A conceptual dynamic vegetation-soil model for arid and semiarid zones

Abstract. Plant ecosystems in arid and semiarid climates show high complexity, since they depend on water availability to carry out their vital processes. In these climates, water stress is the main factor controlling vegetation development and its dynamic evolution. The available water-soil content results from the water balance in the system, where the key issues are the soil, the vegetation and the atmosphere. However, it is the vegetation, which modulates, to a great extent, the water fluxes and the feedback mechanisms between soil and atmosphere. Thus, soil moisture content is most relevant for plant growth maintenance and final water balance assessment. A conceptual dynamic vegetation-soil model (called HORAS) for arid and semi-arid zones has been developed. This conceptual model, based on a series of connected tanks, represents in a way suitable for a Mediterranean climate, the vegetation response to soil moisture fluctuations and the actual leaf biomass influence on soil water availability and evapotranspiration. Two tanks were considered using at each of them the water balance and the appropriate dynamic equation for all considered fluxes. The first one corresponds to the interception process, whereas the second one models the evolution of moisture by the upper soil. The model parameters were based on soil and vegetation properties, but reduced their numbers. Simulations for dominant species, Quercus coccifera L., were carried out to calibrate and validate the model. Our results show that HORAS succeeded in representing the vegetation dynamics and, on the one hand, reflects how following a fire this monoculture stabilizes after 9 years. On the other hand, the model shows the adaptation of the vegetation to the variability of climatic and soil conditions, demonstrating that in the presence or shortage of water, the vegetation regulates its leaf biomass as well as its rate of transpiration in an attempt to minimize total water stress.

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A conceptual dynamic vegetation-soil model for arid and semiarid zones

Hydrology and Earth System Sciences Discussions ◽

10.5194/hessd-4-3469-2007 ◽

2007 ◽

Vol 4 (5) ◽

pp. 3469-3499 ◽

Cited By ~ 2

Author(s):

D. I. Quevedo ◽

F. Francés

Keyword(s):

Soil Moisture ◽

Water Stress ◽

Water Balance ◽

Vegetation Type ◽

Moisture Determination ◽

State Variables ◽

Time Step ◽

Available Water ◽

Soil Model ◽

Arid And Semiarid

Abstract. Plant ecosystems in arid and semiarid zones show high complexity from the point of view of water resources, since they depend on water availability to carry out their vital processes. In these climates, water stress is the main factor controlling vegetation development. The available water in the system results from a water balance where the soil, vegetation and the atmosphere are the key issues; but it is the vegetation which modulates (to a great extent) the total balance of water and the mechanisms of the feedback between soil and atmosphere, being the knowledge about soil moisture quite relevant for assessing available water and, as a consequence, for growth and plants maintenance and the final water balance in the system. A conceptual dynamic vegetation-soil model (CDVSM) for arid and semiarid zones was developed. This model based in a tank type conceptualization represents in a suitable way, for Mediterranean climate, the vegetation responses to soil moisture fluctuations. Two tanks interconnected were considered using the water balance equation and the appropriate dynamic equation for all considered fluxes. The first one corresponds to the interception process done by the vegetation. The second one models the upper soil moisture determination. In this tank parameters are based on soil and vegetation properties. The transpiration of the vegetation is a function of the soil moisture, the vegetation type and the biomass. Once all water state variables are evaluated at each time step, the modifications in the biomass are made as a function of transpiration rate and water stress. Simulations for monoculture of Quercus Coccifera L. were carried out. Results shows that CDVSM is able to represent the vegetation dynamic, reflecting how the monoculture is stabilized around 0.7 of relative biomass, with adaptation to the soil moisture fluctuations in the long term. The model shows the vegetation adaptation to the variability of the climatic conditions, demonstrating how either in the presence or shortage of water, the vegetation regulates its biomass as well as its rate of transpiration trying to minimize the total water stress.

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Evaluation of DSSAT soil-water balance module under cropped and bare soil conditions

Brazilian Archives of Biology and Technology ◽

10.1590/s1516-89132003000400001 ◽

2003 ◽

Vol 46 (4) ◽

pp. 489-498 ◽

Cited By ~ 11

Author(s):

Rogério Teixeira de Faria ◽

Walter Truman Bowen

Keyword(s):

Soil Moisture ◽

Water Balance ◽

Soil Water ◽

Water Flux ◽

Soil Water Potential ◽

Bare Soil ◽

Root Water Uptake ◽

Soil Water Balance ◽

Soil Conditions ◽

Soil Water Flux

The performance of the soil water balance module (SWBM) in the models of DSSAT v3.5 was evaluated against soil moisture data measured in bare soil and dry bean plots, in Paraná, southern Brazil. Under bare soil, the SWBM showed a low performance to simulate soil moisture profiles due to inadequacies of the method used to calculate unsaturated soil water flux. Improved estimates were achieved by modifying the SWBM with the use of Darcy's equation to simulate soil water flux as a function of soil water potential gradient between consecutive soil layers. When used to simulate water balance for the bean crop, the modified SWBM improved soil moisture estimation but underpredicted crop yield. Root water uptake data indicated that assumptions on the original method limited plant water extraction for the soil in the study area. This was corrected by replacing empirical coefficients with measured values of soil hydraulic conductivity at different depths.

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Testing the Robustness of a Physically-Based Hydrological Model in Two Data Limited Inland Valley Catchments in Dano, Burkina Faso

Hydrology ◽

10.3390/hydrology7030043 ◽

2020 ◽

Vol 7 (3) ◽

pp. 43

Author(s):

Mouhamed Idrissou ◽

Bernd Diekkrüger ◽

Bernhard Tischbein ◽

Boubacar Ibrahim ◽

Yacouba Yira ◽

...

Keyword(s):

Soil Moisture ◽

Water Balance ◽

Burkina Faso ◽

Hydrological Model ◽

Model Performance ◽

Surface Flow ◽

Small Scale ◽

Model Parameters ◽

Inland Valley ◽

Physically Based

This study investigates the robustness of the physically-based hydrological model WaSiM (water balance and flow simulation model) for simulating hydrological processes in two data sparse small-scale inland valley catchments (Bankandi-Loffing and Mebar) in Burkina Faso. An intensive instrumentation with two weather stations, three rain recorders, 43 piezometers, and one soil moisture station was part of the general effort to reduce the scarcity of hydrological data in West Africa. The data allowed us to successfully parameterize, calibrate (2014–2015), and validate (2016) WaSiM for the Bankandi-Loffing catchment. Good model performance concerning discharge in the calibration period (R2 = 0.91, NSE = 0.88, and KGE = 0.82) and validation period (R2 = 0.82, NSE = 0.77, and KGE = 0.57) was obtained. The soil moisture (R2 = 0.7, NSE = 0.7, and KGE = 0.8) and the groundwater table (R2 = 0.3, NSE = 0.2, and KGE = 0.5) were well simulated, although not explicitly calibrated. The spatial transposability of the model parameters from the Bankandi-Loffing model was investigated by applying the best parameter-set to the Mebar catchment without any recalibration. This resulted in good model performance in 2014–2015 (R2 = 0.93, NSE = 0.92, and KGE = 0.84) and in 2016 (R2 = 0.65, NSE = 0.64, and KGE = 0.59). This suggests that the parameter-set achieved in this study can be useful for modeling ungauged inland valley catchments in the region. The water balance shows that evaporation is more important than transpiration (76% and 24%, respectively, of evapotranspiration losses) and the surface flow is very sensitive to the observed high interannual variability of rainfall. Interflow dominates the uplands, but base flow is the major component of stream flow in inland valleys. This study provides useful information for the better management of soil and scarce water resources for smallholder farming in the area.

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A performance assessment method for SAR satellite-derived surface soil moisture data using a soil-water balance model, meteorological observations, and soil pedotransfer functions.

10.5194/egusphere-egu2020-3387 ◽

2020 ◽

Author(s):

John Beale ◽

Toby Waine ◽

Ronald Corstanje ◽

Jonathan Evans

Keyword(s):

Regression Analysis ◽

Soil Moisture ◽

Water Balance ◽

Surface Soil ◽

Cosmic Ray ◽

Water Balance Model ◽

Balance Model ◽

Model Parameters ◽

Surface Soil Moisture

The validation of surface soil moisture products derived from SAR satellites data is challenged by the difficulty of reliably measuring in-situ soil moisture at shallow soil depths of a few centimetres, consistent with the penetration depth of the microwave beam. Our analysis shows that the apparent accuracy of the remote sensing products is underestimated by comparison with inconsistent probe data or measurements at greater soil depths. Our alternative approach uses in-situ meteorological measurements to determine rainfall and potential evapotranspiration, to be used with soil hydrological properties as inputs to a water balance model to estimate surface soil moisture independently of the satellite data. In-situ soil moisture measurements are used to validate and refine the model parameters. The choice of appropriate soil hydrological parameters with which to convert remotely sensed surface soil moisture indices to volumetric moisture content is shown to have a significant impact on the bias and offset in the regression analysis. To illustrate this, Copernicus SSM data is analysed by this method for a number of COSMOS-UK soil moisture monitoring sites, showing a significant improvement in the coefficient of determination, bias and offset over regression analysis using in-situ measurements from soil moisture probes or the cosmic ray soil moisture sensor itself. This will benefit users of such products in agriculture, for example, in determining actual soil moisture deficit.

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Modeling the monthly mean soil-water balance with a statistical-dynamical ecohydrology model as coupled to a two-component canopy model

Hydrology and Earth System Sciences ◽

10.5194/hess-14-2099-2010 ◽

2010 ◽

Vol 14 (10) ◽

pp. 2099-2120 ◽

Cited By ~ 12

Author(s):

J. P. Kochendorfer ◽

J. A. Ramírez

Keyword(s):

Soil Moisture ◽

Water Stress ◽

Water Balance ◽

Soil Water ◽

Soil Texture ◽

Root Zone ◽

Soil Water Balance ◽

Area Index ◽

Two Component ◽

Canopy Model

Abstract. The statistical-dynamical annual water balance model of Eagleson (1978) is a pioneering work in the analysis of climate, soil and vegetation interactions. This paper describes several enhancements and modifications to the model that improve its physical realism at the expense of its mathematical elegance and analytical tractability. In particular, the analytical solutions for the root zone fluxes are re-derived using separate potential rates of transpiration and bare-soil evaporation. Those potential rates, along with the rate of evaporation from canopy interception, are calculated using the two-component Shuttleworth-Wallace (1985) canopy model. In addition, the soil column is divided into two layers, with the upper layer representing the dynamic root zone. The resulting ability to account for changes in root-zone water storage allows for implementation at the monthly timescale. This new version of the Eagleson model is coined the Statistical-Dynamical Ecohydrology Model (SDEM). The ability of the SDEM to capture the seasonal dynamics of the local-scale soil-water balance is demonstrated for two grassland sites in the US Great Plains. Sensitivity of the results to variations in peak green leaf area index (LAI) suggests that the mean peak green LAI is determined by some minimum in root zone soil moisture during the growing season. That minimum appears to be close to the soil matric potential at which the dominant grass species begins to experience water stress and well above the wilting point, thereby suggesting an ecological optimality hypothesis in which the need to avoid water-stress-induced leaf abscission is balanced by the maximization of carbon assimilation (and associated transpiration). Finally, analysis of the sensitivity of model-determined peak green LAI to soil texture shows that the coupled model is able to reproduce the so-called "inverse texture effect", which consists of the observation that natural vegetation in dry climates tends to be most productive in sandier soils despite their lower water holding capacity. Although the determination of LAI based on complete or near-complete utilization of soil moisture is not a new approach in ecohydrology, this paper demonstrates its use for the first time with a new monthly statistical-dynamical model of the water balance. Accordingly, the SDEM provides a new framework for studying the controls of soil texture and climate on vegetation density and evapotranspiration.

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Effects of water stress on evapotranspiration of soybean

Міжвідомчий тематичний науковий збірник Меліорація і водне господарство ◽

10.31073/mivg202101-266 ◽

2021 ◽

pp. 118-127

Author(s):

O. V. Zhuravlov ◽

A. P. Shatkovskyi ◽

V. V. Vasiuta

Keyword(s):

Soil Moisture ◽

Water Stress ◽

Water Balance ◽

Comparative Assessment ◽

Percentage Error ◽

Calculation Methods ◽

Stress Coefficient ◽

Daily Evapotranspiration ◽

Water Stress Coefficient

Based on the results of observations, it was specified that when decreasing soil moisture there is a disproportionate decrease in the average daily evapotranspiration (ET). Thus, in the range of soil moisture of 94-80% minimum moisture-holding capacity (MMHC) ET was 9,76 mm a day, and in the range of 70-62% MMHC - its value decreased by 3 times. When the soil moisture reached 58,5% MMHC, the value of ET did not exceed 0,5 mm a day, which is 20 times less than the initial one. It was determined that the decrease in soil moisture by 10% in the range of 90 - 70% MMHC occurs during 3 days, and from 70 to 60% MMHC and from 60 to 58% MMHC - during 8 days. When soil moisture is 70% MMHC and below, the actual evapotranspiration is less than ETo that proves the effect of water stress on soybeans ET. When calculating water stress coefficient (Ks), a mathematical model based on the dependence of Ks on soil moisture as a percentage of MMHC was obtained. The average absolute percentage error (MAPE) is 8,6%, which corresponds to the high accuracy of the obtained dependence. In the range of soil moisture from 58 to 80% MMHC, the water stress coefficient is calculated by the formula Ks =-0.0011·FC²+0.1925·FC-7,4541. When having soil moisture as 80% MMHC and above, Ks = 1. A comprehensive comparative assessment of existing methods for calculating waster stress coefficient Ks was taken and it was found out that the actual values of Ks when having soil moisture as 80-70 and 60-65% MMHC by 8-14 % and 72-32 %, respectively, less than Ks FAO 56, and by 35-40 % larger than those determined by Saxton method. It was proved the need of taking into account the reduction in evapotranspiration when calculating water balance under water stress of plants. The calculation of evapotranspiration (ETs) by the Penman-Monteith method, without taking into account the water stress coefficient, showed that the value of the actual and calculated water balance coincides only when soil moisture does not exceed 62% MMHC. With a further decrease in soil moisture, the estimated soil moisture was 20% less than the actual, which led to the errors in determining soil moisture after irrigation, because its actual value was almost 100% MMHC, and the estimated one was only 60% MMHC. It was proved that the determination of water balance by calculation methods without taking into account the water stress coefficient leads to significant errors.

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Modeling the monthly mean soil-water balance with a statistical-dynamical ecohydrology model as coupled to a two-component canopy model

Hydrology and Earth System Sciences Discussions ◽

10.5194/hessd-5-579-2008 ◽

2008 ◽

Vol 5 (2) ◽

pp. 579-648

Author(s):

J. P. Kochendorfer ◽

J. A. Ramírez

Keyword(s):

Soil Moisture ◽

Water Stress ◽

Water Balance ◽

Soil Water ◽

Soil Texture ◽

Root Zone ◽

Soil Water Balance ◽

Area Index ◽

Two Component ◽

Canopy Model

Abstract. The statistical-dynamical annual water balance model of Eagleson (1978) is a pioneering work in the analysis of climate, soil and vegetation interactions. This paper describes several enhancements and modifications to the model that improve its physical realism at the expense of its mathematical elegance and analytical tractability. In particular, the analytical solutions for the root zone fluxes are re-derived using separate potential rates of transpiration and bare-soil evaporation. Those potential rates, along with the rate of evaporation from canopy interception, are calculated using the two-component Shuttleworth-Wallace (1985) canopy model. In addition, the soil column is divided into two layers, with the upper layer representing the dynamic root zone. The resulting ability to account for changes in root-zone water storage allows for implementation at the monthly timescale. This new version of the Eagleson model is coined the Statistical-Dynamical Ecohydrology Model (SDEM). The ability of the SDEM to capture the seasonal dynamics of the local-scale soil-water balance is demonstrated for two grassland sites in the US Great Plains. Sensitivity of the results to variations in peak green Leaf Area Index (LAI) suggests that the mean peak green LAI is determined by some minimum in root zone soil moisture during the growing season. That minimum appears to be close to the soil matric potential at which the dominant grass species begins to experience water stress and well above the wilting point, thereby suggesting an ecological optimality hypothesis in which the need to avoid water-stress-induced leaf abscission is balanced by the maximization of carbon assimilation (and associated transpiration). Finally, analysis of the sensitivity of model-determined peak green LAI to soil texture shows that the coupled model is able to reproduce the so-called "inverse texture effect", which consists of the observation that natural vegetation in dry climates tends to be most productive in sandier soils despite their lower water holding capacity. Although the determination of LAI based on near-complete utilization of soil moisture is not a new approach in ecohydrology, this paper demonstrates its use for the first time with a new monthly statistical-dynamical model of the water balance. Accordingly, the SDEM provides a new framework for studying the controls of soil texture and climate on vegetation density and evapotranspiration.

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Measurement of the influence of low water availability on the productivity of Agave weberi cultivated under controlled irrigation

Canadian Journal of Plant Science ◽

10.4141/cjps2013-256 ◽

2014 ◽

Vol 94 (2) ◽

pp. 439-444 ◽

Cited By ~ 2

Author(s):

Steven J. Bergsten ◽

J. Ryan Stewart

Keyword(s):

Soil Moisture ◽

Nutrient Uptake ◽

Water Availability ◽

Irrigation System ◽

Biomass Accumulation ◽

Dry Weight ◽

Energy Crop ◽

Soil Conditions ◽

Controlled Irrigation ◽

Dry Soil

Bergsten, S. J. and Stewart, J. R. 2014. Measurement of the influence of low water availability on the productivity of Agave weberi cultivated under controlled irrigation. Can. J. Plant Sci. 94: 439–444. In recent years, research has focused on determining the potential of Agave to be utilized for bioenergy production due to its ability to grow in arid and marginal lands. However, little is known regarding its productivity under limited water conditions. Most Agave species can tolerate low soil-moisture levels, but it is unclear at what point productivity will be significantly constrained. Using an automated irrigation system under greenhouse conditions, we evaluated the effects of low to high volumetric water content (VWC) levels on biomass accumulation and nutrient uptake of a putative bioenergy crop, Agave weberi. Plants were exposed to four constant VWC levels (0.05, 0.12, 0.19, and 0.26 m3 m−3). Shoot dry weight of plants in the 0.26 m3 m−3 treatment was significantly higher than those in the 0.05 m3 m−3 treatment, but not than those in the intermediate treatments. Both chlorophyll count and nutrient uptake decreased as VWC level decreased. Although plants were fairly productive under moderately dry soil conditions, it would be expected that over time, plants receiving high levels of irrigation would have greater growth than plants in dry soil moisture levels. However, similar yields between the well-watered and moderately dry treatments suggest that A. weberi should be further evaluated as a candidate energy crop in more long-term field trials.

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Global monthly water stress: 1. Water balance and water availability

Water Resources Research ◽

10.1029/2010wr009791 ◽

2011 ◽

Vol 47 (7) ◽

Cited By ~ 229

Author(s):

L. P. H. van Beek ◽

Yoshihide Wada ◽

Marc F. P. Bierkens

Keyword(s):

Water Stress ◽

Water Balance ◽

Water Availability

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A water stress index based on water balance modelling for discrimination of grapevine quality and yield

OENO One ◽

10.20870/oeno-one.2014.48.1.1655 ◽

2014 ◽

Vol 48 (1) ◽

pp. 1 ◽

Cited By ~ 1

Author(s):

Rémi Gaudin ◽

Kamal Kansou ◽

Jean-Christophe Payan ◽

Anne Pellegrino ◽

Christian Gary

Keyword(s):

Water Stress ◽

Water Balance ◽

Soil Water ◽

Water Deficit ◽

Water Balance Model ◽

Stress Index ◽

Balance Model ◽

Soil Conditions ◽

Water Stress Index ◽

Berry Quality

Aims: A water stress index based on a water balance model was tested as a tool for classifying the water stress paths experienced by grapevines in various French Mediterranean vineyards. The relations between the index value and grapevine yield and berry quality (sugars, organic acids, anthocyanins) at harvest were investigated.Methods and results: A data set of 102 situations, each combining one location, one variety, one vintage and one water regime (irrigation or, most often, no irrigation), was collected for the study. The Fraction of Transpirable Soil Water (FTSW) was simulated by a unique-soil-reservoir water balance model at a daily time step. Five classes of water deficit were delimited from specific decreasing thresholds of FTSW over four periods between flowering and harvest. These thresholds were derived from predawn leaf water potential values because over decades, grapegrowers and researchers have shared references and built expertise by using this variable throughout the Mediterranean region. A water stress index resulting from the levels of water deficit reached at each of the four periods of the cycle was calculated. This index was correlated with yield per vine, berry weight, and berry sugar and organic acid contents but not with berry anthocyanin content.Conclusion: A simple water stress index, based on the water balance model, exhibited significant correlations with yield and berry quality for various cultivars and pedo-climatic conditions in Mediterranean vineyards.Significance and impact of the study: This water stress index is a valuable tool for explaining the variations in grape yield and quality among various locations and years because it reflects the vineyard water stress history in relation to rainfall regime and soil conditions. Improvement would come from the simulation of FTSW during winter, notably for soils of high Total Transpirable Soil Water. One potential application is the quantification of water stress change brought by irrigation in Mediterranean vineyards, and its relation to grapevine production.

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