| 1. |
- Khurana, Swamini, 1989-, et al.
(författare)
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Interactive effects of microbial functional diversity and carbon availability on decomposition - A theoretical exploration
- 2023
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Ingår i: Ecological Modelling. - 0304-3800 .- 1872-7026. ; 486
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Tidskriftsartikel (refereegranskat)abstract
- Microbial functional diversity in litter and soil has been hypothesized to affect the rate of decomposition of organic matter and other soil ecosystem functions. However, there are no clear theoretical expectations on how these effects might change with substrate availability, heterogeneity in the substrate chemistry, and different aspects of functional diversity itself (number of microbial groups vs. distribution of functional traits). To explore how these factors shape the decomposition-diversity relation, we carry out numerical experiments using a flexible reaction network comprising microbial processes and interactions with bioavailable carbon (extracellular degradation, uptake, respiration, growth, and mortality), and ecological processes (competition among the different groups). We also considered diverse carbon substrates, in terms of varying nominal oxidation state of carbon (NOSC). The reaction network was used to test the effects of (i) number of microbial groups, (ii) number of carbon pools, (iii) microbial functional diversity, and (iv) amount of bioavailable carbon. We found that the decomposition rate constant increases with increasing substrate concentration and heterogeneity, as well as with increasing microbial functional diversity or variance of microbial traits, albeit these biological factors are less important. The multivariate dependence of the decomposition rate constant (and other decomposition and mi-crobial growth metrics) on substrate and microbial factors can be described using power laws with exponents lower than one, indicating that diversity effects on decomposition and microbial growth are reduced at high substrate concentration and heterogeneity, or at high microbial diversity.
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| 2. |
- Khurana, Swamini, 1989-, et al.
(författare)
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Microbial mediated carbon and nitrogen cycling in the spatially heterogeneous vadose zone : A modeling study
- 2024
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Ingår i: Vadose Zone Journal. - 1539-1663. ; 23:2
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Tidskriftsartikel (refereegranskat)abstract
- Spatially distributed properties of the subsurface result in varying water saturation and preferential flow paths, which lead to heterogeneous solute transport patterns and heterogeneous microbial environments. This, in turn, influences the distribution of nutrients and energy gradients, microbial biomass, and activity thereof. By their very nature, current field sampling techniques do not resolve subsampling scale heterogeneities in microbial biomass and activity, resulting in inaccurate estimates of microbially mediated carbon and nitrogen turnover in the heterogeneous subsurface. Thus, in this study, we undertook a numerical modeling approach to study the impact of spatial heterogeneity on microbially mediated carbon and nitrogen turnover in the vadose zone. We adapted an established biogeochemical process network that captures a variety of respiration pathways, carbon decomposition strategies, and microbial life processes to simulate microbially mediated carbon and nitrogen turnover in variably saturated spatially heterogeneous settings, using an established numerical tool (OGS#BRNS). The fractionation of microbial communities into active and inactive states, as well as immobile and mobile states followed could be linked to the bulk average saturation. Lastly, we identified three reactive systems, distinguished by the rate ratio of aerobic respiration and transfer of oxygen from the air to the water phase, to evaluate the impact of spatial heterogeneity on carbon and nitrogen removal in subsurface heterogeneous domains. Specifically, when this ratio is approximately 1, there is no impact on carbon removal, while when this ratio is very high, then carbon removal decreases as the domain tends to be oxygen limited.
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| 3. |
- Lennon, J. T., et al.
(författare)
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Priorities, opportunities, and challenges for integrating microorganisms into Earth system models for climate change prediction
- 2024
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Ingår i: mBio. - 2161-2129 .- 2150-7511.
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Tidskriftsartikel (refereegranskat)abstract
- Climate change jeopardizes human health, global biodiversity, and sustainability of the biosphere. To make reliable predictions about climate change, scientists use Earth system models (ESMs) that integrate physical, chemical, and biological processes occurring on land, the oceans, and the atmosphere. Although critical for catalyzing coupled biogeochemical processes, microorganisms have traditionally been left out of ESMs. Here, we generate a "top 10" list of priorities, opportunities, and challenges for the explicit integration of microorganisms into ESMs. We discuss the need for coarse-graining microbial information into functionally relevant categories, as well as the capacity for microorganisms to rapidly evolve in response to climate-change drivers. Microbiologists are uniquely positioned to collect novel and valuable information necessary for next-generation ESMs, but this requires data harmonization and transdisciplinary collaboration to effectively guide adaptation strategies and mitigation policy.
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| 4. |
- Schwarz, Erik, 1992-, et al.
(författare)
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Spatial Control of Microbial Pesticide Degradation in Soil : A Model-Based Scenario Analysis
- 2022
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 56:20, s. 14427-14438
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Tidskriftsartikel (refereegranskat)abstract
- Microbial pesticide degraders are heterogeneously distributed in soil. Their spatial aggregation at the millimeter scale reduces the frequency of degrader–pesticide encounter and can introduce transport limitations to pesticide degradation. We simulated reactive pesticide transport in soil to investigate the fate of the widely used herbicide 4-chloro-2-methylphenoxyacetic acid (MCPA) in response to differently aggregated distributions of degrading microbes. Four scenarios were defined covering millimeter scale heterogeneity from homogeneous (pseudo-1D) to extremely heterogeneous degrader distributions and two precipitation scenarios with either continuous light rain or heavy rain events. Leaching from subsoils did not occur in any scenario. Within the topsoil, increasing spatial heterogeneity of microbial degraders reduced macroscopic degradation rates, increased MCPA leaching, and prolonged the persistence of residual MCPA. In heterogeneous scenarios, pesticide degradation was limited by the spatial separation of degrader and pesticide, which was quantified by the spatial covariance between MCPA and degraders. Heavy rain events temporarily lifted these transport constraints in heterogeneous scenarios and increased degradation rates. Our results indicate that the mild millimeter scale spatial heterogeneity of degraders typical for arable topsoil will have negligible consequences for the fate of MCPA, but strong clustering of degraders can delay pesticide degradation.
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