Impact of climate change on ivy (Hedera helix L.) expansion in forests of Central Poland

The article refers to a broader context of scientific debates on the effect of climate warming on shifts in species ranges and describes the recent changes in the distribution and life strategy of Hedera helix close to its eastern limit, in light of climate changes. European ivy is an ecotone species, occurring in fringe communities, in deciduous and mixed deciduous forests in fresh and moist habitats that are occupied by oak-hornbeam and riparian alder-ash forests in Central Poland. Since the mid-20th century, the ivy, a species rarely reproducing generatively, has become an expansive plant with a growing number of sites where flowering and fruiting individuals are encountered. We studied the distribution, habitat requirements and flowering of H. helix in Central Poland in the years 2015–2017 and compared to the situation in the mid-1970s. Climate changes in terms of average air temperatures and precipitation amounts for the past four decades were also assessed. Within the study area, 474 stands of naturally growing Hedera have recently been identified. Ivy was found to reproduce generatively on 121 of those locations. There has been an almost 10-fold increase in the number of fruiting ivy specimens since the mid-1970s of the 20th century. Changes in the species life strategy can be ascribed to the increase in both average air temperatures and solar radiation intensity observed for the past decades. Both enhanced fragmentation of woodland tracts and development of forest ecotones and forest canopy openings promote the expansion of H. helix, while its habitat preferences remain unchanged