Enhanced ozone strongly reduces carbon sink strength of adult beech {Fagus sylvatica) - Resume from the free-air fumigation study at Kranzberg Forest

摘要

Ground-level ozone (O_3) has gained awareness as an agent of climate change. In this respect, key results are comprehended from a unique 8-year free-air 0_3-fumigation experiment, conducted on adult beech (Fagus sylvatica) at Kranzberg Forest (Germany). A novel canopy O_3 exposure methodology was employed that allowed whole-tree assessment in situ under twice-ambient O_3 levels. Elevated O_3 significantly weakened the C sink strength of the tree-soil system as evidenced by lowered photosynthesis and 44% reduction in whole-stem growth, but increased soil respiration. Associated effects in leaves and roots at the gene, cell and organ level varied from year to year, with drought being a crucial determinant of O_3 responsiveness. Regarding adult individuals of a late-successional tree species, empirical proof is provided first time in relation to recent modelling predictions that enhanced ground-level O_3 can substantially mitigate the C sequestration of forests in view of climate change.