High atmospheric demand for water can limit forest carbon uptake and transpiration as severely as dry soil

Sulman, Benjamin N.; Roman, Daniel T.; Yi, K.; Wang, Lixin; Phillips, Richard P.; Novick, Kimberly A.

doi:10.1002/2016gl069416

Cited by 214 publications

(166 citation statements)

References 63 publications

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“…Such synoptic conditions are the most common weather pattern associated with Australian heat waves (Steffen et al, 2014). However, these weather patterns did not result in increased amounts of available energy at the surface, which was in contrast to heat waves observed in Europe and the USA (see Sect.…”

Section: Consequences Of Australian Heat Waves On Energy Fluxesmentioning

confidence: 57%

“…identified an increased vapour pressure deficit as detrimental to transpiration and net carbon uptake, finding that increased vapour pressure deficit is more detrimental than increased temperatures alone -with or without the imposition of drought. A recent study by Sulman et al (2016) confirmed that episodes of elevated vapour pressure deficit could reduce carbon uptake regardless of changes in soil moisture. Here, all ecosystems responded with increased carbon uptake to the precipitation events and the associated lower temperatures and vapour pressure deficit.…”

Section: The Effect Of Intermittent Precipitation During the Heat Wavementioning

confidence: 81%

“…An increased fraction of energy going into the latent rather than the sensible heat during HW2 at the drier sites (MW and TW) does not only have important consequences on the soil moisturetemperature feedback but also on ameliorating vapour pressure deficit (Fig. 3) and reducing the atmospheric demand that acts as a stressor on plants (Sulman et al, 2016). During HW1, the time of maximum carbon uptake at the woodland sites was earlier in the morning than during BGH, and we observed strongly reduced carbon uptake throughout the day.…”

Section: The Effect Of Intermittent Precipitation During the Heat Wavementioning

confidence: 99%

“…MW sites included (i) a coastal heath Banksia woodland (Gingin: AU-Gin); (ii) a semi-arid eucalypt woodland dominated by Salmon gum (Eucalyptus salmonophloia), with Gimlet (E. salubrious) and other eucalypts (Great Western Woodlands: AU-Gww); and (iii) a semi-arid mallee ecosystem (Calperum: AU-Cpr), which is characterised by an association of mallee eucalypts (E. dumosa, E. incrassata, E. oleosa and E. socialis) and spinifex hummocks (Triodia basedowii; Sun et al, 2015;Meyer et al, 2015). TW sites are classified as dry sclerophyll woodlands and include the following: (i) Wombat (AU-Wom), a secondary re-growth of Messmate Stringybark (E. oblique), NarrowLeaved Peppermint (E. radiate) and Candlebark (E. rubida); (ii) Whroo (AU-Whr), a box woodland mainly composed of Grey Box (E. microcarpa) and Yellow Gum (E. leucoxylon) with smaller numbers of Ironbark (E. sideroxylon) and Golden Wattle (Acacia pycnantha); (iii) Cumberland Plains (AU-Cum), where the canopy is dominated by Gumtopped Box (E. moluccana) and Red Ironbark (E. fibrosa), which host an expanding population of mistletoe (Amyema miquelii).…”

Section: Sitesmentioning

confidence: 99%

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Carbon uptake and water use in woodlands and forests in southern Australia during an extreme heat wave event in the “Angry Summer” of 2012/2013

et al. 2016

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Abstract. As a result of climate change warmer temperatures are projected through the 21st century and are already increasing above modelled predictions. Apart from increases in the mean, warm/hot temperature extremes are expected to become more prevalent in the future, along with an increase in the frequency of droughts. It is crucial to better understand the response of terrestrial ecosystems to such temperature extremes for predicting land-surface feedbacks in a changing climate. While land-surface feedbacks in drought conditions and during heat waves have been reported from Europe and the US, direct observations of the impact of such extremes on the carbon and water cycles in Australia have been lacking. During the 2012/2013 summer, Australia experienced a record-breaking heat wave with an exceptional spatial extent that lasted for several weeks. In this study we synthesised eddy-covariance measurements from seven woodlands and one forest site across three biogeographic regions in southern Australia. These observations were combined with model results from BIOS2 (Haverd et al., 2013a, b) to investigate the effect of the summer heat wave on the carbon and water exchange of terrestrial ecosystems which are known for their resilience toward hot and dry conditions. We found that water-limited woodland and energy-limited forest ecosystems responded differently to the heat wave. During the most intense part of the heat wave, the woodlands experienced decreased latent heat flux (23 % of background value), increased Bowen ratio (154 %) and reduced carbon uptake (60 %). At the same time the forest ecosystem showed increased latent heat flux (151 %), reduced Bowen ratio (19 %) and increased carbon uptake (112 %). Higher temperatures caused increased ecosystem respiration at all sites (up to 139 %). During daytime all ecosystems remained carbon sinks, but carbon uptake was reduced in magnitude. The number of hours during which the ecosystem acted as a carbon sink was also reduced, which switched the woodlands into a carbon source on a daily average. Precipitation occurred after the first, most intense part of the heat wave, and the subsequent cooler temperatures in the temperate woodlands led to recovery of the carbon sink, decreased the Bowen ratio (65 %) and hence increased evaporative cooling. Gross primary productivity in the woodlands recovered quickly with precipitation and cooler temperatures but respiration remained high. While the forest proved relatively resilient to this short-term heat extreme the response of the woodlands is the first direct evidence that the carbon sinks of large areas of Australia may not be sustainable in a future climate with an increased number, intensity and duration of heat waves.

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Section: Consequences Of Australian Heat Waves On Energy Fluxesmentioning

confidence: 57%

Section: The Effect Of Intermittent Precipitation During the Heat Wavementioning

confidence: 81%

Section: The Effect Of Intermittent Precipitation During the Heat Wavementioning

confidence: 99%

Section: Sitesmentioning

confidence: 99%

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Carbon uptake and water use in woodlands and forests in southern Australia during an extreme heat wave event in the “Angry Summer” of 2012/2013

et al. 2016

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“…The water saving benefits to plants of high CO 2 have the potential to counteract high temperature and VPD which occur during drought events [69]. However, while these effects are likely to be helpful during baseline or average conditions [70][71][72], but may not be able to compensate during extreme events (e.g. [73]).…”

Section: Plant Stress Under "Hot" Droughtsmentioning

confidence: 99%

Plants and Drought in a Changing Climate

Swann¹

2018

Preprint

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Purpose of review Climate is changing in response to rising concentrations of atmospheric CO 2 and it is commonly asserted that this will cause droughts to become more frequent and severe. However, different metrics of drought give diverging estimates of future impacts. I present a summary of the significant yet underappreciated influence that plant stomatal and growth responses to CO 2 have on drought, and highlight new insights into the impacts of drought on plants in a warmer world. Recent findings Plants influence the water availability on land, and thus reduce the duration and intensity of droughts under higher CO 2 conditions. Plants are concurrently more vulnerable to mortality when droughts occur under hotter conditions. Summary The frequency and severity of drought in the future depends on the response of plants to a changing climate-ignoring plant responses leads to over-prediction of drought. Nonetheless, the impact of current frequencies of drought on plants could lead to higher mortality rates in the future as plants must withstand drought stress simultaneously with hotter temperatures.

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Urban heat island‐induced increases in evapotranspirative demand

Zipper

Schatz

Kucharik

et al. 2017

Geophysical Research Letters

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Although the importance of vegetation in mitigating the urban heat island (UHI) is known, the impacts of UHI‐induced changes in micrometeorological conditions on vegetation are not well understood. Here we show that plant water requirements are significantly higher in urban areas compared to rural areas surrounding Madison, WI, driven by increased air temperature with minimal effects of decreased air moisture content. Local increases in impervious cover are strongly associated with increased evapotranspirative demand in a consistent manner across years, with most increases caused by elevated temperatures during the growing season rather than changes in changes in growing season length. Potential evapotranspiration is up to 10% higher due to the UHI, potentially mitigating changes to the water and energy balances caused by urbanization. Our results indicate that local‐scale land cover decisions (increases in impervious cover) can significantly impact evapotranspirative demand, with likely implications for water and carbon cycling in urban ecosystems.

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High atmospheric demand for water can limit forest carbon uptake and transpiration as severely as dry soil

Cited by 214 publications

References 63 publications

Carbon uptake and water use in woodlands and forests in southern Australia during an extreme heat wave event in the “Angry Summer” of 2012/2013

Carbon uptake and water use in woodlands and forests in southern Australia during an extreme heat wave event in the “Angry Summer” of 2012/2013

Plants and Drought in a Changing Climate

Urban heat island‐induced increases in evapotranspirative demand

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