Liman Anna-Sara, Dalin Peter, Björkman Christer
Department of Ecology, Swedish University of Agricultural Sciences Uppsala, Sweden.
Ecol Evol. 2015 Jul;5(13):2694-702. doi: 10.1002/ece3.1527. Epub 2015 Jun 18.
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.
种群数量随时间的变化会影响我们识别景观调节的群落组装差异的能力。然而，迄今为止，大多数景观尺度的研究只涵盖了时间上的快照，从而忽略了种群和群落的时间动态。在本文中，我们展示的数据说明了区域尺度上种群密度的时间变化如何影响景观调节的干扰生境斑块中重新定殖和种群增长的变化。我们在10个采用四年轮伐期（矮林周期）的柳树短轮伐期矮林生物能源林中，对4种常见昆虫物种（2种杂食性昆虫和2种食草性昆虫）进行了8年的监测。将这些定期受到干扰的林分中的种群密度与同一区域内17个未受干扰的天然灰柳林分中的密度进行比较。采用时间序列方法，利用年份之间的自然变化，在两种不同区域密度水平下，将重新定殖作为景观组成的函数进行统计建模。景观组成，即森林与开阔农业生境的相对比例，在四种物种中的三种中，很大程度上决定了柳树砍伐后重新定殖种群的密度。然而，在区域密度较低的年份，景观组成的影响无法检测到。我们的结果表明，景观调节的重新定殖会随时间变化，并且在设计和评估景观水平的研究时，考虑种群的时间动态可能至关重要。
