| 1. |
- Cordero, Irene, et al.
(författare)
-
High intensity perturbations induce an abrupt shift in soil microbial state
- 2023
-
Ingår i: ISME Journal. - 1751-7362. ; 17:12, s. 2190-2199
-
Tidskriftsartikel (refereegranskat)abstract
- Soil microbial communities play a pivotal role in regulating ecosystem functioning. But they are increasingly being shaped by human-induced environmental change, including intense “pulse” perturbations, such as droughts, which are predicted to increase in frequency and intensity with climate change. While it is known that soil microbial communities are sensitive to such perturbations and that effects can be long-lasting, it remains untested whether there is a threshold in the intensity and frequency of perturbations that can trigger abrupt and persistent transitions in the taxonomic and functional characteristics of soil microbial communities. Here we demonstrate experimentally that intense pulses of drought equivalent to a 30-year drought event (<15% WHC) induce a major shift in the soil microbial community characterised by significantly altered bacterial and fungal community structures of reduced complexity and functionality. Moreover, the characteristics of this transformed microbial community persisted after returning soil to its previous moisture status. As a result, we found that drought had a strong legacy effect on bacterial community function, inducing an enhanced growth rate following subsequent drought. Abrupt transitions are widely documented in aquatic and terrestrial plant communities in response to human-induced perturbations. Our findings demonstrate that such transitions also occur in soil microbial communities in response to high intensity pulse perturbations, with potentially deleterious consequences for soil health.
|
|
| 2. |
- de Nijs, Evy A., et al.
(författare)
-
Soil microbial moisture dependences and responses to drying–rewetting : The legacy of 18 years drought
- 2019
-
Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 25:3, s. 1005-1015
-
Tidskriftsartikel (refereegranskat)abstract
- Climate change will alter precipitation patterns with consequences for soil C cycling. An understanding of how fluctuating soil moisture affects microbial processes is therefore critical to predict responses to future global change. We investigated how long-term experimental field drought influences microbial tolerance to lower moisture levels (“resistance”) and ability to recover when rewetted after drought (“resilience”), using soils from a heathland which had been subjected to experimental precipitation reduction during the summer for 18 years. We tested whether drought could induce increased resistance, resilience, and changes in the balance between respiration and bacterial growth during perturbation events, by following a two-tiered approach. We first evaluated the effects of the long-term summer drought on microbial community functioning to drought and drying–rewetting (D/RW), and second tested the ability to alter resistance and resilience through additional perturbation cycles. A history of summer drought in the field selected for increased resilience but not resistance, suggesting that rewetting after drought, rather than low moisture levels during drought, was the selective pressure shaping the microbial community functions. Laboratory D/RW cycles also selected for communities with a higher resilience rather than increased resistance. The ratio of respiration to bacterial growth during D/RW perturbation was lower for the field drought-exposed communities and decreased for both field treatments during the D/RW cycles. This suggests that cycles of D/RW also structure microbial communities to respond quickly and efficiently to rewetting after drought. Our findings imply that microbial communities can adapt to changing climatic conditions and that this might slow the rate of soil C loss predicted to be induced by future cyclic drought.
|
|
| 3. |
- Hicks, Lettice C., et al.
(författare)
-
Bacteria constrain the fungal growth response to drying-rewetting
- 2019
-
Ingår i: Soil Biology and Biochemistry. - : Elsevier BV. - 0038-0717. ; 134, s. 108-112
-
Tidskriftsartikel (refereegranskat)abstract
- Bacteria and fungi are the two principal decomposer groups in soils, determining rates of biogeochemical cycling. Rewetting of dry soils induces enormous dynamics in biogeochemistry. Bacteria have been shown to exhibit large variation in growth over time upon drying-rewetting (D/RW), however, in studies to date, fungal growth has shown limited responsiveness. Here we investigated whether fungal growth responses to D/RW are constrained by competition with bacteria by using the bactericide bronopol to suppress bacterial growth during D/RW. We examined responses for two different soils, previously shown to exhibit different bacterial growth responses to D/RW. Experimental elimination of bacterial growth lead to increased fungal growth in both soils upon D/RW, indicating a competitive release of fungal growth when bacteria were suppressed. We also observed a pronounced fungal growth response to D/RW for one of the soils, which has not been previously reported. In this case, even when rewetting with water (i.e. without bacterial suppression), fungal growth increased to reach rates 10-times greater than in the moist control soil. The peak in fungal growth coincided with a secondary peak of respiration, revealing a functional importance of fungi for C-cycling during D/RW. The decline in fungal growth following this peak also coincided with the onset of exponential bacterial growth, further strengthening evidence for a negative correlation between bacteria and fungi, suggesting that competition with bacteria can constrain the fungal growth response to D/RW.
|
|
| 4. |
- Hicks, Lettice C., et al.
(författare)
-
Nutrient limitation may induce microbial mining for resources from persistent soil organic matter
- 2021
-
Ingår i: Ecology. - : Wiley. - 0012-9658 .- 1939-9170. ; 102:6
-
Tidskriftsartikel (refereegranskat)abstract
- Fungi and bacteria are the two principal microbial groups in soil, responsible for the breakdown of organic matter (OM). The relative contribution of fungi and bacteria to decomposition is thought to impact biogeochemical cycling at the ecosystem scale, whereby bacterially dominated decomposition supports the fast turnover of easily available substrates, whereas fungal-dominated decomposition leads to the slower turnover of more complex OM. However, empirical support for this is lacking. We used soils from a detritus input and removal treatment experiment in an old-growth coniferous forest, where above- and belowground litter inputs have been manipulated for 20 yr. These manipulations have generated variation in OM quality, as defined by energetic content and proxied as respiration per g soil organic matter (SOM) and the δ13C signature in respired CO2 and microbial PLFAs. Respiration per g SOM reflects the availability and lability of C substrate to microorganisms, and the δ13C signature indicates whether the C used by microorganisms is plant derived and higher quality (more δ13C depleted) or more microbially processed and lower quality (more δ13C enriched). Surprisingly, higher quality C did not disproportionately benefit bacterial decomposers. Both fungal and bacterial growth increased with C quality, with no systematic change in the fungal-to-bacterial growth ratio, reflecting the relative contribution of fungi and bacteria to decomposition. There was also no difference in the quality of C targeted by bacterial and fungal decomposers either for catabolism or anabolism. Interestingly, respired CO2 was more δ13C enriched than soil C, suggesting preferential use of more microbially processed C, despite its lower quality. Gross N mineralization and consumption were also unaffected by differences in the ratio of fungal-to-bacterial growth. However, the ratio of C to gross N mineralization was lower than the average C/N of SOM, meaning that microorganisms specifically targeted N-rich components of OM, indicative of selective microbial N-mining. Consistent with the δ13C data, this reinforces evidence for the use of more microbially processed OM with a lower C/N ratio, rather than plant-derived OM. These results challenge the widely held assumption that microorganisms favor high-quality C sources and suggest that there is a trade-off in OM use that may be related to the growth-limiting factor for microorganisms in the ecosystem.
|
|
| 5. |
- Hicks, Lettice C., et al.
(författare)
-
Simulated rhizosphere deposits induce microbial N-mining that may accelerate shrubification in the subarctic
- 2020
-
Ingår i: Ecology. - : Wiley. - 0012-9658 .- 1939-9170. ; 101:9
-
Tidskriftsartikel (refereegranskat)abstract
- Climate change is exposing high-latitude systems to warming and a shift towards more shrub-dominated plant communities, resulting in increased leaf-litter inputs at the soil surface, and more labile root-derived organic matter (OM) input in the soil profile. Labile OM can stimulate the mineralization of soil organic matter (SOM); a phenomenon termed “priming.” In N-poor subarctic soils, it is hypothesized that microorganisms may “prime” SOM in order to acquire N (microbial N-mining). Increased leaf-litter inputs with a high C/N ratio might further exacerbate microbial N demand, and increase the susceptibility of N-poor soils to N-mining. We investigated the N-control of SOM mineralization by amending soils from climate change–simulation treatments in the subarctic (+1.1°C warming, birch litter addition, willow litter addition, and fungal sporocarp addition) with labile OM either in the form of glucose (labile C; equivalent to 400 µg C/g fresh [fwt] soil) or alanine (labile C + N; equivalent to 400 µg C and 157 µg N/g fwt soil), to simulate rhizosphere inputs. Surprisingly, we found that despite 5 yr of simulated climate change treatments, there were no significant effects of the field-treatments on microbial process rates, community structure or responses to labile OM. Glucose primed the mineralization of both C and N from SOM, but gross mineralization of N was stimulated more than that of C, suggesting that microbial SOM use increased in magnitude and shifted to components richer in N (i.e., selective microbial N-mining). The addition of alanine also resulted in priming of both C and N mineralization, but the N mineralization stimulated by alanine was greater than that stimulated by glucose, indicating strong N-mining even when a source of labile OM including N was supplied. Microbial carbon use efficiency was reduced in response to both labile OM inputs. Overall, these findings suggest that shrub expansion could fundamentally alter biogeochemical cycling in the subarctic, yielding more N available for plant uptake in these N-limited soils, thus driving positive plant–soil feedbacks.
|
|
| 6. |
- Hicks, Lettice C., et al.
(författare)
-
Soil Microbial Responses to 28 Years of Nutrient Fertilization in a Subarctic Heath
- 2020
-
Ingår i: Ecosystems. - : Springer Science and Business Media LLC. - 1432-9840 .- 1435-0629. ; 23:5, s. 1107-1119
-
Tidskriftsartikel (refereegranskat)abstract
- Arctic and subarctic soils are typically characterized by low nitrogen (N) availability, suggesting N-limitation of plants and soil microorganisms. Climate warming will stimulate the decomposition of organic matter, resulting in an increase in soil nutrient availability. However, it remains unclear how soil microorganisms in N-limited soils will respond, as the direct effect of inorganic N addition is often shown to inhibit microbial activity, while elevated N availability may have a positive effect on microorganisms indirectly, due to a stimulation of plant productivity. Here we used soils from a long-term fertilization experiment in the Subarctic (28 years at the time of sampling) to investigate the net effects of chronic N-fertilization (100 kg N ha−1 y−1, added together with 26 kg P and 90 kg K ha−1 y−1, as expected secondary limiting nutrients for plants) on microbial growth, soil C and N mineralization, microbial biomass, and community structure. Despite high levels of long-term fertilization, which significantly increased primary production, we observed relatively minor effects on soil microbial activity. Bacterial growth exhibited the most pronounced response to long-term fertilization, with higher rates of growth in fertilized soils, whereas fungal growth remained unaffected. Rates of basal soil C and N mineralization were only marginally higher in fertilized soils, whereas fertilization had no significant effect on microbial biomass or microbial community structure. Overall, these findings suggest that microbial responses to long-term fertilization in these subarctic tundra soils were driven by an increased flow of labile plant-derived C due to stimulated plant productivity, rather than by direct fertilization effects on the microbial community or changes in soil physiochemistry.
|
|
| 7. |
- Hicks, Lettice C., et al.
(författare)
-
The legacy of mixed planting and precipitation reduction treatments on soil microbial activity, biomass and community composition in a young tree plantation
- 2018
-
Ingår i: Soil Biology and Biochemistry. - : Elsevier BV. - 0038-0717. ; 124, s. 227-235
-
Tidskriftsartikel (refereegranskat)abstract
- Drought events are expected to increase as a consequence of climate change, with the potential to influence both plant and soil microbial communities. Mixed planting may be an option to mitigate drought stress to plants, however, the extent to which mixed planting mitigates the indirect effect of drought (reduced plant-derived carbon input) on soil microorganisms remains unknown. Using soils from a young experimental plantation in Central Europe, we investigated whether mixed planting (oak monoculture, and oak admixed with 1–3 other tree species) under simulated drought (50% precipitation reduction for 2 years) influenced soil microbial activity, biomass and community composition. To focus on legacy effects - i.e. indirect effects mediated by plant composition and a history of drought, rather than direct effects of reduced water availability - soils were measured at a standardised moisture content (28 ± 1% water holding capacity). Rates of bacterial growth and respiration were lower in soils with a legacy of drought. In contrast, fungal growth was not affected by a history of drought, suggesting that fungi were less adversely affected by reduced plant-input during drought, compared to bacteria. The effect of drought on the fungal-to-bacterial growth ratio was influenced by mixed planting, leading to a disproportionate decrease in bacterial growth in drought-exposed soils under oak monoculture than when oak was admixed with two or three different tree species. The presence of a particular tree species (with specific functional traits) in the admixture, rather than increased tree richness per se, may explain this response. Microbial biomass parameters, reflecting both the direct and indirect effects of past drought conditions, were consistently lower in drought-exposed soils than controls. While bacteria were more sensitive to the indirect effect of drought than fungi, the biomass concentrations suggested that the direct effect of reduced moisture affected both groups similarly. Overall, our findings demonstrate that drought can have lasting effects on microbial communities, with consequences for microbial function. Results also suggest that admixing oak with other tree species may alleviate the drought-legacy effect on bacteria and increase tolerance to future drought.
|
|
| 8. |
- Hicks, Lettice C., et al.
(författare)
-
Toward a function-first framework to make soil microbial ecology predictive
- 2022
-
Ingår i: Ecology. - : Wiley. - 0012-9658 .- 1939-9170. ; 103:e03594
-
Tidskriftsartikel (refereegranskat)abstract
- Soil microbial communities perform vital ecosystem functions, such as the decomposition of organic matter to provide plant nutrition. However, despite the functional importance of soil microorganisms, attribution of ecosystem function to particular constituents of the microbial community has been impeded by a lack of information linking microbial function to community composition and structure. Here, we propose a function-first framework to predict how microbial communities influence ecosystem functions. We first view the microbial community associated with a specific function as a whole and describe the dependence of microbial functions on environmental factors (e.g., the intrinsic temperature dependence of bacterial growth rates). This step defines the aggregate functional response curve of the community. Second, the contribution of the whole community to ecosystem function can be predicted, by combining the functional response curve with current environmental conditions. Functional response curves can then be linked with taxonomic data in order to identify sets of “biomarker” taxa that signal how microbial communities regulate ecosystem functions. Ultimately, such indicator taxa may be used as a diagnostic tool, enabling predictions of ecosystem function from community composition. In this paper, we provide three examples to illustrate the proposed framework, whereby the dependence of bacterial growth on environmental factors, including temperature, pH, and salinity, is defined as the functional response curve used to interlink soil bacterial community structure and function. Applying this framework will make it possible to predict ecosystem functions directly from microbial community composition.
|
|
| 9. |
|
|
| 10. |
|
|
| 11. |
- 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.
|
|
| 12. |
- Hicks, Lettice, et al.
(författare)
-
Microbial resilience to drying-rewetting is partly driven by selection for quick colonizers
- 2022
-
Ingår i: Soil Biology and Biochemistry. - : Elsevier BV. - 0038-0717. ; 167
-
Tidskriftsartikel (refereegranskat)abstract
- Rewetting dry soil induces enormous changes in microbial growth and biogeochemistry. Upon drying-rewetting (D/RW), bacteria have been shown to exhibit two different responses: (1) a more resilient response where bacteria start growing immediately with a quick recovery after rewetting and (2) a less resilient response where there is a pronounced lag-period before bacterial growth starts to increase exponentially. A shift towards a more resilient bacterial growth response has previously been shown to be induced by exposing soils to repeated cycles of D/RW. Here, we test the hypothesis that this response is driven by selection for a bacterial community with traits for quick colonization of labile carbon (C) resources made available upon D/RW. To do so, we compared the responses of soils that had been exposed to either (i) three cycles of D/RW, (ii) three pulses of glucose addition to moist soil or (iii) three pulses of litter addition to moist soil, before all soils were subjected to a D/RW event where bacterial growth, fungal growth and respiration rates were monitored. As expected, exposing the soil to a series of D/RW events resulted in a more resilient bacterial growth response, as well as a faster recovery of fungal growth. Pre-treating the soils with pulses of glucose accelerated the recovery of bacteria after D/RW, but did not select for a bacterial resilience that could match the pre-treatment with exposure to D/RW. Pre-treatment with pulses of litter showed a trend for an accelerated recovery of bacterial growth to D/RW, but to a lesser extent than that induced by pulses of glucose. In contrast, pre-treatment of soil with either pulses of glucose or pulses of litter both led to a faster recovery of fungal growth following D/RW, matching that induced by repeated D/RW cycles. These results suggest that selection for quick colonizers partly explains the shift to a more resilient microbial response to repeated cycles of D/RW, accounting for ca. 60% increase in bacterial resilience and 100% of the increase in fungal resilience compared that induced by repeated D/RW cycles.
|
|
| 13. |
- 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.
|
|
| 14. |
- Leizeaga, Ainara, et al.
(författare)
-
Using a tropical elevation gradient to evaluate the impact of land‐use intensity and forest restoration on the microbial use of organic matter under climate change
- 2022
-
Ingår i: Global Biogeochemical Cycles. - 0886-6236. ; 36:4
-
Tidskriftsartikel (refereegranskat)abstract
- We investigated how legacies of land use and climate affected the microbial use of organic matter (OM) along a tropical climate gradient in Ethiopia. Four levels of land-use intensity ranging from croplands to pristine forests were assessed along a gradient from cool and moist high altitude (MAT = 16°C, MAP = 2,200 mm) to hot and dry lowland sites (MAT = 20°C, MAP = 1,050 mm). We resolved the biomass, structure, and growth rates of microbial decomposer communities together with the rates of carbon (C) and nitrogen (N) transformation. To target the legacies of climate and land use, samples were assessed at optimal moisture and standardized temperature in the laboratory. Microbial biomass and the fungal-to-bacterial ratio increased with both legacies of drier climates and higher land-use intensities. In contrast, fungal growth rates increased in humid climates, but were unaffected by land use. The ratio of C mineralization to gross N mineralization decreased with higher humidity and more intensive land use, suggesting a change in microbial resource use from more nutrient-poor to nutrient-rich OM. Mineralization of nutrient-poor OM implied a lower nutrient availability to microbes in arid climates and low-intensity land uses, while the mineralization of nutrient-rich OM in humid sites and higher intensity land uses implied a higher microbial nutrient availability there. The difference in respiration between land uses increased with ecosystem aridity, suggesting that OM turnover and soil fertility were more impacted by land use in drier climates. Together, our results suggest that drier subtropical climates will exacerbate the negative effects of land-use intensification on OM turnover and nutrient provisioning for plants.
|
|
| 15. |
- 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.
|
|
| 16. |
- Li, Xiaojuan, et al.
(författare)
-
Climate and soil properties drive soil organic and inorganic carbon patterns across a latitudinal gradient in southwestern China
- 2023
-
Ingår i: Journal of Soils and Sediments. - : Springer Science and Business Media LLC. - 1614-7480 .- 1439-0108. ; 23:1, s. 91-102
-
Tidskriftsartikel (refereegranskat)abstract
- PurposeDrylands account for 47.2% of land area and contain 15.5% of global carbon (C). However, the variation in organic and inorganic C stocks across latitudinal gradients in arid and semiarid shrubland ecosystems remains understudied, and we lack in-depth understanding of the main drivers of C variation at this spatial scale.MethodsHere, we sampled soils from 95 sites across a latitudinal gradient to explore both the latitudinal patterns and potential drivers of soil organic carbon density (SOCD) and soil inorganic carbon density (SICD). We also assessed variation in SOCD and SICD down the soil profile, by sampling soils at four depths (0 – 10 cm, 10 – 20 cm, 20 – 30 cm, and 30 – 50 cm).ResultBoth SOCD and SICD exhibited a binomial relationship with latitude (P < 0.01). Soil properties accounted for the greatest variation in SOCD, with the most important explanatory factor being exchangeable calcium, followed by mean annual temperature, pH, plant diversity, and silt content. Soil pH and plant diversity were more important in explaining variation in SOCD in the subsoil (> 20 cm depth) than the topsoil. For SICD, soil properties explained the greatest variation at all depths. Soil pH explained the most variance in SICD, followed by exchangeable calcium and mean annual temperature in the topsoil (i.e., 0 – 10 cm and 10 – 20 cm). In the subsoil (i.e., 20 – 30 cm and 30 – 50 cm), exchangeable calcium was the most important predictor, followed by soil organic carbon, mean annual temperature, and pH.ConclusionOur study shows that soil properties are a strong predictor of latitudinal patterns of soil organic and inorganic C in arid and semiarid shrubland ecosystems. We also identified differences in potential drivers of SOCD and SICD with depth, advancing our understanding of large-scale patterns of C storage in arid and semiarid soils.
|
|
| 17. |
- Li, Xiaojuan, et al.
(författare)
-
Latitudinal patterns of light and heavy organic matter fractions in arid and semi-arid soils
- 2022
-
Ingår i: Catena. - : Elsevier BV. - 0341-8162. ; 215
-
Tidskriftsartikel (refereegranskat)abstract
- Semi-arid and arid ecosystems are important for the global C cycle. Despite this, it remains unclear how organic matter fractions vary across latitudinal gradients, and what drives this variation, in dry ecosystems. In this study, we sampled soils from 100 sites across a latitudinal gradient in the dry valleys of southwestern China to explore the latitudinal patterns of light fraction organic matter (LFOM) and heavy fraction organic matter (HFOM) at two soil depths (0–10 cm and 10–20 cm). Across the studied gradient, HFOM accounted for a larger fraction of soil organic matter than LFOM. LFOM increased exponentially with increasing latitude at both 0–10 cm and 10–20 cm depths. Heavy fraction organic C increased linearly with increasing latitude at both depths, while heavy fraction organic N only increased with latitude in soils from 10 to 20 cm depth. Latitudinal patterns of LFOM were mainly explained by climate, with the most important driver being mean annual temperature, followed by mean annual precipitation. Soil physicochemical factors – in particular cation exchange capacity and silt content – explained the most variation in HFOM. Total microbial biomass was also important in explaining variation in HFOM, especially in the 10–20 cm soil layer. Overall, our results shed light on the spatial distribution of organic matter fractions in arid and semi-arid regions. We also identify candidate drivers of the variation in LFOM and HFOM in arid and semi-arid regions, finding that climate primarily explains variation in LFOM while soil physiochemistry primarily explains variation in HFOM.
|
|
| 18. |
|
|
| 19. |
- Na, Meng, et al.
(författare)
-
Semi-continuous C supply reveals that priming due to N-mining is driven by microbial growth demands in temperate forest plantations
- 2022
-
Ingår i: Soil Biology & Biochemistry. - : Elsevier BV. - 0038-0717. ; 173
-
Tidskriftsartikel (refereegranskat)abstract
- Nitrogen (N) availability is a powerful controller of soil carbon (C) cycling in temperate forests, affecting plant productivity and microbial activities. Enhanced rhizosphere input from increased plant productivity can stimulate the decomposition of native soil organic matter (SOM), termed the “priming effect”, with an effect size that is affected by N availability. Using soils from N-fertilization field-experiments conducted in larch and mixed forest plantations, we investigated how N availability influenced the priming of soil organic C (SOC) mineralization and soil organic N (SON) mineralization by adding 13C-labelled glucose semi-continuously (every third day) to simulate the semi-continuous delivery of rhizosphere inputs. We found that semi-continuous additions of glucose induced a repeating pattern for the priming of SOC mineralization with an initial decrease followed by an increase. This repeating pattern of SOC mineralization reversely coincided with repeating dynamics in the level of bacterial growth which first increased followed by a decrease. The labile C additions induced a gradually increasing priming of SON mineralization, which was greater than the priming of SOC mineralization (i.e. “selective microbial N-mining”). The priming of SOC mineralization and SON mineralization were both reduced by N fertilization. Increased priming of SON mineralization was related to stimulated bacterial growth and changes in the microbial C use efficiency. These responses suggested that increased microbial demand for N drove the observed N-mining responses. This microbial N-mining could not be explained by increased oxidative enzyme activities, and was instead linked to microbial growth. In the larch forest with high C-quality, the high priming of SOM mineralization were linked to bacterial growth, while in the mixed forest with low C-quality, the high levels of priming of SOM mineralization was linked to fungal growth. We also observed that labile C input initially decoupled the C and N mineralization from SOM. Within 16 days, however, a new equilibrium developed, where both C and N mineralization from SOM were similarly enhanced by labile C input. Overall, our results suggest that semi-continuous rhizosphere inputs can induce a sustained priming of SOM mineralization driven by the microbial demand for N – increasing the release of CO2 – but that N fertilization could reduce the soil C loss, contributing to enhanced soil C sequestration.
|
|
| 20. |
|
|
| 21. |
- Neurauter, Markus, et al.
(författare)
-
Soil microbial resource limitation along a subarctic ecotone from birch forest to tundra heath
- 2023
-
Ingår i: Soil Biology & Biochemistry. - : Elsevier BV. - 0038-0717. ; 177
-
Tidskriftsartikel (refereegranskat)abstract
- Soil microorganisms regulate the decomposition of organic matter. However, microbial activities can also be rate-limited by the resource in lowest supply. Arctic ecosystems are being exposed to pronounced climate warming, with arctic greening, treeline advance and shrubification resulting in increased plant-derived carbon (C) inputs to soils, and faster rates of decomposition releasing mineral nutrients, potentially shifting the limiting factor for microbial growth. Here we used a “space-for-time” approach across a subarctic ecotone (birch forest, tree line, shrub and tundra sites). N and P fertilization treatments were also applied in the field, to test whether changes in resource limitation could be induced through nutrient loading of soils. In these soils, we measured the responses of bacterial and fungal growth as well as soil respiration to full factorial additions of C, nitrogen (N) and phosphorus (P) (“limiting factor assays”: LFA) to infer how the limiting factor for microbial growth would be affected by future climate change. We found that bacteria were triple-limited by C, N and P, while fungi were co-limited by C and N, with no shift in the limiting factor for bacterial or fungal growth across the ecotone. However, bacterial responses to the LFA were stronger in the tundra, showing 9-fold stronger increases in response to LFA-CNP addition compared to that in the forest. In contrast, fungal responses to the LFA were stronger in the forest, showing a 120% higher growth in response to LFA-CN addition, with no detectable response to LFA-CN addition in the tundra. These contrasting results suggested competitive interactions for resources between the two decomposer groups. Fertilization in the field shifted the bacterial resource limitation, but had no effect on the limiting factor for fungal growth. Together, our findings suggest that resource limitations for soil microorganisms will not change due to future warming, but rather affect degrees of fungal-to-bacterial dominance.
|
|
| 22. |
- Nottingham, Andrew T., et al.
(författare)
-
Nutrient limitations to bacterial and fungal growth during cellulose decomposition in tropical forest soils
- 2018
-
Ingår i: Biology and Fertility of Soils. - : Springer Science and Business Media LLC. - 0178-2762 .- 1432-0789. ; 54:2, s. 219-228
-
Tidskriftsartikel (refereegranskat)abstract
- Nutrients constrain the soil carbon cycle in tropical forests, but we lack knowledge on how these constraints vary within the soil microbial community. Here, we used in situ fertilization in a montane tropical forest and in two lowland tropical forests on contrasting soil types to test the principal hypothesis that there are different nutrient constraints to different groups of microorganisms during the decomposition of cellulose. We also tested the hypotheses that decomposers shift from nitrogen to phosphorus constraints from montane to lowland forests, respectively, and are further constrained by potassium and sodium deficiency in the western Amazon. Cellulose and nutrients (nitrogen, phosphorus, potassium, sodium, and combined) were added to soils in situ, and microbial growth on cellulose (phospholipid fatty acids and ergosterol) and respiration were measured. Microbial growth on cellulose after single nutrient additions was highest following nitrogen addition for fungi, suggesting nitrogen as the primary limiting nutrient for cellulose decomposition. This was observed at all sites, with no clear shift in nutrient constraints to decomposition between lowland and montane sites. We also observed positive respiration and fungal growth responses to sodium and potassium addition at one of the lowland sites. However, when phosphorus was added, and especially when added in combination with other nutrients, bacterial growth was highest, suggesting that bacteria out-compete fungi for nitrogen where phosphorus is abundant. In summary, nitrogen constrains fungal growth and cellulose decomposition in both lowland and montane tropical forest soils, but additional nutrients may also be of critical importance in determining the balance between fungal and bacterial decomposition of cellulose.
|
|
| 23. |
- Rahman, Md Masudur, et al.
(författare)
-
Effects of drought legacy and tree species admixing on bacterial growth and respiration in a young forest soil upon drying and rewetting
- 2018
-
Ingår i: Soil Biology and Biochemistry. - : Elsevier BV. - 0038-0717. ; 127, s. 148-155
-
Tidskriftsartikel (refereegranskat)abstract
- In the context of future climate change, the flush of CO2 emissions from soils after drying-rewetting events could have a strong impact on the terrestrial carbon balance. Mixed forests may be more resistant and resilient to drought events compared to monocultures, and as such may modulate the effects of drought on soil functioning belowground. We investigated the influence of mixed planting and drought legacy on respiration and bacterial growth rates (3H Leucine incorporation) in response to drying-rewetting. Soils were sampled from a 7-year old tree diversity experiment (FORBIO), where oak (Quercus robur L.) trees admixed with one or three other tree species were subjected to ∼50% precipitation reduction for 2 years (“drought legacy”). Respiration increased immediately after rewetting, whereas bacterial growth only started after a distinct lag phase of ca. 7 h. A legacy of drought reduced bacterial growth and respiration rates upon rewetting, however tree species admixing did not modulate the drought legacy effect. Our results suggest that prolonged decrease in precipitation may lead to a reduced CO2 pulse upon drying-rewetting and admixing up to three tree species with oak in a young afforestation would not alleviate drought legacy effects on bacterial growth and respiration rates.
|
|
| 24. |
- Scaini, Anna, et al.
(författare)
-
Pathways from research to sustainable development: Insights from ten research projects in sustainability and resilience
- 2024
-
Ingår i: AMBIO. - : SPRINGER. - 0044-7447 .- 1654-7209.
-
Tidskriftsartikel (refereegranskat)abstract
- Drawing on collective experience from ten collaborative research projects focused on the Global South, we identify three major challenges that impede the translation of research on sustainability and resilience into better-informed choices by individuals and policy-makers that in turn can support transformation to a sustainable future. The three challenges comprise: (i) converting knowledge produced during research projects into successful knowledge application; (ii) scaling up knowledge in time when research projects are short-term and potential impacts are long-term; and (iii) scaling up knowledge across space, from local research sites to larger-scale or even global impact. Some potential pathways for funding agencies to overcome these challenges include providing targeted prolonged funding for dissemination and outreach, and facilitating collaboration and coordination across different sites, research teams, and partner organizations. By systematically documenting these challenges, we hope to pave the way for further innovations in the research cycle.
|
|
| 25. |
- Tang, Yuqian, et al.
(författare)
-
Higher resistance and resilience of bacterial growth to drought in grasslands with historically lower precipitation
- 2023
-
Ingår i: Soil Biology and Biochemistry. - : Elsevier BV. - 0038-0717. ; 177
-
Tidskriftsartikel (refereegranskat)abstract
- Climate change is expected to alter precipitation regimes, resulting in longer periods of drought and heavier precipitation events. Even though the direct effect of water availability on soil microbial processes is well documented, the influence of precipitation legacy on microbial resistance and resilience to drought remains unclear. Using soils from a natural mean annual precipitation (MAP) gradient (∼550–950 mm yr−1) equipped with long-term (>8 yr) rain-out shelters, we investigated how the history of precipitation influenced microbial ‘resistance’ (tolerance to drying) and ‘resilience’ (ability to recover growth rates following rewetting) to drought. We found that bacterial growth was more resistant and resilient to drought in sites with lower MAP. In contrast, the precipitation-reduction treatments had no detectable influence on microbial drought resistance or resilience. The microbial carbon-use efficiency immediately after rewetting was higher in soils from lower precipitation sites. In contrast, the steady-state microbial growth rates and respiration (under standardized moisture conditions) were consistent along the precipitation gradient. The variation in microbial drought resistance and resilience across the precipitation gradient was linked to the microbial community structure. Taken together, our results suggest that historical precipitation regimes – and the associated differences in exposure to drought – had selected for bacterial communities that were more resistant and resilient to drought.
|
|
| 26. |
- Wang, Bin, et al.
(författare)
-
Silicon fertilization enhances the resistance of tobacco plants to combined Cd and Pb contamination : Physiological and microbial mechanisms
- 2023
-
Ingår i: Ecotoxicology and Environmental Safety. - : Elsevier BV. - 0147-6513. ; 255
-
Tidskriftsartikel (refereegranskat)abstract
- Remediation of soil contaminated with cadmium (Cd) and lead (Pb) is critical for tobacco production. Silicon (Si) fertilizer can relieve heavy metal stress and promote plant growth, however, it remains unknown whether fertilization with Si can mitigate the effects of Cd and Pb on tobacco growth and alter microbial community composition in polluted soils. Here we assessed the effect of two organic (OSiFA, OSiFB) and one mineral Si fertilizer (MSiF) on Cd and Pb accumulation in tobacco plants, together with responses in plant biomass, physiological parameters and soil bacterial communities in pot experiments. Results showed that Si fertilizer relieved Cd and Pb stress on tobacco, thereby promoting plant growth: Si fertilizer reduced available Cd and Pb in the soil by 37.3 % and 28.6 %, respectively, and decreased Cd and Pb contents in the plant tissue by 42.0–55.5 % and 17.2–25.6 %, resulting in increased plant biomass by 13.0–30.5 %. Fertilization with Si alleviated oxidative damage by decreasing malondialdehyde content and increasing peroxidase and ascorbate peroxidase content. In addition, Si fertilization increased photosynthesis, chlorophyll and carotenoid content. Microbial community structure was also affected by Si fertilization. Proteobacteria and Actinobacteria were the dominant phylum in the Cd and Pb contaminated soils, but Si fertilization reduced the abundance of Actinobacteria. Si fertilization also altered microbial metabolic pathways associated with heavy metal resistance. Together, our results suggest that both organic and mineral Si fertilizers can promote tobacco growth by relieving plant physiological stress and favoring a heavy metal tolerant soil microbial community.
|
|
| 27. |
- Yang, Xinyi, et al.
(författare)
-
Mechanisms underlying the responses of microbial carbon and nitrogen use efficiencies to nitrogen addition are mediated by topography in a subtropical forest
- 2023
-
Ingår i: Science of the Total Environment. - 0048-9697. ; 880
-
Tidskriftsartikel (refereegranskat)abstract
- Microbial carbon use efficiency (CUE) and nitrogen use efficiency (NUE) are key parameters determining the fate of C and N in soils. Atmospheric N deposition has been found to heavily impact multiple soil C and N transformations, but we lack understanding of the responses of CUE and NUE to N deposition, and it remains uncertain whether responses may be mediated by topography. Here, a N addition experiment with three treatment levels (0, 50 and 100 kg N ha−1 yr−1) was conducted in the valley and on the slope of a subtropical karst forest. Nitrogen addition increased microbial CUE and NUE at both topographic positions, but the underlying mechanisms differed. In the valley, the increase in CUE was associated with an increase in soil fungal richness:biomass and lower litter C:N, whereas on the slope, the response was linked with a reduced ratio of dissolved soil organic C (DOC) to available phosphorus (AVP) which reduced respiration, and increased root N:P stoichiometry. In the valley, the increase in NUE was explained by stimulated microbial N growth relative to gross N mineralization, which was associated with increased ratios of soil total dissolved N:AVP and fungal richness:biomass. In contrast, on the slope, the increase in NUE was attributed to reduced gross N mineralization, linked to increased DOC:AVP. Overall, our results highlight how topography-driven soil substrate availability and microbial properties can regulate microbial CUE and NUE.
|
|
| 28. |
- Yuan, Mingyue, et al.
(författare)
-
Limiting resources for soil microbial growth in climate change simulation treatments in the Subarctic
- 2024
-
Ingår i: Ecology. - 0012-9658. ; 105:1
-
Tidskriftsartikel (refereegranskat)abstract
- The microbial use of resources to sustain life and reproduce influences for example, decomposition and plant nutrient provisioning. The study of “limiting factors” has shed light on the interaction between plants and their environment. Here, we investigated whether carbon (C), nitrogen (N), or phosphorus (P) was limiting for soil microorganisms in a subarctic tundra heath, and how changes in resource availability associated with climate change affected this. We studied samples in which changes in resource availability due to climate warming were simulated by the addition of birch litter and/or inorganic N. To these soils, we supplied factorial C (as glucose), N (as NH4NO3), and P (as KH2PO4/K2HPO4) additions (“limiting factor assays,” LFA), to determine the limiting factors. The combination of C and P induced large growth responses in all soils and, combined with a systematic tendency for growth increases by C, this suggested that total microbial growth was primarily limited by C and secondarily by P. The C limitation was alleviated by the field litter treatment and strengthened by N fertilization. The microbial growth response to the LFA-C and LFA-P addition was strongest in the field-treatment that combined litter and N addition. We also found that bacteria were closer to P limitation than fungi. Our results suggest that, under a climate change scenario, increased C availability resulting from Arctic greening, treeline advance, and shrubification will reduce the microbial C limitation, while increased N availability resulting from warming will intensify the microbial C limitation. Our results also suggest that the synchronous increase of both C and N availability might lead to a progressive P limitation of microbial growth, primarily driven by bacteria being closer to P limitation. These shifts in microbial resource limitation might lead to a microbial targeting of the limiting element from organic matter, and also trigger competition for nutrients between plants and microorganisms, thus modulating the productivity of the ecosystem.
|
|
| 29. |
- Yuan, Mingyue, et al.
(författare)
-
Will a legacy of enhanced resource availability accelerate the soil microbial response to future climate change?
- 2022
-
Ingår i: Soil Biology and Biochemistry. - : Elsevier BV. - 0038-0717. ; 165
-
Tidskriftsartikel (refereegranskat)abstract
- Soil microorganisms play an integral role in the regulation of carbon (C) cycling. In high-latitude ecosystems, climate warming is leading to higher plant productivity, shrub expansion and faster nutrient cycling; all of which increase resource availability to soil microorganisms. To understand how a legacy of enhanced resource availability affects the functional traits of microbial communities, and their feedbacks to further environment change, we collected soils from a field-experiment in a subarctic dry heath, where the consequences of climate warming were simulated by adding birch litter or inorganic N as either chronic additions during three years or as a single extreme addition. Soils were then re-exposed to the same resource or a modified resource environment in the laboratory and were monitored for 2 months. We hypothesized that a history of resource input would affect microbial functional profiles, which could result in two possibilities: 1) soil microbes exposed to a historical resource input would perform better when presented with the same resource, because the communities would be specialized to use the added resource, or 2) soil microbes would perform better when presented with a new resource, because the added resource would relieve the nutrient limitation induced by the previous resource input. We also hypothesized that with the same resource, a chronic and long-term input (i.e., a press disturbance) would select for K-strategists (i.e., fungi), while a sudden and large input (i.e., a pulse disturbance) would select for r-strategists (i.e., bacteria). We observed that bacteria in soils exposed to a history of N input showed a stronger growth response to new litter addition, while fungi in soils with a history of litter input showed a stronger growth response to both new litter and new N additions. When presented with new litter, the increase of fungal growth in soil from the extreme litter field-treatment was lower than in the chronic litter field-treatment, demonstrating that a pulse disturbance could weaken the stimulation of fungal growth. When presented with new litter, the increases of bacterial growth did not differ between the chronic N field-treatment and the extreme N field-treatment, suggesting that bacterial responses were not favoured by a press disturbance. We conclude that the enhanced resource availabilities expected in warming arctic soils will generate a positive microbial feedback to climate change.
|
|
