“…No significant ozone effect on height was found but in contrast for basal stem diameter a small (À3.2%) but significant negative effect (F 1,132 ¼ 11.24, p < 0.001) of ozone was found similar to that reported in a meta-analysis of forest tree ozone responses (Wittig et al, 2009), indicating that ozone exposure is likely to impact biomass yield. This will require further confirmatory analysis from longer-term studies, but suggests that Populus biomass yield is likely to be detrimentally affected by future increased ozone concentrations, which are consistent with previous reports (Bohler et al, 2007;Bortier et al, 2000;Karnosky et al, 1996;Wittig et al, 2009;Woo and Hinckley, 2005). Such decreases in productivity are likely to be related to decreased photosynthetic activity (Bortier et al, 2000;Coleman et al, 1995;Degl'Innocenti et al, 2007;Lorenzini et al, 1999) and reduced leaf area (Wittig et al, 2009).…”