title: Growth reduction after defoliation is independent of CO2supply in deciduous and evergreen young oaks.
abstract: Reduced productivity of trees after defoliation might be caused by limited carbon (C) availability. We investigated the combined effect of different atmospheric CO2concentrations (160, 280 and 560 ppm) and early season defoliation on the growth and C reserves (nonstructural carbohydrates (NSC)) of saplings of two oak species with different leaf habits (deciduous Quercus petraea and evergreen Quercus ilex). In both species, higher CO2supply significantly enhanced growth. Defoliation had a strong negative impact on growth (stronger for Q. ilex), but the relative reduction of growth caused by defoliation within each CO2treatment was very similar across all three CO2concentrations. Low CO2and defoliation led to decreased NSC tissue concentrations mainly in the middle of the growing season in Q. ilex, but not in Q. petraea. However, also in Q. ilex, NSC increased in woody tissues in defoliated and low-CO2saplings towards the end of the growing season. Although the saplings were C limited under these specific experimental conditions, growth reduction after defoliation was not directly caused by C limitation. Rather, growth of trees followed a strong allometric relationship between total leaf area and conductive woody tissue, which did not change across species, CO2concentrations and defoliation treatments.
authors.affiliation: Department of Environmental Sciences - Botany, University of Basel, Schönbeinstrasse 6, Basel, CH-4056, Switzerland.
authors.forename: Sandra
authors.initials: S
authors.lastname: Schmid
authors.affiliation: Instituto Pirenaico de Ecologia (IPE-CSIC), Av. Nuestra Señora de la Victoria, 16, Jaca, 22700, Spain.
authors.forename: Sara
authors.initials: S
authors.lastname: Palacio
authors.affiliation: Department of Environmental Sciences - Botany, University of Basel, Schönbeinstrasse 6, Basel, CH-4056, Switzerland.
authors.forename: Günter
authors.initials: G
authors.lastname: Hoch
mesh_terms: D002244:Carbon / Q000378:metabolism; D002245:Carbon Dioxide; D017753:Ecosystem; D010788:Photosynthesis; D018515:Plant Leaves; D029963:Quercus / Q000254:growth & development* / Q000502:physiology; D012621:Seasons
chemical_list: D002245:Carbon Dioxide; D002244:Carbon
keywords: 
  Quercus ilex
  ; 
  Quercus petraea
  ; biomass allocation; carbon reserves; growth reduction; herbivory; nonstructural carbohydrates; starch