Limiting factors for soil microbial growth in climate change simulation treatments in the Subarctic

2020 ◽  
Author(s):  
Mingyue Yuan ◽  
Meng Na ◽  
Lettice Hicks ◽  
Johannes Rousk
Keyword(s):  
Climate Change ◽  
Bacterial Growth ◽  
N Mineralization ◽  
Microbial Growth ◽  
Fungal Growth ◽  
Plant Productivity ◽  
Limiting Factors ◽  
Limiting Factor ◽  
Soil Microbial ◽  
C Limitation

<p>Soil microorganisms play a crucial role in the regulation of nutrient cycling, and are thought to be either limited by low nutrient availability, or by labile carbon supplied by nutrient limited plant productivity. It remains unknown how climate change will affect the rate-limiting resources for decomposer microorganisms in the Arctic, rendering feedbacks to climate change highly uncertain. In this study, we focused on the responses of soil microbial community processes to simulated climate change in a subarctic tundra system in Abisko, Sweden, using litter additions to represent arctic greening and inorganic N fertilizer additions to represent a faster nutrient cycling due to arctic warming. We hypothesized that 1) the plant community would shift and plant productivity would increase in response to N fertilization, 2) microbial process rates would be stimulated by both plant litter and fertilizer additions, and 3) the growth limiting factors for decomposer microorganisms would shift toward nutrient limitation in response to higher plant material input, and towards C-limitation in response to N-fertilizer additions.</p><p> </p><p>We assessed the responses of the plant community composition (vegetation surveys) and productivity (NDVI), microbial processes (bacterial growth, fungal growth, C and N mineralization) along with an assessment of the limiting factors for fungal and bacterial growth. The growth-limiting factors were determined by full factorial additions of nutrients (C, N, P), with measurement of microbial growth and respiration following brief incubations in the laboratory. We found that plant productivity was ca. 15% higher in the N fertilized plots. However, field-treatments had limited effects on bacterial growth, fungal growth and the fungal-to-bacterial growth ratio in soils. Field-treatments also had no significant effect on the rate of soil C mineralization, but did affect rates of gross N mineralization. Gross N mineralization was twice as high in N fertilized plots compared to the control. In control soils, bacterial growth increased 4-fold in response to C, indicating that bacterial growth was C limited. Bacterial growth remained C limited in soils from all field-treatments. However, in the N fertilized soils, the C limitation was 1.8-times greater than the control, while in soils with litter input, the C limitation was 0.83-times the control, suggesting that the N fertilized soils were moving towards stronger C-limitation and the litter addition soils were becoming less C-limited. The limiting factor for fungal growth was difficult to resolve. We presumed that the competition of fungi with bacteria decreased our resolution to detect the limiting factor. Therefore, factorial nutrient addition were combined with low amount of bacterial specific inhibitors.</p>

How does simulated climate change affect the susceptibility of SOM to priming by LMWOS in the Subarctic?

2021 ◽  
Author(s):  
Meng Na ◽  
Mingyue Yuan ◽  
Lettice Hicks ◽  
Johannes Rousk
Keyword(s):  
Climate Change ◽  
Plant Communities ◽  
N Mineralization ◽  
Fungal Growth ◽  
N Fertilization ◽  
C Mineralization ◽  
Soil C ◽  
Gross N Mineralization ◽  
Simulated Climate ◽  
Simulated Climate Change

<p>Soil organic matter (SOM) stabilization plays an important role in the long-term storage of carbon (C). However, many ecosystems are undergoing climate change, which will change the soil C balance via altered plant communities and productivity that change C inputs, and altered C losses via changes in SOM decomposition. The ongoing change of aboveground plant communities in the Subarctic (“greening”) will increase rhizosphere inputs containing low molecular weight organic substances (LMWOS), which will likely affect C-starved microbial decomposers and their subsequent contribution to SOM mineralization (priming effect).In the present study, we simulated the effects of climate change with N fertilization (simulating warming enhanced nutrient cycling) and litter additions (simulating arctic greening) in Abisko, Sweden. The 6 sampled field-treatments included a full factorial combination of 3-years of chronic N addition and litter additions, as well as, a single year of extreme climate change (3x N fertilizer or litter additions in one growth season). We found that N treatments changed plant community composition and productivityand that the associated shift in belowground LMWOS induced shifts in the soil microbial community. In the chronic N fertilization treatments, plant productivity, and therefore belowground LMWOS input, increased. This coincided with a tendency for more bacterial dominated decomposition (lower fungi/bacterial growth ratio). However, N treatments had no effect on soil C mineralization, but increased gross N mineralization.</p><p>These responses in belowground communities and processes driven by rhizosphere input prompted the next question: how does simulated climate change affect the susceptibility of SOM to priming by LMWOS? To assess this question and determine the microbial mechanisms underpinning priming of SOM mineralization, we added a factorial set of additions including <sup>13</sup>C-glucose with and without mineral N, and <sup>13</sup>C-alanine semi-continuously (every 48 hours) to simulate the effect of rhizosphere LMWOS on SOM mineralization and microbial activity. We incubated these samples for 2 weeks and assessed the priming of soil C and gross N mineralization, bacterial and fungal growth rates, PLFAs, enzyme activities, and microbial C use efficiency (CUE). We found that alanine addition primed soil C mineralization by 34%, which was higher than soil C priming induced by glucose and glucose with N. Furthermore, glucose primed fungal growth, whereas the alanine primed bacterial growth, but microbial PLFAs did not respond to either treatment. The C enzyme acquisition activity was higher than N enzyme acquisition activity in all the treatments, while P enzyme acquisition activity was higher than C for all the treatments. Surprisingly, this suggested a chronic microbial limitation by P, which was unaffected by field and lab treatments. LMWOS additions generally reduced microbial CUE. Responses of microbial mineralization of N from SOM to LMWOS suggested a directed microbial effort towards targeting resources that limited bacterial or fungal growth, suggesting that microbial SOM-use shifted to N-rich components (selective microbial “N-mining”), in contrast with enzyme results. Surprisingly, alanine primed the highest N mineralization compared other additions indicating that there was strong N-mining even if N was sufficient.</p>

scholarly journals Microbial growth and carbon use efficiency show seasonal responses in a multifactorial climate change experiment

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Eva Simon ◽  
Alberto Canarini ◽  
Victoria Martin ◽  
Joana Séneca ◽  
Theresa Böckle ◽  
...  
Keyword(s):  
Climate Change ◽  
Microbial Growth ◽  
Future Research ◽  
Global Changes ◽  
Summer Drought ◽  
Microbial Physiology ◽  
Soil Microbial ◽  
Carbon Use Efficiency ◽  
Use Efficiency ◽  
Climate Change Drivers

Abstract Microbial growth and carbon use efficiency (CUE) are central to the global carbon cycle, as microbial remains form soil organic matter. We investigated how future global changes may affect soil microbial growth, respiration, and CUE. We aimed to elucidate the soil microbial response to multiple climate change drivers across the growing season and whether effects of multiple global change drivers on soil microbial physiology are additive or interactive. We measured soil microbial growth, CUE, and respiration at three time points in a field experiment combining three levels of temperature and atmospheric CO2, and a summer drought. Here we show that climate change-driven effects on soil microbial physiology are interactive and season-specific, while the coupled response of growth and respiration lead to stable microbial CUE (average CUE = 0.39). These results suggest that future research should focus on microbial growth across different seasons to understand and predict effects of global changes on soil carbon dynamics.

Effects of simulated drought and warming on microbial responses to drying and rewetting in contrasting land-uses

2020 ◽  
Author(s):  
Ainara Leizeaga ◽  
Lettice C. Hicks ◽  
Albert C. Brangarí ◽  
Menale Wondie ◽  
Hans Sandén ◽  
...  
Keyword(s):  
Microbial Community ◽  
Microbial Communities ◽  
Bacterial Growth ◽  
Forest Soils ◽  
Fungal Growth ◽  
Land Uses ◽  
Soil Microbial ◽  
Drying And Rewetting ◽  
Microbial Responses ◽  
Simulated Drought

<p>Climate change will increase temperatures and the frequency and intensity of extreme drought and rainfall events. When a drought period is followed by a rainfall event, there is a big CO<sub>2</sub> pulse from soil to the atmosphere which is regulated by soil microorganisms. In the present study, we set out to investigate how simulated drought and warming affects the soil microbial responses to drying and rewetting (DRW), and how those responses will interact with the level of land degradation. Previous work has shown that exposure DRW cycles in the laboratory and in the field can induce changes in the microbial community such that it resumes growth rates faster after a DRW cycle. In addition, it has been observed that a history of drought in both a humid heathland ecosystem in Northern Europe and in semi-arid grasslands in Texas can select for microorganisms with a higher carbon use efficiency (CUE) during DRW. In this study we tested if these observations could be extended to subtropical environments.</p><p>Rain shelters and open top chambers (OTC) were installed in Northwestern Ethiopia in two contrasting land-uses; a degraded cropland and a pristine forest. Soils were sampled (>1-year field treatments) and exposed to a DRW cycle in the laboratory. Microbial growth and respiration responses were followed with high temporal resolution over 3 weeks. We hypothesized that (i) simulated drought would result in more resilient and efficient microbial communities to DRW, while (ii) simulated warming should leave microbial community traits linked to moisture unchanged. In addition, (iii) we hypothesized that microbial communities would recover growth rates faster in the cropland since that ecosystem is more prone to DRW events.</p><p>Microbial responses in both land-uses and treatments universally showed a highly resilient type of community response with both bacterial growth and fungal growth increasing immediately upon rewetting, linked with the expected respiration pulse. The field treatments simulating drought and warming did not affect the already high resilience of soil microbial communities to DRW cycles. However, differences between the rates of recovery between fungi and bacteria were observed. Fungal growth recovered faster than bacterial growth, peaking c. 15 h in comparison to bacteria that peaked at c.20h after rewetting. Simulated drought reduced the microbial CUE during rewetting in croplands without affecting the forest soils. The CUE was also elevated in the warming treatments in both land-uses, and generally higher in croplands than in forest soils. Taken together, the responses in microbial CUE during the rewetting of dry soils were likely linked to either (i) differences in resource availability which were higher in warming treatments and in croplands compared to forests, or (ii) selection of  more efficient microbial communities due to a higher exposure to DRW events driven by the higher temperatures in the cropland, and increased evapotranspiration in the warming treatments.</p><div> <div> <div> </div> </div> </div>

Is microbial resilience to drying-rewetting driven by selection for quick colonizers?

2020 ◽  
Author(s):  
Lettice Hicks ◽  
Simon Lin ◽  
Johannes Rousk
Keyword(s):  
Bacterial Growth ◽  
Growth Response ◽  
Microbial Growth ◽  
Fungal Growth ◽  
Growth Responses ◽  
Labile C ◽  
Lag Period ◽  
Selection For ◽  
Resilient Response ◽  
Pre Treatment

<p>Climate change is exposing terrestrial ecosystems to more extreme drought and rainfall events, resulting in an increased frequency and intensity of drying-rewetting (D/RW) events in soils. Rewetting a dry soil induces enormous dynamics in both microbial growth and biogeochemistry, including a large pulse of CO<sub>2 </sub>release to the atmosphere. Upon D/RW, two different microbial growth responses have been identified; a more resilient response where bacteria start growing immediately with a quick recovery after rewetting and a less resilient response where there is a lag-period of up to 30 hours of near-zero growth before bacteria start to grow. The resilience of microbial growth following D/RW has important implications for the ecosystem C budget, since an extended lag-period of no growth during a time of high CO<sub>2 </sub>release will result in net soil C loss. In natural systems, it has been found that a legacy of drought led to a more resilient bacterial growth response upon rewetting, with a reduced lag-period before the onset of growth. Exposing soils to repeated cycles of D/RW in the laboratory has also been shown to shift bacterial growth responses to a more resilient type. We hypothesised that this shift in response is explained by selection for a microbial community which is quick at colonizing the labile C resources made available upon D/RW.  </p><p>In order to test our hypothesis, we pre-treated soils by exposing them to either (i) three cycles of D/RW, (ii) three pulses of glucose addition or (iii) three pulses of litter addition. The substrate additions were used to simulate the labile C release in soils during D/RW, thereby enabling us to investigate if the colonization of new substrate is the causal mechanism explaining the observed shift in bacterial resilience in soils with a history of D/RW. The pre-treated soils – along with an unamended control soil – were then exposed to the same D/RW event, with bacterial growth, fungal growth and respiration responses measured at high temporal resolution over 4 days. As previously reported, exposing the soil to a series of D/RW events resulted in a more resilient bacterial growth response, with the lag-period reduced from ca. 30 hours to an immediate initiation of growth. Pre-treating the soils with glucose reduced the lag-period before the onset of bacterial growth by ca. 50% whereas pre-treatment with litter induced only a marginally (< 10%) more resilient bacterial growth response to D/RW. Interestingly, pre-treatment of the soils with glucose and litter both induced a more resilient fungal growth response, with the responses resembling the shift in fungal resilience induced by exposing the soils to repeated cycles of D/RW. Overall, our results show that selection for quick colonizers partly explains the shift to more resilient microbial growth in soils exposed to repeated D/RW events, but further investigation is required to identify additional factors contributing to the shift in resilience.</p>

Microbial temperature adaptation across a European gradient

2021 ◽  
Author(s):  
Carla Cruz Paredes ◽  
Daniel Tajmel ◽  
Johannes Rousk
Keyword(s):  
Microbial Communities ◽  
Community Composition ◽  
Bacterial Growth ◽  
Microbial Community Composition ◽  
Thermal Adaptation ◽  
Soil Microbial Communities ◽  
Fungal Growth ◽  
Fungal Communities ◽  
Soil Microbial

<p>Temperature is one of the most important environmental factors controlling both microbial growth and respiration. Warmer temperatures accelerate the rate at which microorganisms respire. Therefore, it is expected that climate warming will induce losses of carbon to the atmosphere through soil microbial respiration, representing a positive feedback to climate warming. However, there are multiple gaps in our understanding on responses of microorganisms to warming. For instance, long-term experiments have shown that the increase in soil respiration found in warming experiments diminishes with time, recovering to ambient values. This suggests that soil C losses might not be as extensive as previously suggested. This can be due to substrate depletion or shifts in the microbial community composition that led to thermal adaptation. To test thermal adaptation of soil microbial communities to their climate, variation along latitudinal gradients is a useful context. Such geographical gradients have long-term and large temperature differences thus patterns in thermal adaptation should have had sufficient time for ecological and evolutionary processes to act, allowing us to test if soil microbial communities have adapted to thermal regimes.</p><p>We investigated a latitudinal gradient across Europe with 76 sites that spanned a gradient of decadal mean annual temperature (MAT) from -3.1 to 18.3°C. We investigated if respiration, bacterial and fungal growth responses were adapted to long-term temperature differences in this gradient. We did this by estimating the temperature dependences of bacterial growth, fungal growth and respiration. We determined the temperature sensitivity (Q<sub>10</sub>), the minimum temperature (T<sub>min</sub>) for growth and the optimum temperature (T<sub>opt</sub>) for growth. These metrics were then correlated to MAT. Additionally, we sequenced bacterial (16S) and fungal (ITS) amplicons from the different sites to also assess variance in community composition and structure. We hypothesized that microbes should be adapted to their historical temperature; microbial communities in warmer environments will be warm-shifted and vice versa.</p><p>We could effectively represent temperature relationships for bacterial growth, fungal growth, and respiration for all soils. As expected, temperature relationships correlated with the environmental temperature of the site, such that higher temperatures resulted in microbial communities with warm-adapted growth and respiration. This could be seen as a strong positive correlation between T<sub>min</sub> values and environmental temperatures which range from -14 to -5°C for bacteria, -11.5 to -4°C for fungi and -8 to -2°C for respiration. We found that MAT explains the microbial communities’ temperature dependencies for bacterial growth and respiration, but not for fungal growth. With 1°C rise in MAT, T<sub>min</sub> increased 0.17°C for bacterial growth, while T<sub>min</sub> for respiration increased by 0.11. Similarly, bacterial and fungal communities’ composition were correlated with MAT (r<sup>2</sup>=0.38; r<sup>2</sup>=0.62), and T<sub>min</sub> (r<sup>2</sup>=0.16; r<sup>2</sup>=0.21). These findings suggest that thermal adaptation occurs in processes such as bacterial growth and respiration, probably due to shifts in the microbial community composition. However, fungal growth seems to be less sensitive to changes in temperature, even though fungal communities’ composition was correlated with MAT.</p>

scholarly journals Forest defoliator pests alter carbon and nitrogen cycles

2016 ◽  
Vol 3 (10) ◽  
pp. 160361 ◽  
Author(s):  
Anne l-M-Arnold ◽  
Maren Grüning ◽  
Judy Simon ◽  
Annett-Barbara Reinhardt ◽  
Norbert Lamersdorf ◽  
...  
Keyword(s):  
Climate Change ◽  
Leaf Litter ◽  
Soil Microbial Activity ◽  
Quercus Petraea ◽  
Oak Forests ◽  
Operophtera Brumata ◽  
Winter Moth ◽  
Carbon And Nitrogen ◽  
Soil Microbial ◽  
C And N

Climate change may foster pest epidemics in forests, and thereby the fluxes of elements that are indicators of ecosystem functioning. We examined compounds of carbon (C) and nitrogen (N) in insect faeces, leaf litter, throughfall and analysed the soils of deciduous oak forests ( Quercus petraea  L.) that were heavily infested by the leaf herbivores winter moth ( Operophtera brumata  L.) and mottled umber ( Erannis defoliaria  L.). In infested forests, total net canopy-to-soil fluxes of C and N deriving from insect faeces, leaf litter and throughfall were 30- and 18-fold higher compared with uninfested oak forests, with 4333 kg C ha −1 and 319 kg N ha −1 , respectively, during a pest outbreak over 3 years. In infested forests, C and N levels in soil solutions were enhanced and C/N ratios in humus layers were reduced indicating an extended canopy-to-soil element pathway compared with the non-infested forests. In a microcosm incubation experiment, soil treatments with insect faeces showed 16-fold higher fluxes of carbon dioxide and 10-fold higher fluxes of dissolved organic carbon compared with soil treatments without added insect faeces (control). Thus, the deposition of high rates of nitrogen and rapidly decomposable carbon compounds in the course of forest pest epidemics appears to stimulate soil microbial activity (i.e. heterotrophic respiration), and therefore, may represent an important mechanism by which climate change can initiate a carbon cycle feedback.

scholarly journals Temperate Fruit Trees under Climate Change: Challenges for Dormancy and Chilling Requirements in Warm Winter Regions

Horticulturae ◽  
2021 ◽  
Vol 7 (4) ◽  
pp. 86
Author(s):  
Abdel-Moety Salama ◽  
Ahmed Ezzat ◽  
Hassan El-Ramady ◽  
Shamel M. Alam-Eldein ◽  
Sameh Okba ◽  
...  
Keyword(s):  
Climate Change ◽  
Organic Compounds ◽  
Fruit Trees ◽  
Fruit Tree ◽  
Limiting Factor ◽  
Dormancy Breaking ◽  
Warm Winter ◽  
Winter Chill ◽  
Chilling Requirements ◽  
The Tropics

Adequate chill is of great importance for successful production of deciduous fruit trees. However, temperate fruit trees grown under tropical and subtropical regions may face insufficient winter chill, which has a crucial role in dormancy and productivity. The objective of this review is to discuss the challenges for dormancy and chilling requirements of temperate fruit trees, especially in warm winter regions, under climate change conditions. After defining climate change and dormancy, the effects of climate change on various parameters of temperate fruit trees are described. Then, dormancy breaking chemicals and organic compounds, as well as some aspects of the mechanism of dormancy breaking, are demonstrated. After this, the relationships between dormancy and chilling requirements are delineated and challenging aspects of chilling requirements in climate change conditions and in warm winter environments are demonstrated. Experts have sought to develop models for estimating chilling requirements and dormancy breaking in order to improve the adaption of temperate fruit trees under tropical and subtropical environments. Some of these models and their uses are described in the final section of this review. In conclusion, global warming has led to chill deficit during winter, which may become a limiting factor in the near future for the growth of temperate fruit trees in the tropics and subtropics. With the increasing rate of climate change, improvements in some managing tools (e.g., discovering new, more effective dormancy breaking organic compounds; breeding new, climate-smart cultivars in order to solve problems associated with dormancy and chilling requirements; and improving dormancy and chilling forecasting models) have the potential to solve the challenges of dormancy and chilling requirements for temperate fruit tree production in warm winter fruit tree growing regions.

scholarly journals Climate change alters temporal dynamics of alpine soil microbial functioning and biogeochemical cycling via earlier snowmelt

2021 ◽  
Author(s):  
Arthur A. D. Broadbent ◽  
Helen S. K. Snell ◽  
Antonios Michas ◽  
William J. Pritchard ◽  
Lindsay Newbold ◽  
...  
Keyword(s):  
Climate Change ◽  
Temporal Dynamics ◽  
Biogeochemical Cycling ◽  
Soil Microbial ◽  
Alpine Soil

scholarly journals Historical climate controls soil respiration responses to current soil moisture

2017 ◽  
Vol 114 (24) ◽  
pp. 6322-6327 ◽  
Author(s):  
Christine V. Hawkes ◽  
Bonnie G. Waring ◽  
Jennifer D. Rocca ◽  
Stephanie N. Kivlin
Keyword(s):  
Climate Change ◽  
Soil Moisture ◽  
Soil Respiration ◽  
Carbon Cycling ◽  
Large Scale ◽  
Microbial Respiration ◽  
Rainfall Gradient ◽  
Soil Microbial ◽  
Historical Climate ◽  
Moisture Dependence

Ecosystem carbon losses from soil microbial respiration are a key component of global carbon cycling, resulting in the transfer of 40–70 Pg carbon from soil to the atmosphere each year. Because these microbial processes can feed back to climate change, understanding respiration responses to environmental factors is necessary for improved projections. We focus on respiration responses to soil moisture, which remain unresolved in ecosystem models. A common assumption of large-scale models is that soil microorganisms respond to moisture in the same way, regardless of location or climate. Here, we show that soil respiration is constrained by historical climate. We find that historical rainfall controls both the moisture dependence and sensitivity of respiration. Moisture sensitivity, defined as the slope of respiration vs. moisture, increased fourfold across a 480-mm rainfall gradient, resulting in twofold greater carbon loss on average in historically wetter soils compared with historically drier soils. The respiration–moisture relationship was resistant to environmental change in field common gardens and field rainfall manipulations, supporting a persistent effect of historical climate on microbial respiration. Based on these results, predicting future carbon cycling with climate change will require an understanding of the spatial variation and temporal lags in microbial responses created by historical rainfall.

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