scholarly journals Temperature sensitivity of SOM decomposition governed by aggregate protection and microbial communities

2019 ◽  
Vol 5 (7) ◽  
pp. eaau1218 ◽  
Author(s):  
Shuqi Qin ◽  
Leiyi Chen ◽  
Kai Fang ◽  
Qiwen Zhang ◽  
Jun Wang ◽  
...  
Keyword(s):  
Microbial Communities ◽  
Temperature Sensitivity ◽  
Temperature Response ◽  
Climate Feedback ◽  
Soil C ◽  
Active Pool ◽  
Pool Model ◽  
Som Decomposition

Temperature sensitivity (Q10) of soil organic matter (SOM) decomposition is a crucial parameter for predicting the fate of soil carbon (C) under global warming. However, our understanding of its regulatory mechanisms remains inadequate, which constrains its accurate parameterization in Earth system models and induces large uncertainties in predicting terrestrial C-climate feedback. Here, we conducted a long-term laboratory incubation combined with a two-pool model and manipulative experiments to examine potential mechanisms underlying the depth-associated Q10 variations in active and slow soil C pools. We found that lower microbial abundance and stronger aggregate protection were coexisting mechanisms underlying the lower Q10 in the subsoil. Of them, microbial communities were the main determinant of Q10 in the active pool, whereas aggregate protection exerted more important control in the slow pool. These results highlight the crucial role of soil C stabilization mechanisms in regulating temperature response of SOM decomposition, potentially attenuating the terrestrial C-climate feedback.

scholarly journals Quantifying and isolating stable soil organic carbon using long-term bare fallow experiments

2010 ◽  
Vol 7 (11) ◽  
pp. 3839-3850 ◽  
Author(s):  
P. Barré ◽  
T. Eglin ◽  
B. T. Christensen ◽  
P. Ciais ◽  
S. Houot ◽  
...  
Keyword(s):  
Simulation Models ◽  
Co2 Concentration ◽  
Turnover Time ◽  
Soil C ◽  
Climate Conditions ◽  
Stable Pool ◽  
Pool Model ◽  
Bare Fallow ◽  
The Stability

Abstract. The stability of soil organic matter (SOM) is a major source of uncertainty in predicting atmospheric CO2 concentration during the 21st century. Isolating the stable soil carbon (C) from other, more labile, C fractions in soil is of prime importance for calibrating soil C simulation models, and gaining insights into the mechanisms that lead to soil C stability. Long-term experiments with continuous bare fallow (vegetation-free) treatments in which the decay of soil C is monitored for decades after all inputs of C have stopped, provide a unique opportunity to assess the quantity of stable soil C. We analyzed data from six bare fallow experiments of long-duration (>30 yrs), covering a range of soil types and climate conditions, and sited at Askov (Denmark), Grignon and Versailles (France), Kursk (Russia), Rothamsted (UK), and Ultuna (Sweden). A conceptual three pool model dividing soil C into a labile pool (turnover time of a several years), an intermediate pool (turnover time of a several decades) and a stable pool (turnover time of a several centuries or more) fits well with the long term C decline observed in the bare fallow soils. The estimate of stable C ranged from 2.7 g C kg−1 at Rothamsted to 6.8 g C kg−1 at Grignon. The uncertainty associated with estimates of the stable pool was large due to the short duration of the fallow treatments relative to the turnover time of stable soil C. At Versailles, where there is least uncertainty associated with the determination of a stable pool, the soil contains predominantly stable C after 80 years of continuous bare fallow. Such a site represents a unique research platform for characterization of the nature of stable SOM and its vulnerability to global change.

Effect of forest soil warming on the rate and temperature sensitivity of microbial C and N processes in a temperate mountain forest

2020 ◽  
Author(s):  
Carolina Urbina Malo ◽  
Ye Tian ◽  
Chupei Shi ◽  
Shasha Zhang ◽  
Marilena Heitger ◽  
...  
Keyword(s):  
Forest Soil ◽  
Temperature Sensitivity ◽  
Enzyme Activities ◽  
Thermal Acclimation ◽  
Soil Warming ◽  
Soil C ◽  
Soil Microbial ◽  
C And N ◽  
N Acquisition

<p>Despite the intensified efforts to understand the impacts of climate change on forest soil C dynamics, few studies have addressed the long term effects of warming on microbially mediated soil C and nutrient processes. In the few long-term soil warming experiments the initial stimulation of soil C cycling diminished with time, due to thermal acclimation of the microbial community or due to depletion of labile soil C as the major substrate for heterotrophic soil microbes. Thermal acclimation can arise as a consequence of prolonged warming and is defined as the direct organism response to elevated temperature across annual to decadal time-scales which manifest as a physiological change of the soil microbial community. This mechanism is clearly different from apparent thermal acclimation, where the attenuated response of soil microbial processes to warming is due to the exhaustion of the labile soil C pool.</p><p>The Achenkirch experiment, situated in the Northern Limestone Alps, Austria (47°34’ 50’’ N; 11°38’ 21’’ E; 910 m a.s.l.) is a long term (>15 yrs) soil warming experiment that has provided key insights into the effects of global warming on the forest soil C cycle. At the Achenkirch site, we have observed a sustained positive response of heterotrophic soil respiration and of soil CO<sub>2</sub> efflux to warming after nine years (2013), making it an appropriate setting for testing hypotheses about continued or decreasing warming effects at decadal scales. We collected soil from six warmed and six control plots in October 2019, from 0-10 cm and 10-20 cm depth, and incubated them at three different temperatures: ambient, +4, and +10 °C. We measured potential soil enzyme activities with fluorimetric assays, gross rates of protein depolymerization, N mineralization, and nitrification with <sup>15</sup>N isotope pool dilution approaches, and microbial growth, respiration, and C use efficiency (CUE) based on the <sup>18</sup>O incorporation in DNA and gas analysis.  Our preliminary results show that potential enzyme activities of aminopeptidase, N-acetylglucosaminidase, b-glucosidase, and acid phosphatase were stimulated by decadal soil warming by 1.7- to 3.5-fold, measured at the same i.e. ambient temperature. In contrast, the temperature sensitivity (Q10) remained unaltered between warmed and control soils for all enzyme activities (Q10=1.63-2.28), except for aminopeptidase where we observed a decrease in Q10 by 25% in warmed topsoils (0-10 cm). Aminopeptidase also had the highest temperature-sensitivity (Q10=2.39), causing a decrease of the enzymatic C: N acquisition ratio with warming. These results indicate an increasing investment in microbial N acquisition with warming. We will follow these trends based on results on gross rates of soil C and N processes, allowing to delineate decadal soil warming effects on soil microbial biogeochemistry and to understand their effect on the cross-talk between organic C and N cycling in calcareous forest soils.</p>

scholarly journals Long-term reindeer grazing limits warming-induced increases in CO 2 released by tundra heath soil: potential role of soil C quality

2015 ◽  
Vol 10 (9) ◽  
pp. 094020 ◽  
Author(s):  
Maria Väisänen ◽  
Sofie Sjögersten ◽  
David Large ◽  
Trevor Drage ◽  
Sari Stark
Keyword(s):  
Potential Role ◽  
Soil C

scholarly journals On the Role of Radiative Processes in Stratosphere–Troposphere Coupling

2009 ◽  
Vol 22 (15) ◽  
pp. 4154-4161 ◽  
Author(s):  
Kevin M. Grise ◽  
David W. J. Thompson ◽  
Piers M. Forster
Keyword(s):  
Climate Change ◽  
Temperature Response ◽  
Longwave Radiation ◽  
Tropospheric Temperature ◽  
Radiative Processes ◽  
Ozone Trends ◽  
Radiation Induced ◽  
Polar Stratosphere

Abstract Climate change in the Southern Hemisphere (SH) polar stratosphere is associated with substantial changes in the atmospheric circulation that extend to the earth’s surface. The mechanisms that drive the changes in the SH troposphere are not fully understood, but most previous hypotheses have focused on the role of atmospheric dynamics rather than that of radiation. This study quantifies the radiative response of temperatures in the SH polar troposphere to the forcing from long-term temperature and ozone trends in the SH polar stratosphere. A novel methodology is employed that explicitly neglects changes in tropospheric dynamics and hence isolates the component of the tropospheric temperature response that is radiatively driven by the overlying stratospheric trends. The results reveal that both the amplitude and seasonality of the observed cooling of the middle and upper SH polar troposphere over the past few decades are consistent with a reduction in downwelling longwave radiation induced by cooling in the SH polar stratosphere. The results are compared with analogous calculations for trends in the Northern Hemisphere (NH) polar stratosphere. Both the observations and radiative calculations imply that the comparatively weak trends in the NH polar stratosphere have not played a central role in driving NH tropospheric climate change. Overall, the results suggest that radiative processes play a key role in coupling the large trends in SH polar stratospheric temperatures to tropospheric levels. The tropospheric radiative temperature response documented here could be important for triggering the changes in internal tropospheric dynamics associated with stratosphere–troposphere coupling.

Does long-term soil warming affect microbial element limitation? A test by short-term assays of microbial growth responses to labile C, N and P additions

2020 ◽  
Author(s):  
Chupei Shi ◽  
Carolina Urbina Malo ◽  
Ye Tian ◽  
Shasha Zhang ◽  
Marilena Heitger ◽  
...  
Keyword(s):  
Microbial Communities ◽  
Nutrient Limitation ◽  
Microbial Growth ◽  
Soil Samples ◽  
Growth Responses ◽  
Soil Warming ◽  
Soil C ◽  
Soil Microbial ◽  
Limiting Nutrients

<p>Human activities have caused global warming by 0.95 °C since the industrial revolution, and average temperatures in Austria have risen by almost 2 °C since 1880. Increased global mean temperatures have been reported to accelerate carbon (C) cycling, but also to promote nitrogen (N) and phosphorus (P) dynamics in terrestrial ecosystems. However, the extent of warming-induced increases in soil C, N and P processes can differ, causing an eventual uncoupling of biogeochemical C, N and P cycles, and leading to altered elemental imbalances between available plant and soil resources and soil microbial communities. The altered dynamics in soil C and nutrient availability caused by increased soil temperature could shift the growth-limiting element for soil microorganisms, with strong repercussions on the decomposition, mineralization and sequestration of organic C and nutrients. The latter relates to the conservative cycling of limiting elements while elements in excess are mineralized and released at greater rates by microbial communities.</p><p>Despite the many laboratory and in situ studies investigating factors that limit soil microbial activity, most of them explored nutrient addition effects on soil respiration or soil enzyme activities. A critical assessment, however, clearly indicated the inappropriateness of these measures to deduce growth-limiting nutrients for soil microbes. Similar to studies of plant nutrient limitation, unequivocal assessment of soil microbial element limitation can only be derived from the response of microbial growth to element amendments. To our knowledge this has not been performed on soils undergoing long-term soil warming.</p><p>In this study, we therefore investigated the effect of long-term soil warming on microbial nutrient limitation based on microbial growth measurements in a temperate calcareous forest soil. Soil samples were taken from two soil depths (0-10, 10-20 cm) in both control and heated plots in the Achenkirch soil warming project (>15 yrs soil warming by + 4 °C). Soil samples were pre-incubated at their corresponding field temperature after sieving and removal of visible roots. The soils were amended with different combinations of glucose-C, inorganic/organic N and inorganic/organic P in a full factorial design, the nutrients being dissolved in <sup>18</sup>O-water. After 24 hours of incubation, microbial growth was measured based on the <sup>18</sup>O incorporation into genomic DNA. Nutrient (co)limitation was determined by comparing microbial growth responses upon C and nutrient additions relative to unamended controls. Basal respiration was also measured based on the increase in headspace CO<sub>2</sub>, allowing to estimate microbial C use efficiency (CUE). The fate of C and nutrient amendments was finally traced by measurements of inorganic and organic extractable and microbial biomass C, N and P. This study will thereby provide key insights into potential shifts in limiting nutrients for microbial growth under long-term soil warming, and into concomitant effects on soil C and nutrient cycles.</p>

scholarly journals Changes in the temperature sensitivity of SOM decomposition with grassland succession: implications for soil C sequestration

2013 ◽  
Vol 3 (15) ◽  
pp. 5045-5054 ◽  
Author(s):  
He Nianpeng ◽  
Wang Ruomeng ◽  
Gao Yang ◽  
Dai Jingzhong ◽  
Wen Xuefa ◽  
...  
Keyword(s):  
Temperature Sensitivity ◽  
C Sequestration ◽  
Soil C ◽  
Soil C Sequestration ◽  
Som Decomposition

scholarly journals Nonnegligible role of warming-induced soil drying in regulating warming effect on soil respiration

2018 ◽  
Author(s):  
Enzai Du
Keyword(s):  
Soil Respiration ◽  
Annual Variation ◽  
Precipitation Anomaly ◽  
Soil Drying ◽  
Phase Pattern ◽  
Soil Warming ◽  
Soil C ◽  
C Dynamics

AbstractBased on results of a 26-year soil warming experiment (soil temperature being elevated by 5 °C) in a Harvard hardwood forest, Melillo et al. demonstrated a four-phase pattern of long-term warming effect on soil respiration, while the mechanisms were not fully elucidated because they neglected the indirect effect due to warming-induced soil drying. By showing a significant correlation between precipitation anomaly and inter-annual variation of warming effect on soil respiration, we suggest a nonnegligible role of warming-induced soil drying in regulating the long-term warming effect on soil respiration. Our analysis recommends further efforts to consider both the direct and indirect (i.e., warming-induced soil drying) warming effects to gain more in-depth understanding of the long-term soil C dynamics.

Integrated carbon-nitrogen-phosphorus cycling for sustainable agriculture – a knowledge gap and investigation of the role of phosphatase enzymes

2021 ◽  
Author(s):  
Victoria Janes-Bassett ◽  
Phil Haygarth ◽  
Martin Blackwell ◽  
Malika Mezeli ◽  
Gavin Stewart ◽  
...  
Keyword(s):  
Enzyme Activity ◽  
Crop Yields ◽  
Organic P ◽  
Experimental Conditions ◽  
P Deficiency ◽  
Soil C ◽  
P Addition ◽  
Phosphatase Enzyme

<p>Phosphorus is closely linked to other nutrient cycles, notably carbon and nitrogen, therefore, to understand potential risks to food production models are required that simulate integrated nutrient cycling over long timescales. The soil-plant system model N14CP meets these requirements and simulates both semi-natural and agricultural environments. N14CP has been validated both spatially and temporally across a range of long-term agricultural experimental sites comparing soil C, N and P, and crop yields, and in most instances performs well. However, under experimental conditions where N is applied in the absence of P, the model indicates exhaustion of P reserves and a decline in yields that is not observed at these sites, highlighting a gap in the model process representation. Potential sources of this ‘missing P’ such as enhanced atmospheric deposition, weathering and flexible plant stoichiometries were explored yet cannot account for this deficit. We hypothesise that access of organic P through other mechanisms not fully represented within the model, such as phosphatase enzymes, could be part of this explanation.</p><p>In order to test this, we conducted a meta-analysis of phosphatase enzyme activity in agricultural settings, comparing response to P sufficient and deficient conditions. Results suggest phosphatase enzyme activity is higher in P deficient conditions compared to inorganic P addition, yet lower compared to organic P addition. Meta-regression analysis indicates magnitude of P addition and pH of substrate are significant factors influencing enzyme response. However, due to numerous additional processes and adaption strategies in response to P deficiency and the difficulty isolating the role of phosphatase enzymes it is not possible to determine the degree to which this mechanism alone accounts for the missing P. We discuss the continuing need for additional empirical evidence to understand the cycling of organic P, and the development of models to include these processes to inform sustainable land management and ensure long-term food security.</p>

scholarly journals Temperature sensitivity of permafrost carbon release mediated by mineral and microbial properties

2021 ◽  
Vol 7 (32) ◽  
pp. eabe3596
Author(s):  
Shuqi Qin ◽  
Dan Kou ◽  
Chao Mao ◽  
Yongliang Chen ◽  
Leiyi Chen ◽  
...  
Keyword(s):  
Temperature Sensitivity ◽  
Temperature Response ◽  
Climate Feedback ◽  
The Tibetan Plateau ◽  
Dual Roles ◽  
Microbial Properties ◽  
C Dynamics ◽  
Mineral Associations ◽  
Carbon Release ◽  
Permafrost Soils

Temperature sensitivity (Q10) of permafrost carbon (C) release upon thaw is a vital parameter for projecting permafrost C dynamics under climate warming. However, it remains unclear how mineral protection interacts with microbial properties and intrinsic recalcitrance to affect permafrost C fate. Here, we sampled permafrost soils across a 1000-km transect on the Tibetan Plateau and conducted two laboratory incubations over 400- and 28-day durations to explore patterns and drivers of permafrost C release and its temperature response after thaw. We find that mineral protection and microbial properties are two types of crucial predictors of permafrost C dynamics upon thaw. Both high C release and Q10 are associated with weak organo-mineral associations but high microbial abundances and activities, whereas high microbial diversity corresponds to low Q10. The attenuating effects of mineral protection and the dual roles of microbial properties would make the permafrost C-climate feedback more complex than previously thought.

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