To what extent do current and projected increases in surface ozone affect photosynthesis and stomatal conductance of trees? A meta-analytic review of the last 3 decades of experiments.

摘要: The surface concentration of ozone ([O(3)]) has risen from less than 10 ppb prior to the industrial revolution a day-time mean approximately 40 over much northern temperate zone. If current global emission trends continue, [O(3)] is projected rise further 50% this century, with larger increases in many locations including Northern Hemisphere forests. This review uses statistical meta-analysis determine effects, and their confidence limits, both elevations on light-saturated photosynthetic CO(2) uptake (A(sat)) stomatal conductance (g(s)) trees. In total, 348 measurements A(sat) 61 studies 266 measures g(s) 55 were reviewed. Results suggested that elevation occurred since depressing by 11% (CI 9-13%) 13% 11-15%), respectively, where CI 95% interval. contrast angiosperms, gymnosperms not significantly affected. Both drought elevated [CO(2)] decreased effect ambient [O(3)]. Younger trees (<4 years) affected older Elevation above levels caused progressively losses g(s), gymnosperms. are consistent expectation damage photosynthesis depends cumulative (O(3)) into leaf. Thus, factors lower lessen damage. Where recorded, an overall decline 0.21% per mmol m(-2) estimated O(3) was calculated. These findings suggest rising [O(3)], often overlooked aspect atmospheric change, ability boreal forests assimilate carbon transfer water vapour atmosphere, significant potential effects terrestrial sinks regional hydrologies.