scholarly journals Including Stable Carbon Isotopes to Evaluate the Dynamics of Soil Carbon in the Land‐Surface Model ORCHIDEE

2019 ◽  
Vol 11 (11) ◽  
pp. 3650-3669 ◽  
Author(s):  
Marta Camino‐Serrano ◽  
Marwa Tifafi ◽  
Jérôme Balesdent ◽  
Christine Hatté ◽  
Josep Peñuelas ◽  
...  
Keyword(s):  
Soil Carbon ◽  
Carbon Isotopes ◽  
Land Surface ◽  
Stable Carbon Isotopes ◽  
Land Surface Model ◽  
Surface Model ◽  
Stable Carbon

scholarly journals The use of radiocarbon <sup>14</sup>C to constrain carbon dynamics in the soil module of the land surface model ORCHIDEE (SVN r5165)

2018 ◽  
Author(s):  
Marwa Tifafi ◽  
Marta Camino-Serrano ◽  
Christine Hatté ◽  
Hector Morras ◽  
Lucas Moretti ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Soil Carbon ◽  
Land Surface ◽  
Carbon Stock ◽  
Land Surface Model ◽  
Carbon Dynamics ◽  
Total Carbon ◽  
Soil Parameters ◽  
Surface Model

Abstract. Despite the importance of soil as a large component of the terrestrial ecosystems, the soil compartments are not well represented in the Land Surface Models (LSMs). Indeed, soils in current LSMs are generally represented based on a very simplified schema that can induce a misrepresentation of the deep dynamics of soil carbon. Here, we present a new version of the IPSL-Land Surface Model called ORCHIDEE-SOM, incorporating the 14C dynamic in the soil. ORCHIDEE-SOM, first, simulates soil carbon dynamics for different layers, down to 2 m depth. Second, concentration of dissolved organic carbon (DOC) and its transport are modeled. Finally, soil organic carbon (SOC) decomposition is considered taking into account the priming effect. After implementing the 14C in the soil module of the model, we evaluated model outputs against observations of soil organic carbon and 14C activity (F14C) for different sites with different characteristics. The model managed to reproduce the soil organic carbon stocks and the F14C along the vertical profiles. However, an overestimation of the total carbon stock was noted, but was mostly marked on the surface. Then, thanks to the introduction of 14C, it has been possible to highlight an underestimation of the age of carbon in the soil. Thereafter, two different tests on this new version have been established. The first was to increase carbon residence time of the passive pool and decrease the flux from the slow pool to the passive pool. The second was to establish an equation of diffusion, initially constant throughout the profile, making it vary exponentially as a function of depth. The first modifications did not improve the capacity of the model to reproduce observations whereas the second test showed a decrease of the soil carbon stock overestimation, especially at the surface and an improvement of the estimates of the carbon age. This assumes that we should focus more on vertical variation of soil parameters as a function of depth, mainly for diffusion, in order to upgrade the representation of global carbon cycle in LSMs, thereby helping to improve predictions of the future response of soil organic carbon to global warming.

Stable carbon isotopes as powerful tools for studying land-atmosphere flux exchanges and improving land surface models

2021 ◽  
Author(s):  
Aliénor Lavergne ◽  
Laia Andreu-Hayles ◽  
Soumaya Belmecheri ◽  
Rossella Guerrieri ◽  
Heather Graven
Keyword(s):  
Carbon Isotopes ◽  
Land Surface ◽  
Stable Carbon Isotopes ◽  
Environmental Changes ◽  
Carbon Sink ◽  
Stable Carbon ◽  
Land Surface Models ◽  
Terrestrial Plants ◽  
Plant Materials ◽  
Surface Models

&lt;p&gt;The stable isotopic compositions of carbon and oxygen in terrestrial plants can provide valuable insights into plant eco-physiological responses to environmental changes at seasonal to annual resolution. Yet, the potential of these datasets to study land-atmosphere interactions remains under-exploited. Here, we present some examples of how stable carbon isotopes (&amp;#948;&lt;sup&gt;13&lt;/sup&gt;C) measured in plant materials (leaves and tree-rings) can be used to explore changes in the magnitude and variability of carbon and water flux exchanges between the vegetation and the atmosphere and to improve land surface models.&lt;strong&gt; &lt;/strong&gt;&lt;/p&gt;&lt;p&gt;First, we show that the discrimination against &lt;sup&gt;13&lt;/sup&gt;C (&amp;#916;&lt;sup&gt;13&lt;/sup&gt;C), calculated as the difference in &amp;#948;&lt;sup&gt;13&lt;/sup&gt;C between the source atmospheric CO&lt;sub&gt;2 &lt;/sub&gt;and the plant material studied, varies strongly between regions and biomes and is useful for better understanding the CO&lt;sub&gt;2&lt;/sub&gt; fertilisation effect of plant growth. For example, tree-ring &amp;#916;&lt;sup&gt;13&lt;/sup&gt;C records from boreal evergreen forests in North America increased linearly with rising CO&lt;sub&gt;2&lt;/sub&gt; during the 20&lt;sup&gt;th&lt;/sup&gt; century, suggesting that those forests have actively contributed to the land carbon sink by removing CO&lt;sub&gt;2&lt;/sub&gt; from the atmosphere at a relatively constant rate. However, such an increase in&amp;#160;&amp;#916;&lt;sup&gt;13&lt;/sup&gt;C with rising CO&lt;sub&gt;2&lt;/sub&gt; is not observed everywhere. We found that over the same time period, while some forests had a fairly constant &amp;#916;&lt;sup&gt;13&lt;/sup&gt;C, others exhibited a slight decrease in &amp;#916;&lt;sup&gt;13&lt;/sup&gt;C over time, which might indicate a reduction of the capacity of trees to absorb CO&lt;sub&gt;2&lt;/sub&gt;. Using a response function approach, we show that the differences between sites and regions are most likely the result of different evaporative demands and soil water availability conditions experienced by forests.&lt;strong&gt; &lt;/strong&gt;&lt;/p&gt;&lt;p&gt;We then discuss how predictions of the coupled carbon and water cycles by vegetation models can be improved by incorporating stable carbon isotopes to constrain the model representation of carbon-water fluxes regulation by leaf stomata. Specifically, we examine and evaluate simulations from the JULES vegetation model at different eddy-covariance forest sites where stable carbon isotopic data and canopy flux measurements are available. Overall, our analyses have strong implications for the understanding of historical changes in the strength of the CO&lt;sub&gt;2&lt;/sub&gt; fertilisation effect and in the water use efficiency of terrestrial ecosystems across regions.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;

scholarly journals Evaluating two soil carbon models within a global land surface model using surface and spaceborne observations of atmospheric CO<sub>2</sub> mole fractions

2020 ◽  
Author(s):  
Tea Thum ◽  
Julia E. S. M. Nabel ◽  
Aki Tsuruta ◽  
Tuula Aalto ◽  
Edward J. Dlugokencky ◽  
...  
Keyword(s):  
Soil Carbon ◽  
Land Surface ◽  
Seasonal Cycle ◽  
Land Surface Model ◽  
Carbon Stocks ◽  
Atmospheric Co2 ◽  
Surface Model ◽  
Global Land ◽  
Soil Carbon Stocks ◽  
Surface Observations

Abstract. The trajectories of soil carbon (C) in the changing climate are of utmost importance, as soil carbon is a substantial carbon storage with a large potential to impact the atmospheric carbon dioxide (CO2) burden. Atmospheric CO2 observations integrate all processes affecting C exchange between the surface and the atmosphere. Therefore they provide a benchmark for carbon cycle models. We evaluated two distinct soil carbon models (CBALANCE and YASSO) that were implemented to a global land surface model (JSBACH) against atmospheric CO2 observations. We transported the biospheric carbon fluxes obtained by JSBACH using the atmospheric transport model TM5 to obtain atmospheric CO2. We then compared these results with surface observations from Global Atmosphere Watch (GAW) stations as well as with column XCO2 retrievals from the GOSAT satellite. The seasonal cycles of atmospheric CO2 estimated by the two different soil models differed. The estimates from the CBALANCE soil model were more in line with the surface observations at low latitudes (0 N–45 N) with only 1 % bias in the seasonal cycle amplitude (SCA), whereas YASSO was underestimating the SCA in this region by 32 %. YASSO gave more realistic seasonal cycle amplitudes of CO2 at northern boreal sites (north of 45 N) with underestimation of 15 % compared to 30 % overestimation by CBALANCE. Generally, the estimates from CBALANCE were more successful in capturing the seasonal patterns and seasonal cycle amplitudes of atmospheric CO2 even though it overestimated soil carbon stocks by 225 % (compared to underestimation of 36 % by YASSO) and its predictions of the global distribution of soil carbon stocks was unrealistic. The reasons for these differences in the results are related to the different environmental drivers and their functional dependencies of these two soil carbon models. In the tropical region the YASSO model showed earlier increase in season of the heterotophic respiration since it is driven by precipitation instead of soil moisture as CBALANCE. In the temperate and boreal region the role of temperature is more dominant. There the heterotophic respiration from the YASSO model had larger annual variability, driven by air temperature, compared to the CBALANCE which is driven by soil temperature. The results underline the importance of using sub-yearly data in the development of soil carbon models when they are used in shorter than annual time scales.

Dynamics of soil carbon following destruction of tropical rainforest and the subsequent establishment ofImperatagrassland in Indonesian Borneo using stable carbon isotopes

2012 ◽  
Vol 18 (8) ◽  
pp. 2606-2616 ◽  
Author(s):  
Yusuke Yonekura ◽  
Seiichi Ohta ◽  
Yoshiyuki Kiyono ◽  
Darul Aksa ◽  
Kazuhito Morisada ◽  
...  
Keyword(s):  
Soil Carbon ◽  
Carbon Isotopes ◽  
Stable Carbon Isotopes ◽  
Tropical Rainforest ◽  
Stable Carbon

scholarly journals An observational constraint on stomatal function in forests: evaluating coupled carbon and water vapor exchange with carbon isotopes in the Community Land Model (CLM 4.5)

2016 ◽  
Author(s):  
Brett Raczka ◽  
Henrique F. Duarte ◽  
Charles D. Koven ◽  
Daniel Ricciuto ◽  
Peter E. Thornton ◽  
...  
Keyword(s):  
Carbon Isotopes ◽  
Land Surface ◽  
Nitrogen Limitation ◽  
Stable Carbon Isotopes ◽  
Stable Carbon Isotope ◽  
Atmospheric Co2 ◽  
Stable Carbon ◽  
Conifer Forest ◽  
Isotope Discrimination ◽  
Community Land Model

Abstract. Land surface models are useful tools to quantify contemporary and future climate impact on terrestrial carbon cycle processes, provided they can be appropriately constrained and tested with observations. Stable carbon isotopes of CO2 offer the potential to improve model representation of the coupled carbon and water cycles because they are strongly influenced by stomatal function. Recently, a representation of stable carbon isotope discrimination was incorporated into the Community Land Model component of the Community Earth System Model. Here, we tested the model's capability to simulate whole-forest isotope discrimination in a subalpine conifer forest at Niwot Ridge, Colorado, USA. We distinguished between isotopic behavior in response to a decrease of δ13C within atmospheric CO2 (Suess effect) vs. photosynthetic discrimination (Δcanopy), by creating a site-customized atmospheric CO2 and δ13C of CO2 time series. We implemented a seasonally-varying Vcmax model calibration that best matched site observations of net CO2 carbon exchange, latent heat exchange and biomass. The model accurately simulated observed δ13C of needle and stem tissue, but underestimated the δ13C of bulk soil carbon by 1–2 ‰. The model overestimated the multi-year (2006–2012) average Δcanopy relative to prior data-based estimates by 5–6 ‰. The amplitude of the average seasonal cycle of Δcanopy (i.e. higher in spring/fall as compared to summer) was correctly modeled but only with an alternative nitrogen limitation formulation for the model. The model attributed most of the seasonal variation in discrimination to the net assimilation rate (An), whereas inter-annual variation in simulated Δcanopy during the summer months was driven by stomatal response to vapor pressure deficit. Soil moisture did not influence modeled Δcanopy. The model simulated a 10 % increase in both photosynthetic discrimination and water use efficiency (WUE) since 1850 as a result of CO2 fertilization, forced by constant climate conditions. This increasing trend in discrimination is counter to well-established relationships between discrimination and WUE. The isotope observations used here to constrain CLM suggest 1) the model overestimated stomatal conductance and 2) the default CLM approach to representing nitrogen limitation (post-photosynthetic limitation) was not capable of reproducing observed trends in discrimination. These findings demonstrate that isotope observations can provide important information related to stomatal function driven by environmental stress from VPD and nitrogen limitation.

scholarly journals Timescales of the permafrost carbon cycle and legacy effects of temperature overshoot scenarios

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Philipp de Vrese ◽  
Victor Brovkin
Keyword(s):  
Soil Carbon ◽  
Land Surface ◽  
Organic Matter Content ◽  
Land Surface Model ◽  
Matter Content ◽  
Steady States ◽  
The Arctic ◽  
Surface Model ◽  
Legacy Effects ◽  
Atmospheric Conditions

AbstractMinimizing the risks and impacts of climate change requires limiting the global temperature increase to 1.5 °C above preindustrial levels, while the difficulty of reducing carbon emissions at the necessary rate increases the likelihood of temporarily overshooting this climate target. Using simulations with the land surface model JSBACH, we show that it takes high-latitude ecosystems and the state of permafrost-affected soils several centuries to adjust to the atmospheric conditions that arise at the 1.5 °C-target. Here, a temporary warming of the Arctic entails important legacy effects and we show that feedbacks between water-, energy- and carbon cycles allow for multiple steady-states in permafrost regions, which differ with respect to the physical state of the soil, the soil carbon concentrations and the terrestrial carbon uptake and -release. The steady-states depend on the soil organic matter content at the point of climate stabilization, which is significantly affected by an overshoot-induced soil carbon loss.

Sign in / Sign up

Export Citation Format

Share Document