Contrasting response of grassland versus forest carbon and water fluxes to spring drought in Switzerland

Wolf, Sebastian; Eugster, Werner; Ammann, Christof; Häni, Matthias; Zielis, S.; Hiller, Rebecca; Stieger, J.; Imer, D.; Merbold, Lutz; Buchmann, Nina

doi:10.1088/1748-9326/8/3/035007

Cited by 126 publications

(133 citation statements)

References 41 publications

(34 reference statements)

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“…Such a strong effect of droughts (compared to high temperatures alone) on GPP and the generally decreasing effect of drought on GPP is consistent with other studies (e.g. Ciais et al, 2005;Zhao and Running, 2010;Wolf et al, 2013;Zscheischler et al, 2014a, d, c) where water stress directly forces plants to close their stomata to limit transpiration, reducing photosynthesis. Similarly, Jung et al (2017) found that water availability is a much bigger control on the inter annual variability of GPP (IAV, which is controlled to a large degree by extreme events) compared to a smaller temperature control on a global In contrast to the small response of GPP to heat, however, R eco generally increased during most high temperature extreme events (Fig.…”

supporting

confidence: 91%

“…Teuling et al, 2010). Other important aspects to include in future studies are the timing of the extreme during the growing season, which can significantly influence the response (Schwalm et al, 2010;De Boeck and Verbeeck, 2011;Wolf et al, 2013). Eddy covariance measurements continue to be collected so for several FLUXNET sites increasingly long time series are becoming available.…”

mentioning

confidence: 99%

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Impacts of droughts and extreme temperature events on gross primary production and ecosystem respiration: a systematic assessment across ecosystems and climate zones

Buttlar¹,

Zscheischler²,

Rammig³

et al. 2017

Preprint

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Abstract.Extreme climatic events, such as droughts and heat stress induce anomalies in ecosystem-atmosphere CO 2 fluxes, such as gross primary production (GPP) and ecosystem respiration (R eco ), and, hence, can change the net ecosystem carbon balance.However, despite our increasing understanding of the underlying mechanisms, the magnitudes of the impacts of different types of extremes on GPP and R eco within and between ecosystems remain poorly predicted. Here we aim to identify the major 5 factors controlling the amplitude of extreme event impacts on GPP, R eco , and the resulting net ecosystem production (NEP).We focus on the impacts of heat and drought and their combination. We identified hydrometeorological extreme events in consistently downscaled water availability and temperature measurements over a 30 year time period. We then used FLUXNET eddy-covariance flux measurements to estimate the CO 2 flux anomalies during these extreme events across dominant vegetation types and climate zones. Overall, our results indicate that short-term heat extremes increased respiration more strongly than 10 they down-regulated GPP, resulting in a moderate reduction of the ecosystem's carbon sink potential. In the absence of heat stress, droughts tended to have smaller and similarly dampening effects on both GPP and R eco , and, hence, often resulted in neutral NEP responses. The combination of drought and heat typically led to a strong decrease in GPP, whereas heat and drought impacts on respiration partially offset each other. Taken together, compound heat and drought events led to the strongest C sink reduction compared to any single-factor extreme. A key insight of this paper, however, is that duration matters most: 15 for heat stress during droughts, the magnitude of impacts systematically increased with duration, whereas under heat stress without drought, the response of R eco over time turned from an initial increase to a down-regulation after about two weeks.This confirms earlier theories that not only the magnitude but also the duration of an extreme event determines its impact. Our study corroborates the results of several local site-level case studies, but as a novelty generalizes these findings at the global scale. Specifically, we find that the different response functions of the two antipodal land-atmosphere fluxes GPP and R eco can 20 also result in increasing NEP during certain extreme conditions. Apparently counterintuitive findings of this kind bear great potential for scrutinizing the mechanisms implemented in state-of-the-art terrestrial biosphere models and provide a benchmark for future model development and testing.

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supporting

confidence: 91%

mentioning

confidence: 99%

Impacts of droughts and extreme temperature events on gross primary production and ecosystem respiration: a systematic assessment across ecosystems and climate zones

Buttlar¹,

Zscheischler²,

Rammig³

et al. 2017

Preprint

Self Cite

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show abstract

“…Due to the stochastic nature of the turbulent flow, there is always a random error component in the observations. In addition, imperfect spectral corrections and gap-filling procedures as well as calibration problems may be sources of systematic errors (Richardson et al, 2012;Wilson et al, 2002). The uncertainty of EC flux data is typically 20-30 % for annual carbon budget Baldocchi, 2003).…”

Section: Differences Between Observations and Site Simulationsmentioning

confidence: 99%

“…Granier et al (2008) reported that EWUE increased linearly with soil water deficit duration and intensity at a young beech forest site in north-eastern France. Moreover, EWUE also increased substantially at two forest sites, but not at grassland sites, during the 2011 spring drought in Switzerland (Wolf et al, 2013). However, no differences in EWUE were shown between abundant-and lowrainfall years at a boreal Scots pine forest site in southeastern Finland, even though GPP was reduced during lowrainfall years with long-lasting drought periods (Ge et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

Response of water use efficiency to summer drought in a boreal Scots pine forest in Finland

et al. 2017

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Abstract. The influence of drought on plant functioning has received considerable attention in recent years, however our understanding of the response of carbon and water coupling to drought in terrestrial ecosystems still needs to be improved. A severe soil moisture drought occurred in southern Finland in the late summer of 2006. In this study, we investigated the response of water use efficiency to summer drought in a boreal Scots pine forest (Pinus sylvestris) on the daily time scale mainly using eddy covariance flux data from the Hyytiälä (southern Finland) flux site. In addition, simulation results from the JSBACH land surface model were evaluated against the observed results. Based on observed data, the ecosystem level water use efficiency (EWUE; the ratio of gross primary production, GPP, to evapotranspiration, ET) showed a decrease during the severe soil moisture drought, while the inherent water use efficiency (IWUE; a quantity defined as EWUE multiplied with mean daytime vapour pressure deficit, VPD) increased and the underlying water use efficiency (uWUE, a metric based on IWUE and a simple stomatal model, is the ratio of GPP multiplied with a square root of VPD to ET) was unchanged during the drought. The decrease in EWUE was due to the stronger decline in GPP than in ET. The increase in IWUE was because of the decreased stomatal conductance under increased VPD. The unchanged uWUE indicates that the trade-off between carbon assimilation and transpiration of the boreal Scots pine forest was not disturbed by this drought event at the site. The JS-BACH simulation showed declines of both GPP and ET under the severe soil moisture drought, but to a smaller extent compared to the observed GPP and ET. Simulated GPP and ET led to a smaller decrease in EWUE but a larger increase in IWUE because of the severe soil moisture drought in comparison to observations. As in the observations, the simulated uWUE showed no changes in the drought event. The model deficiencies exist mainly due to the lack of the limiting effect of increased VPD on stomatal conductance during the low soil moisture condition. Our study provides a deeper understanding of the coupling of carbon and water cycles in the boreal Scots pine forest ecosystem and suggests possible improvements to land surface models, which play an important role in the prediction of biosphere-atmosphere feedbacks in the climate system.

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“…For instance, Mamolos et al [30] recorded an earlier maximum aboveground biomass of early-season species in response to drought in a Mediterranean lowland grassland. A case study in Switzerland indicates that the full flowering of dandelion and cocksfoot grass was 11 days earlier under spring drought than the annual mean flowering [31]. Using remote sensing datasets, the response of grassland phenology to drought on larger scales have been recently investigated.…”

Section: Introductionmentioning

confidence: 99%

Grassland Phenology Response to Drought in the Canadian Prairies

2017

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Drought is a significant climatic disturbance in grasslands, yet the impact drought caused by global warming has on grassland phenology is still unclear. Our research investigates the long-term variability of grassland phenology in relation to drought in the Canadian prairies from 1982 to 2014. Based on the start of growing season (SOG) and the end of growing season (EOG) derived from Global Inventory Modeling and Mapping Studies (GIMMS) NDVI3g datasets, we found that grasslands demonstrated complex phenology trends over our study period. We retrieved the drought conditions of the prairie ecozone at multiple time scales from the 1-to 12-month Standardized Precipitation Evapotranspiration Index (SPEI). We evaluated the correlations between the detrended time series of phenological metrics and SPEIs through Pearson correlation analysis and identified the dominant drought where the maximum correlations were found for each ecozone and each phenological metric. The dominant drought over preceding months account for 14-33% and 26-44% of the year-to-year variability of SOG and EOG, respectively, and fewer water deficits would favor an earlier SOG and delayed EOG. The drought-induced shifts in SOG and EOG were determined based on the correlation between the dominant drought and the year-to-year variability using ordinary least square (OLS) method. Our research also quantifies the correlation between precipitation and the evolution of the dominant droughts and the drought-induced shifts in grassland phenology. Every millimeter (mm) increase in precipitation accumulated over the dominant periods would cause SOG to occur 0.06-0.21 days earlier, and EOG to occur 0.23-0.45 days later. Our research reveals a complex phenology response in relation to drought in the Canadian prairie grasslands and demonstrates that drought is a significant factor in the timing of both SOG and EOG. Thus, it is necessary to include drought-related climatic variables when predicting grassland phenology response to climate change and variability.

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Contrasting response of grassland versus forest carbon and water fluxes to spring drought in Switzerland

Cited by 126 publications

References 41 publications

Impacts of droughts and extreme temperature events on gross primary production and ecosystem respiration: a systematic assessment across ecosystems and climate zones

Impacts of droughts and extreme temperature events on gross primary production and ecosystem respiration: a systematic assessment across ecosystems and climate zones

Response of water use efficiency to summer drought in a boreal Scots pine forest in Finland

Grassland Phenology Response to Drought in the Canadian Prairies

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