Biomass allocation, needle structural characteristics and nutrient composition in Scots pine seedlings exposed to elevated CO2 and O3 concentrations

Abstract

Three-year-old Scots pine (Pinus sylvestris L.) seedlings were exposed to ambient or elevated ozone (O 3 ) (1.5×ambient) and carbon dioxide (CO 2 ) (590 µmol mol -1 ) concentrations during two growing seasons in open-top field chambers (OTCs). Five different treatments were applied in the chambers: filtered air, ambient air, elevated O 3 , elevated CO 2 , and elevated O 3 and CO 2 combined. Ambient plots outside the OTCs were also included, but the chamber ambient was used as a control in O 3 and CO 2 treatments due to a significant chamber effect. Increases in yellowing and chlorotic mottling of previous-year (C+1) needles and in the amount of cytoplasmic ribosomes and electron density of the chloroplast stroma in current-year (C) and C+1 needle mesophyll cells were observed in elevated O 3 at both CO 2 concentrations. Elevated O 3 alone caused a non-significant 10.9% decrease in plant total dry mass and a significant decrease in manganese (Mn) content of C needles. CO 2 enrichment caused a significant increase in needle cross-sectional width after the first year of exposure, and an accumulation of starch and slight curling and swelling of the chloroplast thylakoids in the mesophyll tissue of C needles after the second year of exposure. Calcium and Mn contents were increased and copper and nitrogen contents were decreased, significantly, in CO 2 -exposed needles. A non-significant 19.1% increase in plant total dry mass was measured in elevated CO 2 alone, whereas a 14.8% reduction in total dry mass, together with a significant reduction in current-year main shoot length, was found in the combined treatment. Overall, in spite of decreases in O 3 -induced visible injuries by CO 2 , elevated CO 2 levels were not able to counteract the impact of O 3 in this experiment.

Impacts of elevated atmospheric CO2 on forest trees and forest ecosystems: knowledge gaps

“…Since these two gases generally induce opposite sets of physiological responses, there is considerable uncertainty as to how tree growth and productivity and forest ecosystem functions will be affected by these two interacting pollutants (Barnes and Wellburn, 1998;Saxe et al, 1998). The few studies done for multiple years with trees planted in the ground have largely shown that O 3 offsets the growth enhancement of elevated atmospheric CO 2 both for hardwood trees (Broadmeadow and Jackson, 2000;Isebrands et al, 2001) and conifers (Broadmeadow and Jackson, 2000;Utriainen et al, 2000). The magnitude of the O 3 offset depends on the O 3 sensitivity of the species (Broadmeadow and Jackson, 2000;Karnosky et al, in press) and the concentrations of each pollutant, although research needs to be done with tree species to characterize dose responses.…”

Elevated CO2 ameliorated oxidative stress induced by elevated O3 in Quercus mongolica

“…Nevertheless, studies on their combined effects are less, and moreover, inconsistent results were reported in these studies. Some demonstrated that elevated CO 2 ameliorated the detrimental effects of O 3 (Volin and Reich 1996;Kellomaki and Wang 1997;Sehmer et al 1998;Volin et al 1998;Grams et al 1999;Broadmeadow and Jackson 2000;Lutz et al 2000;Gaucher et al 2003;Darbah et al 2008), whereas others showed that elevated CO 2 did not provide protection against the negative effects of O 3 (Karnosky et al 1998;Kytoviita et al 1999;Utriainen et al 2000;Isebrands et al 2001;Paoletti et al 2007) or even exacerbated them (Polle et al 1993;Kull et al 1996;Wustman et al 2001). The reason for the negative role of CO 2 is that relaxation of antioxidative system, as a consequence of long term exposure, can make trees more susceptible to O 3 -induced oxidative stress (Karnosky 2003).…”

Temporal and Spatial Change in Diameter Growth of Boreal Scots Pine, Norway Spruce, and Birch under Recent-Generation (CMIP5) Global Climate Model Projections for the 21st Century

“…Table 4. Number (%) of sample plots of the National Forest Inventory (NFI11) on different upland forest sites for southern (old Forestry Centre units 1-6), central (7)(8)(9)(10), and northern (11-13) boreal regions. The upland site types included poor (dry heath, Calluna type, CT), quite poor (dryish heath, Vaccinium type, VT), medium (fresh heath, Myrtillus type, MT), and rich (grove-like heath, Oxalis-Myrtillus type, OMaT) sites.…”