Review: Response of water use efficiency to summer drought in boreal Scots pine forests in Finland

Abstract. The influence of drought on plant functioning has received considerable attention in recent years, although our understanding of the response of carbon and water coupling in terrestrial ecosystems remains unclear. In this study, we investigated the response of water use efficiency to summer drought in boreal forests at daily time scales mainly using eddy covariance flux data. In addition, simulation results from the JSBACH land surface model were evaluated against the observed results. Two Scots pine (Pinus sylvestris) sites at Hyytiälä (southern Finland) and Sodankylä (northern Finland) were used in the study. Based on observed data, the ecosystem level water use efficiency (EWUE) showed a decrease only during a severe soil moisture drought at Hyytiälä, whereas the inherent water use efficiency (IWUE) increased when there was a severe soil moisture drought at Hyytiälä and a moderate soil moisture drought at Sodankylä. This indicates a decrease in surface conductance at the ecosystem level, but the decrease in evapotranspiration (ET) was alleviated because of the increased vapor pressure deficit (VPD) during drought. Moreover, the changes in IWUE implied that Scots pine has weaker response to drought in the southern site than in the northern site. Thus, IWUE is a more appropriate metric than EWUE for capturing the impact of soil moisture drought on plant functioning at daily time scales. In general, the results from transpiration based ecosystem level water use efficiency (EWUEt) and IWUE, and the transpiration based inherent water use efficiency (IWUEt) from JSBACH simulations were similar to the observed results. The deviated groups of gross primary production (GPP) and evapotranspiration (ET) under severe soil moisture drought in observed data at Hyytiälä were also successfully captured in the simulated results. However, deficiencies in the model were clearly seen by the limitation effect of air humidity on stomatal conductance in observed data. Our study provides a deeper understanding of carbon and water dynamics in the major boreal ecosystem. These findings highlight the importance of choosing a suitable plant functioning indicator when investigating the effects of drought, and suggest 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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Response of water use efficiency to summer drought in a boreal Scots pine forest in Finland

Biogeosciences ◽

10.5194/bg-14-4409-2017 ◽

2017 ◽

Vol 14 (18) ◽

pp. 4409-4422 ◽

Cited By ~ 12

Author(s):

Yao Gao ◽

Tiina Markkanen ◽

Mika Aurela ◽

Ivan Mammarella ◽

Tea Thum ◽

...

Keyword(s):

Soil Moisture ◽

Water Use Efficiency ◽

Water Use ◽

Scots Pine ◽

Land Surface ◽

Pine Forest ◽

Summer Drought ◽

Drought Event ◽

Use Efficiency ◽

Scots Pine Forest

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 JSBACH 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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Drought and mistletoe reduce growth and water-use efficiency of Scots pine

Forest Ecology and Management ◽

10.1016/j.foreco.2013.01.028 ◽

2013 ◽

Vol 296 ◽

pp. 64-73 ◽

Cited By ~ 25

Author(s):

Gabriel Sangüesa-Barreda ◽

Juan Carlos Linares ◽

J. Julio Camarero

Keyword(s):

Water Use Efficiency ◽

Water Use ◽

Scots Pine ◽

Use Efficiency

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Long tree-ring chronologies reveal 20th century increases in water-use efficiency but no enhancement of tree growth at five Iberian pine forests

Global Change Biology ◽

10.1111/j.1365-2486.2010.02373.x ◽

2011 ◽

Vol 17 (6) ◽

pp. 2095-2112 ◽

Cited By ~ 140

Author(s):

LAIA ANDREU-HAYLES ◽

OCTAVI PLANELLS ◽

EMILIA GUTIÉRREZ ◽

ELENA MUNTAN ◽

GERHARD HELLE ◽

...

Keyword(s):

Water Use Efficiency ◽

20Th Century ◽

Water Use ◽

Tree Ring ◽

Tree Growth ◽

Pine Forests ◽

Use Efficiency

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Increase in water-use efficiency and underlying processes in pine forests across a precipitation gradient in the dry Mediterranean region over the past 30 years

Oecologia ◽

10.1007/s00442-011-2010-4 ◽

2011 ◽

Vol 167 (2) ◽

pp. 573-585 ◽

Cited By ~ 70

Author(s):

Kadmiel Maseyk ◽

Debbie Hemming ◽

Alon Angert ◽

Steven W. Leavitt ◽

Dan Yakir

Keyword(s):

Water Use Efficiency ◽

Water Use ◽

Mediterranean Region ◽

Pine Forests ◽

Precipitation Gradient ◽

The Past ◽

Use Efficiency ◽

Underlying Processes

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Wild Miscanthus Germplasm in a Drought-Affected Area: Physiology and Agronomy Appraisals

Agronomy ◽

10.3390/agronomy10050679 ◽

2020 ◽

Vol 10 (5) ◽

pp. 679

Author(s):

Danilo Scordia ◽

Giovanni Scalici ◽

John Clifton-Brown ◽

Paul Robson ◽

Cristina Patanè ◽

...

Keyword(s):

Water Use Efficiency ◽

Water Use ◽

Mediterranean Climate ◽

Biomass Yield ◽

Net Photosynthesis ◽

High Yield ◽

Summer Drought ◽

Mediterranean Regions ◽

Use Efficiency ◽

The Mediterranean

Predictions of future climate scenarios indicate that yields from perennial biomass crops (PBCs) growing in the Mediterranean region are likely to decline due to prolonged drought. Among PBCs, Miscanthus grasses with C4 photosynthesis combine high yield potentials and water use efficiencies. However, the standard commercial clone M. x giganteus (Mxg), with minimal stomatal regulation, is too sensitive to drought for reliable yields in the Mediterranean regions. This paper screened a diverse panel of thirteen Miscanthus genotypes (M. sinensis, M. floridulus, M. sacchariflorus and Mxg) to identify which types could maximize yield under summer drought conditions typical in the South Mediterranean climate. In the second growing season, significant differences were observed for plant height (from 63 to 185 cm), stem number (from 12 to 208 stems plant−1), biomass yield (from 0.17 to 6.4 kg DM plant−1) and whole crop water use efficiency (from 0.11 to 7.0 g L−1). Temporal variation in net photosynthesis, stomatal conductance, transpiration rate and instantaneous water use efficiency identified different strategies adopted by genotypes, and that genotypes selected from M. floridulus and M. sinensis were better adapted to rainfed conditions and could produce six times more biomass than the Mxg. These accessions are being used as parents in experimental breeding aimed at producing future seed-based drought resilient hybrids.

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