scholarly journals Labile carbon limits late winter microbial activity near Arctic treeline

2020 ◽  
Author(s):  
Patrick F. Sullivan ◽  
Madeline C. Stokes ◽  
Cameron K. McMillan ◽  
Michael N. Weintraub
Keyword(s):  
Nutrient Cycling ◽  
Microbial Activity ◽  
Microbial Respiration ◽  
Soil Microbial Communities ◽  
The Arctic ◽  
Late Winter ◽  
Soil Microbial ◽  
Arctic Soils ◽  
Labile C ◽  
Soil Temperatures

It is well established that soil microbial communities remain active during much of the Arctic winter, despite soil temperatures that are often well below −10°C1. Overwinter microbial activity has important effects on global carbon (C) budgets2, nutrient cycling and vegetation community composition3. Microbial respiration is highly temperature sensitive in frozen soils, as liquid water and solute availability decrease rapidly with declining temperature4. Thus, temperature is considered the ultimate control on overwinter soil microbial activity in the Arctic. Warmer winter soils are thought to yield greater microbial respiration of available C, greater overwinter CO2 efflux and a flush of nutrients that could be available for plant uptake at thaw3. Rising air temperature, combined with changes in timing and/or depth of snowpack development, is leading to warmer Arctic winter soils5. Using observational and experimental approaches in the field and in the laboratory, we demonstrate that persistently warm winter soils can lead to labile C starvation of the microbial community and reduced respiration rates, despite the high C content of most arctic soils. If Arctic winter soil temperatures continue to rise, microbial C limitation will reduce cold season CO2 emissions and alter soil nutrient cycling, if not countered by greater labile C inputs.

Effect of Drought and Recovery on Grazing Animal, Microbial, and Fungal Response in a Diverse Multi-Crop Rotation

2020 ◽  
Author(s):  
Douglas Landblom ◽  
Songul Senturklu
Keyword(s):  
Nutrient Cycling ◽  
Beef Cattle ◽  
Microbial Activity ◽  
Crop Rotation ◽  
Cover Crop ◽  
Crop Production ◽  
Microbial Respiration ◽  
Soil Nutrient ◽  
Soil Microbial ◽  
Animal Grazing

<p>Beef cattle grazing, soil microbial respiration, and Rhizobia spp. populations serve important roles in soil nutrient cycling and during periods of drought, when abnormal precipitation declines, forage production for animal grazing and performance are negatively impacted. Soil nutrient availability is essential for adequate crop production and extended drought reduces soil microbial activity and therefore nutrient cycling. During the 2017 growing season between April and October in the northern Great Plains region of the USA, effective precipitation for crop production and animal grazing was severely reduced due an exceptional drought as classified by the US Drought Monitor. At the NDSU – Dickinson Research Extension Center, Dickinson, North Dakota, USA, a long-term integrated system that includes yearling steer grazing within a diverse multi-crop rotation (spring wheat, cover crop, corn, pea-barley intercrop, and sunflower). Within the rotation of cash and forage crops, beef cattle graze the pea-barley, corn, and cover crop (13-specie) within the rotation and is being utilized to monitor the effects of animal, microbial and fungal activity over time and space in the crop and animal production system. Nitrogen fertilizer has been replaced in the system by soil microbial and fungal activity (Potential Mineralizable Nitrogen: 8.4 mg N/kg) such that for each 1% increase in SOM there is a corresponding increase of 18.8 kg of potential nitrogen mineralized per ha. Animal grazing days are severely reduced when precipitation is inadequate for soil microbial respiration to occur. What is even more concerning, when relying on microbial activity to supply plant nutrients, is recovery time for microbial activity to fully recover from exceptional drought as was the case in this research project. Compared to the 2016 crop production year that preceded the 2017 drought, cover crop (13-specie), pea-barley, and corn yields were reduced 86, 33, and 64% during the 2017 drought. This decline in crop production reduced the number of days of grazing by an average 50% and average daily gains were also reduced. Steer average daily gains were 1.05 0.95, and 0.83 kg/steer/day in 2017 when grazing pea-barley, corn, and cover crop, respectively. For this research that relies on soil derived plant nutrients soil analysis for microbial and Rhizobia spp. biomass began recovery in 2018 and continued into 2019 as evidenced by large percentage increases in organism biomass; however, complete production recovery did not occur by the end of the 2019 grazing season in which days of grazing were reduced compared to the 2016 grazing season. Biological animal, crop, microbial, fungal, and nutrient replacement recovery will be presented in the poster.</p>

Will the temperature sensitivity of Arctic soil bacterial communities alter under warmed soil conditions?

2021 ◽  
Author(s):  
Ruud Rijkers ◽  
Johannes Rousk ◽  
Rien Aerts ◽  
James Taylor Weedon
Keyword(s):  
Community Structure ◽  
Soil Respiration ◽  
Bacterial Communities ◽  
Soil Microbial Communities ◽  
Climate Feedback ◽  
The Arctic ◽  
Soil Conditions ◽  
Soil Microbial ◽  
Arctic Soils ◽  
Soil Bacterial

<p>Soil temperatures are rising in the Arctic and will likely increase soil microbial activity. The magnitude of subsequent carbon effluxes is difficult to predict but is critical for evaluating the strength of the soil carbon-climate feedback as climate change intensifies. Soil respiration in the Arctic has a relatively high sensitivity to temperature increases. This is hypothesized to be a consequence of physiological adaptation of soil microbial communities to low temperatures. A variety of experimental and gradient studies have suggested that the growth-temperature relationship of bacterial communities will adapt to soil warming.  It remains an open question whether this is driven by changes in community structure. In order to test this hypothesis, we collected 8 soils from the sub- to High Arctic and exposed them to a 0-30 ⁰C temperature gradient. We determined the temperature relationships and community composition of the resulting bacterial communities. To account for substrate depletion we sampled both after 100 days, as well as after a standardized amount of respiration. Temperature relationships were computed by fitting a square root model to leucine incorporation rates measured from 0-40 ⁰C. We will show the relationship between legacy effects of the soil thermal regime and the degree of temperature adaption and discuss whether the soil bacterial community structure is likely to influence soil respiration in Arctic soils under future climate conditions.</p>

Evaluating carbon dynamics and microbial activity in arctic soils under warmer temperatures

2008 ◽  
Vol 88 (1) ◽  
pp. 31-44 ◽  
Author(s):  
Maren Oelbermann ◽  
Michael English ◽  
Sherry L Schiff
Keyword(s):  
Microbial Activity ◽  
Soil Microorganisms ◽  
Microbial Respiration ◽  
Soil Microbial Activity ◽  
Phase 2 ◽  
Metabolic Diversity ◽  
Soil Horizons ◽  
Organic C ◽  
Soil Microbial ◽  
Arctic Soils

A large portion of carbon (C) is stored in the world’s soils, including those of peatlands, wetlands and permafrost. However, there is disagreement regarding the effects of climate change on the rate of organic matter decomposition in permafrost soils of the arctic. In this study it was hypothesized that soil exposed to a higher ambient temperature would have a greater flux of CO2 as well as a change in the metabolic diversity of culturable soil microorganisms. To evaluate this hypothesis we determined soil C dynamics, soil microbial respiration and activity, and 13C and 15N fractionation in laboratory incubations (at 14 and 21°C) for an organic-rich soil (Mesic Organic Cryosol) and a mineral soil (Turbic Cryosol) collected at the Daring Lake Research Station in Canada’s Northwest Territories. Soil organic C (SOC) and nitrogen (N) stocks (g m-2) and concentration (%) were significantly different (P < 0.05) between soil horizons for both soil types. Stable isotope analysis showed a significant enrichment in δ13C and δ15N with depth and a depletion in δ13C and δ15N with increasing SOC and N concentration. In laboratory incubations, microbial respiration showed three distinct phases of decomposition: a phase with a rapidly increasing rate of respiration (phase 1), a phase in which respiration reached a peak midway through the incubation (phase 2), and a phase in the latter part of the incubation in which respiration stabilized at a lower flux than that of the first phase (phase 3). Fluxes of CO2 were significantly greater at 21°C than at 14°C. The δ13C of the evolved CO2 became significantly enriched with time with the greatest enrichment occurring in phase 2 of the incubation. Soil microbial activity, as measured using Biolog EcoplatesTM, showed a significantly greater average well color development, richness, and Shannon index at 21°C; again the greatest change occurred in phase 2 of the incubation. Principal component analysis (PCA) of the Biolog data also showed a change in the distinct clustering of the soil microbial activity, showing that C sources from the soil were metabolized differently with time at 21 than at 14°C, and between soil horizons. Our results show that Canadian arctic soils contain large stores of C, which readily decompose, and that substantial increases in CO2 emissions and changes in the metabolic diversity of culturable soil microorganisms may occur when ambient temperatures increase from 14 to 21°C. Key words: CO2 flux, C fractionation, global warming, soil organic C and N, stable isotopes

scholarly journals Arctic riparian shrub expansion indicates a shift from streams gaining water to those that lose flow

2020 ◽  
Vol 1 (1) ◽  
Author(s):  
Anna K. Liljedahl ◽  
Ina Timling ◽  
Gerald V. Frost ◽  
Ronald P. Daanen
Keyword(s):  
Microbial Communities ◽  
Soil Microbial Communities ◽  
Late Summer ◽  
Field Measurements ◽  
The Arctic ◽  
Shrub Expansion ◽  
Riparian Ecosystems ◽  
Stream Length ◽  
Area Index ◽  
Soil Microbial

AbstractShrub expansion has been observed across the Arctic in recent decades along with warming air temperatures, but tundra shrub expansion has been most pronounced in protected landscape positions such as floodplains, streambanks, water tracks, and gullies. Here we show through field measurements and laboratory analyses how stream hydrology, permafrost, and soil microbial communities differed between streams in late summer with and without tall shrubs. Our goal was to assess the causes and consequences of tall shrub expansion in Arctic riparian ecosystems. Our results from Toolik Alaska, show greater canopy height and density, and distinctive plant and soil microbial communities along stream sections that lose water into unfrozen ground (talik) compared to gaining sections underlain by shallow permafrost. Leaf Area Index is linearly related to the change in streamflow per unit stream length, with the densest canopies coinciding with increasingly losing stream sections. Considering climate change and the circumpolar scale of riparian shrub expansion, we suggest that permafrost thaw and the resulting talik formation and shift in streamflow regime are occurring across the Low Arctic.

scholarly journals Increased microbial expression of organic nitrogen cycling genes in long-term warmed grassland soils

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Joana Séneca ◽  
Andrea Söllinger ◽  
Craig W. Herbold ◽  
Petra Pjevac ◽  
Judith Prommer ◽  
...  
Keyword(s):  
Nitrogen Cycling ◽  
Cell Walls ◽  
Organic Nitrogen ◽  
Soil Microbial Communities ◽  
Microbial Cell ◽  
Ambient Conditions ◽  
Soil Microbial ◽  
Soil Temperatures ◽  
Microbial Turnover

AbstractGlobal warming increases soil temperatures and promotes faster growth and turnover of soil microbial communities. As microbial cell walls contain a high proportion of organic nitrogen, a higher turnover rate of microbes should also be reflected in an accelerated organic nitrogen cycling in soil. We used a metatranscriptomics and metagenomics approach to demonstrate that the relative transcription level of genes encoding enzymes involved in the extracellular depolymerization of high-molecular-weight organic nitrogen was higher in medium-term (8 years) and long-term (>50 years) warmed soils than in ambient soils. This was mainly driven by increased levels of transcripts coding for enzymes involved in the degradation of microbial cell walls and proteins. Additionally, higher transcription levels for chitin, nucleic acid, and peptidoglycan degrading enzymes were found in long-term warmed soils. We conclude that an acceleration in microbial turnover under warming is coupled to higher investments in N acquisition enzymes, particularly those involved in the breakdown and recycling of microbial residues, in comparison with ambient conditions.

scholarly journals Soil microbial biomass, activity and community composition along altitudinal gradients in the High Arctic (Billefjorden, Svalbard)

2018 ◽  
Vol 15 (6) ◽  
pp. 1879-1894 ◽  
Author(s):  
Petr Kotas ◽  
Hana Šantrůčková ◽  
Josef Elster ◽  
Eva Kaštovská
Keyword(s):  
Community Structure ◽  
Microbial Biomass ◽  
High Arctic ◽  
The Arctic ◽  
Soil Parameters ◽  
Organic Carbon Content ◽  
Soil Microbial ◽  
Environmental Controls ◽  
Arctic Soils ◽  
Tundra Ecosystem

Abstract. The unique and fragile High Arctic ecosystems are vulnerable to global climate warming. The elucidation of factors driving microbial distribution and activity in arctic soils is essential for a comprehensive understanding of ecosystem functioning and its response to environmental change. The goals of this study were to investigate microbial biomass and activity, microbial community structure (MCS), and their environmental controls in soils along three elevational transects in the coastal mountains of Billefjorden, central Svalbard. Soils from four different altitudes (25, 275, 525 and 765 m above sea level) were analyzed for a suite of characteristics including temperature regimes, organic matter content, base cation availability, moisture, pH, potential respiration, and microbial biomass and community structure using phospholipid fatty acids (PLFAs). We observed significant spatial heterogeneity of edaphic properties among transects, resulting in transect-specific effects of altitude on most soil parameters. We did not observe any clear elevation pattern in microbial biomass, and microbial activity revealed contrasting elevational patterns between transects. We found relatively large horizontal variability in MCS (i.e., between sites of corresponding elevation in different transects), mainly due to differences in the composition of bacterial PLFAs, but also a systematic altitudinal shift in MCS related to different habitat preferences of fungi and bacteria, which resulted in high fungi-to-bacteria ratios at the most elevated sites. The biological soil crusts on these most elevated, unvegetated sites can host microbial assemblages of a size and activity comparable to those of the arctic tundra ecosystem. The key environmental factors determining horizontal and vertical changes in soil microbial properties were soil pH, organic carbon content, soil moisture and Mg2+ availability.

scholarly journals Is microbial activity in tropical forests limited by phosphorus availability? Evidence from a tropical forest in China

2019 ◽  
Author(s):  
Taiki Mori ◽  
Xiankai Lu ◽  
Cong Wang ◽  
Qinggong Mao ◽  
Senhao Wang ◽  
...  
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Tropical Forest ◽  
Microbial Activity ◽  
Tropical Forests ◽  
Microbial Respiration ◽  
P Fertilization ◽  
Soil Microbial ◽  
Prevailing Paradigm ◽  
P Addition

AbstractThe prevailing paradigm for soil microbial activity in tropical forests is that microbial activity is limited by phosphorus (P) availability. Thus, exogenous P addition should increase rates of organic matter decomposition. Studies have also confirmed that soil respiration is accelerated when P is added experimentally. However, we hypothesize that the increased rates of soil microbial respiration could be due to the release of organic material from the surface of soil minerals when P is added, because P is more successful at binding to soil particles than organic compounds. In this study, we demonstrate that P addition to soil is associated with significantly higher dissolved organic carbon (DOC) content in a tropical evergreen forest in southern China. Our results indicate that P fertilization stimulated soil respiration but suppressed litter decomposition. Results from a second sorption experiment revealed that the recovery ratio of added DOC in the soil of a plot fertilized with P for 9 years was larger than the ratio in the soil of a non-fertilized plot, although the difference was small. We also conducted a literature review on the effects of P fertilization on the decomposition rates of litter and soil organic matter at our study site. Previous studies have consistently reported that P addition led to higher response ratios of soil microbial respiration than litter decomposition. Therefore, experiments based on P addition cannot be used to test whether microbial activity is P-limited in tropical forest soils, because organic carbon desorption occurs when P is added. Our findings suggest that the prevailing paradigm on the relationship between P and microbial activity in tropical forest soils should be re-evaluated.

scholarly journals Biochar alleviates metal toxicity and improves microbial community functions in a soil co-contaminated with cadmium and lead

Biochar ◽  
2021 ◽  
Author(s):  
Nahid Azadi ◽  
Fayez Raiesi
Keyword(s):  
Heavy Metals ◽  
Low Temperature ◽  
Organic Carbon ◽  
Enzymatic Activity ◽  
Microbial Activity ◽  
Contaminated Soils ◽  
Metal Availability ◽  
Soil Microbial ◽  
Labile C ◽  
Cadmium And Lead

AbstractSoil amendment with biochar alleviates the toxic effects of heavy metals on microbial functions in single-metal contaminated soils. Yet, it is unclear how biochar application would improve microbial activity and enzymatic activity in soils co-polluted with toxic metals. The present research aimed at determining the response of microbial and biochemical attributes to addition of sugarcane bagasse biochar (SCB) in cadmium (Cd)-lead (Pb) co-contaminated soils. SCBs (400 and 600 °C) decreased the available concentrations of Cd and Pb, increased organic carbon (OC) and dissolved organic carbon (DOC) contents in soil. The decrease of metal availability was greater with 600 °C SCB than with 400 °C SCB, and metal immobilization was greater for Cd (16%) than for Pb (12%) in co-spiked soils amended with low-temperature SCB. Biochar application improved microbial activity and biomass, and enzymatic activity in the soils co-spiked with metals, but these positive impacts of SCB were less pronounced in the co-spiked soils than in the single-spiked soils. SCB decreased the adverse impacts of heavy metals on soil properties largely through the enhanced labile C for microbial assimilation and partly through the immobilization of metals. Redundancy analysis further confirmed that soil OC was overwhelmingly the dominant driver of changes in the properties and quality of contaminated soils amended with SCB. The promotion of soil microbial quality by the low-temperature SCB was greater than by high-temperature SCB, due to its higher labile C fraction. Our findings showed that SCB at lower temperatures could be applied to metal co-polluted soils to mitigate the combined effects of metal stresses on microbial and biochemical functions.

scholarly journals Temperature sensitivity of soil microbial communities: An application of macromolecular rate theory to microbial respiration

2016 ◽  
Vol 121 (6) ◽  
pp. 1420-1433 ◽  
Author(s):  
Charlotte J. Alster ◽  
Akihiro Koyama ◽  
Nels G. Johnson ◽  
Matthew D. Wallenstein ◽  
Joseph C. von Fischer
Keyword(s):  
Microbial Communities ◽  
Temperature Sensitivity ◽  
Microbial Respiration ◽  
Soil Microbial Communities ◽  
Rate Theory ◽  
Soil Microbial
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