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2 produkter
2 produkter
1 064 kr
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Since nutrients can become limiting resources in ecological systems, the way that these nutrients are recycled, as well as their actual exhaustion, is of great importance to the growth and stability of populations, and their resistance to perturbations. Thus the topic of nutrient cycling and food web dynamics is of crucial importance in ecology and this book is an synthesis of the area. A number of years ago, the data available on the cycling of nutrients within food chains was scant compared with the subject of food webs and communities generally. However, the time is now right for a summary of an awakening of interest in this important topic. The author is an authority in ecological modelling who has ably described and explained the topic in a clear and readable way. It should be useful reading for all with an interest in ecology. A final chapter discusses the implications for the major problem of global climate change. This book should be of interest to advanced undergraduates/research workers in ecology and biology/environmental scientists.
536 kr
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Cybernetics, a science concerned with understanding how systems are regulated, has reflected the preoccupations of the century in which it was born. Regulation is important in twentieth century society, where both machines and social organizations are complex. Cybernetics focused on and became primarily associated with the homeostasis or stability of system behavior and with the negative feedbacks that stabilize systems. It paid less attention to the processes opposite to negative feedback, the positive feedback processes that act to change systems. We attempt to redress the balance here by illustrating the enormous importance of positive feedbacks in natural systems. In an article in the American Scientist in 1963, Maruyama called for increased attention to this topic, noting that processes of change could occur when a "deviation in anyone component of the system caused deviations in other components that acted back on the first component to reinforce of amplify the initial deviation." The deviation amplification is the result of positive feedback among system components. Maruyama demonstrated by numerous examples that the neglect of such processes was unjustified and suggested that a new branch of cybernetics, "the second cybernetics," be devoted to their study.