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Alfonso Calera - One of the best experts on this subject based on the ideXlab platform.
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estimating evapotranspiration of an apple orchard using a remote sensing based Soil Water Balance
Remote Sensing, 2016Co-Authors: Magali Odilara, Isidro Campos, Christopher M U Neale, Samuel Ortegafarias, Carlos Pobleteecheverria, Claudio Balbontin, Alfonso CaleraAbstract:The main goal of this research was to estimate the actual evapotranspiration (ETc) of a drip-irrigated apple orchard located in the semi-arid region of Talca Valley (Chile) using a remote sensing-based Soil Water Balance model. The methodology to estimate ETc is a modified version of the Food and Agriculture Organization of the United Nations (FAO) dual crop coefficient approach, in which the basal crop coefficient (Kcb) was derived from the Soil adjusted vegetation index (SAVI) calculated from satellite images and incorporated into a daily Soil Water Balance in the root zone. A linear relationship between the Kcb and SAVI was developed for the apple orchard Kcb = 1.82·SAVI − 0.07 (R2 = 0.95). The methodology was applied during two growing seasons (2010–2011 and 2012–2013), and ETc was evaluated using latent heat fluxes (LE) from an eddy covariance system. The results indicate that the remote sensing-based Soil Water Balance estimated ETc reasonably well over two growing seasons. The root mean square error (RMSE) between the measured and simulated ETc values during 2010–2011 and 2012–2013 were, respectively, 0.78 and 0.74 mm·day−1, which mean a relative error of 25%. The index of agreement (d) values were, respectively, 0.73 and 0.90. In addition, the weekly ETc showed better agreement. The proposed methodology could be considered as a useful tool for scheduling irrigation and driving the estimation of Water requirements over large areas for apple orchards.
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estimation of total available Water in the Soil layer by integrating actual evapotranspiration data in a remote sensing driven Soil Water Balance
Journal of Hydrology, 2016Co-Authors: Isidro Campos, Jose Gonzalezpiqueras, Arnaud Carrara, J Villodre, Alfonso CaleraAbstract:Summary The total available Water ( τ ) by plants that could be stored in its root Soil layer is a key parameter when applying Soil Water Balance models. Since the transpiration rate of a vegetation stand could be the best proxy about the Soil Water content into the root Soil layer, we propose a methodology for estimating τ by using as basic inputs the evapotranspiration rate of the stand and time series of multispectral imagery. This methodology is based on the inverted formulation of the Soil Water Balance model. The inversion of the model was addressed by using an iterative approach, which optimizes the τ parameter to minimize the difference between measured and modeled ET. This methodology was tested for a Mediterranean holm oak savanna (dehesa) for which eddy covariance measurements of actual ET were available. The optimization procedure was performed by using a continuous dataset (in 2004) of daily ET measurements and 16 sets of 8 daily ET measurements, resulting in τ values of 325 and 305 mm, respectively. The use of these τ values in the RSWB model for the validation period (2005–2008) allowed us to estimate dehesa ET with a RMSE = 0.48 mm/day. The model satisfactorily reproduces the Water stress process. The sensitivity of τ estimates was evaluated regarding two of the more uncertain parameters in the RSWB model. These parameters are the average fraction of τ that can be depleted from the root zone without producing moisture stress ( p τ ) and the Soil evaporation component. The results of this analysis indicated relatively little influence from the evaporation component and the need for adequate knowledge about p τ for estimating τ .
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remote sensing based Soil Water Balance to estimate mediterranean holm oak savanna dehesa evapotranspiration under Water stress conditions
Journal of Hydrology, 2013Co-Authors: Isidro Campos, Arnaud Carrara, J Villodre, Alfonso CaleraAbstract:Summary This paper aims to present the use of a remote sensing-based Soil Water Balance to estimate holm oak woodland evapotranspiration (ET). The model is based on the assimilation of MODIS reflectance-based vegetation indices in the dual crop coefficient methodology. A daily Water Balance was performed on the root zone Soil to estimate plant Water stress. The methodology was evaluated with respect to the actual ET measured by eddy covariance in Mediterranean holm oak savanna (dehesa) for five consecutive years (2004–2008). The model adequately reproduced the absolute values and tendencies measured at daily and weekly periods. Root mean square error (RMSE) was 0.50 mm/day for daily values and 2.70 mm/week for weekly accumulated values. The analysis demonstrated the presence of a long period of Water stress during the summer and at the beginning of fall. Measured ET dropped during these periods, and the model replicated this tendency accurately, reaching a stress coefficient value close to 0.2. To be operative, the proposed method required low ground data (reference evapotranspiration and precipitation) and the results indicated a simple, robust method that can be used to map ET and Water stress in the dehesa ecosystem.
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assessing satellite based basal crop coefficients for irrigated grapes vitis vinifera l
Agricultural Water Management, 2010Co-Authors: Isidro Campos, Christopher M U Neale, Claudio Balbontin, Alfonso Calera, Jose GonzalezpiquerasAbstract:A combined methodology of basal crop coefficient (Kcb) derived from vegetation indices (VI) obtained from satellite images and a daily Soil Water Balance in the root zone of the crop was proposed to accurately estimate the daily grape crop coefficient and actual evapotranspiration. The modeled values were compared with field measurements of crop evapotranspiration (ET) using an energy Balance eddy-covariance flux tower and adjusted for closure using the measured Bowen ratio. A linear relation between Kcb and VI for vineyard was obtained, Kcb = 1.44 x NDVI-0.10 and Kcb = 1.79 x SAVI-0.08. The correlation of the measured crop coefficient (Kc) and modeled (Kcrf) exhibits a linear tendency, Kc = 0.96Kcrf, r2 = 0.67. Other derived parameters such as weekly Kc and daily and weekly ET show good consistency with measurements and higher coefficients of determination. The study of the Soil Water Balance suggests the importance of Soil Water storage in grapes within the La Mancha region. These results validate the use of remote sensing as a tool for the estimation of evapotranspiration of irrigated wine grapes planted on trellis systems.
Isidro Campos - One of the best experts on this subject based on the ideXlab platform.
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estimating evapotranspiration of an apple orchard using a remote sensing based Soil Water Balance
Remote Sensing, 2016Co-Authors: Magali Odilara, Isidro Campos, Christopher M U Neale, Samuel Ortegafarias, Carlos Pobleteecheverria, Claudio Balbontin, Alfonso CaleraAbstract:The main goal of this research was to estimate the actual evapotranspiration (ETc) of a drip-irrigated apple orchard located in the semi-arid region of Talca Valley (Chile) using a remote sensing-based Soil Water Balance model. The methodology to estimate ETc is a modified version of the Food and Agriculture Organization of the United Nations (FAO) dual crop coefficient approach, in which the basal crop coefficient (Kcb) was derived from the Soil adjusted vegetation index (SAVI) calculated from satellite images and incorporated into a daily Soil Water Balance in the root zone. A linear relationship between the Kcb and SAVI was developed for the apple orchard Kcb = 1.82·SAVI − 0.07 (R2 = 0.95). The methodology was applied during two growing seasons (2010–2011 and 2012–2013), and ETc was evaluated using latent heat fluxes (LE) from an eddy covariance system. The results indicate that the remote sensing-based Soil Water Balance estimated ETc reasonably well over two growing seasons. The root mean square error (RMSE) between the measured and simulated ETc values during 2010–2011 and 2012–2013 were, respectively, 0.78 and 0.74 mm·day−1, which mean a relative error of 25%. The index of agreement (d) values were, respectively, 0.73 and 0.90. In addition, the weekly ETc showed better agreement. The proposed methodology could be considered as a useful tool for scheduling irrigation and driving the estimation of Water requirements over large areas for apple orchards.
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estimation of total available Water in the Soil layer by integrating actual evapotranspiration data in a remote sensing driven Soil Water Balance
Journal of Hydrology, 2016Co-Authors: Isidro Campos, Jose Gonzalezpiqueras, Arnaud Carrara, J Villodre, Alfonso CaleraAbstract:Summary The total available Water ( τ ) by plants that could be stored in its root Soil layer is a key parameter when applying Soil Water Balance models. Since the transpiration rate of a vegetation stand could be the best proxy about the Soil Water content into the root Soil layer, we propose a methodology for estimating τ by using as basic inputs the evapotranspiration rate of the stand and time series of multispectral imagery. This methodology is based on the inverted formulation of the Soil Water Balance model. The inversion of the model was addressed by using an iterative approach, which optimizes the τ parameter to minimize the difference between measured and modeled ET. This methodology was tested for a Mediterranean holm oak savanna (dehesa) for which eddy covariance measurements of actual ET were available. The optimization procedure was performed by using a continuous dataset (in 2004) of daily ET measurements and 16 sets of 8 daily ET measurements, resulting in τ values of 325 and 305 mm, respectively. The use of these τ values in the RSWB model for the validation period (2005–2008) allowed us to estimate dehesa ET with a RMSE = 0.48 mm/day. The model satisfactorily reproduces the Water stress process. The sensitivity of τ estimates was evaluated regarding two of the more uncertain parameters in the RSWB model. These parameters are the average fraction of τ that can be depleted from the root zone without producing moisture stress ( p τ ) and the Soil evaporation component. The results of this analysis indicated relatively little influence from the evaporation component and the need for adequate knowledge about p τ for estimating τ .
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remote sensing based Soil Water Balance to estimate mediterranean holm oak savanna dehesa evapotranspiration under Water stress conditions
Journal of Hydrology, 2013Co-Authors: Isidro Campos, Arnaud Carrara, J Villodre, Alfonso CaleraAbstract:Summary This paper aims to present the use of a remote sensing-based Soil Water Balance to estimate holm oak woodland evapotranspiration (ET). The model is based on the assimilation of MODIS reflectance-based vegetation indices in the dual crop coefficient methodology. A daily Water Balance was performed on the root zone Soil to estimate plant Water stress. The methodology was evaluated with respect to the actual ET measured by eddy covariance in Mediterranean holm oak savanna (dehesa) for five consecutive years (2004–2008). The model adequately reproduced the absolute values and tendencies measured at daily and weekly periods. Root mean square error (RMSE) was 0.50 mm/day for daily values and 2.70 mm/week for weekly accumulated values. The analysis demonstrated the presence of a long period of Water stress during the summer and at the beginning of fall. Measured ET dropped during these periods, and the model replicated this tendency accurately, reaching a stress coefficient value close to 0.2. To be operative, the proposed method required low ground data (reference evapotranspiration and precipitation) and the results indicated a simple, robust method that can be used to map ET and Water stress in the dehesa ecosystem.
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assessing satellite based basal crop coefficients for irrigated grapes vitis vinifera l
Agricultural Water Management, 2010Co-Authors: Isidro Campos, Christopher M U Neale, Claudio Balbontin, Alfonso Calera, Jose GonzalezpiquerasAbstract:A combined methodology of basal crop coefficient (Kcb) derived from vegetation indices (VI) obtained from satellite images and a daily Soil Water Balance in the root zone of the crop was proposed to accurately estimate the daily grape crop coefficient and actual evapotranspiration. The modeled values were compared with field measurements of crop evapotranspiration (ET) using an energy Balance eddy-covariance flux tower and adjusted for closure using the measured Bowen ratio. A linear relation between Kcb and VI for vineyard was obtained, Kcb = 1.44 x NDVI-0.10 and Kcb = 1.79 x SAVI-0.08. The correlation of the measured crop coefficient (Kc) and modeled (Kcrf) exhibits a linear tendency, Kc = 0.96Kcrf, r2 = 0.67. Other derived parameters such as weekly Kc and daily and weekly ET show good consistency with measurements and higher coefficients of determination. The study of the Soil Water Balance suggests the importance of Soil Water storage in grapes within the La Mancha region. These results validate the use of remote sensing as a tool for the estimation of evapotranspiration of irrigated wine grapes planted on trellis systems.
Xianfang Song - One of the best experts on this subject based on the ideXlab platform.
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a root zone model for estimating Soil Water Balance and crop yield responses to deficit irrigation in the north china plain
Agricultural Water Management, 2013Co-Authors: Shaoyuan Feng, Xianfang SongAbstract:The development of Water-conserving and sustainable agricultural management practices is essential and significant to alleviate the rapid depletion of groundWater resources in the North China Plain (NCP). Estimating drainage out of the root zone and improving Water use efficiency could provide a basis to assist in reasonable utilization of groundWater resources for agricultural irrigation in the NCP. This study proposed a new Soil Water Balance model to quantify drainage out of the root zone by incorporating the Darcy's law. This model was connected with the Jensen crop Water production function to simulate Soil Water components and relative crop yield under deficit irrigation. Field experiments with the winter wheat and summer maize crop rotation were conducted in Beijing area in the NCP (2007-2009) to evaluate the model. The model could give quite reasonable predictions of Soil Water content in the root zone with the average root mean square error (RMSE), mean relative error (RE) and model efficiency (EF) of 0.02cm3cm-3, 6.69% and 0.78, respectively. The predicted Soil Water flux through the bottom of root zone agreed well with the measured ones supported by the values of RMSE (0.10mmd-1) and EF (0.92). The simulations indicated that the accumulated drainage out of root zone accounted for -27% to 19% of the applied Water (irrigation and precipitation) among different crop seasons. As an application, the model was used to obtain the optimal irrigation management schedules for the hydrologic years of 75%, 50%, and 25% in the study area. The average amount of irrigation saving and reduction of Water losses through drainage under optimal irrigation alternative were about 175mm and 101.9mm, respectively. This study shows that the developed root zone model has minimal input requirement, robust physical meaning and satisfactory simulation performance, which is more applicable and feasible for agricultural Water management in the semi-arid area. 2013 Elsevier B.V.
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a root zone model for estimating Soil Water Balance and crop yield responses to deficit irrigation in the north china plain
Agricultural Water Management, 2013Co-Authors: Shaoyuan Feng, Xianfang SongAbstract:The development of Water-conserving and sustainable agricultural management practices is essential and significant to alleviate the rapid depletion of groundWater resources in the North China Plain (NCP). Estimating drainage out of the root zone and improving Water use efficiency could provide a basis to assist in reasonable utilization of groundWater resources for agricultural irrigation in the NCP. This study proposed a new Soil Water Balance model to quantify drainage out of the root zone by incorporating the Darcy's law. This model was connected with the Jensen crop Water production function to simulate Soil Water components and relative crop yield under deficit irrigation. Field experiments with the winter wheat and summer maize crop rotation were conducted in Beijing area in the NCP (2007–2009) to evaluate the model. The model could give quite reasonable predictions of Soil Water content in the root zone with the average root mean square error (RMSE), mean relative error (RE) and model efficiency (EF) of 0.02cm3cm−3, 6.69% and 0.78, respectively. The predicted Soil Water flux through the bottom of root zone agreed well with the measured ones supported by the values of RMSE (0.10mmd−1) and EF (0.92). The simulations indicated that the accumulated drainage out of root zone accounted for −27% to 19% of the applied Water (irrigation and precipitation) among different crop seasons. As an application, the model was used to obtain the optimal irrigation management schedules for the hydrologic years of 75%, 50%, and 25% in the study area. The average amount of irrigation saving and reduction of Water losses through drainage under optimal irrigation alternative were about 175mm and 101.9mm, respectively. This study shows that the developed root zone model has minimal input requirement, robust physical meaning and satisfactory simulation performance, which is more applicable and feasible for agricultural Water management in the semi-arid area.
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a root zone model for estimating Soil Water Balance and crop yield responses to deficit irrigation in the north china plain
AGUFM, 2012Co-Authors: Shaoyuan Feng, Xianfang SongAbstract:The development of Water-conserving and sustainable agricultural management practices is essential and significant to alleviate the rapid depletion of groundWater resources in the North China Plain (NCP). Estimating drainage out of the root zone and improving Water use efficiency could provide a basis to assist in reasonable utilization of groundWater resources for agricultural irrigation in the NCP. This study proposed a new Soil Water Balance model to quantify drainage out of the root zone by incorporating the Darcy's law. This model was connected with the Jensen crop Water production function to simulate Soil Water components and relative crop yield under deficit irrigation. Field experiments with the winter wheat and summer maize crop rotation were conducted in Beijing area in the NCP (2007-2009) to evaluate the model. The model could give quite reasonable predictions of Soil Water content in the root zone with the average root mean square error (RMSE), mean relative error (RE) and model efficiency (EF) of 0.02 cm(3) cm(-3), 6.69% and 0.78, respectively. The predicted Soil Water flux through the bottom of root zone agreed well with the measured ones supported by the values of RMSE (0.10 mm d(-1)) and EF (0.92). The simulations indicated that the accumulated drainage out of root zone accounted for -27% to 19% of the applied Water (irrigation and precipitation) among different crop seasons. As an application, the model was used to obtain the optimal irrigation management schedules for the hydrologic years of 75%, 50%, and 25% in the study area. The average amount of irrigation saving and reduction of Water losses through drainage under optimal irrigation alternative were about 175 mm and 101.9 mm, respectively. This study shows that the developed root zone model has minimal input requirement, robust physical meaning and satisfactory simulation performance, which is more applicable and feasible for agricultural Water management in the semi-arid area. (c) 2013 Elsevier B.V. All rights reserved.
A Sahli - One of the best experts on this subject based on the ideXlab platform.
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simulation of yield decline as a result of Water stress with a robust Soil Water Balance model
Agricultural Water Management, 2006Co-Authors: Dirk Raes, Sam Geerts, E C Kipkorir, Joost Wellens, A SahliAbstract:Abstract The relative yield decline that is expected under specific levels of Water stress at different moments in the growing period is estimated by integrating the FAO Ky approach [Doorenbos, J., Kassam, A.H., 1979. Yield response to Water. FAO Irrigation and Drainage Paper No. 33. Rome, Italy] in the Soil Water Balance model BUDGET. The Water stored in the root zone is determined in the Soil Water Balance model on a daily basis by keeping track of incoming and outgoing Water fluxes at its boundary. Given the simulated Soil Water content in the root zone, the corresponding crop Water stress is determined. Subsequently, the yield decline is estimated with the Ky approach. In the Ky approach the relation between Water stress in a particular growth stage and the corresponding expected yield is described by a linear function. To account for the effect of Water stresses in the various growth stages, the multiplicative, seasonal and minimal approach are integrated in the model. To evaluate the model, the simulated yields for two crops under various levels of Water stress in two different environments were compared with observed yields: winter wheat under three different Water application levels in the North of Tunisia, and maize in three different farmers’ fields in different years in the South West of Burkina Faso. Simulated crop yields agreed well with observed yields for both locations using the multiplicative approach. The correlation value (R2) between observed and simulated yields ranged from 0.87 to 0.94 with very high modeling efficiencies. The root mean square error values are relatively small and ranged between 7 and 9%. The minimal and seasonal approaches performed significantly less accurately in both of the study areas. Estimation of yields on basis of relative transpiration performed significantly better than estimations on basis of relative evapotranspiration in Burkina Faso. A sensitivity analysis showed that the model is robust and that good estimates can be obtained in both regions even by using indicative values for the required crop and Soil parameters. The minimal input requirement, the robustness of the model and its ability to describe the effect on seasonal yield of Water stress occurring at particular moments in the growing period, make the model very useful for the design of deficit irrigation strategies. BUDGET is public domain software and hence freely available. An installation disk and manual can be downloaded from the web.
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simulation of yield decline as a result of Water stress with a robust Soil Water Balance model
Agricultural Water Management, 2006Co-Authors: Dirk Raes, Sam Geerts, E C Kipkorir, Joost Wellens, A SahliAbstract:The relative yield decline that is expected under specific levels of Water stress at different moments in the growing period is estimated by integrating the FAO Ky approach [Doorenbos, J., Kassam, A.H., 1979. Yield response to Water. FAO Irrigation and Drainage Paper No. 33. Rome, Italy]inthe SoilWater Balancemodel BUDGET. TheWater storedin therootzone isdetermined inthe Soil Water Balance model on a daily basis by keeping track of incoming and outgoing Water fluxes at its boundary. Given the simulated Soil Water content in the root zone, the corresponding crop Water stress is determined. Subsequently, the yield decline is estimated with the Ky approach. In the Ky approach the relation between Water stress in a particular growth stage and the corresponding expected yield is described by a linear function. To account for the effect of Water stresses in the various growth stages, the multiplicative, seasonal and minimal approach are integrated in the model. To evaluate the model, the simulated yields for two crops under various levels of Water stress in two differentenvironmentswere compared withobservedyields:winter wheatunder threedifferent Water application levels in the North of Tunisia, and maize in three different farmers’ fields in different years in the South West of Burkina Faso. Simulated crop yields agreed well with observed yields for both locations using the multiplicative approach. The correlation value (R 2 ) between observed and simulated yieldsranged from0.87 to0.94 withveryhigh modelingefficiencies. The rootmeansquare error values are relatively small and ranged between 7 and 9%. The minimal and seasonal approaches
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simulation of yield decline as a result of Water stress with a robust Soil Water Balance model
Agricultural Water Management, 2006Co-Authors: Dirk Raes, Sam Geerts, E C Kipkorir, Joost Wellens, A SahliAbstract:The relative yield decline that is expected under specific levels of Water stress at different moments in the growing period is estimated by integrating the FAO Ky approach [Doorenbos, J., Kassam, A.H., 1979. Yield response to Water. FAO Irrigation and Drainage Paper No. 33. Rome, Italy]inthe SoilWater Balancemodel BUDGET. TheWater storedin therootzone isdetermined inthe Soil Water Balance model on a daily basis by keeping track of incoming and outgoing Water fluxes at its boundary. Given the simulated Soil Water content in the root zone, the corresponding crop Water stress is determined. Subsequently, the yield decline is estimated with the Ky approach. In the Ky approach the relation between Water stress in a particular growth stage and the corresponding expected yield is described by a linear function. To account for the effect of Water stresses in the various growth stages, the multiplicative, seasonal and minimal approach are integrated in the model. To evaluate the model, the simulated yields for two crops under various levels of Water stress in two differentenvironmentswere compared withobservedyields:winter wheatunder threedifferent Water application levels in the North of Tunisia, and maize in three different farmers’ fields in different years in the South West of Burkina Faso. Simulated crop yields agreed well with observed yields for both locations using the multiplicative approach. The correlation value (R 2 ) between observed and simulated yieldsranged from0.87 to0.94 withveryhigh modelingefficiencies. The rootmeansquare error values are relatively small and ranged between 7 and 9%. The minimal and seasonal approaches
Ignacio Rodrigueziturbe - One of the best experts on this subject based on the ideXlab platform.
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stochastic Soil Water Balance under seasonal climates
Proceedings of The Royal Society A: Mathematical Physical and Engineering Sciences, 2015Co-Authors: Xue Feng, Amilcare Porporato, Ignacio RodrigueziturbeAbstract:The analysis of Soil Water partitioning in seasonally dry climates necessarily requires careful consideration of the periodic climatic forcing at the intra-annual timescale in addition to daily scale variabilities. Here, we introduce three new extensions to a stochastic Soil moisture model which yields seasonal evolution of Soil moisture and relevant hydrological fluxes. These approximations allow seasonal climatic forcings (e.g. rainfall and potential evapotranspiration) to be fully resolved, extending the analysis of Soil Water partitioning to account explicitly for the seasonal amplitude and the phase difference between the climatic forcings. The results provide accurate descriptions of probabilistic Soil moisture dynamics under seasonal climates without requiring extensive numerical simulations. We also find that the transfer of Soil moisture between the wet to the dry season is responsible for hysteresis in the hydrological response, showing asymmetrical trajectories in the mean Soil moisture and in the transient Budyko's curves during the ‘dry-down‘ versus the ‘rewetting‘ phases of the year. Furthermore, in some dry climates where rainfall and potential evapotranspiration are in-phase, annual evapotranspiration can be shown to increase because of inter-seasonal Soil moisture transfer, highlighting the importance of Soil Water storage in the seasonal context.
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ecohydrology of Water controlled ecosystems Soil moisture and plant dynamics
2005Co-Authors: Ignacio Rodrigueziturbe, Amilcare PorporatoAbstract:Foreword Gabriel Katul Preface 1. Introduction 2. Stochastic Soil moisture dynamics and Water Balance 3. Crossing properties of Soil moisture dynamics 4. Plant Water stress 5. Applications to natural ecosystems 6. Coupled dynamics of photosynthesis, transpiration and Soil Water Balance: from hourly to growing-season time scale 7. Plant strategies and Water use 8. Seasonal and interannual fluctuations in Soil moisture dynamics 9. Spatial scale issues in Soil moisture dynamics 10. Hydrologic controls on nutrient cycles 11. Hydrologic variability and ecosystem structure References Species index Subject index.
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Soil Water Balance and ecosystem response to climate change
The American Naturalist, 2004Co-Authors: Amilcare Porporato, Edoardo Daly, Ignacio RodrigueziturbeAbstract:Abstract: Some essential features of the terrestrial hydrologic cycle and ecosystem response are singled out by confronting empirical observations of the Soil Water Balance of different ecosystems with the results of a stochastic model of Soil moisture dynamics. The simplified framework analytically describes how hydroclimatic variability (especially the frequency and amount of rainfall events) concurs with Soil and plant characteristics in producing the Soil moisture dynamics that in turn impact vegetation conditions. The results of the model extend and help interpret the classical curve of Budyko, which relates evapotranspiration losses to a dryness index, describing the partitioning of precipitation into evapotranspiration, runoff, and deep infiltration. They also provide a general classification of Soil Water Balance of the world ecosystems based on two governing dimensionless groups summarizing the climate, Soil, and vegetation conditions. The subsequent analysis of the links among Soil moisture dyna...
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coupled dynamics of photosynthesis transpiration and Soil Water Balance part ii stochastic analysis and ecohydrological significance
Journal of Hydrometeorology, 2004Co-Authors: Edoardo Daly, Amilcare Porporato, Ignacio RodrigueziturbeAbstract:The coupled dynamics of Soil moisture, transpiration, and assimilation are studied at the daily time scale by temporally upscaling the hourly time scale results obtained in a companion paper. The effects of Soil and vegetation characteristics on Soil moisture dynamics at the daily time scale and the parameters characterizing the dependence of transpiration and assimilation on Soil Water content are analyzed and discussed. The daily leaf carbon assimilation is then coupled to a stochastic Soil moisture model to obtain a probabilistic description of the carbon assimilation during a growing season. The rainfall regime, in terms of both frequency and amount of precipitation, controls the mean assimilation during a growing season that reaches a maximum for an intermediate range of daily rainfall probabilities, indicating the existence of a rainfall regime that is most effective for plant productivity. The analysis of the duration and frequency of periods of no assimilation provides a measure of plant Water stress as a function of the Soil, vegetation, and climate characteristics. The results are in good agreement with the dynamic Water stress defined in Porporato et al. on the basis of the crossing properties of the stochastic Soil moisture dynamics.
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coupled dynamics of photosynthesis transpiration and Soil Water Balance part i upscaling from hourly to daily level
Journal of Hydrometeorology, 2004Co-Authors: Edoardo Daly, Amilcare Porporato, Ignacio RodrigueziturbeAbstract:Abstract The governing equations of Soil moisture dynamics, photosynthesis, and transpiration are reviewed and coupled to study the dependence of plant carbon assimilation on Soil moisture. The model follows the scheme of the Soil–plant–atmosphere continuum (SPAC) and uses a simplified model of the atmospheric boundary layer to arrive at an upscaled, parsimonious representation at the daily time scale. The analysis of Soil moisture, transpiration, and carbon assimilation dynamics provides an assessment of the role of Soil, plant, and boundary layer characteristics on the diurnal courses of photosynthesis and transpiration rates, while the subsequent upscaling at the daily level provides a functional dependence of stomatal conductance on Soil moisture that is in good agreement with field experiments. The upscaled dependence of transpiration and carbon assimilation on Soil moisture is used in Part II of this paper to explore the impact of Soil moisture dynamics on plant conditions when rainfall variability ...
