Plant rooting strategies in water‐limited ecosystems

Collins, D. B.; Bras, Rafael L.

doi:10.1029/2006wr005541

Cited by 119 publications

(137 citation statements)

References 53 publications

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“…The majority of previous root studies were undertaken with the aim of estimating carbon stocks, carbon turnover and characterisation of nutrient cycling (Barton and Montagu 2006;Mokany et al 2006;Zerihun et al 2006), while little or no consideration was given to the influence of root biomass and distribution on uptake of water by vegetation (Guswa et al 2004;Collins and Bras 2007). Studies aiming to estimate carbon sequestration are generally focused on developing allometric relationships to estimate carbon stocks from measurements of diameter at breast height (DBH), stem volume and height .…”

Section: Introductionmentioning

confidence: 99%

Root biomass distribution and soil properties of an open woodland on a duplex soil

et al. 2009

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Section: Introductionmentioning

confidence: 99%

Root biomass distribution and soil properties of an open woodland on a duplex soil

et al. 2009

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“…It is important to note that differences in root distribution have been shown to influence transpiration rates and groundwater recharge (e.g., Finch, 1998;Collins and Bras, 2007). Although examining such impacts is beyond the scope of the present study, it would be interesting to include the effects of root distribution in future studies of groundwater-land surface coupling.…”

Section: Experimental Design: Model Sensitivity Experimentsmentioning

confidence: 99%

Quantifying the impact of groundwater depth on evapotranspiration in a semi-arid grassland region

Soylu

Istanbulluoglu

Lenters

et al. 2011

Hydrol. Earth Syst. Sci.

114

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Abstract.Interactions between shallow groundwater and land surface processes play an important role in the ecohydrology of riparian zones. Some recent land surface models (LSMs) incorporate groundwater-land surface interactions using parameterizations at varying levels of detail. In this paper, we examine the sensitivity of land surface evapotranspiration (ET) to water table depth, soil texture, and two commonly used soil hydraulic parameter datasets using four models with varying levels of complexity. The selected models are Hydrus-1D, which solves the pressure-based Richards equation, the Integrated Biosphere Simulator (IBIS), which simulates interactions among multiple soil layers using a (water-content) variant of the Richards equation, and two forms of a steady-state capillary flux model coupled with a single-bucket soil moisture model. These models are first evaluated using field observations of climate, soil moisture, and groundwater levels at a semi-arid site in south-central Nebraska, USA. All four models are found to compare reasonably well with observations, particularly when the effects of groundwater are included. We then examine the sensitivity of modelled ET to water table depth for various model formulations, node spacings, and soil textures (using soil hydraulic parameter values from two different sources, namely Rawls and Clapp-Hornberger). The results indicate a strong influence of soil texture and water table depth on groundwater contributions to ET. Furthermore, differences in texturespecific, class-averaged soil parameters obtained from the two literature sources lead to large differences in the simulated depth and thickness of the "critical zone" (i.e., the zone within which variations in water table depth strongly Correspondence to: M. E. Soylu (evren@huskers.unl.edu) impact surface ET). Depending on the depth-to-groundwater, this can also lead to large discrepancies in simulated ET (in some cases by more than a factor of two). When the Clapp-Hornberger soil parameter dataset is used, the critical zone becomes significantly deeper, and surface ET rates become much higher, resulting in a stronger influence of deep groundwater on the land surface energy and water balance. In general, we find that the simulated sensitivity of ET to the choice of soil hydraulic parameter dataset is greater than the sensitivity to soil texture defined within each dataset, or even to the choice of model formulation. Thus, our findings underscore the need for future modelling and field-based studies to improve the predictability of groundwater-land surface interactions in numerical models, particularly as it relates to the parameterization of soil hydraulic properties.

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“…Optimality approaches have been explored previously for modelling root water uptake (e.g. Heimann, 1996, 1998;van Wijk and Bouten, 2001;Laio et al , 2006;Collins and Bras, 2007), but we are only aware of one that modelled a dynamically adapting root distribution (Kleidon and Heimann, 1996). However, the resulting model was deemed impractical for implementation into coupled biogeochemical or ecohydrological models due to its large computational demands.…”

Section: Introductionmentioning

confidence: 99%

An optimality-based model of the coupled soil moisture and root dynamics

Schymanski

Sivapalan

Roderick

et al. 2008

Hydrol. Earth Syst. Sci.

140

126

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Abstract. The main processes determining soil moisture dynamics are infiltration, percolation, evaporation and root water uptake. Modelling soil moisture dynamics therefore requires an interdisciplinary approach that links hydrological, atmospheric and biological processes. Previous approaches treat either root water uptake rates or root distributions and transpiration rates as given, and calculate the soil moisture dynamics based on the theory of flow in unsaturated media. The present study introduces a different approach to linking soil water and vegetation dynamics, based on vegetation optimality. Assuming that plants have evolved mechanisms that minimise costs related to the maintenance of the root system while meeting their demand for water, we develop a model that dynamically adjusts the vertical root distribution in the soil profile to meet this objective. The model was used to compute the soil moisture dynamics, root water uptake and fine root respiration in a tropical savanna over 12 months, and the results were compared with observations at the site and with a model based on a fixed root distribution. The optimality-based model reproduced the main features of the observations such as a shift of roots from the shallow soil in the wet season to the deeper soil in the dry season and substantial root water uptake during the dry season. At the same time, simulated fine root respiration rates never exceeded the upper envelope determined by the observed soil Correspondence to: S. J. Schymanski (sschym@bgc-jena.mpg.de) respiration. The model based on a fixed root distribution, in contrast, failed to explain the magnitude of water use during parts of the dry season and largely over-estimated root respiration rates. The observed surface soil moisture dynamics were also better reproduced by the optimality-based model than the model based on a prescribed root distribution. The optimality-based approach has the potential to reduce the number of unknowns in a model (e.g. the vertical root distribution), which makes it a valuable alternative to more empirically-based approaches, especially for simulating possible responses to environmental change.

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Plant rooting strategies in water‐limited ecosystems

Cited by 119 publications

References 53 publications

Root biomass distribution and soil properties of an open woodland on a duplex soil

Root biomass distribution and soil properties of an open woodland on a duplex soil

Quantifying the impact of groundwater depth on evapotranspiration in a semi-arid grassland region

An optimality-based model of the coupled soil moisture and root dynamics

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