Field Performances of Mediterranean Oaks in Replicate Common Gardens for Future Reforestation under Climate Change in Central and Southern Europe: First Results from a Four-Year Study

Abstract

Climate change imposes severe stress on European forests, with forest degradation already visible in several parts of Europe. Thus adaptation of forestry applications in Mediterranean areas and central Europe is necessary. Proactive forestry management may include the planting of Mediterranean oak species in oak-bearing Central European regions. Five replicate common gardens of Greek and Italian provenances of Quercus ilex, Q. pubescens and Q. frainetto seedlings (210 each per plantation) were established in Central Italy, NE Greece (two) and Southern Germany (two, including Q. robur) to assess their performance under different climate conditions. Climate and soil data of the plantation sites are given and seedling establishment was monitored for survival and morphological parameters. After 3 years (2019) survival rates were satisfactory in the German and Italian sites, whereas the Greek sites exerted extremely harsh conditions for the seedlings, including extreme frost and drought events. In Germany, seedlings suffered extreme heat and drought periods in 2018 and 2019 but responded well. Provenances were ranked for each country for their performance after plantation. In Greece and Italy, Q. pubescens was the best performing species. In Germany, Q. pubescens and Q. robur performed best. We suggest that Greek or Italian provenances of Q. pubescens may be effectively used for future forestation purposes in Central Europe. For the establishment of Quercus plantations in Northern Greece, irrigation appears to be a crucial factor in seedling establishment.

Potential Impacts of Climate Change on the Habitat Suitability of the Dominant Tree Species in Greece

“…Q. pubescens is a semi-deciduous species that can withstand water limitation, with recent studies showing that it can be as resistant to drought stress as evergreen oaks such as Quercus ilex [84]. Q. frainetto, on the other hand, seems to be less tolerant to drought compared with the two other oaks in the study [85]. This ecophysiological knowledge seems to agree with the projected relative habitat loss in our study (Table 2).…”

Diurnal photosynthetic performance of two oak species from two provenances in a Mediterranean and a central European common garden

“…The measurements were performed in oaks seedlings of an existing common garden experiment, established within the FutureOaks project (more details given by Bantis et al 2021). In this project, Mediterranean oaks of identical accessions were evaluated for their potential as alternative tree species for altitudinal and latitudinal assisted migration.…”

“…Q. frainetto is generally regarded as less drought-resistant compared to Q. pubescens, as quite a low leaf water potential levels cannot be avoided even with almost complete stomatal closure during severe drought (Fotelli et al 2000, Siam et al 2009. Consistently, lower photosynthetic rates, water-use efficiency, predawn leaf water potentials, and finally, growth and survival are reported for Q. frainetto vs. Q. pubescens (Bantis et al 2019(Bantis et al , 2021Pollastrini et al 2020). The higher drought sensitivity of Q. frainetto is also indicated by changes in chlorophyll fluorescence parameters, such as a decline of the performance index PIabs (Bantis et al 2019).…”

“…The attempt to establish the species in central European ecosystems (e.g., in Germany) corresponds to the approach of assisted range expansion, which imitates natural migration processes, but is unlikely to occur at the velocity of climate change due to landscape fragmentation (Vitt et al 2010, Winder et al 2011 or slow migration speed of the target species. To test the performance of these oak species, coming from different regions of the Mediterranean area, from the perspective of assisted migration, a replicate common garden experiment has been established (Bantis et al 2021). In a common garden experiment, two or more species and different provenances are transplanted to a common environment to allow their more direct comparison.…”

Impacts of Climate Change on Tree Physiology and Responses of Forest Ecosystems

“…Common gardens and provenance trials are an experimental approach offering longterm information regarding the potential of different forest species and origins to adapt to future climate. In order to assess the suitability of different Mediterranean oak species for potential assisted migration schemes in central Europe, Bantis et al [5], established a four common garden experiment and evaluated the early field performance of oak seedlings of different species and provenances. Based on survival rates, morphological, and physiological features, they concluded that Quercus pubescens may be a suitable candidate forest tree for poor and dry soils under the expected summer heat and drought conditions in Central Europe.…”