Temporal disparity in leaf chlorophyll content and leaf area index across a growing season in a temperate deciduous forest

Croft, Holly; Chen, Jing M.; Zhang, Yongqin

doi:10.1016/j.jag.2014.06.005

Cited by 46 publications

(30 citation statements)

References 58 publications

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“…N Area trends are adjusted according to variations in SLA, with higher SLA values at the start of the season compensating for the higher N Mass values seen in early season. Notably, both N Mass and N Area are both high at the start of the season, relative to Chl Leaf (Croft et al ., b; Croft et al ., ). Photosynthesis rates display a similar seasonal profile to Chl Leaf , increasing slowly at the start of the season, until values stabilize in the middle of the growing season, and declining during leaf senescence.…”

Section: Resultsmentioning

confidence: 99%

“…The LAI maps are shown to demonstrate the deviation between physiology and canopy structure, where LAI is more spatially consistent in the middle of the season (202–266) and also as

{Vcmax}_{25}

begins to decline. This also demonstrates the importance in distinguishing overall leaf area from leaf photosynthetic capacity (Croft et al ., , ).…”

Section: Resultsmentioning

confidence: 99%

“…In contrast to some other studies, who found relatively stable relationships between N Leaf and Vcmax (Ellsworth et al ., ; Kattge et al ., ), this research found weaker correlations between

{Vcmax}_{25}

and N Area ( R 2 = 0.62, P < 0.001), which was in large part due to the divergence in the seasonal profile of both variables (Fig. ), confirming previous studies that found that leaf physiological development continues longer than morphological development (Wilson et al ., ; Xu & Baldocchi, ; Croft et al ., ). The high leaf nitrogen results at the start of the season are due to inorganic N present in buds prior to leaf flushing (Migita et al ., ).…”

Section: Discussionmentioning

confidence: 97%

See 2 more Smart Citations

Leaf chlorophyll content as a proxy for leaf photosynthetic capacity

Croft

Chen

Luo

et al. 2017

Global Change Biology

466

335

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Improving the accuracy of estimates of forest carbon exchange is a central priority for understanding ecosystem response to increased atmospheric CO levels and improving carbon cycle modelling. However, the spatially continuous parameterization of photosynthetic capacity (Vcmax) at global scales and appropriate temporal intervals within terrestrial biosphere models (TBMs) remains unresolved. This research investigates the use of biochemical parameters for modelling leaf photosynthetic capacity within a deciduous forest. Particular attention is given to the impacts of seasonality on both leaf biophysical variables and physiological processes, and their interdependent relationships. Four deciduous tree species were sampled across three growing seasons (2013-2015), approximately every 10 days for leaf chlorophyll content (Chl ) and canopy structure. Leaf nitrogen (N ) was also measured during 2014. Leaf photosynthesis was measured during 2014-2015 using a Li-6400 gas-exchange system, with A-Ci curves to model Vcmax. Results showed that seasonality and variations between species resulted in weak relationships between Vcmax normalized to 25°C (Vcmax25) and N (R = 0.62, P < 0.001), whereas Chl demonstrated a much stronger correlation with Vcmax25 (R = 0.78, P < 0.001). The relationship between Chl and N was also weak (R = 0.47, P < 0.001), possibly due to the dynamic partitioning of nitrogen, between and within photosynthetic and nonphotosynthetic fractions. The spatial and temporal variability of Vcmax25 was mapped using Landsat TM/ETM satellite data across the forest site, using physical models to derive Chl . TBMs largely treat photosynthetic parameters as either fixed constants or varying according to leaf nitrogen content. This research challenges assumptions that simple N -Vcmax25 relationships can reliably be used to constrain photosynthetic capacity in TBMs, even within the same plant functional type. It is suggested that Chl provides a more accurate, direct proxy for Vcmax25 and is also more easily retrievable from satellite data. These results have important implications for carbon modelling within deciduous ecosystems.

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Section: Resultsmentioning

confidence: 99%

“…The LAI maps are shown to demonstrate the deviation between physiology and canopy structure, where LAI is more spatially consistent in the middle of the season (202–266) and also as

{Vcmax}_{25}

begins to decline. This also demonstrates the importance in distinguishing overall leaf area from leaf photosynthetic capacity (Croft et al ., , ).…”

Section: Resultsmentioning

confidence: 99%

“…In contrast to some other studies, who found relatively stable relationships between N Leaf and Vcmax (Ellsworth et al ., ; Kattge et al ., ), this research found weaker correlations between

{Vcmax}_{25}

Section: Discussionmentioning

confidence: 97%

See 1 more Smart Citation

Leaf chlorophyll content as a proxy for leaf photosynthetic capacity

Croft

Chen

Luo

et al. 2017

Global Change Biology

466

335

View full text Add to dashboard Cite

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“…The relationships of NEP to VPD and PAR display an interesting temporal component with different responses in fall as compared to spring; this indicates an underlying hysteresis, affected by plant physiological factors or a dependence on other environmental controls (Niu et al, 2011). In the case of PAR, for example, the same light intensity did not lead to the equivalent NEP response in spring as it did in summer or fall months, which could be due to a delay in the photosynthetic efficiency in the spring, as chlorophyll is accumulating (Croft et al, 2014). Fig.…”

Section: Intra-annual Dependency Of Carbon Exchange On Environmental mentioning

confidence: 95%

Trends of carbon fluxes and climate over a mixed temperate–boreal transition forest in southern Ontario, Canada

Froelich

Croft

Chen

et al. 2015

Agricultural and Forest Meteorology

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“…The comparative analyses focus on the consistency of temporal profiles and data gap occurrences for major land cover types. Since NDVI has been widely used for LAI estimation, both LAI and NDVI products are frequently compared (Croft et al, ; Hadria et al, ). Given the known saturation issues with the NDVI‐LAI relationship, LAI can be evaluated with other spectral data or VI products (e.g., enhanced VI and soil‐adjusted VI; Biudes et al, ; Houborg et al, ).…”

Section: Product Validation and Evaluationmentioning

confidence: 99%

An Overview of Global Leaf Area Index (LAI): Methods, Products, Validation, and Applications

Fang

Baret

Plummer

et al. 2019

Reviews of Geophysics

507

252

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Leaf area index (LAI) is a critical vegetation structural variable and is essential in the feedback of vegetation to the climate system. The advancement of the global Earth Observation has enabled the development of global LAI products and boosted global Earth system modeling studies. This overview provides a comprehensive analysis of LAI field measurements and remote sensing estimation methods, the product validation methods and product uncertainties, and the application of LAI in global studies. First, the paper clarifies some definitions related to LAI and introduces methods to determine LAI from field measurements and remote sensing observations. After introducing some major global LAI products, progresses made in temporal compositing and prospects for future LAI estimation are analyzed. Subsequently, the overview discusses various LAI product validation schemes, uncertainties in global moderate resolution LAI products, and high resolution reference data. Finally, applications of LAI in global vegetation change, land surface modeling, and agricultural studies are presented. It is recommended that (1) continued efforts are taken to advance LAI estimation algorithms and provide high temporal and spatial resolution products from current and forthcoming missions; (2) further validation studies be conducted to address the inadequacy of current validation studies, especially for underrepresented regions and seasons; and (3) new research frontiers, such as machine learning algorithms, light detection and ranging technology, and unmanned aerial vehicles be pursued to broaden the production and application of LAI.

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Temporal disparity in leaf chlorophyll content and leaf area index across a growing season in a temperate deciduous forest

Cited by 46 publications

References 58 publications

Leaf chlorophyll content as a proxy for leaf photosynthetic capacity

Leaf chlorophyll content as a proxy for leaf photosynthetic capacity

Trends of carbon fluxes and climate over a mixed temperate–boreal transition forest in southern Ontario, Canada

An Overview of Global Leaf Area Index (LAI): Methods, Products, Validation, and Applications

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