Comparison of the Root Water Uptake Term of Four Simulation Models PDF Download

Author: Peter Willigen
Publisher:
ISBN:
Category :
Languages : en
Pages : 65

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Author: Parikshit Verma
Publisher:
ISBN:
Category :
Languages : en
Pages : 234

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Book Description
Root water uptake by plants mediates the exchange of water, carbon and energy between land surface and atmosphere and is important in hydrological, climatological, agricultural and ecological studies. Field measurements show that root water uptake could be significantly affected by root water compensation and hydraulic redistribution. We thus use a root water uptake model able to describe these two mechanisms and show their importance when vegetation is growing in shallow water-table environments or duplex soils. The model is based on the Richards equation for the water-flow in soils, with a term for root water uptake being a function of the water potential difference between root xylem and the soil. We describe the flow in the xylem using the Darcy's equation.The model is used in three studies aimed at highlighting the role that root water compensation and hydraulic redistribution might have on the overall root water uptake. In the first study, the model in one dimension is applied to a site near Sydney, Australia, to investigate how native trees growing on duplex soils are able to sustain transpiration rate despite long periods with little or no rain. The model was able to reproduce sap-flux data and the pattern of soil, root and leaf water potential for several months. Scenarios with different root depths showed that trees were able to adjust their water-uptake rates from different soil layers based on soil moisture availability; thus, root water compensation appears to be a key mechanism to maintain sustained transpiration rates. In a second study we investigated the contribution of root water compensation and hydraulic redistribution to root water uptake in shallow water-table environments. We compared the results of our model with a more commonly used root water uptake model. In the third study, we extended the 1D-model to two dimensions, thereby being able to simulate horizontal hydraulic redistribution and the interaction between species with different root systems. In the 2D-model, the roots were assumed to be a continuum in soil and the root systems were described in terms of xylem conductivity fields. Scenarios are presented to show that the 2D-model is able to reproduce observed flow patterns through roots in parts of the soil with different degrees of moisture. The studies presented in this thesis show the further development and use of a modeling approach that is gaining increasing interest in the recent literature. These studies present a realistic description of the role that root water compensation and hydraulic redistribution play in plant water use. The 2D-model introduces a representation of the root system that allows for modelling vertical (hydraulic lift) and horizontal hydraulic redistribution of water in soil, and an efficient description of the interaction between species with different root systems.

Author: Martin J. Kropff
Publisher: Int. Rice Res. Inst.
ISBN: 0851987451
Category : Science
Languages : en
Pages : 277

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General introduction; Empirical models for crop-weed competition; Eco-physiological models for crop-weed competition; Mechanisms of competition for light; Mechanisms of competition for water; Mechanisms of competition for nitrogen; Eco-physiological characterization of the species; Understanding crop-weed interaction in field situation; The impact of environmental and genetic factors; Practical applications.

Author: R. A. Feddes
Publisher: Halsted Press
ISBN: 9780470264638
Category : Crop yields
Languages : en
Pages : 188

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Book Description
Theory of field water use: basics of water flow i unsaturated soils;water uptake by plants roots;numerical approximation of flow in soil-root systems. Theory of crop production:mathematical description of growts;water and actual production;calculation of potential production. Theprogram:program for field water use, SWATR;program for crop production,CROPR;execution of SWATR; execution of CROPR.

Author: Jun J. Abe
Publisher: Springer Science & Business Media
ISBN: 9401729239
Category : Science
Languages : en
Pages : 444

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The root is the organ that functions as the interface between the plant and the earth environment. Many human management practices involving crops, forests and natural vegetation also affect plant growth through the soil and roots. Understanding the morphology and function of roots from the cellular level to the level of the whole root system is required for both plant production and environmental protection. This book is at the forefront of plant root science (rhizology), catering to professional plant scientists and graduate students. It covers root development, stress physiology, ecology, and associations with microorganisms. The chapters are selected papers originally presented at the 6th Symposium of the International Society of Root Research, where plant biologists, ecologists, soil microbiologists, crop scientists, forestry scientists, and environmental scientists, among others, gathered to discuss current research results and to establish rhizology as a newly integrated research area.

Author: Lajpat Ahuja
Publisher: Water Resources Publication
ISBN: 9781887201087
Category : Technology & Engineering
Languages : en
Pages : 388

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Book Description
This publication comes with computer software and presents a comprehensive simulation model designed to predict the hydrologic response, including potential for surface and groundwater contamination, of alternative crop-management systems. It simulates crop development and the movement of water, nutrients and pesticides over and through the root zone for a representative unit area of an agricultural field over multiple years. The model allows simulation of a wide spectrum of management practices and scenarios with special features such as the rapid transport of surface-applied chemicals through macropores to deeper depths and the preferential transport of chemicals within the soil matrix via mobile-immobile zones. The transfer of surface-applied chemicals (pesticides in particular) to runoff water is also an important component.

Author: Gordon Bonan
Publisher: Cambridge University Press
ISBN: 1107043786
Category : Mathematics
Languages : en
Pages : 459

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Book Description
Provides an essential introduction to modeling terrestrial ecosystems in Earth system models for graduate students and researchers.

Author: Leilah Krounbi
Publisher:
ISBN:
Category : Deficit irrigation
Languages : en
Pages : 218

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Author: J. Goudriaan
Publisher: Springer Science & Business Media
ISBN: 9401107505
Category : Science
Languages : en
Pages : 247

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We dedicate this book to professor C. T. de Wit (1924 - 1993) who initiated Production Ecology as a school of thought at the Wageningen Agricultural Univer sity (see Rabbinge et at. , 1990). To acknowledge the leading role of C. T. de Wit, a recently formed graduate school at this university in Production Ecology was named after him. Production Ecology is the study of ecological processes, with special attention to flows of energy and matter as factors that determine the productivity of ecological systems. Agro-ecosystems are a special case of ecosystems which are much better suited for the productivity approach than natural ecosystems are. This is the reason for the strong role of agricultural research in production ecology. On the other hand, it must be recognized that the spatial heterogeneity of natural ecosys tems and their species richness may alter some ecophysiological relationships. However, the basic physical, chemical and physiological processes will be the same. De Wit introduced the state variable approach as the basis for simulation mod elling. In this approach the floating character of nature is schematized into a series of snapshots over time in which the states are frozen at each separate moment. The current state determines how the rates of change will lead to the next snapshot. This way of thinking enables a clear and workable representation of interacting simul taneous processes, without compromising on the mathematics.

Author: Marco Bittelli
Publisher:
ISBN: 0199683093
Category : Science
Languages : en
Pages : 461

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Book Description
This innovative study presents concepts and problems in soil physics, and provides solutions using original computer programs. It provides a close examination of physical environments of soil, including an analysis of the movement of heat, water and gases. The authors employ the programminglanguage Python, which is now widely used for numerical problem solving in the sciences. In contrast to the majority of the literature on soil physics, this text focuses on solving, not deriving, differential equations for transport. Using numerical procedures to solve differential equations allowsthe solution of quite difficult problems with fairly simple mathematical tools. Numerical methods convert differential into algebraic equations, which can be solved using conventional methods of linear algebra. Each chapter introduces a soil physics concept, and proceeds to develop computer programsto solve the equations and illustrate the points made in the discussion.Problems at the end of each chapter help the reader practise using the concepts introduced. The text is suitable for advanced undergraduates, graduates and researchers of soil physics. It employs an open source philosophy where computer code is presented, explained and discussed, and provides thereader with a full understanding of the solutions. Once mastered, the code can be adapted and expanded for the user's own models, fostering further developments. The Python tools provide a simple syntax, Object Oriented Programming techniques, powerful mathematical and numerical tools, and a userfriendly environment.