Preface &amp;quot;Stable Isotopes and Biogeochemical Cycles in Terrestrial Ecosystems''

Bahn, Michael; Buchmann, Nina; Knohl, Alexander

doi:10.5194/bg-9-3979-2012

Cited by 6 publications

(4 citation statements)

References 28 publications

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“…Just as isotopic information was critical for informing early SOM models [Jenkinson and Rayner, 1977;Van Veen and Paul, 1981;Torn et al, 1997], application of isotopic data should rapidly advance microbial-explicit models too. Numerous possibilities exist for using isotopic data, to estimate biogeochemical fluxes and C stabilization [Bahn et al, 2012;Behrens et al, 2008;Kayler et al, 2011] (Table 3). Isotope natural abundance can be used to validate process representations in models across space and time, such as using spatial extrapolations of 15 N distributions [Amundson et al, 2003, as in Houlton et al, 2015 and 13 C and 14 C [Torn et al, 2002].…”

Section: 1002/2015gb005188mentioning

confidence: 99%

Explicitly representing soil microbial processes in Earth system models

Wieder

Allison

Davidson

et al. 2015

Global Biogeochemical Cycles

340

304

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Microbes influence soil organic matter decomposition and the long‐term stabilization of carbon (C) in soils. We contend that by revising the representation of microbial processes and their interactions with the physicochemical soil environment, Earth system models (ESMs) will make more realistic global C cycle projections. Explicit representation of microbial processes presents considerable challenges due to the scale at which these processes occur. Thus, applying microbial theory in ESMs requires a framework to link micro‐scale process‐level understanding and measurements to macro‐scale models used to make decadal‐ to century‐long projections. Here we review the diversity, advantages, and pitfalls of simulating soil biogeochemical cycles using microbial‐explicit modeling approaches. We present a roadmap for how to begin building, applying, and evaluating reliable microbial‐explicit model formulations that can be applied in ESMs. Drawing from experience with traditional decomposition models, we suggest the following: (1) guidelines for common model parameters and output that can facilitate future model intercomparisons; (2) development of benchmarking and model‐data integration frameworks that can be used to effectively guide, inform, and evaluate model parameterizations with data from well‐curated repositories; and (3) the application of scaling methods to integrate microbial‐explicit soil biogeochemistry modules within ESMs. With contributions across scientific disciplines, we feel this roadmap can advance our fundamental understanding of soil biogeochemical dynamics and more realistically project likely soil C response to environmental change at global scales.

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Section: 1002/2015gb005188mentioning

confidence: 99%

Explicitly representing soil microbial processes in Earth system models

Wieder

Allison

Davidson

et al. 2015

Global Biogeochemical Cycles

340

304

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show abstract

“…Stable isotopes are a powerful tool for identifying autotrophic and heterotrophic respiration in soils (δ 13 CO2) (Bahn et al, 2012). When drawing a "Keeling plot" for the analysis of δ 13 CO 2 isotopic signals (Keeling, 1958), the model determines, by a linear regression approach, the carbon isotopic signal of the CO2 sources of a specific ecosystem that contributed to increases in atmospheric CO2.…”

Section: Co2 and δ 13 Co2 In Air Samplesmentioning

confidence: 99%

Role of soil pore structure in water infiltration and CO2 exchange between the atmosphere and underground air in the vadose zone: A combined laboratory and field approach

Pla

Cuezva

Martı́nez-Martı́nez

et al. 2017

CATENA

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The soils above caves represent a membrane that regulates the connection between the underground environment and the outside atmosphere. In this study, soils from two different field sites (Cueva de Altamira and Cueva del Rull in Spain) are investigated. Field results are analysed and linked to laboratory tests. Several laboratory experiments are performed to quantify CO2 diffusion coefficients and water infiltration rates in these soils under different degrees of soil water saturation and compaction.Tests confirm that the grain size distribution, organic matter content, mineral composition and water content of soils affect gas transport through the soil pore network. Both field and lab results reveal that Altamira soil has a coarser texture and therefore has higher CO 2 diffusion coefficients, infiltration rates and hydraulic conductivity values than Rull soil. Rull soil contains a higher proportion of fine particles and organic matter, which explains the lower fluid transport coefficients.When soils are near saturation, fluid transport does not depend on the physical properties of soil but depends on the soil water content. In this state, liquid transport regulates the available space within the soil pores, which leads to a reduction in the gaseous diffusion coefficient of the soil. After rainfall episodes, the connection between the exterior atmosphere and underground cavities is hindered due to a rise in the soil water content, which is responsible for the closure of the overlying membrane. This study demonstrates that soil-produced CO2 reaches the underground atmosphere through diffusion processes that are controlled by the intrinsic properties of soil (porosity, grain size distribution, texture, mineralogy and organic matter content) and soil water content.

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“…Exposing plants to 13 C enriched CO 2 can provide important constraints on simulated C allocation (Ehleringer et al, 2000). The posttreatment carbon isotope composition (δ 13 C) of organic matter and respired CO 2 can serve as a tracer of plant C allocation (Atkin, 2015;Bahn et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

Evaluating the Community Land Model in a pine stand with shading manipulations and <sup>13</sup>CO<sub>2</sub> labeling

et al. 2016

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Abstract. Carbon allocation and flow through ecosystems regulates land surface-atmosphere CO 2 exchange and thus is a key, albeit uncertain, component of mechanistic models. The Partitioning in Trees and Soil (PiTS) experimentmodel project tracked carbon allocation through a young Pinus taeda stand following pulse labeling with 13 CO 2 and two levels of shading. The field component of this project provided process-oriented data that were used to evaluate terrestrial biosphere model simulations of rapid shifts in carbon allocation and hydrological dynamics under varying environmental conditions. Here we tested the performance of the Community Land Model version 4 (CLM4) in capturing short-term carbon and water dynamics in relation to manipulative shading treatments and the timing and magnitude of carbon fluxes through various compartments of the ecosystem. When calibrated with pretreatment observations, CLM4 was capable of closely simulating stand-level biomass, transpiration, leaf-level photosynthesis, and pre-labeling 13 C values. Over the 3-week treatment period, CLM4 generally reproduced the impacts of shading on soil moisture changes, relative change in stem carbon, and soil CO 2 efflux rate. Transpiration under moderate shading was also simulated well by the model, but even with optimization we were not able to simulate the high levels of transpiration observed in the heavy shading treatment, suggesting that the BallBerry conductance model is inadequate for these conditions. The calibrated version of CLM4 gave reasonable estimates of label concentration in phloem and in soil surface CO 2 after 3 weeks of shade treatment, but it lacks the mechanisms needed to track the labeling pulse through plant tissues on shorter timescales. We developed a conceptual model for photosynthate transport based on the experimental observations, and we discussed conditions under which the hypothesized mechanisms could have an important influence on model behavior in larger-scale applications. Implications for future experimental studies are described, some of which are already being implemented in follow-on studies.

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Preface "Stable Isotopes and Biogeochemical Cycles in Terrestrial Ecosystems''

Cited by 6 publications

References 28 publications

Explicitly representing soil microbial processes in Earth system models

Explicitly representing soil microbial processes in Earth system models

Role of soil pore structure in water infiltration and CO2 exchange between the atmosphere and underground air in the vadose zone: A combined laboratory and field approach

Evaluating the Community Land Model in a pine stand with shading manipulations and <sup>13</sup>CO<sub>2</sub> labeling

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Preface &quot;Stable Isotopes and Biogeochemical Cycles in Terrestrial Ecosystems''

Cited by 6 publications

References 28 publications

Explicitly representing soil microbial processes in Earth system models

Explicitly representing soil microbial processes in Earth system models

Role of soil pore structure in water infiltration and CO2 exchange between the atmosphere and underground air in the vadose zone: A combined laboratory and field approach

Evaluating the Community Land Model in a pine stand with shading manipulations and &lt;sup&gt;13&lt;/sup&gt;CO&lt;sub&gt;2&lt;/sub&gt; labeling

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Resources

About

Preface "Stable Isotopes and Biogeochemical Cycles in Terrestrial Ecosystems''

Evaluating the Community Land Model in a pine stand with shading manipulations and <sup>13</sup>CO<sub>2</sub> labeling