title: Early Summer Drought Stress During the First Growing Year Stimulates Extra Shoot Growth in Oak Seedlings (Quercus petraea).
abstract: More severe summer droughts are predicted for mid-latitudes in Europe. To evaluate the impact on forest ecosystems and more specifically on forest regeneration, we studied the response to summer drought in oak seedlings (Quercus petraea). Acorns were collected from different mother trees in three stands in Belgium, sown in pots and grown in non-heated greenhouse conditions. We imposed drought on the seedlings in early summer by first watering the pots to saturation and then stopping any watering. Weight of the pots and stomatal conductance were regularly measured. Re-watering followed this drought period of 5 weeks. Height of the seedlings and apical bud development were observed. Stomatal resistance increased toward the end of the experiment in the drought-treated group and was restored after re-watering. The seedlings from the drought treatment displayed a higher probability to produce additional shoot growth after re-watering (p ≤ 0.05). A higher competition for water (two plants per pot) increased this chance. Although this chance was also higher for smaller seedlings, the actual length of the extra growth after re-watering was higher for larger seedlings (p ≤ 0.01). Both in the drought-treated and in the control group the autochthonous provenance growing on a xeric site produced less extra shoots compared to the two other provenances. Finally, stressed plants showed less developed apical buds compared to the control group after re-watering, suggesting a phenological effect on the growth cycle of oaks (p ≤ 0.0001). The higher chance for an extra shoot growth after the drought period can be considered as a compensation for the induced growth arrest during the drought period.
authors.affiliation: Research Institute for Nature and ForestGeraardsbergen, Belgium; Department of Biometrics and Agricultural Informatics, Corvinus University of BudapestBudapest, Hungary; Department of Forest Reproductive Material and Plantation Management, Institute of Silviculture and Forest Protection, University of West HungarySopron, Hungary.
authors.forename: Arion
authors.initials: A
authors.lastname: Turcsán
authors.affiliation: Laboratory of Plant Ecology, Department of Applied Ecology and Environmental Biology, Ghent University Ghent, Belgium.
authors.forename: Kathy
authors.initials: K
authors.lastname: Steppe
authors.affiliation: Department of Soil Science and Water Management, Corvinus University of Budapest Budapest, Hungary.
authors.forename: Edit
authors.initials: E
authors.lastname: Sárközi
authors.affiliation: College of Commerce, Catering and Tourism, Budapest Business School Budapest, Hungary.
authors.forename: Éva
authors.initials: É
authors.lastname: Erdélyi
authors.affiliation: Agency for Nature and Forest Brussels, Belgium.
authors.forename: Marc
authors.initials: M
authors.lastname: Missoorten
authors.affiliation: Agency for Nature and Forest Brussels, Belgium.
authors.forename: Ghislain
authors.initials: G
authors.lastname: Mees
authors.affiliation: Research Institute for Nature and Forest Geraardsbergen, Belgium.
authors.forename: Kristine V
authors.initials: KV
authors.lastname: Mijnsbrugge
keywords: apical bud; drought; general linear mixed models; oak seedling; re-watering; shoot growth