Interactive effects of elevated CO2 and neighbourhood competition on the radial growth of European beech (Fagus sylvatica L.) seedlings

• Published in: European journal of forest research 2020-06, Vol.139 (3), p.499-512
• Main Authors: Badraghi, Aysan, Marek, Michal V.
• Format: Article
• Language: English
• Subjects: Beech; Biomedical and Life Sciences; Carbon dioxide; Climate change; Competition; Fagus sylvatica; Forestry; Herbivores; Life Sciences; Original Paper; Picea abies; Pine trees; Plant diversity; Plant Ecology; Plant Sciences; Plant species; Precipitation; Seedlings; Species diversity; Statistical analysis; Trees
• ISSN: 1612-4669; 1612-4677
• DOI: 10.1007/s10342-020-01264-w

This paper explores the effects of three types of admixture treatments: (1) monospecific (M: European beech surrounded by six European beech seedlings), (2) single-admixture (S: European beech surrounded by six Norway spruce seedlings), and (3) group-admixture (G: European beech surrounded by three Norway spruce and three European beech seedlings), and two different CO 2 concentrations ([CO 2 ]): ambient [AMB CO2 , 385 μmol (CO 2 ) mol −1 ] and elevated [ELE CO2 , 770 μmol (CO 2 ) mol −1 ] on the stem diameter increment (DI), based on a 7-year monitoring of the diameter growth of European beech ( Fagus sylvatica L.) seedlings. Furthermore, to improve our understanding of the influence of climatic variables, we assessed the effects of precipitation and temperature on radial growth. After 7 years’ experience (irrespective of admixture treatment), our data were not able to confirm the effect of elevated CO 2 on the diameter growth ( p value = 0.35), but the result was changed when the effect of elevated CO 2 was considered under the different types of admixture. Elevated CO 2 along with single-admixture increased the diameter increment significantly ( p value = 0.001). In contrast, we characterized a significant effect of AMB CO2  × G interaction on DI ( p value = 0.002). But DI was unaffected by elevated CO 2 in M ( p value = 0.77). In both [CO 2 ], inter-specific competition with spruce resulted in the highest radial growth. The inter-specific interaction was most pronounced in the lower proportion with spruce (S) in ELE CO2 , while in ambient CO 2 , the higher proportion with spruce (G) had the greatest effect on the radial growth. With respect to the climatic factors, our observations showed that temperature had a stronger influence than precipitation in ELE CO2 , but in AMB CO2 , precipitation had the strongest effect on the radial growth as indicated by the statistically significant correlation between climatic variables and radial growth. Overall, our result suggested that seedlings growth was more under the control of climate and edaphic factors than dependent on tree species diversity and CO 2 concentrations.