Unveiling the ghosts of landscapes past: Changes in landscape connectivity over the last decades are still shaping current woodland plant assemblages

Abstract

Abstract In ever‐changing landscapes, there is increasing evidence that current plant assemblages are shaped by the temporal dynamics of landscape connectivity. So far, attempts to take the temporal dynamics of connectivity into account have only focused on the degree of connectivity at one or several moments in time, but neglected the cumulative effects of temporal changes in connectivity. We investigated the effects of the temporal dynamics of landscape connectivity (i.e. the degree of connectivity, the magnitude and the variability of its temporal changes) over the last seven decades on current woodland plant herbaceous assemblages. The assemblages were described using a taxonomic approach combined with a functional approach based on four traits linked to the colonisation capacity of plant species. The taxonomic diversity of current woodland assemblages did not respond to the degree of connectivity nor to the magnitude and the variability of temporal changes, but the mean and/or the diversity of trait values linked to their colonisation capacity did. Responses, mainly driven by generalist species, were modulated by the type of connectivity trend experienced by woodlands. In woodlands experiencing an upward connectivity trend, high magnitude of temporal changes in connectivity increased the abundance of species that invest mostly in sexual reproduction at the expense of vegetative reproduction whereas the degree of connectivity and the variability of its temporal changes had no effect. In woodlands experiencing a downward connectivity trend, the diversity of seed mass values was independent on the magnitude but decreased with the variability of temporal changes, and increased with the degree of connectivity. Synthesis. Overall, we show that, besides the degree of connectivity, the cumulative effects of decades of changes in connectivity shape woodland plant community assembly by selecting for particular trait values in plant species. This study opens new perspectives for integrating the temporal dynamics of landscape connectivity in the theoretical framework of plant assembly rules. It should also be considered in the development of management strategies to restore and maintain landscape connectivity.