Current Issues in Production Ecology – serie

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.

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.

Potato is the fourth major staple food in the world and is still rapidly gaining importance, especially in the tropics. In May, 1994 the second international potato modelling conference was held in Wageningen, the Netherlands, as a summerschool of the C. T. de Wit Graduate School. The conference was sponsored by DLO, SCRI, SSCR, W AU and the LEB-Fund. Over 80 scientists participated, coming from 16 countries. Of each crop physiological and modelling subject, a leading scientist was requested to write a review of the most recent developments in his or her field. The reviews, with highlights from the authors' own work, are such that the physiological work described is of interest to the modeller and the modelling work to the crop physiologist. Applications of the quantitative approach are also reviewed in the concluding chapters that deal with decision support systems, breeding and agro-ecological zoning. An outstanding point of this book is that both the crop ecology and the modelling of a broad range of biotic and abiotic factors are treated by scientists representing groups which are specialized in the subject. The two related disciplines met during the conference and thus wrote the chapters with each other's interest in mind. The book highlights the limitations for potato growth and development from the viewpoints of both the crop physiologist and the crop-systems analyst.

Systems approaches are excellent in integrating insights in the physical, chemical, Systemsapproachesareexcellentinintegratinginsightsinthephysical,chemical, physiological and ecological processes that dictate the behaviour of living systems, of physiologicalandecologicalprocessesthatdictatethebehaviouroflivingsystems,of which which agro-ecosystems agro-ecosystems are are important importantones. ones. Furthermore, Furthermore, they theyhelp help to tobridge bridge the the gap gap between betweendetailed detailed process processoriented oriented studies studies and and higher higherintegration integration levels. levels.Systems Systems approaches approaches are are roughly roughlycategorized categorized in inthree three groups groups of of studies: studies: (i) (i) predictive predictive studies studies to to support support decision decision making making and and guide guide interventions, interventions, (ii) (ii) systems systemsanalysis analysis and and simulation simulation in inorder order to toget get insight insight and and understanding understandingof of the the functioning functioningof of (living) (living) systems, systems, and and (iii) (iii) explorative explorative studies studies to to investigate investigate possible possible options options for for development development and and trade trade offs offs of of aims, aims,objectives objectives and andconstraints. constraints. All All these these systems systems approaches approaches are are now nowwidely widely used used in inecological ecological systems systems including including agriculture, agriculture, and and applied appliedin in land landuse use planning. planning.This This book book is is an an introduction introduction to toone one of ofthe the major majorfields: fields: systems systems analysis analysis and and simula- simula- tion. tion.

Systems approaches are excellent in integrating insights in the physical, chemical, Systemsapproachesareexcellentinintegratinginsightsinthephysical,chemical, physiological and ecological processes that dictate the behaviour of living systems, of physiologicalandecologicalprocessesthatdictatethebehaviouroflivingsystems,of which which agro-ecosystems agro-ecosystems are are important importantones. ones. Furthermore, Furthermore, they theyhelp help to tobridge bridge the the gap gap between betweendetailed detailed process processoriented oriented studies studies and and higher higherintegration integration levels. levels.Systems Systems approaches approaches are are roughly roughlycategorized categorized in inthree three groups groups of of studies: studies: (i) (i) predictive predictive studies studies to to support support decision decision making making and and guide guide interventions, interventions, (ii) (ii) systems systemsanalysis analysis and and simulation simulation in inorder order to toget get insight insight and and understanding understandingof of the the functioning functioningof of (living) (living) systems, systems, and and (iii) (iii) explorative explorative studies studies to to investigate investigate possible possible options options for for development development and and trade trade offs offs of of aims, aims,objectives objectives and andconstraints. constraints. All All these these systems systems approaches approaches are are now nowwidely widely used used in inecological ecological systems systems including including agriculture, agriculture, and and applied appliedin in land landuse use planning. planning.This This book book is is an an introduction introduction to toone one of ofthe the major majorfields: fields: systems systems analysis analysis and and simula- simula- tion. tion.

This text addresses methodological issues of production ecology, and contains scientific contributions written by nine specialists. A central issue is the combination of the agricultural model with reliable data in relation to scale. A model is developed with data from a single point, whereas decisions are to be made for areas of land. Such an approach requires the use of a skilful treatment of available data and information. The book is divided into four parts: advanced information science yields the best possible models in an efficient way; geographical information systems combine various layers of spatial information; statistics upscale local information towards regions and test its reliability; and modern trends in automated modelling are identified. The book is illustrated with various practical studies, ranging from the individual model to the whole European community. It aims at a readership of graduate and post-graduate agricultural scientists, practitioners and politicians.

Under leadership of CT de Wit a large amount of modeling, building prototypes and also application, was carried out in the 1970s and 1980s. Comprehensive models were built, evaluated and carefully documented in the areas of crop growth production, plant breeding, soil water and nutrients, and in crop protection. Simulation techniques and biophysical theories developed in parallel. Simulation and experimentation always went hand in hand. Much of this work is documented in a long series of PhD theses under supervision of De Wit, in the series of Simulation Monographs (PUDOC), and in numerous other publications. This work has inspired many scientists across the global science community. The CT de Wit Graduate School of Production Ecology (PE) of the Wageningen University builds further on this platform and finds new subjects for research on and with models, and data. The PE platform provides also an excellent opportunity to develop contacts, cooperation and joint software with research groups in related fields and abroad. This book precipitates from such an exploration in new directions. We realize that modem information systems and statistics can offer a substantial contribution to the modelling framework. Good examples can be found here, and these provide a clear direction for the years to come.