The Structure and Dynamics of Agricultural Landscapes as Drivers of Biodiversity - Landscape Ecology for Sustainable Environment and Culture - page 277

to farmers' decisions (Joannon et al. 2008 ). Agricultural practices in a field follow
crop management sequences and depend on cropping systems (pluriannual crop
rotation and management). Cropping systems are furthermore spatially distributed
on the farm territory according to environmental conditions in fields (e.g. soil
type), spatial structure of field patterns on farms and logistic constraints (Thenail
and Baudry 2004 ). As a result, the cropping systems mosaic is highly heteroge-
neous in space and time. This additional heterogeneity may be of great importance
for species (insects, weeds, mammals) using crops for at least part of their life
(Vasseur et al. in press ).
Studies on the influence of landscape patterns on biodiversity have focused on
spatial heterogeneity. On the contrary, temporal heterogeneity has been less
studied in landscape ecology (Metzger 2008 ). Not considering this dimension is a
limitation. Past landscape structure can affect present ecological processes, and
there is often a time lag between landscape change and responses by organisms
(Ernoult et al. 2006 ; Krauss et al. 2010 ; Auffret and Cousins 2011 ). Moreover, in
dynamic landscapes the rate of habitat turnover and associated change in land-
scape structure can sometimes be more important for species survival than the
spatial organization of resource patches (Fahrig 1992 ).
Along this gradient of heterogeneities, the respective role of landscape design
(field size, shape, presence of hedgerows etc.) and of cropping practices in the
management of biodiversity is a central question. This question is of importance to
model population dynamics and to design management plans. A landscape mosaic
is built from both design and practices; therefore it is more and more important to
foster our capacity to disentangle their effects.
In this chapter, we present how different approaches of landscape heterogeneity,
first oriented toward semi natural habitats, and then recognizing the role of crops
and their dynamics, may give insights on the fate of biodiversity in agricultural
landscapes. We will then discuss their relative efficiency according to landscape
and species types. This will give clues for designing agri-environmental schemes
for biodiversity.
14.2 The Role of Semi-Natural Elements
in Agricultural Landscapes
When looking at the effect of landscape structure on biodiversity in agricultural
landscapes the main emphasis has been put on considering the effect of semi
natural elements (Billeter et al. 2008 ; Tscharntke et al. 2005a ). They are consid-
ered as habitats, refuges, sources, corridors for many species that use crop fields
for part of their life cycle and by species which are restricted to them (Deckers
et al. 2005 ; Forman and Baudry 1984 ). This approach has been the first to be used
by landscape ecologists who considered agricultural landscapes as sets of semi-
natural elements embedded in a neutral agricultural matrix. We studied the effects