Modelling the effects of land cover and climate change on soil water partitioning in a boreal headwater catchment

Wang, Hailong; Tetzlaff, Doerthe; Soulsby, Chris

doi:10.1016/j.jhydrol.2018.02.002

Cited by 42 publications

(28 citation statements)

References 99 publications

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“…In this case study changes to forest composition had a greater influence on discharge extremes than did changes to meteorological forcing under the rcp8.5 emissions scenario as predicted by CMIP5 GCMs (Figure ), similar to the findings of Wang et al () in a boreal oceanic climate. Numerical limitations of CMIP5 GCMs cause a regional fall season bias in the underestimation of tropical cyclone frequency (Wuebbles et al, ) and therefore extreme precipitation (e.g., Knighton, Steinschneider, & Walter, ).…”

Section: Resultssupporting

confidence: 87%

“…Perhaps, as a result, relatively few model‐based studies have been conducted examining the role of forest cover on runoff. Soil column modeling with HYDRUS‐1D demonstrated that tree canopy interception and increased evapotranspiration could have a larger effect on the land surface runoff response than changes to local meteorology in a boreal headwater catchment in Scotland (Wang et al, ). Blöschl et al () performed mechanistic watershed‐scale hydrologic simulations of a large catchment in Austria to evaluate the influence of forest cover on extreme runoff generation.…”

Section: Introductionmentioning

confidence: 99%

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Possible Increases in Flood Frequency Due to the Loss of Eastern Hemlock in the Northeastern United States: Observational Insights and Predicted Impacts

Knighton

Conneely

Walter

2019

Water Resources Research

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Trees exert a fundamental control on the hydrologic cycle, yet previous research is unclear about the nuanced relationship between forest cover and riverine flood frequency. In the Northeastern United States, warming air temperatures have resulted in a decline of Eastern Hemlock (EH), and subsequent increases in observed catchment water yield. We evaluated the possibility of EH loss leading to a changed flooding regime. We first investigated plant hydraulic regulation by root water uptake in EH and American Beech (AB; a candidate successional species) through stable isotope analysis of stream, soil water, and plant xylem water. EH xylem water showed evidence of deeper soil water uptake than AB during both wet and dry seasons, suggesting species succession may be an important mechanism for altering catchment “plant accessible water.” Next, we estimated catchment flood frequency with mechanistic hydrologic simulations for present conditions, and two hypothetical cases where all EH is succeeded by AB. The largest change to catchment extreme discharge after AB succession coincided with fall season tropical moisture export‐derived precipitation. We observed reduced sensitivity under future climatic forcing with an ensemble simulation of five localized constructed analogs downscaled general circulation models. Thus, the influence of forest composition on the flood regime may be most related to the temporal alignment of the synoptic‐scale processes that generate Atlantic Basin tropical cyclones and regional plant phenology of the Northeast United States. Our results provide a justification for using physically based hydrologic models incorporating plant hydraulic regulation when evaluating future flooding frequency.

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Section: Resultssupporting

confidence: 87%

Section: Introductionmentioning

confidence: 99%

Possible Increases in Flood Frequency Due to the Loss of Eastern Hemlock in the Northeastern United States: Observational Insights and Predicted Impacts

Knighton

Conneely

Walter

2019

Water Resources Research

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“…Vegetation affects water flow and storage through the partitioning of precipitation into “green water” fluxes back to the atmosphere as evapotranspiration ( ET ) and “blue water” fluxes to groundwater recharge and streamflow (Soulsby, Braun, Sprenger, Weiler, & Tetzlaff, ; Wang, Tetzlaff, & Soulsby, ). Globally, plant transpiration ( Ec ) is an important component in the water balance, accounting for over half of terrestrial ET and yields an overall annual flux greater than the flow from all of the world's rivers (Jasechko et al, ; Miralles, De Jeu, Gash, Holmes, & Dolman, ), although the relative proportion of these fluxes varies across contrasting climate zones and biomes.…”

Section: Introductionmentioning

confidence: 99%

Hysteretic response of sap flow in Scots pine (Pinus sylvestris) to meteorological forcing in a humid low‐energy headwater catchment

2019

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Transpiration mediated by physiology is driven by the meteorological variables.Understanding their relationships is crucial to advancing terrestrial ecohydrological studies. Here, we used sap flow measurements in Scots pine to examine the temporal responses of transpiration to temperature (Ta), vapour pressure deficit (VPD), and net radiation (Rn). Seasonal variations and the hysteresis between sap flux density (Js) and meteorological variables were investigated. The results show that VPD and Rn were dominant factors influencing hourly Js. Daily peaks of Js lagged behind peaks of Ta, VPD, and Rn, by~2-4 hr. Anticlockwise hysteresis loops between Js and Ta and VPD were observed, and the size of loops change with prevailing weather conditions (i.e., rainy or rainless) and seasons. Longer time lags were found in April and September than in other months. The hysteresis is partly related to the low energy, humid nature of the site which resulted in limited moisture stress to the trees, and thus the trees did not necessarily need a conservation mechanism to restrict water loss as proposed by other studies in semi-arid areas. Release and refill of trunk water storage could plausibly contribute to the hysteresis, although the effect may be entwined with atmospheric demand making it difficult to separate without sophisticated measurements. This study highlights the diversity in plant water relations across temporal scales and seasons and calls for more work across geographic locations and climates.

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“…Such altered climatic conditions and/or changes in vegetation cover are likely to modify the partitioning of water in the critical zone into evaporation, transpiration, and recharge fluxes Wang et al, 2018). As it has been shown that dynamics of evapotranspiration (ET) fluxes affect the water ages of catchment runoff (van der Velde et al, 2012;Birkel et al, 2012;Ali et al, 2014) and groundwater recharge (Sprenger et al, 2016), a better understanding of the ET dynamics and their effect on water ages and storage dynamics is needed.…”

Section: Introductionmentioning

confidence: 99%

Water ages in the critical zone of long-term experimental sites in northern latitudes

Sprenger¹,

Tetzlaff

Buttle

et al. 2018

Hydrol. Earth Syst. Sci.

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Abstract. As northern environments undergo intense changes due to a warming climate and altered land use practices, there is an urgent need for improved understanding of the impact of atmospheric forcing and vegetation on water storage and flux dynamics in the critical zone. We therefore assess the age dynamics of water stored in the upper 50 cm of soil, and in evaporation, transpiration, or recharge fluxes at four soil-vegetation units of podzolic soils in the northern latitudes with either heather or tree vegetation (Bruntland Burn in Scotland, Dorset in Canada, and Krycklan in Sweden). We derived the age dynamics with the physically based SWIS (Soil Water Isotope Simulator) model, which has been successfully used to simulate the hydrometric and isotopic dynamics in the upper 50 cm of soils at the study sites. The modelled subsurface was divided into interacting fast and slow flow domains. We tracked each day's infiltrated water through the critical zone and derived forward median travel times (which show how long the water takes to leave the soil via evaporation, transpiration, or recharge), and median water ages (to estimate the median age of water in soil storage or the evaporation, transpiration, and recharge fluxes). Resulting median travel times were time-variant, mainly governed by major recharge events during snowmelt in Dorset and Krycklan or during the wetter winter conditions in Bruntland Burn. Transpiration travel times were driven by the vegetation growth period with the longest travel times (200 days) for waters infiltrated in early dormancy and the shortest travel times during the vegetation period. However, long tails of the travel time distributions in evaporation and transpiration revealed that these fluxes comprised waters older than 100 days. At each study site, water ages of soil storage, evaporation, transpiration, and recharge were all inversely related to the storage volume of the critical zone: water ages generally decreased exponentially with increasing soil water storage. During wet periods, young soil waters were more likely to be evapotranspired and recharged than during drier periods. While the water in the slow flow domain showed longterm seasonal dynamics and generally old water ages, the water ages of the fast flow domain were generally younger and much flashier. Our results provide new insights into the mixing and transport processes of soil water in the upper layer of the critical zone, which is relevant for hydrological modelling at the plot to catchment scales as the common assumption of a well-mixed system in the subsurface holds for neither the evaporation, transpiration, or recharge.

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Modelling the effects of land cover and climate change on soil water partitioning in a boreal headwater catchment

Cited by 42 publications

References 99 publications

Possible Increases in Flood Frequency Due to the Loss of Eastern Hemlock in the Northeastern United States: Observational Insights and Predicted Impacts

Possible Increases in Flood Frequency Due to the Loss of Eastern Hemlock in the Northeastern United States: Observational Insights and Predicted Impacts

Hysteretic response of sap flow in Scots pine (Pinus sylvestris) to meteorological forcing in a humid low‐energy headwater catchment

Water ages in the critical zone of long-term experimental sites in northern latitudes

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