Why and how we should study field boundary biodiversity in an agrarian landscape context

Field boundaries are generally considered as important semi-natural environments in agrarian landscapes. The aim of this paper is to provide a methodological framework towards a holistic approach for field boundary studies. First, an overview of the successive milestones that have been passed in the history of hedgerow studies is given. These are classified a posteriori and then related to the succession of dominant ecological paradigms. Secondly, we show how former results have been used and integrated into a multiple scale approach involving agronomic and ecological studies in hedgerow network landscapes of western France. The hypothesis is that the main determinants of hedgerow biodiversity are related to farming activities. This hypothesis has been tested in three hedgerow network landscapes differing in their density of hedgerows and their relative abundance of grassland versus crops. The dominant agriculture of the region is dairy production, utilising grassland, maize and cereals. We focus on plant biodiversity and relate it to farming activities described from the boundary up to the landscape. The results show that the composition of the plant assemblages of the herb layer of field boundaries depends upon complex interactions between local structure, herb layer management, field use, farm types and landscape structure. The latter factors are related to the diversity of farming systems. Finally, the advantages of such an approach in terms of fundamental and applied landscape management aspects are discussed, showing how our framework of hedgerow studies expands by successive incorporation, rather than by rejection of former approaches. The main lesson is that it is necessary to capitalise on closer collaboration between ecologists and agronomists in order to stimulate future development of field boundary management and planning. (C) 2002 Elsevier Science B.V. All rights reserved.