Bachelor Thesis

Funktionelle Blatteigenschaften der Flaumeiche (Quercus pubescens Willd.) in verschiedenen geographischen Herkünften und Klimawandelszenarien

Robert Weigel (11/2011-05/2012)

Support: Camilla Wellstein, Carl Beierkuhnlein

Due to the anthropogenic climate change the temperatures in Germany will rise and more frequent extreme weather events like drought events are to be expected. The upcoming climatic conditions in the course of this century in Germany, will increasingly match the climatic envelopes of water stress resistant tree species like Quercus pubescens Willd. (Q. pubescens). The response of Q. pubescens to water stress has to be investigated in detail, to asses the forest ecological potential to substitute other Quercus species in face of increased drought stress. The ability for adaptation or acclimatisation is necessary for a plant or a taxon to persist under different environmental conditions and stress situations like chronic or short term water stress. Adaptation and acclimatisation are often achieved by the change of several parameters of an organism and so cause intraspecific variability. For this reason the influence of adaptation and acclimatisation on the intraspecific variability of leaf morphological parameters was examined in this experiment. Four different provenances (Bulgary, Germany, Hungary, Italy) of Q. pubescens were exposed to different, simulated climatic conditions. These consisted of combinations of three classes of drought (no drought, drought initialized before leaf sprouting, drought initialized after leaf sprouting) beside two classes of warming (warming of 2.7 °C in heated units compared to unheated units). As proxies for the intraspecific variability, and so as proxies for adaptation and acclimatisation of Q. pubescens the leaf morphological parameters specific leaf area (SLA), stomatal density (SD), stomatal length (lS), potential conductance index (PCI), number of stomata per leaf (NS), leaf area (LA) and degree of leaf hairiness were measured in this experiment. Not taking the simulated climatic conditions in account the provenances differed in average values for SLA, SD, lS, PCI and degree of hairiness. Looking at the simulated climatic conditions warming caused lower SLA and higher lS while in regarding of the drought treatment only the shorter drought initialized after the leaf sprouting caused lower lS and higher SD with invariant PCI and lower degree of occurrence of single hair. Further on, lS correlated positively with LA, leaf dry mass, PCI and negatively with bunch hair density, LA correlated positively with leaf dry mass and SD correlated positively with PCI and negatively with lS 2. Only for the bunch hair a provenance specific reaction of leaf morphological parameters towards climate manipulation could be observed. The experiment shows, that Q. pubescens responses phenotypically plastic to changed environmental conditions and that its provenances show differences in leaf morphological parameters. With Q. pubescens as a in general water stress tolerant broadleaved tree species with high intraspecific variability, it is worth investigating if it can provide high functionality at locations in Germany, which will be affected by climate change.