought duration and intensity, with long-term climate mediating that difference. At the local scale assessed in the field experiment, we observed that the spatial patterns of soil microbial communities were driven by soil properties and vegetation. Growing season drought affected roots only at trait level, but did not significantly affect microbial communities. Positive effects of compost on aboveground plant productivity and fungal growth were detectable after three years. Compost amendments also increased the percentage of total soil carbon, but no net increase in soil carbon stocks was detected. Spatial variability in roots and microbial communities was larger than the treatment effects, and was important in shaping microbial community composition and determining grassland responses to drought.Taken together, these findings suggest that roots and microbial communities are likely to be tolerant to drought a within the timescale of this experiment, but we did not observe an increase soil carbon sequestration or drought resilience when adding compost. This thesis highlights the importance of considering soil processes as complementary to aboveground observations when studying carbon dynamics, predicting ecosystem responses to environmental change, and developing sustainable land management practices.
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| 9. |
- Guasconi, Daniela, 1992-, et al.
(författare)
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Vegetation, topography, and soil depth drive microbial community structure in two Swedish grasslands
- 2023
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Ingår i: FEMS Microbiology Ecology. - 0168-6496 .- 1574-6941. ; 99:8
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Tidskriftsartikel (refereegranskat)abstract
- Soil microbial diversity and community composition are shaped by various factors linked to land management, topographic position,and vegetation. To study the effects of these drivers, we characterized fungal and bacterial communities from bulk soil at four soildepths ranging from the surface to below the rooting zone of two Swedish grasslands with differing land-use histories, each includingboth an upper and a lower catenary position. We hypothesized that differences in plant species richness and plant functional groupcomposition between the four study sites would drive the variation in soil microbial community composition and correlate withmicrobial diversity, and that microbial biomass and diversity would decrease with soil depth following a decline in resource availability.While vegetation was identified as the main driver of microbial community composition, the explained variation was significantlyhigher for bacteria than for fungi, and the communities differed more between grasslands than between catenary positions. Microbialbiomass derived from DNA abundance decreased with depth, but diversity remained relatively stable, indicating diverse microbialcommunities even below the rooting zone. Finally, plant-microbial diversity correlations were significant only for specific plant andfungal functional groups, emphasizing the importance of functional interactions over general species richness
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| 10. |
- Johansson, Anna, et al.
(författare)
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Long-term soil organic carbon changes after cropland conversion to grazed grassland in Southern Sweden
- 2024
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Ingår i: Soil use and management. - 0266-0032 .- 1475-2743. ; 40:1
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Tidskriftsartikel (refereegranskat)abstract
- There is growing awareness of the potential value of agricultural land for climate change mitigation. In Sweden, cropland areas have decreased by approximately 30% over recent decades, creating opportunities for these former croplands to be managed for climate change mitigation by increasing soil organic carbon (SOC) stocks. One potential land-use change is conversion of cropland to grazed grasslands, but the long-term effect of such change in management is not well understood and likely varies with soil type and site-specific conditions. Through sampling of mineral and peatland soils within a 75-year chronosequence of land converted from crop production to grazed grassland, we assessed how time since conversion, catenary position, and soil depth affected SOC storage. The SOC stocks calculated at an equivalent soil or ash mass increased through time since conversion in mineral soils at all topographic positions, at a rate of ~0.65% year−1. Soils at low topographic positions gained the most carbon. Peat SOC stock gains after conversion were large, but only marginally significant and only when calculated at an equivalent ash mass. We conclude that the conversion of mineral soil to grazed grassland promotes SOC accumulation at our sites, but climate change mitigation potential would need to be evaluated through a full greenhouse gas balance.
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