Soil heterotrophic respiration as a function of water content and temperature in a mechanistic pore-scale model

2020 ◽  
Author(s):  
Mehdi Gharasoo ◽  
Linden Fairbairn ◽  
Fereidoun Rezanezhad ◽  
Philippe Van Cappellen
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Case Studies ◽  
Water Saturation ◽  
Empirical Models ◽  
Heterotrophic Respiration ◽  
Scale Model ◽  
Respiration Rates ◽  
Bioavailable Fraction ◽  
Soil Heterotrophic Respiration

<p>Soil heterotrophic respiration has been considered as a key source of CO<sub>2</sub> flux into the atmosphere and thus plays an important role in global warming. Although the relationship between soil heterotrophic respiration and soil water content has been frequently studied both theoretically and experimentally, model development has thus far been empirically based. Empirical models are often limited to the specific condition of their case studies and cannot be used as a general platform for modeling. Moreover, it is difficult to extend the empirical models by theoretically defined affinities to any desired degree of accuracy. As a result, it is of high priority to develop process-based models that are able to describe the mechanisms behind this phenomenon with more deterministic terms.</p><p>Here we present a mechanistic, mathematically-driven model that is based on the common geometry of a pore in porous media. Assuming that the aerobic respiration of bacteria requires oxygen as an electron acceptor and dissolved organic carbon (DOC) as a substrate, the CO<sub>2</sub> fluxes are considered a function of the bioavailable fraction of both DOC and oxygen. In this modeling approach, the availability of oxygen is controlled by its penetration into the aquatic phase through the interface between air and water. DOC on the other hand is only available to a section of the soil that is in contact with water. As the water saturation in the pore changes, it dynamically and kinematically impacts these interfaces through which the mass transfer of nutrients occurs, and therefore the CO<sub>2</sub> fluxes are directly controlled by water content. We showcased the model applicability on several case studies and illustrated the model capability in simulating the observed microbial respiration rates versus the soil water contents. Furthermore, we showed the model potential to accept additional physically-motivated parameters in order to explain respiration rates in frozen soils or at different temperatures.</p>

The influence of soil structure on heterotrophic respiration response to soil water content

2020 ◽  
Author(s):  
Michael Herbst ◽  
Wolfgang Tappe ◽  
Sirgit Kummer ◽  
Harry Vereecken
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Soil Structure ◽  
Water Saturation ◽  
Textural Properties ◽  
Heterotrophic Respiration ◽  
Soil Heterotrophic Respiration ◽  
Undisturbed Soils ◽  
Soil Water Saturation

<p>Soil respiration causes one of the largest terrestrial carbon fluxes and its accurate prediction is still a matter of on-going research. Understanding the functional link between soil heterotrophic respiration and soil water content is relevant for the estimation of climate change impacts on soil CO<sub>2</sub> emissions. <br>In order to quantify the effect of air-drying and sieving with 2 mm meshes on the soil heterotrophic respiration response to water content we incubated intact cores and sieved samples of two loamy and two sandy agricultural topsoils for six levels of effective soil water saturation. We further measured soil textural properties and the soil water retention characteristics of the soils with the aim to identify potential correlations between soil physical parameters and moisture sensitivity functions of heterotrophic respiration. <br>The incubation of sieved and intact soils showed distinct differences in the response of soil heterotrophic respiration to soil water saturation. The sieved soils exposed threshold-type behaviour, whereas the undisturbed soils exposed a quadratic increase of heterotrophic respiration with increasing effective soil water content. Additionally, we found significant correlations between the moisture response functions of the undisturbed soils and soil textural properties.<br>From the comparison of intact and sieved soil incubations we conclude that the destruction of soil structure by sieving hampers the transferability of measured soil moisture response of heterotrophic respiration to real-world conditions. For modelling purposes we suggest the use of a quadratic function between relative respiration and effective saturation for soils with a clay fraction < 20 %.</p>

scholarly journals Spatial-and temporal-patterns of global soil heterotrophic respiration in terrestrial ecosystems

2019 ◽  
Author(s):  
Xiaolu Tang ◽  
Shaohui Fan ◽  
Manyi Du ◽  
Wenjie Zhang ◽  
Sicong Gao ◽  
...  
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Temporal Patterns ◽  
Heterotrophic Respiration ◽  
Spatial And Temporal Patterns ◽  
Carbon Loss ◽  
Global Land ◽  
Global Soil ◽  
Soil Heterotrophic Respiration

Abstract. Soil heterotrophic respiration (RH) is one of the largest and most uncertain components of the terrestrial carbon cycle, directly reflecting carbon loss from soil to the atmosphere. However, high variations and uncertainties of RH existing in global carbon cycling models require an urgent development of data-derived RH dataset. To fill this knowledge gap, this study applied Random Forest (RF) algorithm – a machine learning approach, to (1) develop a globally gridded RH dataset and (2) investigate its spatial- and temporal-patterns from 1980 to 2016 at the global scale by linking field observations from the Global Soil Respiration Database and global environmental drivers – temperature, precipitation, soil water content, etc. Finally, a globally gridded RH dataset was developed covering from 1980 to 2016 with a spatial resolution of half degree and a temporal resolution of one year. Globally, the average annual RH was 57.2 ± 0.6 Pg C a−1 from 1980 to 2016, with a significantly increasing trend of 0.036 ± 0.007 Pg C a−2. However, the temporal trend of the carbon loss from RH varied with climate zones that RH showed significant increasing trends in boreal and temperate areas, in contrast, such trend was absent in tropical regions. Temperature driven RH dominated 39 % of global land and was mainly distributed at a high latitude. While the areas dominated by precipitation and soil water content were mainly semi-arid and tropical areas, accounting for 36 % and 25 % of the global land, respectively, suggesting variations in the dominance of environmental controls on the spatial patterns of RH. The developed globally gridded RH dataset will further aid in understanding of the mechanisms of global soil carbon dynamics, serving as a benchmark to constrain global vegetation models. The dataset is publicly available at https://doi.org/10.6084/m9.figshare.8882567 (Tang et al., 2019a).

scholarly journals Spatial and temporal patterns of global soil heterotrophic respiration in terrestrial ecosystems

2020 ◽  
Vol 12 (2) ◽  
pp. 1037-1051 ◽  
Author(s):  
Xiaolu Tang ◽  
Shaohui Fan ◽  
Manyi Du ◽  
Wenjie Zhang ◽  
Sicong Gao ◽  
...  
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Heterotrophic Respiration ◽  
Spatial And Temporal Patterns ◽  
Carbon Loss ◽  
Global Land ◽  
Increasing Trend ◽  
Global Soil ◽  
Soil Heterotrophic Respiration

Abstract. Soil heterotrophic respiration (RH) is one of the largest and most uncertain components of the terrestrial carbon cycle, directly reflecting carbon loss from soils to the atmosphere. However, high variations and uncertainties of RH existing in global carbon cycling models require RH estimates from different angles, e.g., a data-driven angle. To fill this knowledge gap, this study applied a Random Forest (RF) algorithm (a machine learning approach) to (1) develop a globally gridded RH dataset and (2) investigate its spatial and temporal patterns from 1980 to 2016 at the global scale by linking field observations from the Global Soil Respiration Database and global environmental drivers (temperature, precipitation, soil water content, etc.). Finally, a globally gridded RH dataset was developed covering from 1980 to 2016 with a spatial resolution of half a degree and a temporal resolution of 1 year. Globally, the average annual RH was 57.2±0.6 Pg C a−1 from 1980 to 2016, with a significantly increasing trend of 0.036±0.007 Pg C a−2. However, the temporal trend of the carbon loss from RH varied in climate zones, and RH showed a significant and increasing trend in boreal and temperate areas. In contrast, such a trend was absent in tropical regions. Temperature-driven RH dominated 39 % of global land and was primarily distributed at high-latitude areas. The areas dominated by precipitation and soil water content were mainly semiarid and tropical areas, accounting for 36 % and 25 % of global land area, respectively, suggesting variations in the dominance of environmental controls on the spatial patterns of RH. The developed globally gridded RH dataset will further aid in the understanding of the mechanisms of global soil carbon dynamics, serving as a benchmark to constrain terrestrial biogeochemical models. The dataset is publicly available at https://doi.org/10.6084/m9.figshare.8882567 (Tang et al., 2019a).

Soil heterotrophic respiration is insensitive to changes in soil water content but related to microbial access to organic matter

Geoderma ◽  
2016 ◽  
Vol 274 ◽  
pp. 68-78 ◽  
Author(s):  
Gabriel Y.K. Moinet ◽  
Ellen Cieraad ◽  
John E. Hunt ◽  
Anitra Fraser ◽  
Matthew H. Turnbull ◽  
...  
Keyword(s):  
Organic Matter ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Heterotrophic Respiration ◽  
Soil Heterotrophic Respiration

scholarly journals Leveraging the signature of heterotrophic respiration on atmospheric CO<sub>2</sub> for model benchmarking

2020 ◽  
Vol 17 (5) ◽  
pp. 1293-1308 ◽  
Author(s):  
Samantha J. Basile ◽  
Xin Lin ◽  
William R. Wieder ◽  
Melannie D. Hartman ◽  
Gretchen Keppel-Aleks
Keyword(s):  
Large Scale ◽  
Transport Model ◽  
Heterotrophic Respiration ◽  
Atmospheric Co2 ◽  
Scale Model ◽  
Future Research ◽  
Tracer Transport ◽  
Test Bed ◽  
Model Simulations ◽  
Soil Heterotrophic Respiration

Abstract. Spatial and temporal variations in atmospheric carbon dioxide (CO2) reflect large-scale net carbon exchange between the atmosphere and terrestrial ecosystems. Soil heterotrophic respiration (HR) is one of the component fluxes that drive this net exchange, but, given observational limitations, it is difficult to quantify this flux or to evaluate global-scale model simulations thereof. Here, we show that atmospheric CO2 can provide a useful constraint on large-scale patterns of soil heterotrophic respiration. We analyze three soil model configurations (CASA-CNP, MIMICS, and CORPSE) that simulate HR fluxes within a biogeochemical test bed that provides each model with identical net primary productivity (NPP) and climate forcings. We subsequently quantify the effects of variation in simulated terrestrial carbon fluxes (NPP and HR from the three soil test-bed models) on atmospheric CO2 distributions using a three-dimensional atmospheric tracer transport model. Our results show that atmospheric CO2 observations can be used to identify deficiencies in model simulations of the seasonal cycle and interannual variability in HR relative to NPP. In particular, the two models that explicitly simulated microbial processes (MIMICS and CORPSE) were more variable than observations at interannual timescales and showed a stronger-than-observed temperature sensitivity. Our results prompt future research directions to use atmospheric CO2, in combination with additional constraints on terrestrial productivity or soil carbon stocks, for evaluating HR fluxes.

Adaptability of Cornus Alba Seedling under Drought Stress in Highway Greening

2011 ◽  
Vol 90-93 ◽  
pp. 3262-3267
Author(s):  
Wen Yuan Xu ◽  
Long Sun ◽  
Li Qiang Mu
Keyword(s):  
Drought Stress ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Drought Resistance ◽  
Control Method ◽  
Water Saturation ◽  
Focal Point ◽  
Water Saturation Deficit ◽  
Cornus Alba

The drought resistance adaptation mechanism of highway greening plants was always the focal point which the researcher payed attention. This experiment took Cornus alba as the study object and examines its resistance to drought stress by using the potting and water control method. The researcher measured bond water content, water saturation deficit, relevant water content, relevant content of osmotic water, and osmotic potential when full turgor and turgor were both zero. Other water condition indexes also were analyzed systematically. Finally, a comprehensive evaluation on the drought resistance of Cornus alba by fuzzy mathematics’ anti-membership function was conducted. According to the experiment result, Cornus alba had the highest drought resistance at B-level treatment (soil water content: 53.60%), followed by D-level (soil water content: 29.90%) treatment. Cornus alba had strong endurance and resistance to drought stress. This study could provide a scientific basis for the future introduction of other urban greenbelt plants and the choice of excellent traits.

Soil Water Content and Soil Respiration Rates Are Reduced for Years Following Wildfire in a Hot and Dry Climate

2020 ◽  
Vol 34 (12) ◽  
Author(s):  
Sol C. Cooperdock ◽  
Christine V. Hawkes ◽  
Derry R. Xu ◽  
Daniel O. Breecker
Keyword(s):  
Soil Respiration ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Respiration Rates

Response of heterotrophic respiration and oxidation of atmospheric CH4 to changes in soil moisture and temperature in drylands across a global climate and ecosystem gradient

2020 ◽  
Author(s):  
Thomas Hessilt ◽  
Daniel Lyberth Hauptmann ◽  
Jesper Riis Christiansen
Keyword(s):  
Soil Moisture ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Global Climate ◽  
Heterotrophic Respiration ◽  
Mean Annual Temperature ◽  
Specific Response ◽  
Carbon Turnover ◽  
Site Specific

&lt;p&gt;Soil moisture and temperature collectively regulate the production and consumption of carbon in soils. With expected changes in both the soil thermal and hydrological regimes globally, experimental data on carbon turnover under these changes in contrasting ecosystems are important for constraining predictive models of soil carbon turnover. We investigated the effect of changes in soil water and temperature on heterotrophic respiration (Rh) and net methane uptake (MU) in soils from grassland ecosystems in Arctic, temperate and subtropical climates.&lt;br&gt;The temperature sensitivity of RH increased with decreasing mean annual temperature, but there was no indication of a site-specific response of Rh to changes in soil moisture. All sites displayed MU, primarily controlled by the soil water content with little temperature dependence. Thus, the optimum temperature for MU did not differ between sites despite the differences in the climate. However, the optimal soil water content for the relative maximum MU decreased with increasing mean annual temperature at the sites.&lt;br&gt;These results point to site-specific adaptation of the microbial community that governs the sensitivity of Rh to temperature, but not soil moisture and the dependency of MU to soil moisture alone. We would also like to discuss how this insight can be used to inform ecosystem models.&lt;/p&gt;

scholarly journals Respiration characteristics and its responses to hydrothermal seasonal changes in reconstructed soils

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Na Lei ◽  
Juan Li ◽  
Tianqing Chen
Keyword(s):  
Soil Respiration ◽  
Water Content ◽  
Respiration Rate ◽  
Exponential Function ◽  
Seasonal Changes ◽  
Volumetric Water Content ◽  
Heterotrophic Respiration ◽  
Autotrophic Respiration ◽  
Monthly Average ◽  
Respiration Rates

AbstractSeasonal changes in respiration and the components of four reconstructed soils (gravel + meteorite + lou; gravel + shale + lou; gravel + sand + lou; and gravel + soft rock + lou) in barren gravel land were monitored using the soil carbon flux measurement system. The results showed that (1) the monthly average respiration rate and the rates of the components in the four reconstructed soils were the highest in summer and lowest in winter. In winter, the monthly average respiration rates of the four reconstructed soils were not different (p > 0.05). In summer, the monthly average respiration rate of the sand or meteorite reconstructed soil was different from that of the other three (p < 0.05). (2) The heterotrophic and autotrophic respiration rates were different between the four reconstructed soils (p < 0.05). The contribution of heterotrophic respiration to total respiration in the four reconstructed soils was greater than that of autotrophic respiration throughout the year. In winter, autotrophic respiration accounts for the smallest proportion of total respiration. As the temperature rises, the proportion of autotrophic respiration to total respiration gradually increases and peaks in summer. In summer, the proportion of heterotrophic respiration in the total respiration is the smallest. With the decrease in temperature, the proportion of heterotrophic respiration in total respiration gradually increases and peaks in winter. (3) The maximum and minimum values of the monthly average respiration rate of the four reconstructed soils coincided with the months of maximum and minimum soil temperature. The soil volumetric water content changed with the amount of precipitation. The correlation between soil respiration and temperature was greater than that between soil respiration and volumetric water content. (4) The correlation in seasonal variation between respiration of the four remodelled soils and hydrothermal factors in the study area can be characterised by an exponential function and power-exponential function.

scholarly journals Leveraging the signature of heterotrophic respiration on atmospheric CO<sub>2</sub> for model benchmarking

2019 ◽  
Author(s):  
Samantha J. Basile ◽  
Xin Lin ◽  
William R. Wieder ◽  
Melannie D. Hartman ◽  
Gretchen Keppel-Aleks
Keyword(s):  
Large Scale ◽  
Net Primary Productivity ◽  
Transport Model ◽  
Heterotrophic Respiration ◽  
Atmospheric Co2 ◽  
Scale Model ◽  
Future Research ◽  
Tracer Transport ◽  
Model Simulations ◽  
Soil Heterotrophic Respiration

Abstract. Spatial and temporal variations in atmospheric carbon dioxide (CO2) reflect large-scale net carbon exchange between the atmosphere and terrestrial ecosystems. Soil heterotrophic respiration (HR) is one of the component fluxes that drive this net exchange but, given observational limitations, it is difficult to quantify this flux or to evaluate global-scale model simulations thereof. Here, we show that atmospheric CO2 can provide a useful constraint on large-scale patterns of soil heterotrophic respiration. We analyze three soil model configurations (CASA-CNP, MIMICS and CORPSE) that simulate HR fluxes within a biogeochemical testbed that provides each model with identical net primary productivity (NPP) and climate forcings. We subsequently quantify the effects of variation in simulated terrestrial carbon fluxes (NPP and HR from the three soil testbed models) on atmospheric CO2 distributions using a three-dimensional atmospheric tracer transport model. Our results show that atmospheric CO2 observations can be used to identify deficiencies in model simulations of the seasonal cycle and interannual variability in HR relative to NPP. In particular, the two models that explicitly simulated microbial processes (MIMICS and CORPSE) were more variable than observations at interannual timescales and showed a stronger than observed temperature sensitivity. Our results prompt future research directions to use atmospheric CO2, in combination with additional constraints on terrestrial productivity or soil carbon stocks, for evaluating HR fluxes.

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