Inferring Amazon leaf demography from satellite observations of leaf area index

Caldararu, Silvia; Palmer, Paul I.; Purves, Drew W.

doi:10.5194/bg-9-1389-2012

Cited by 50 publications

(70 citation statements)

References 53 publications

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“…However, these values of leaf production represent very short-term carbon pools as all leaves are expected to fall after a while and, contrary to wood production, cannot be directly connected to long-term variation of the biomass stock. Recent works throughout Amazonia have estimated a large range of leaf residence time, from 6 to 36 months, with a lifespan distribution suggesting a pronounced annual regularity (Caldararu et al, 2012). These authors found that the average leaf lifespan increases from the eastern Amazon, where leaves are typically short-lived, to the evergreen central Amazon Basin.…”

Section: Leaf Phenologymentioning

confidence: 85%

“…Seasonality of leaf phenology in tropical rainforests has been observed either from (i) field measurements of litterfall and leaf production Zalamea and Gonzalez, 2008;Bonal et al, 2008;Sabatier and Puig, 1986) or (ii) satellite data (Huete et al, 2006;Asner et al, 2000Asner et al, , 2004Caldararu et al, 2012;Pennec et al, 2011). The latter studies characterize leaf phenology through variations in different vegetation indices, i.e.…”

mentioning

confidence: 99%

“…The drivers of leaf phenology in tropical rainforests are still studied, but recent results suggest that irradiance is the main driver throughout Amazonia (Bradley et al, 2011). Flushes of new leaves with increased photosynthetic capacity have been observed in the dry season and appeared correlated with seasonal peaks in solar irradiance (Huete et al, 2006;Myneni et al, 2007;Brando et al, 2010;Saleska et al, 2003;Caldararu et al, 2012;Wright and Vanschaik, 1994;De Weirdt et al, 2012).…”

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confidence: 99%

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Asynchronism in leaf and wood production in tropical forests: a study combining satellite and ground-based measurements

Wagner

Rossi²,

Stahl

et al. 2013

Biogeosciences

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Abstract. The fixation of carbon in tropical forests mainly occurs through the production of wood and leaves, both being the principal components of net primary production. Currently field and satellite observations are independently used to describe the forest carbon cycle, but the link between satellite-derived forest phenology and field-derived forest productivity remains opaque. We used a unique combination of a MODIS enhanced vegetation index (EVI) dataset, a wood production model based on climate data and direct litterfall observations at an intra-annual timescale in order to question the synchronism of leaf and wood production in tropical forests. Even though leaf and wood biomass fluxes had the same range (respectively 2.4 ± 1.4 and 2.2 ± 0.4 Mg C ha −1 yr −1 ), they occurred separately in time. EVI increased with leaf renewal at the beginning of the dry season, when solar irradiance was at its maximum. At this time, wood production stopped. At the onset of the rainy season, when new leaves were fully mature and water available again, wood production quickly increased to reach its maximum in less than a month, reflecting a change in carbon allocation from short-lived pools (leaves) to long-lived pools (wood). The time lag between peaks of EVI and wood production (109 days) revealed a substantial decoupling between the leaf renewal assumed to be driven by irradiance and the water-driven wood production. Our work is a first attempt to link EVI data, wood production and leaf phenology at a seasonal timescale in a tropical evergreen rainforest and pave the way to develop more sophisticated global carbon cycle models in tropical forests.

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Section: Leaf Phenologymentioning

confidence: 85%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Asynchronism in leaf and wood production in tropical forests: a study combining satellite and ground-based measurements

Wagner

Rossi²,

Stahl

et al. 2013

Biogeosciences

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“…We will explore the implementation of a leaf demography scheme (Caldararu et al, 2012) that will allow us to account for the effects of leaf age on the isoprene emission, which has implications for atmospheric chemistry, for instance, timing of the seasonal transition from VOC to NO x -limited ozone production. We will explore daily and seasonal average isoprene emission model performance using an off-line version of the vegetation model that is driven by meteorology from the GMAO Modern Era-Retrospective Analysis (Rienecker et al, 2011).…”

Section: Discussionmentioning

confidence: 99%

Photosynthesis-dependent isoprene emission from leaf to planet in a global carbon-chemistry-climate model

et al. 2013

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Abstract. We describe the implementation of a biochemical model of isoprene emission that depends on the electron requirement for isoprene synthesis into the FarquharBall-Berry leaf model of photosynthesis and stomatal conductance that is embedded within a global chemistry-climate simulation framework. The isoprene production is calculated as a function of electron transport-limited photosynthesis, intercellular and atmospheric carbon dioxide concentration, and canopy temperature. The vegetation biophysics module computes the photosynthetic uptake of carbon dioxide coupled with the transpiration of water vapor and the isoprene emission rate at the 30 min physical integration time step of the global chemistry-climate model. In the model, the rate of carbon assimilation provides the dominant control on isoprene emission variability over canopy temperature. A control simulation representative of the present-day climatic state that uses 8 plant functional types (PFTs), prescribed phenology and generic PFT-specific isoprene emission potentials (fraction of electrons available for isoprene synthesis) reproduces 50 % of the variability across different ecosystems and seasons in a global database of 28 measured campaign-average fluxes. Compared to time-varying isoprene flux measurements at 9 select sites, the model authentically captures the observed variability in the 30 min Published by Copernicus Publications on behalf of the European Geosciences Union. 10244 N. Unger et al.: Photosynthesis-dependent isoprene emission from leaf to planet average diurnal cycle (R 2 = 64-96 %) and simulates the flux magnitude to within a factor of 2. The control run yields a global isoprene source strength of 451 TgC yr −1 that increases by 30 % in the artificial absence of plant water stress and by 55 % for potential natural vegetation.

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“…C cycle state variables, including the spatial variability of total biomass (Saatchi et al, 2011;Baccini et al, 2012) and soil carbon (Hiederer and Köchy, 2011), vary at < 1000 km scales. Methanogen-available C sources -such as gross primary production (GPP) and leaf litter -vary substantially at monthly timescales in the wet tropics (Beer et al, 2010;Chave et al, 2010;Caldararu et al, 2012). In the next section, we establish the CH 4 flux resolution and precision requirements based on the variability of potential tropical wetland CH 4 emissions process controls (namely carbon uptake, live biomass and dead organic matter stocks, inundation and precipitation).…”

Section: Wetland Process Controlsmentioning

confidence: 99%

What are the greenhouse gas observing system requirements for reducing fundamental biogeochemical process uncertainty? Amazon wetland CH<sub>4</sub> emissions as a case study

et al. 2016

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Abstract. Understanding the processes controlling terrestrial carbon fluxes is one of the grand challenges of climate science. Carbon cycle process controls are readily studied at local scales, but integrating local knowledge across extremely heterogeneous biota, landforms and climate space has proven to be extraordinarily challenging. Consequently, top-down or integral flux constraints at process-relevant scales are essential to reducing process uncertainty. Future satellite-based estimates of greenhouse gas fluxes -such as CO 2 and CH 4 -could potentially provide the constraints needed to resolve biogeochemical process controls at the required scales. Our analysis is focused on Amazon wetland CH 4 emissions, which amount to a scientifically crucial and methodologically challenging case study. We quantitatively derive the observing system (OS) requirements for testing wetland CH 4 emission hypotheses at a process-relevant scale. To distinguish between hypothesized hydrological and carbon controls on Amazon wetland CH 4 production, a satellite mission will need to resolve monthly CH 4 fluxes at a ∼ 333 km resolution and with a ≤ 10 mg CH 4 m −2 day −1 flux precision. We simulate a range of low-earth orbit (LEO) and geostationary orbit (GEO) CH 4 OS configurations to evaluate the ability of these approaches to meet the CH 4 flux requirements. Conventional LEO and GEO missions resolve monthly ∼ 333 km Amazon wetland fluxes at a 17.0 and 2.7 mg CH 4 m −2 day −1 median uncertainty level. Improving LEO CH 4 measurement precision by √ 2 would only reduce the median CH 4 flux uncertainty to 11.9 mg CH 4 m −2 day −1 . A GEO mission with targeted observing capability could resolve fluxes at a 2.0-2.4 mg CH 4 m −2 day −1 median precision by increasing the observation density in high cloud-cover regions at the expense of other parts of the domain. We find that residual CH 4 concentration biases can potentially reduce the ∼ 5-fold flux CH 4 precision advantage of a GEO mission to a ∼ 2-fold advantage (relative to a LEO mission). For residual CH 4 bias correlation lengths of 100 km, the GEO can nonetheless meet the ≤ 10 mg CH 4 m −2 day −1 requirements for systematic biases ≤ 10 ppb. Our study demonstrates that processdriven greenhouse gas OS simulations can enhance conventional uncertainty reduction assessments by quantifying the OS characteristics required for testing biogeochemical process hypotheses.

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Inferring Amazon leaf demography from satellite observations of leaf area index

Cited by 50 publications

References 53 publications

Asynchronism in leaf and wood production in tropical forests: a study combining satellite and ground-based measurements

Asynchronism in leaf and wood production in tropical forests: a study combining satellite and ground-based measurements

Photosynthesis-dependent isoprene emission from leaf to planet in a global carbon-chemistry-climate model

What are the greenhouse gas observing system requirements for reducing fundamental biogeochemical process uncertainty? Amazon wetland CH<sub>4</sub> emissions as a case study

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Inferring Amazon leaf demography from satellite observations of leaf area index

Cited by 50 publications

References 53 publications

Asynchronism in leaf and wood production in tropical forests: a study combining satellite and ground-based measurements

Asynchronism in leaf and wood production in tropical forests: a study combining satellite and ground-based measurements

Photosynthesis-dependent isoprene emission from leaf to planet in a global carbon-chemistry-climate model

What are the greenhouse gas observing system requirements for reducing fundamental biogeochemical process uncertainty? Amazon wetland CH&lt;sub&gt;4&lt;/sub&gt; emissions as a case study

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What are the greenhouse gas observing system requirements for reducing fundamental biogeochemical process uncertainty? Amazon wetland CH<sub>4</sub> emissions as a case study