ABSTRACT
Sir Arthur Tansley [87] provided the first formal definition of an ecosystem, although the concept's roots emerged many years earlier [55]. Tansley observed that, " . . . the more fundamental conception is . . . the whole system (in the sense of physics), including not only the organism-complex, but also the whole complex of physical factors forming what we call the environment of the biomethe habitat factors in the widest sense." Besides including the environment's physical and biological components, he also suggested the important impact of cultural activities upon ecosystems, noting that, "we cannot confine ourselves to the so-called 'natural' entities and ignore the processes and expressions of vegetation now so abundantly provided us by the activities of man." Thus, Tansley's original consideration of an ecosystem's myriad components provides a backdrop to the topic at hand: agricultural systems as ecosystems.
