The match and mismatch between photosynthesis and land surface phenology of deciduous forests

D’Odorico, Petra; Gonsamo, Alemu; Gough, Christopher M.; Bohrer, Gil; Morison, J. I. L.; Wilkinson, Matthew; Hanson, Paul J.; Gianelle, Damiano; Fuentes, José D.; Buchmann, Nina

doi:10.1016/j.agrformet.2015.07.005

Cited by 92 publications

(63 citation statements)

References 68 publications

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“…NDVI, EVI, and MTCI respond to greenness, wetness and dryness dynamics, from which LSP extraction in as predominantly snow covered areas as circumpolar region is far from trivial. These shortcomings are well documented in previous studies (Delbart et al 2005;Delbart et al 2006;D'Odorico et al 2015;Gonsamo et al 2012a;Jin and Eklundh 2014;White et al 2009).…”

Section: Introductionmentioning

confidence: 57%

Circumpolar vegetation dynamics product for global change study

Gonsamo

Chen

2016

Remote Sensing of Environment

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Land surface phenology (LSP) and vegetation growth of the circumpolar north are changing in response to more pronounced warming in the region. We here introduce the first phenology index (PI) based vegetation dynamics product, comprising start (SOS), end (EOS), length of growing season (LOS), and growing season integrated annual normalized difference vegetation index (NDVI), specifically designed for the entire circumpolar north (> 45 o N) using SPOT VGT data starting from 1999. PI combines the merits of NDVI and normalized difference infrared index (NDII) by taking the difference of squared greenness (from NDVI) and wetness (from NDII) to remove the soil and snow cover dynamics from key vegetation LSP cycles. The results show that the circumpolar vegetation dynamics and their spatial distributions are realistically detected. Further validation based on North American and European deciduous broadleaf, evergreen needleleaf and mixed forests, and wetland flux tower sites shows good agreements between the LSP dates from the circumpolar vegetation dynamics and ground phenology estimates from CO 2 flux measurements. The validation also proves that the circumpolar vegetation dynamics product is an improvement over the operational global MODIS Combined Land Cover Dynamics (MCD12Q2) product for the circumpolar region. The results are further compared with the interannual variability of sea ice extent and leading teleconnection patterns in the region. The circumpolar averaged results show that, the growing season integrated annual NDVI is significantly increasing (0.68% yr -1 , p=0.006) and well correlated with the growing season sea ice extent trend © 2016. This manuscript version is made available under the Elsevier user license http://www.elsevier.com/open-access/userlicense/1.0/ (p=0.007). The circumpolar vegetation dynamics is more related to Polar/ Eurasia pattern (i.e., indicator of circumpolar vortex) than to Scandinavian Pattern (SCA) and North Atlantic Oscillation (NAO). In view of the considerable scientific and policy importance of the circumpolar region, particularly the arctic ecosystems, the presented circumpolar vegetation dynamics product will greatly contribute to study changes in plant growth, phenology, photosynthetic capacity, and associated feedbacks under climate change.

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Section: Introductionmentioning

confidence: 57%

Circumpolar vegetation dynamics product for global change study

Gonsamo

Chen

2016

Remote Sensing of Environment

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“…However, this amounts to only 5 days in DBF (see Table S1). At finer temporal and spatial resolution, a lag between leaf phenology/greenness and GPP seasonality has been observed (Shen et al ., ; D'Odorico et al ., ) both at the start and end of the growing season in deciduous vegetation. Although the maps in Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Ongoing efforts to exploit reflectance-based observations to indicate GPP seasonality also in boreal ecosystems have lead to the development of improved vegetation indices with lower sensitivity to snow and background changes and higher consistency in the relationship to canopy development and GPP. Examples are the plant phenology index (Jin & Eklundh, 2014) or the phenology index (Gonsamo et al, 2012;D'Odorico et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

Satellite chlorophyll fluorescence measurements reveal large‐scale decoupling of photosynthesis and greenness dynamics in boreal evergreen forests

Walther

Voigt

Thum

et al. 2016

Global Change Biology

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Mid‐to‐high latitude forests play an important role in the terrestrial carbon cycle, but the representation of photosynthesis in boreal forests by current modelling and observational methods is still challenging. In particular, the applicability of existing satellite‐based proxies of greenness to indicate photosynthetic activity is hindered by small annual changes in green biomass of the often evergreen tree population and by the confounding effects of background materials such as snow. As an alternative, satellite measurements of sun‐induced chlorophyll fluorescence (SIF) can be used as a direct proxy of photosynthetic activity. In this study, the start and end of the photosynthetically active season of the main boreal forests are analysed using spaceborne SIF measurements retrieved from the GOME‐2 instrument and compared to that of green biomass, proxied by vegetation indices including the Enhanced Vegetation Index (EVI) derived from MODIS data. We find that photosynthesis and greenness show a similar seasonality in deciduous forests. In high‐latitude evergreen needleleaf forests, however, the length of the photosynthetically active period indicated by SIF is up to 6 weeks longer than the green biomass changing period proxied by EVI, with SIF showing a start‐of‐season of approximately 1 month earlier than EVI. On average, the photosynthetic spring recovery as signalled by SIF occurs as soon as air temperatures exceed the freezing point (2–3 °C) and when the snow on the ground has not yet completely melted. These findings are supported by model data of gross primary production and a number of other studies which evaluated in situ observations of CO2 fluxes, meteorology and the physiological state of the needles. Our results demonstrate the sensitivity of space‐based SIF measurements to light‐use efficiency of boreal forests and their potential for an unbiased detection of photosynthetic activity even under the challenging conditions interposed by evergreen boreal ecosystems.

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“…Phenology Index combines the merits of NDVI and NDII by taking the difference of squared greenness and wetness to remove the soil and snow cover dynamics from key vegetation dynamics cycles, was validated, and found to be a better estimator of SOS, EOS, and LOS for northern ecosystems (Gonsamo et al, 2012a;D'Odorico et al, 2015;Gonsamo & Chen, 2016).…”

Section: Methodsmentioning

confidence: 99%

Changes in vegetation phenology are not reflected in atmospheric CO₂ and ¹³C/¹²C seasonality

Gonsamo

D’Odorico

Chen

et al. 2017

Global Change Biology

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Northern terrestrial ecosystems have shown global warming-induced advances in start, delays in end, and thus increased lengths of growing season and gross photosynthesis in recent decades. The tradeoffs between seasonal dynamics of two opposing fluxes, CO uptake through photosynthesis and release through respiration, determine the influence of the terrestrial ecosystem on the atmospheric CO and C/ C seasonality. Here, we use four CO observation stations in the Northern Hemisphere, namely Alert, La Jolla, Point Barrow, and Mauna Loa Observatory, to determine how changes in vegetation productivity and phenology, respiration, and air temperature affect both the atmospheric CO and C/ C seasonality. Since the 1960s, the only significant long-term trend of CO and C/ C seasonality was observed at the northern most station, Alert, where the spring CO drawdown dates advanced by 0.65 ± 0.55 days yr , contributing to a nonsignificant increase in length of the CO uptake period (0.74 ± 0.67 days yr ). For Point Barrow station, vegetation phenology changes in well-watered ecosystems such as the Canadian and western Siberian wetlands contributed the most to C/ C seasonality while the CO seasonality was primarily linked to nontree vegetation. Our results indicate significant increase in the Northern Hemisphere soil respiration. This means, increased respiration of C depleted plant materials cancels out the C gain from enhanced vegetation activities during the start and end of growing season. These findings suggest therefore that parallel warming-induced increases both in photosynthesis and respiration contribute to the long-term stability of CO and C/ C seasonality under changing climate and vegetation activity. The summer photosynthesis and the soil respiration in the dormant seasons have become more vigorous which lead to increased peak-to-through CO amplitude. As the relative magnitude of the increased photosynthesis in summer months is more than the increased respiration in dormant months, we have the increased overall carbon uptake rates in the northern ecosystems.

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The match and mismatch between photosynthesis and land surface phenology of deciduous forests

Cited by 92 publications

References 68 publications

Circumpolar vegetation dynamics product for global change study

Circumpolar vegetation dynamics product for global change study

Satellite chlorophyll fluorescence measurements reveal large‐scale decoupling of photosynthesis and greenness dynamics in boreal evergreen forests

Changes in vegetation phenology are not reflected in atmospheric CO₂ and ¹³C/¹²C seasonality

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The match and mismatch between photosynthesis and land surface phenology of deciduous forests

Cited by 92 publications

References 68 publications

Circumpolar vegetation dynamics product for global change study

Circumpolar vegetation dynamics product for global change study

Satellite chlorophyll fluorescence measurements reveal large‐scale decoupling of photosynthesis and greenness dynamics in boreal evergreen forests

Changes in vegetation phenology are not reflected in atmospheric CO2 and 13C/12C seasonality

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Changes in vegetation phenology are not reflected in atmospheric CO₂ and ¹³C/¹²C seasonality