tailieunhanh - LANDSCAPE ECOLOGY A Top-Down Approach - Chapter 8

Hệ sinh thái không phải là máy móc cũng không superorganisms, nhưng hệ thống chứ không phải mở đòi hỏi phải có một "phép tính xác suất có điều kiện" để định lượng. Autocatalysis, hoặc gián tiếp hỗ, khi nó xảy ra trong hệ thống duyên hệ mở, có thể hoạt động như một cơ quan chính thức nonmechanical, (sensu Aristotle) truyền đạt tổ chức hệ thống trao đổi dinh dưỡng. Các khó khăn mà autocatalysis tác dụng khi dòng chảy dinh dưỡng có thể được định lượng bằng cách sử dụng lý thuyết thông tin thông qua một chỉ số cấp hệ thống gọi là. | 8_ Quantifying Constraints upon Trophic and Migratory Transfers in Landscapes Robert E. Ulanowicz CONTENTS Introduction Conceptual Background for Ecosystems Not Quite a Mechanism Quantifying Kinetic Constraints Landscapes of Flows Conclusions Acknowledgments Ecosystems are neither machines nor superorganisms but rather open systems that require a calculus of conditional probabilities to quantify. Autocatalysis or indirect mutualism as it occurs in causally open systems may act as a nonmechanical formal agency sensu Aristotle that imparts organization to systems of trophic exchanges. The constraints that autocatalysis exerts upon trophic flows can be quantified using information theory via a system-level index called the ascendency. This quantity also gauges the organizational status of the ecological community. In addition the ascendency can be readily adapted to quantify the patterns of physical movements of biota across a landscape. In particular one can use ascendency to evaluate the effects of constraints to migration even when the details of such constraints remain unknown. Introduction In his recent critique of ecology Peters 1991 warns ecologists to pursue only those concepts that are fully operational. In a strict sense a concept is fully operational only when a well-defined protocol exists for making a series of 2000 by CRC Press LLC measurements that culminate in the assignment of a number or suite of numbers that quantifies the major elements of the idea. Can the ascendency description of ecosystem development be applied to spatial heterogeneities in ecosystems in a way that will yield fruitful insights and or predictions In a recent book Ulanowicz 1997 I attempted to articulate the full meaning import and application of ecosystem ascendency as a quantitative description of development in ecosystems. But the section in that volume that dealt with spatial heterogeneities is notable for its brevity and dearth of specific