Abstract
Variation in population size over time can influence our ability to identify landscape-moderated differences in community assembly. To date, however, most studies at the landscape scale only cover snapshots in time, thereby overlooking the temporal dynamics of populations and communities. In this paper, we present data that illustrate how temporal variation in population density at a regional scale can influence landscape-moderated variation in recolonization and population buildup in disturbed habitat patches. Four common insect species, two omnivores and two herbivores, were monitored over 8 years in 10 willow short-rotation coppice bio-energy stands with a four-year disturbance regime (coppice cycle). The population densities in these regularly disturbed stands were compared to densities in 17 undisturbed natural Salix cinerea (grey willow) stands in the same region. A time series approach was used, utilizing the natural variation between years to statistically model recolonization as a function of landscape composition under two different levels of regional density. Landscape composition, i.e. relative amount of forest vs. open agricultural habitats, largely determined the density of re-colonizing populations following willow coppicing in three of the four species. However, the impact of landscape composition was not detectable in years with low regional density. Our results illustrate that landscape-moderated recolonization can change over time and that considering the temporal dynamics of populations may be crucial when designing and evaluating studies at landscape level.
Highlights
The spatial and temporal scale at which ecological studies are performed can greatly influence our understanding of the composition of natural communities and their dynamics (Wiens 1989; Levin 1992; Chase and Leibold 2002; Hastings 2004, 2010; Hortal et al 2010; Wang and Loreau 2014)
Hierarchy theory predicts that processes operating on finer spatial scales can be constrained by those that influence the system on broader spatial scales; e.g., variation between landscapes can be averaged out as climate and topography becomes increasingly important (Allen and Starr 1982; Sutcliffe et al 1996)
In the shortrotation coppice (SRC) willow stands, mean densities of C. fulvomaculatus were lower in 2003–2006 than in 2007– 2010, but mean densities were similar in the grey willow stands (Fig. 1)
Summary
The spatial and temporal scale at which ecological studies are performed can greatly influence our understanding of the composition of natural communities and their dynamics (Wiens 1989; Levin 1992; Chase and Leibold 2002; Hastings 2004, 2010; Hortal et al 2010; Wang and Loreau 2014). Hierarchy theory predicts that processes operating on finer spatial scales can be constrained by those that influence the system on broader spatial scales; e.g., variation between landscapes can be averaged out as climate and topography becomes increasingly important (Allen and Starr 1982; Sutcliffe et al 1996). Due to such hierarchical effects, the temporal scale of a study must be adjusted to capture large-scale variation, or there is a risk that fine-scale patterns are wrongly estimated. Most studies in landscape ecology to date only cover snapshots in time, despite the risk of identifying false patterns by overlooking the dynamics of populations and communi-
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