Direct soil moisture controls of future global soil carbon changes: An important source of uncertainty

Falloon, Pete; Jones, Chris D.; Ades, Melanie; Paul, Keryn I.

doi:10.1029/2010gb003938

Cited by 193 publications

(159 citation statements)

References 98 publications

(172 reference statements)

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“…The relationship between soil heterotrophic respiration rate and moisture content is a fundamental property for understanding and modeling organic carbon cycling in soils (Falloon et al 2011;Sierra et al 2015;Vincent et al 2006). Various experimental studies have been performed to understand mechanistic processes and factors controlling such a relationship (Franzluebbers 1999;Kakumanu et al 2013;Schjønning et al 1999;Vincent et al 2006).…”

Section: Discussionmentioning

confidence: 99%

“…2) through changing the bioavailability of DOC. The different maximum respiration rates and HR-S curves observed in laboratories and field sites indicate that the relation between organic carbon transfer rate and water content changes with soils (Daly et al 2009;Falloon et al 2011;Skopp et al 1990).…”

Section: Model Calibrationmentioning

confidence: 99%

“…Moisture is one of the most important environmental factors influencing heterotrophic respiration (HR) in soils (Bond-Lamberty and Thomson 2010;Falloon et al 2011;Moyano et al 2013;Orchard and Cook 1983;Sierra et al 2015). It affects soil organic carbon (SOC) bioavailability and the rate of oxygen delivery that affect microbial metabolism in regulating heterotrophic SOC decomposition (Moyano et al 2012;Rodríguez-Iturbe and Porporato 2005).…”

Section: Introductionmentioning

confidence: 99%

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Pore-scale investigation on the response of heterotrophic respiration to moisture conditions in heterogeneous soils

et al. 2016

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The relationship between microbial respiration rate and soil moisture content is an important property for understanding and predicting soil organic carbon degradation, CO 2 production and emission, and their subsequent effects on climate change. This paper reports a pore-scale modeling study to investigate the response of heterotrophic respiration to moisture conditions in soils and to evaluate various factors that affect this response. X-ray computed tomography was used to derive soil pore structures, which were then used for pore-scale model investigation. The porescale results were then averaged to calculate the effective respiration rates as a function of water content in soils. The calculated effective respiration rate first increases and then decreases with increasing soil water content, showing a maximum respiration rate at water saturation degree of 0.75, which is consistent with field and laboratory observations. The relationship between the respiration rate and moisture content is affected by various factors, including pore-scale organic carbon bioavailability, the rate of oxygen delivery, soil pore structure and physical heterogeneity, soil clay content, and microbial drought resistivity. Overall, this study provides mechanistic insights into the soil respiration response to the change in moisture conditions, and reveals a complex relationship between heterotrophic microbial respiration rate and moisture content in soils that is affected by various hydrological, geophysical, and biochemical factors.

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Section: Discussionmentioning

confidence: 99%

Section: Model Calibrationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Pore-scale investigation on the response of heterotrophic respiration to moisture conditions in heterogeneous soils

et al. 2016

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“…For a better simulation of the ALT a higher vertical resolution and extended soil profile will be beneficial. Future model development should ensure a dynamic coupling of soil organic carbon content and soil thermal and hydraulic properties (Falloon et al, 2011), as well as allowing for sub-grid variability and uncertainty in soil properties. A separate peat module for JULES is already under development in order to study peatland carbon dynamics in the boreal zone, and work is underway to couple JULES to a more advanced model of carbon and nitrogen turnover in both mineral and organic soils (Smith et al, 2010).…”

Section: Discussionmentioning

confidence: 99%

Simulation of permafrost and seasonal thaw depth in the JULES land surface scheme

2011

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Abstract. Land surface models (LSMs) need to be able to simulate realistically the dynamics of permafrost and frozen ground. In this paper we evaluate the performance of the LSM JULES (Joint UK Land Environment Simulator), the stand-alone version of the land surface scheme used in Hadley Centre climate models, in simulating the largescale distribution of surface permafrost. In particular we look at how well the model is able to simulate the seasonal thaw depth or active layer thickness (ALT). We performed a number of experiments driven by observation-based climate datasets. Visually there is a very good agreement between areas with permafrost in JULES and known permafrost distribution in the Northern Hemisphere, and the model captures 97 % of the area where the spatial coverage of the permafrost is at least 50 %. However, the model overestimates the total extent as it also simulates permafrost where it occurs sporadically or only in isolated patches. Consistent with this we find a cold bias in the simulated soil temperatures, especially in winter. However, when compared with observations on end-of-season thaw depth from around the Arctic, the ALT in JULES is generally too deep. Additional runs at three sites in Alaska demonstrate how uncertainties in the precipitation input affect the simulation of soil temperatures by affecting the thickness of the snowpack and therefore the thermal insulation in winter. In addition, changes in soil moisture content influence the thermodynamics of soil layers close to freezing. We also present results from three experiments in which the standard model setup was modified to improve physical realism of the simulations in permafrost regions. Extending the soil column to a depth of 60 m and adjusting the soil parameters for organic content had relatively little effect on the Correspondence to: R. Dankers (rutger.dankers@metoffice.gov.uk) simulation of permafrost and ALT. A higher vertical resolution improves the simulation of ALT, although a considerable bias still remains. Future model development in JULES should focus on a dynamic coupling of soil organic carbon content and soil thermal and hydraulic properties, as well as allowing for sub-grid variability in soil types.

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“…There is a general agreement that soil microbial activity has an optimal value when the soil is wet (but not saturated) and decreases at when the soil becomes dry. The reduction in microbial biomass carbon in alternating wet-dry soils observed as from week 24 of incubation could be mostly attributed to water and oxygen limitation of microbial activity: as matric suction increases soil water is held in pores inaccessible to microbes [36]. High microbial biomass carbon under the continuously wet soil moisture in the shallow, wet and duplex at week 3 and 14 may be ascribed to the presence of large soil pore spaces as the soil associations had higher sand content (Table 1) so the organic matter was readily available the soil microbes hence they proliferated.…”

Section: Resultsmentioning

confidence: 99%

Stability of Soil Organic Matter and Soil Loss Dynamics under Short-term Soil Moisture Change Regimes

Parwada¹,

Tol²

2017

Agrotechnology

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Soil properties are known to be influenced Soil Organic Matter (SOM) resident time. However, there is limited information on the interactive effects of SOM quality and soil moisture on SOC and Microbial Biomass Carbon (MBC) hence on soil losses. Therefore, this study investigated the effects of different organic matter and soil moisture in soils with low (<2%) initial SOC content on the SOC, MBC and soil loss with time of organic matter incorporation. Six soils were incubated for 34 weeks at 25°C after adding high quality (C/N=23) Vachellia karroo leaf litter and low quality (C/N=41) Zea mays stover. The effect of SOM quality and soil moisture on the SOC content, MBC and soil loss was significantly (P<0.05) the same within but varied across soils. Soils that were continuously wet lost more SOC than under alternating wet-dry moisture conditions. Microbial biomass carbon was controlled by the availability of organic matter and moist soil conditions. Low MBC values corresponded to high SOC and soil loss. Continuously wet soils with high sand particles promoted rapid loss of SOC compared to alternating wet-dry soils. Therefore, continuously wet sandy soils are likely to contribute more to the climate warming than alternating wet-dry soil moisture. In the wake of the climatic change, addition of OM in continuously wet soils need to be regulated but to reduce soil loss re-application of fresh OM has to be more frequent under continuously wet sandy soils than in alternating wet-dry moisture regimes.

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Direct soil moisture controls of future global soil carbon changes: An important source of uncertainty

Cited by 193 publications

References 98 publications

Pore-scale investigation on the response of heterotrophic respiration to moisture conditions in heterogeneous soils

Pore-scale investigation on the response of heterotrophic respiration to moisture conditions in heterogeneous soils

Simulation of permafrost and seasonal thaw depth in the JULES land surface scheme

Stability of Soil Organic Matter and Soil Loss Dynamics under Short-term Soil Moisture Change Regimes

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