scholarly journals Response of water use efficiency to summer drought in boreal Scots pine forests in Finland

2016 ◽  
Author(s):  
Yao Gao ◽  
Tiina Markkanen ◽  
Mika Aurela ◽  
Ivan Mammarella ◽  
Tea Thum ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Water Use Efficiency ◽  
Water Use ◽  
Time Scales ◽  
Scots Pine ◽  
Land Surface ◽  
Summer Drought ◽  
Ecosystem Level ◽  
Use Efficiency ◽  
Daily Time

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.

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

2017 ◽  
Vol 14 (18) ◽  
pp. 4409-4422 ◽  
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.

scholarly journals Quantifying Soil Moisture Impacts on Water Use Efficiency in Terrestrial Ecosystems of China

2021 ◽  
Vol 13 (21) ◽  
pp. 4257
Author(s):  
Xingming Hao ◽  
Jingjing Zhang ◽  
Xue Fan ◽  
Haichao Hao ◽  
Yuanhang Li
Keyword(s):  
Soil Moisture ◽  
Water Use Efficiency ◽  
Water Use ◽  
Land Surface ◽  
Net Primary Production ◽  
Terrestrial Ecosystems ◽  
Sensitivity Coefficient ◽  
Analytical Framework ◽  
Average Value ◽  
Use Efficiency

Soil moisture (SM) significantly affects the exchange of land surface energy and the stability of terrestrial ecosystems. Although some conclusions have been drawn about the effects of SM on the ecosystem water use efficiency (WUE), the influence mechanism and the quantitative assessment framework of SM on WUE are still unclear. This study provides an analysis framework for the feedback relationship between SM and WUE based on the dependence of the evaporation fraction on SM and output datasets from remote sensing and the Global Land Data Assimilation System. The results show that the range of WUE of terrestrial ecosystems of China was0.02–19.26 g C/kg H2O in the growing season with an average value of 1.05 g C/kg H2O. They also show a downward trend in43.99% of the total area. In the evapotranspiration (ET) pathway, SM negatively affected WUE, and the sensitivity coefficient ranged from −18.49 to −0.04. In the net primary production (NPP) pathway, the sensitivity coefficient ranged from −68.66 to 43.19. Under the dual effects of the ET and NPP pathways, the influence of SM on WUE was negative in 84.62% of the area. Variation in SM led to significant WUE variability. Generally, the percentage change in WUE (ΔWUE) ranged from 0% to 190.86%, with an average value of 28.02%. The maximum ΔWUE ranged from 0% to 758.78%, with an average value of 109.29%. The WUE of forest ecosystems showed strong resistance to SM variation, whereas that of non-forest vegetation was more sensitive to SM variation. This analytical framework provides a new perspective on the feedback relationship between WUE and SM in terrestrial ecosystems.

Water demand and water use efficiency of winter barley in Hungary

2011 ◽  
Vol 59 (1) ◽  
pp. 13-22
Author(s):  
Z. Varga-Haszonits ◽  
E. Enzsölné Gerencsér ◽  
Z. Lantos ◽  
Z. Varga
Keyword(s):  
Soil Moisture ◽  
Water Supply ◽  
Water Use Efficiency ◽  
Water Use ◽  
Potential Evapotranspiration ◽  
Growth Period ◽  
Winter Barley ◽  
Potential Yield ◽  
Yield Data ◽  
Use Efficiency

The temporal and spatial variability of soil moisture, evapotranspiration and water use were investigated for winter barley. Evaluations were carried out on a database containing meteorological and yield data from 15 stations. The spatial distribution of soil moisture, evapotranspiration and water use efficiency (WUE) was evaluated from 1951 to 2000 and the moisture conditions during the growth period of winter barley were investigated. The water supply was found to be favourable, since the average values of soil moisture remained above the lower limit of favourable water content throughout the growth period, except for September–December and May–June. The actual evapotranspiration tended to be close to the potential evapotranspiration, so the water supplies were favourable throughout the vegetation period. The calculated values of WUE showed an increasing trend from 1960 to 1990, but the lower level of agricultural inputs caused a decline after 1990. The average values of WUE varied between 0.87 and 1.09 g/kg in different counties, with higher values in the northern part of the Great Hungarian Plain. The potential yield of winter barley can be calculated from the maximum value of WUE. Except in the cooler northern and western parts of the country, the potential yield of winter barley, based on the water supply, could exceed 10 t/ha.

Studies of the Drip Method of Irrigation

1972 ◽  
Vol 8 (2) ◽  
pp. 171-175 ◽  
Author(s):  
I. P. Abrol ◽  
S. P. Dixit
Keyword(s):  
Soil Moisture ◽  
Water Use Efficiency ◽  
Water Use ◽  
Soil Strength ◽  
Surface Evaporation ◽  
Evaporation Losses ◽  
Use Efficiency ◽  
Reduced Surface

SUMMARYA comparison has been made of drip and conventional check basin methods of irrigation, using onions and ladies finger as test crops. Significant increases in yield and water use efficiency in drip irrigated over conventionally irrigated plots resulted from increased availability of soil moisture at low tensions and reduced surface evaporation losses. Reduced soil strength in drip irrigated plots was also a factor resulting in increased yield of onions.

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