| 1. |
- Brangarí, Albert C., et al.
(författare)
-
A soil microbial model to analyze decoupled microbial growth and respiration during soil drying and rewetting
- 2020
-
Ingår i: Soil Biology and Biochemistry. - : Elsevier BV. - 0038-0717 .- 1879-3428. ; 148
-
Tidskriftsartikel (refereegranskat)abstract
- Soils are continuously exposed to cycles of drying and rewetting (D/RW), which drive pronounced fluctuations in soil carbon (C) fluxes. These C dynamics are characterized by a decoupled behavior between microbial biomass synthesis (growth) and CO2 production (respiration). In general, respiration rates peak shortly after RW and subsequently decrease, while the growth peaks lag several hours behind. Despite the significance of these dynamics for the soil C budget and the global C cycle, this feature has so far been overlooked in biogeochemical models and the underlying mechanisms are still unclear. We present a new process-based soil microbial model that incorporates a wide range of physical, chemical and biological mechanisms thought to affect D/RW responses. Results show that the model is able to capture the respiration dynamics in soils exposed to repeated cycles of D/RW, and also to single events in which moisture was kept constant after RW. In addition, the model reproduces, for the first time, the responses of microbial growth to D/RW. We have identified the C accumulation during dry periods, the drought-legacy effect on the synthesis of new biomass, and osmoregulation as the strongest candidate mechanisms to explain these C dynamics. The model outputs are further compared to earlier process-based models, highlighting the advances generated by the new model. This work thus represents a step towards unravelling the microbial responses to drought and rainfall events, with implications for our understanding of C cycle and C sequestration in soils.
|
|
| 2. |
- Brangari, Albert C., et al.
(författare)
-
Ecological and soil hydraulic implications of microbial responses to stress - A modeling analysis
- 2018
-
Ingår i: Advances in Water Resources. - : Elsevier BV. - 0309-1708 .- 1872-9657. ; 116, s. 178-194
-
Tidskriftsartikel (refereegranskat)abstract
- A better understanding of microbial dynamics in porous media may lead to improvements in the design and management of a number of technological applications, ranging from the degradation of contaminants to the optimization of agricultural systems. To this aim, there is a recognized need for predicting the proliferation of soil microbial biomass (often organized in biofilms) under different environments and stresses. We present a general multi-compartment model to account for physiological responses that have been extensively reported in the literature. The model is used as an explorative tool to elucidate the ecological and soil hydraulic consequences of microbial responses, including the production of extracellular polymeric substances (EPS), the induction of cells into dormancy, and the allocation and reuse of resources between biofilm compartments. The mechanistic model is equipped with indicators allowing the microorganisms to monitor environmental and biological factors and react according to the current stress pressures. The feedbacks of biofilm accumulation on the soil water retention are also described. Model runs simulating different degrees of substrate and water shortage show that adaptive responses to the intensity and type of stress provide a clear benefit to microbial colonies. Results also demonstrate that the model may effectively predict qualitative patterns in microbial dynamics supported by empirical evidence, thereby improving our understanding of the effects of pore-scale physiological mechanisms on the soil macroscale phenomena.
|
|
| 3. |
- Brangarí, Albert C., et al.
(författare)
-
Soil depth and tillage can characterize the soil microbial responses to drying-rewetting
- 2022
-
Ingår i: Soil Biology & Biochemistry. - : Elsevier BV. - 0038-0717. ; 173
-
Tidskriftsartikel (refereegranskat)abstract
- The influence of climate on soil microorganisms governs the input and output fluxes of carbon (C) from soils. The study of the drastic responses to drying-rewetting offers an opportunity to assess an aspect of ‘soil health’ via evaluating the role of microbes in soil biochemistry and C cycling. Recent evidence has consistently shown that communities exposed to extreme moisture fluctuations recurrently can better cope with the stress generated by them and exhibit a ‘resilient’ microbial response after rewetting (fast recovery of microbial communities to the pre-disturbance growth levels), whereas otherwise they show a more ‘sensitive’ response (slow recovery). However, it is still not known if land-use management can alter these responses. In this study, we investigated this issue by performing a drying-rewetting experiment on soil samples from two land-uses (permanent pastures and tilled croplands) and two depths (0–5 cm and 20–30 cm), and measured bacterial growth, fungal growth, and respiration at high temporal resolution. We then derived a series of indicators of soil health based on the characteristics of these microbial responses to drying-rewetting. Results showed categorically different patterns in soils from pastures and croplands, confirming the capacity of land use to change soil functioning. Tillage practices cancelled the stratification in the top 30 cm of soil and increased the exposure and adaptation of soil microorganisms to conditions of water stress, which caused shifts in the microbial responses to drying-rewetting. The sensitive patterns in bacterial growth found in undisturbed pastures were replaced by resilient responses in both shallow and deep croplands. Fungi showed a tendency for faster recoveries in croplands but patterns were consistently resilient in all sites and depths, indicating that fungi were little affected by land-use-induced dis- turbances. Respiration exhibited resilient-like responses in shallow samples, but in depth, they were sensitive in pastures and resilient in croplands. We also observed an alternated sequence of bacterial and fungal growth over time that suggested competition and different strategies of reactivation after rewetting by the two types of microorganisms.
|
|
| 4. |
- Brangarí, Albert C., et al.
(författare)
-
The mechanisms underpinning microbial resilience to drying and rewetting - A model analysis
- 2021
-
Ingår i: Soil Biology and Biochemistry. - : Elsevier BV. - 0038-0717 .- 1879-3428. ; 162
-
Tidskriftsartikel (refereegranskat)abstract
- Soil moisture is one of the most important factors controlling the activity and diversity of soil microorganisms. Soils exposed to pronounced cycles of drying and rewetting (D/RW) exhibit disconnected patterns in microbial growth and respiration at RW. These patterns differ depending on the preceding soil moisture history, leading to contrasting amounts of carbon retained in the soil as biomass versus that respired as CO2. The mechanisms underlying these microbially-induced dynamics are still unclear. In this work, we used the process-based soil microbial model EcoSMMARTS to offer candidate explanations for: i) how soil moisture can shape the structure of microbial communities, ii) how soil moisture history affects the responses during D/RW, iii) what microbial mechanisms control the shape, intensity and duration of these responses, and iv) what carbon sources sustain the increased biogeochemical rates after RW. We first evaluated the response to D/RW in bacterial communities previously exposed to two different stress histories (‘moderate’ vs ‘severe’ soil moisture regimes). We found that both the history of soil moisture and the harshness of the dry period preceding the rewetting shaped the structure and physiology of microbial communities. The characteristics of these communities determined the harshness experienced and the nature of the responses to RW obtained. Modelled communities exposed to extended severe conditions showed a resilient response to D/RW, whereas those exposed to moderate environments exhibited a more sensitive response. We then interchanged the soil moisture regimes and found that the progressive adaptation of microbial physiology and structure to new environmental conditions resulted in a switch in the response patterns. These microbial changes also determined the contribution of biomass synthesis, osmoregulation, mineralization by cell residues, and disruption of soil aggregates to CO2 emissions.
|
|
| 5. |
- He, Haoran, et al.
(författare)
-
Deciphering microbiomes dozens of meters under our feet and their edaphoclimatic and spatial drivers
- 2024
-
Ingår i: Global Change Biology. - 1354-1013. ; 30:1
-
Tidskriftsartikel (refereegranskat)abstract
- Microbes inhabiting deep soil layers are known to be different from their counterpart in topsoil yet remain under investigation in terms of their structure, function, and how their diversity is shaped. The microbiome of deep soils (>1 m) is expected to be relatively stable and highly independent from climatic conditions. Much less is known, however, on how these microbial communities vary along climate gradients. Here, we used amplicon sequencing to investigate bacteria, archaea, and fungi along fifteen 18-m depth profiles at 20–50-cm intervals across contrasting aridity conditions in semi-arid forest ecosystems of China's Loess Plateau. Our results showed that bacterial and fungal α diversity and bacterial and archaeal community similarity declined dramatically in topsoil and remained relatively stable in deep soil. Nevertheless, deep soil microbiome still showed the functional potential of N cycling, plant-derived organic matter degradation, resource exchange, and water coordination. The deep soil microbiome had closer taxa–taxa and bacteria–fungi associations and more influence of dispersal limitation than topsoil microbiome. Geographic distance was more influential in deep soil bacteria and archaea than in topsoil. We further showed that aridity was negatively correlated with deep-soil archaeal and fungal richness, archaeal community similarity, relative abundance of plant saprotroph, and bacteria–fungi associations, but increased the relative abundance of aerobic ammonia oxidation, manganese oxidation, and arbuscular mycorrhizal in the deep soils. Root depth, complexity, soil volumetric moisture, and clay play bridging roles in the indirect effects of aridity on microbes in deep soils. Our work indicates that, even microbial communities and nutrient cycling in deep soil are susceptible to changes in water availability, with consequences for understanding the sustainability of dryland ecosystems and the whole-soil in response to aridification. Moreover, we propose that neglecting soil depth may underestimate the role of soil moisture in dryland ecosystems under future climate scenarios.
|
|
| 6. |
- He, Haoran, et al.
(författare)
-
Linking soil depth to aridity effects on soil microbial community composition, diversity and resource limitation
- 2023
-
Ingår i: Catena. - 0341-8162. ; 232
-
Tidskriftsartikel (refereegranskat)abstract
- With ongoing climate change, aridity is increasing worldwide, affecting biodiversity and ecosystem function in drylands. However, how the depth-profile microbial community structure and metabolic limitations change along aridity gradients are still poorly explored. Here, 16S rRNA and ITS amplicon sequencing and ecoenzymatic stoichiometry analysis were used to investigate both bacterial and fungal diversities and resource limitations in 1 m depth profiles across a wide aridity gradient (0.51–0.78) in a semiarid region. Results showed a sharp decrease in microbial diversity with soil depth, accompanied by an increase in microbial phosphorus (P) vs. N (nitrogen) limitation and a decrease in microbial carbon (C) vs. nutrient limitation. Aridity led to a strong shift in microbial community composition, but aridity has a threshold effect on microbial resource limitation through impacts on soil pH and C/P or N/P. When the aridity threshold (1-precipitation/evapotranspiration) exceeds 0.65, relationship between aridity and microbial resource demand was decoupled; but at aridity threshold = 0.65, microbial relative C limitation and C-acquiring enzyme activity dropped. These results suggest that aridity might have a stronger influence on microbial community composition, than on diversity, shaped by inherent soil biotic factors (i.e., MBC:MBP or MBN:MBP). These findings suggest that soil microbial diversity or enzymatic stoichiometry may be not necessary to mirror changes in water availability in the drylands, while aridity would be well explained by microbial community composition.
|
|
| 7. |
- Hicks, Lettice
(författare)
-
Increased Above- and Belowground Plant Input Can Both Trigger Microbial Nitrogen Mining in Subarctic Tundra Soils
- 2022
-
Ingår i: Ecosystems. - : Springer Science and Business Media LLC. - 1432-9840 .- 1435-0629. ; 25:1, s. 105-121
-
Tidskriftsartikel (refereegranskat)abstract
- Low nitrogen (N) availability in the Arctic and Subarctic constrains plant productivity, resulting in low litter inputs to soil. Increased N availability and litter inputs as a result of climate change, therefore, have the potential to impact the functioning of these ecosystems. We examined plant and microbial responses to chronic inorganic N (5 g m−2 year−1) and/or litter (90 g m−2 year−1), supplied during three growing seasons. We also compared the response to more extreme additions, where the total cumulative additions of N (that is, 15 g m−2) and litter (that is, 270 g m−2) were concentrated into a single growth season. Plant productivity was stimulated by N additions and was higher in the extreme addition plots than those with chronic annual additions. Microbial community structure also differed between the chronic and extreme plots, and there was a significant relationship between plant and microbial community structures. Despite differences in microbial structure, the field treatments had no effect on microbial growth or soil C mineralization. However, gross N mineralization was higher in the N addition plots. This led to a lower ratio of soil C mineralization to gross N mineralization, indicating microbial targeting of N-rich organic matter (“microbial N-mining”), likely driven by the increased belowground C-inputs due to stimulated plant productivity. Surprisingly, aboveground litter addition also decreased ratio of soil C mineralization to gross N mineralization. Together, these results suggest that elevated N availability will induce strong responses in tundra ecosystems by promoting plant productivity, driving changes in above- and belowground community structures, and accelerating gross N mineralization. In contrast, increased litter inputs will have subtle effects, primarily altering the ratio between C and N derived from soil organic matter.
|
|
| 8. |
- Jin-Tao, Li, et al.
(författare)
-
Subarctic winter warming promotes soil microbial resilience to freeze–thaw cycles and enhances the microbial carbon use efficiency
- 2024
-
Ingår i: Global Change Biology. - 1354-1013. ; 30:1
-
Tidskriftsartikel (refereegranskat)abstract
- Climate change is predicted to cause milder winters and thus exacerbate soil freeze–thaw perturbations in the subarctic, recasting the environmental challenges that soil microorganisms need to endure. Historical exposure to environmental stressors can facilitate the microbial resilience to new cycles of that same stress. However, whether and how such microbial memory or stress legacy can modulate microbial responses to cycles of frost remains untested. Here, we conducted an in situ field experiment in a subarctic birch forest, where winter warming resulted in a substantial increase in the number and intensity of freeze–thaw events. After one season of winter warming, which raised mean surface and soil (−8 cm) temperatures by 2.9 and 1.4°C, respectively, we investigated whether the in situ warming-induced increase in frost cycles improved soil microbial resilience to an experimental freeze–thaw perturbation. We found that the resilience of microbial growth was enhanced in the winter warmed soil, which was associated with community differences across treatments. We also found that winter warming enhanced the resilience of bacteria more than fungi. In contrast, the respiration response to freeze–thaw was not affected by a legacy of winter warming. This translated into an enhanced microbial carbon-use efficiency in the winter warming treatments, which could promote the stabilization of soil carbon during such perturbations. Together, these findings highlight the importance of climate history in shaping current and future dynamics of soil microbial functioning to perturbations associated with climate change, with important implications for understanding the potential consequences on microbial-mediated biogeochemical cycles.
|
|
| 9. |
- Li, Jin-Tao, et al.
(författare)
-
Comparing soil microbial responses to drying-rewetting and freezing-thawing events
- 2023
-
Ingår i: Soil Biology and Biochemistry. - : Elsevier BV. - 0038-0717. ; 178
-
Tidskriftsartikel (refereegranskat)abstract
- Climate change is expected to alter the frequency and intensity of soil drying-rewetting (D/RW) and freezing-thawing (F/TW) events, with consequences for the activities of microorganisms. Although both D/RW and F/TW events cause respiration pulses from soil to the atmosphere, it remains unknown whether the underlying microbial control is similar. Recent work has revealed that soil microbial responses to D/RW vary between two extremes: (Type 1) a resilient response, with a fast recovery of growth rates associated with a brief respiration pulse, or (Type 2) a sensitive response, where growth rates recover only after a lag period of no apparent growth associated with a prolonged respiration pulse. However, it remains unknown if these different microbial perturbation responses also occur after F/TW. Here, we directly compared microbial growth, respiration, and carbon-use efficiency (CUE) in response to D/RW and F/TW events. To do this, we selected two forest soils characterized by either sensitive or resilient responses to D/RW. We could confirm that D/RW induced either sensitive or resilient bacterial growth and respiration responses, but also that these distinct responses were found after F/TW. Additionally, F/TW resulted in shorter lag periods before the increase of bacterial growth, smaller respiration pulses, and lower levels of cumulative respiration, bacterial growth and fungal growth after the perturbation than did D/RW. These findings are consistent with a F/TW event imposing a similar stress on soil microorganisms to a D/RW event, but with lower severity. However, there was no significant difference in the microbial CUE between D/RW and F/TW, indicating that microorganisms maintain the stability of their C allocation in response to both types of perturbation. Altogether, our findings suggest that microbial communities are exposed to similar environmental pressures during D/RW and F/TW, implying that strategies to cope with drought can also provide protection to winter frost, and vice versa.
|
|
| 10. |
|
|
