Differential responses of carbon and water vapor fluxes to climate among evergreen needleleaf forests in the USA

Wagle, Pradeep; Xiao, Xiangming; Kolb, Thomas E.; Law, B. E.; Wharton, Sonia; Monson, Russell K.; Chen, Jiquan; Blanken, Peter D.; Novick, Kimberly A.; Dore, Sabina; Noormets, Asko; Gowda, Prasanna H.

doi:10.1186/s13717-016-0053-5

Cited by 17 publications

(14 citation statements)

References 84 publications

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“…Our data indicate that when air temperatures are anomalously high during a dry summer, as in 2015, decreased GPP is further exacerbated by stomatal closure in response to higher VPD and also likely by downregulation of enzymes (Wohlfahrt et al 2018), resulting in substantially lower pWUE. This finding agrees with the wavelet analysis by Wagle et al (2016), which indicates that carbon uptake (NEP or GPP) is constrained more than ET by VPD through restriction of stomatal regulation. This finding also echoes Reichstein et al (2002Reichstein et al ( , 2007, which documents a decrease in WUE at European evergreen needleleaf forests during drier years.…”

Section: Early Growing Seasonsupporting

confidence: 90%

“…In general, VPD and air temperature controlled all three WUE metrics at halfhourly and daily time scales, while atmospheric CO 2 concentration was identified as the most important indicator of monthly WUEs. Our analysis of variable importance using a machine learning technique (BRT) and a traditional statistical method (MLR) partly agree with a wavelet cross-correlation analysis by Wagle et al (2016), which indicates that variations in carbon uptake and evapotranspiration mostly resonate with VPD and air temperature from half-hourly to weekly timescales. The high dependence of WUE on VPD at sub-daily and daily time-scale implies a strong impact of atmospheric water demand on stomatal conductance which directly affects transpiration and indirectly affects photosynthesis.…”

Section: Discussionsupporting

confidence: 71%

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Trends and controls on water-use efficiency of an old-growth coniferous forest in the Pacific Northwest

Jiang

Still

Rastogi

et al. 2019

Environ. Res. Lett.

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At the ecosystem scale, water-use efficiency (WUE) is defined broadly as the ratio of carbon assimilated to water evaporated by an ecosystem. WUE is an important aspect of carbon and water cycling and has been used to assess forest ecosystem responses to climate change and rising atmospheric CO 2 concentrations. This study investigates the influence of meteorological and radiation variables on forest WUE by analyzing an 18 year (1998-2015) half-hourly time series of carbon and water fluxes measured with the eddy covariance technique in an old-growth conifer forest in the Pacific Northwest, USA. Three different metrics of WUE exhibit an overall increase over the period 1998-2007 mainly due to an increase in gross primary productivity (GPP) and a decrease in evapotranspiration (ET). However, the WUE metrics did not exhibit an increase across the period from 2008 to 2015 due to a greater reduction in GPP relative to ET. The strength of associations among particular meteorological variables and WUE varied with the scale of temporal aggregation used. In general, vapor pressure deficit and air temperature appear to control WUE at half-hourly and daily time scales, whereas atmospheric CO 2 concentration was identified as the most important factor controlling monthly WUE. Carbon and water fluxes and the consequent WUE showed a weak correlation to the Standard Precipitation Index, while carbon fluxes were strongly dependent on the combined effect of multiple climate factors. The inferred patterns and controls on forest WUE highlighted have implications for improved understanding and prediction of possible adaptive adjustments of forest physiology in response to climate change and rising atmospheric CO 2 concentrations.

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Section: Early Growing Seasonsupporting

confidence: 90%

Section: Discussionsupporting

confidence: 71%

Trends and controls on water-use efficiency of an old-growth coniferous forest in the Pacific Northwest

Jiang

Still

Rastogi

et al. 2019

Environ. Res. Lett.

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“…Warm phase years see the shortest period of net uptake (70 days) while cool phase years have the longest period of continuous daily −F NEE (115 days). Wind River's net carbon uptake period is relatively short compared to other US evergreen forests (mean=266 days, n=9 forests, stand ages range from 22 to 110 years, mean age=70 years) (Wagle et al 2016). The shorter net uptake period is due to a combination of geography and climate, and forest age and height.…”

Section: Resultsmentioning

confidence: 95%

“…δe is an important driver of canopy gasatmosphere exchange because it influences stomatal conductance and can limit photosynthetic CO 2 uptake at high levels, particularly when soil moisture is limited. The F NEE record at Wind River indicates that maximum half-hourly F NEE uptake occurs, on average, around 12°C and quickly declines once mean air temperatures and δe reach 20°C and 2.0 kPa, respectively (Wagle et al 2016). Net C uptake can occur even at very low temperatures (0°C-5°C) given that there is sufficient light for photosynthesis (Q p >50 MJ m −2 mo −1 ) (Falk et al 2005).…”

Section: Resultsmentioning

confidence: 99%

Climate indices strongly influence old-growth forest carbon exchange

Wharton

Falk

2016

Environ. Res. Lett.

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We present a decade and a half (1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013) of carbon dioxide fluxes from an old-growth stand in the American Pacific Northwest to identify ecosystem-level responses to Pacific teleconnection patterns, including the El Niño/Southern Oscillation (ENSO). This study provides the longest, continuous record of old-growth eddy flux data to date from one of the longest running Fluxnet stations in the world. From 1998 to 2013, average annual net ecosystem exchange ( F NEE ) at Wind River AmeriFlux was −32±84 g C m −2 yr −1 indicating that the late seral forest is on average a small net sink of atmospheric carbon. However, interannual variability is high (>300 g C m −2 yr −1 ) and shows that the stand switches from net carbon sink to source in response to climate drivers associated with ENSO. The old-growth forest is a much stronger sink during La Niña years (mean F NEE =−90 g C m −2 yr −1 ) than during El Niño when the stand turns carbon neutral or into a small net carbon source (mean F NEE =+17 g C m −2 yr −1 ). Forest inventory data dating back to the 1930s show a similar correlation with the lower frequency Pacific North American (PNA) and Pacific Decadal Oscillation (PDO) whereby higher aboveground net primary productivity ( F ANPP ) is associated with cool phases of both the PNA and PDO. These measurements add evidence that carbon exchange in old-growth stands may be more sensitive to climate variability across shorter time scales than once thought.

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“…In recent years, wavelet analysis has been used in many studies of geophysical data, such as river levels, turbulence over plant canopies, and pollutant concentrations (Collineau & Brunet, 1993;Stoy et al, 2013;Terradellas, Soler, Ferreres, & Bravo, 2005;Zeri, Oliveira-Junior, & Bastos Lyra, 2011) and also to study the interactions between environmental drivers and ecosystem fluxes (Braswell et al, 2005;Wagle et al, 2016). Wavelet coherence analysis is able to synthetically identify the points where two variables are correlated in a two dimensional space representing time and frequency.…”

Section: Wavelet Coherence Analysismentioning

confidence: 99%

Timescale effects on the environmental control of carbon and water fluxes of an apple orchard

Montagnani

Zanotelli

Tagliavini

et al. 2017

Ecology and Evolution

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Model parameterization and validation of earth–atmosphere interactions are generally performed using a single timescale (e.g., nearly instantaneous, daily, and annual), although both delayed responses and hysteretic effects have been widely recognized. The lack of consideration of these effects hampers our capability to represent them in empirical‐ or process‐based models. Here we explore, using an apple orchard ecosystem in the North of Italy as a simplified case study, how the considered timescale impacts the relative importance of the single environmental variables in explaining observed net ecosystem exchange (NEE) and evapotranspiration (ET). Using 6 years of eddy covariance and meteorological information as input data, we found a decay of the relative importance of the modeling capability of photosynthetically active radiation in explaining both NEE and ET moving from half‐hourly to seasonal timescale and an increase in the relative importance of air temperature (T) and VPD. Satellite NDVI, used as proxy of leaf development, added little improvement to overall modeling capability. Increasing the timescale, the number of variables needed for parameterization decreased (from 5 to 1), while the proportion of variance explained by the model increased (r 2 from 0.56–0.78 to 0.85–0.90 for NEE and ET respectively). The wavelet coherence and the phase analyses showed that the two variables that increased their relative importance when the scale increased (T, VPD) were not in phase at the correlation peak of both ET and NEE. This phase shift in the time domain corresponds to a hysteretic response in the meteorological variables domain. This work confirms that the model parameterization should be performed using parameters calculated at the appropriate scale. It suggests that in managed ecosystems, where the interannual variability is minimized by the agronomic practices, the use of timescales large enough to include hysteretic and delayed responses reduces the number of required input variables and improves their explanatory capacity.

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Differential responses of carbon and water vapor fluxes to climate among evergreen needleleaf forests in the USA

Cited by 17 publications

References 84 publications

Trends and controls on water-use efficiency of an old-growth coniferous forest in the Pacific Northwest

Trends and controls on water-use efficiency of an old-growth coniferous forest in the Pacific Northwest

Climate indices strongly influence old-growth forest carbon exchange

Timescale effects on the environmental control of carbon and water fluxes of an apple orchard

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