Where does the carbon go? A model–data intercomparison of vegetation carbon allocation and turnover processes at two temperate forest free‐air CO2 enrichment sites

Kauwe, Martin G. De; Medlyn, Belinda E.; Zaehle, Sönke; Walker, Anthony P.; Dietze, Michael C.; Wang, Ying‐Ping; Luo, Yiqi; Jain, Atul K.; Masri, Bassil El; Hickler, Thomas; Wårlind, David; Weng, Ensheng; Parton, William J.; Thornton, P. E.; Wang, Shusen; Prentice, Iain Colin; Asao, Shinichi; Smith, Benjamin; McCarthy, Heather R.; Iversen, Colleen M.; Hanson, Paul J.; Warren, Jeffrey M.; Oren, Ram; Norby, Richard J.

doi:10.1111/nph.12847

Cited by 286 publications

(332 citation statements)

References 79 publications

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“…However, it is not possible to validate the modelled changes in terrestrial carbon storage since no direct proxy exists for carbon stored in terrestrial ecosystems. The CO 2 fertilization effect displayed by CLIMBER2-LPJ as well as other DGVMs, which leads to increases in biomass with increasing CO 2 , seems well understood at the leaf level (De Kauwe et al, 2014) but may be overestimated in models because constraining mechanisms such as nutrient limitation are not taken into account (Reich et al, 2014).…”

Section: Discussionmentioning

confidence: 99%

Modelled interglacial carbon cycle dynamics during the Holocene, the Eemian and Marine Isotope Stage (MIS) 11

Kleinen

Brovkin

Munhoven³

2016

Clim. Past

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Abstract. Trends in the atmospheric concentration of CO 2 during three recent interglacials -the Holocene, the Eemian and Marine Isotope Stage (MIS) 11 -are investigated using an earth system model of intermediate complexity, which we extended with process-based modules to consider two slow carbon cycle processes -peat accumulation and shallowwater CaCO 3 sedimentation (coral reef formation). For all three interglacials, model simulations considering peat accumulation and shallow-water CaCO 3 sedimentation substantially improve the agreement between model results and ice core CO 2 reconstructions in comparison to a carbon cycle set-up neglecting these processes. This enables us to model the trends in atmospheric CO 2 , with modelled trends similar to the ice core data, forcing the model only with orbital and sea level changes. During the Holocene, anthropogenic CO 2 emissions are required to match the observed rise in atmospheric CO 2 after 3 ka BP but are not relevant before this time. Our model experiments show a considerable improvement in the modelled CO 2 trends by the inclusion of the slow carbon cycle processes, allowing us to explain the CO 2 evolution during the Holocene and two recent interglacials consistently using an identical model set-up.

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Section: Discussionmentioning

confidence: 99%

Modelled interglacial carbon cycle dynamics during the Holocene, the Eemian and Marine Isotope Stage (MIS) 11

Kleinen

Brovkin

Munhoven³

2016

Clim. Past

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“…Global and regional observations of land surface fluxes, states, and dynamic vegetation change offer insights into the large-scale interactions between the land surface and atmosphere and hence facilitate model improvements at relevant scales in space and time (Beer et al, 2010;Luo et al, 2012;Randerson et al, 2009). However, to better quantify and reduce uncertainties arising from deficiencies in model process representation, parameters, driver data sets, and initial conditions, there has been significant effort to evaluate and to calibrate LSMs against site-scale ob-servations and experimental manipulations (Baldocchi et al, 2001;De Kauwe et al, 2014;Hanson et al, 2004;Ostle et al, 2009;Raczka et al, 2013;Richardson et al, 2012;Schaefer et al, 2012;Schwalm et al, 2010;Stoy et al, 2013;Williams et al, 2009;Zaehle et al, 2014). Further, model development from these focused site-scale studies, especially in close collaboration with experimentalists, can inform and prioritize new experiments and observations that are specifically designed to advance understanding of critical terrestrial ecosystems and processes (Shi et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

Evaluating the Community Land Model in a pine stand with shading manipulations and 13CO2 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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“…Although C dynamics have been extensively measured and analyzed at site level (18)(19)(20)(21), the respiration and allocation of fixed C and its residence time within the major C pools are difficult and expensive to measure at site level and remain poorly quantified on global scales. As a result, global terrestrial C cycle models rely on land cover type-specific C cycling parameters-based on spatially preassigned plant functional types-to determine C fluxes and C pools (22).…”

mentioning

confidence: 99%

The decadal state of the terrestrial carbon cycle: Global retrievals of terrestrial carbon allocation, pools, and residence times

Bloom

Exbrayat

Velde

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

310

425

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The terrestrial carbon cycle is currently the least constrained component of the global carbon budget. Large uncertainties stem from a poor understanding of plant carbon allocation, stocks, residence times, and carbon use efficiency. Imposing observational constraints on the terrestrial carbon cycle and its processes is, therefore, necessary to better understand its current state and predict its future state. We combine a diagnostic ecosystem carbon model with satellite observations of leaf area and biomass (where and when available) and soil carbon data to retrieve the first global estimates, to our knowledge, of carbon cycle state and process variables at a 1°× 1°r esolution; retrieved variables are independent from the plant functional type and steady-state paradigms. Our results reveal global emergent relationships in the spatial distribution of key carbon cycle states and processes. Live biomass and dead organic carbon residence times exhibit contrasting spatial features (r = 0.3). Allocation to structural carbon is highest in the wet tropics (85-88%) in contrast to higher latitudes (73-82%), where allocation shifts toward photosynthetic carbon. Carbon use efficiency is lowest (0.42-0.44) in the wet tropics. We find an emergent global correlation between retrievals of leaf mass per leaf area and leaf lifespan (r = 0.64-0.80) that matches independent trait studies. We show that conventional land cover types cannot adequately describe the spatial variability of key carbon states and processes (multiple correlation median = 0.41). This mismatch has strong implications for the prediction of terrestrial carbon dynamics, which are currently based on globally applied parameters linked to land cover or plant functional types.carbon cycle | biomass | soil carbon | allocation | residence time T he terrestrial carbon (C) cycle remains the least constrained component of the global C budget (1). In contrast to a relatively stable increase of the ocean CO 2 sink from 0.9 to 2.7 Pg C y −1 over the past 40 y, terrestrial CO 2 uptake has been found to vary between a net 4.1-Pg C y −1 sink to a 0.4-Pg C y −1 source, and accounts for a majority of the interannual variability in atmospheric CO 2 growth. The complex response of terrestrial ecosystem CO 2 exchanges to short-and long-term changes in temperature, water availability, nutrient availability, and rising atmospheric CO 2 (2-6) remains highly uncertain in C cycle model projections (7). As a result, there are large gaps in our understanding of terrestrial C dynamics, including the magnitude and residence times of the major ecosystem C pools (8, 9) and rates of autotrophic respiration (10). Moreover, the impact of climatic extremes on C cycling, such as recent Amazon droughts (11), highlights the importance of understanding the terrestrial C cycle sensitivity to climate variability. To understand terrestrial CO 2 exchanges in the past, present, and future, we need to better constrain current dynamics of ecosystem C cycling from regional to global scales.C uptake, allocati...

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Where does the carbon go? A model–data intercomparison of vegetation carbon allocation and turnover processes at two temperate forest free‐air CO₂ enrichment sites

Cited by 286 publications

References 79 publications

Modelled interglacial carbon cycle dynamics during the Holocene, the Eemian and Marine Isotope Stage (MIS) 11

Modelled interglacial carbon cycle dynamics during the Holocene, the Eemian and Marine Isotope Stage (MIS) 11

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

The decadal state of the terrestrial carbon cycle: Global retrievals of terrestrial carbon allocation, pools, and residence times

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Where does the carbon go? A model–data intercomparison of vegetation carbon allocation and turnover processes at two temperate forest free‐air CO2 enrichment sites

Cited by 286 publications

References 79 publications

Modelled interglacial carbon cycle dynamics during the Holocene, the Eemian and Marine Isotope Stage (MIS) 11

Modelled interglacial carbon cycle dynamics during the Holocene, the Eemian and Marine Isotope Stage (MIS) 11

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

The decadal state of the terrestrial carbon cycle: Global retrievals of terrestrial carbon allocation, pools, and residence times

Contact Info

Product

Resources

About

Where does the carbon go? A model–data intercomparison of vegetation carbon allocation and turnover processes at two temperate forest free‐air CO₂ enrichment sites

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