Impact studies on Nordic forests: effects of elevated CO₂ and fertilization on gas exchange

Abstract

The effects of rising atmospheric carbon dioxide concentration, [CO2], and fertilization on gas exchange of four field-grown tree species were examined using the branch bag technique (Picea abies (L.) Karst., Pinus sylvestris L., Fagus sylvatica L.) or whole tree chambers (Populus trichocarpa Torr. & Gray). Results are presented on changes in light-saturated rates of net photosynthesis (Asat), carboxylation efficiency (α), stomatal conductance (gs), and stomatal limitation of photosynthesis (Ls) after 2–4 years of CO2 exposure. Fertilization alone did not significantly change Asat, α, gs, or Ls for any of the species, but α and Asat were linearly related to foliage nitrogen content when compared across all treatments. No significant CO2 effects were detected for α, gs, or Asat when compared at the same intercellular [CO2], i.e., no downregulation of Asat was apparent. "Long-term" CO2 enrichment increased Asat significantly by 49, 53, 86, and 114% in Populus trichocarpa, Picea abies, F. sylvatica, and Pinus sylvestris, respectively. In all the species the relative CO2 effect on Asat increased linearly with temperature. Thus, application of a simple linear relationship could improve predictions of future tree growth responses to increasing CO2 and temperature in cool climates.

A young afforestation area in Iceland was a moderate sink to CO<sub>2</sub> only a decade after scarification and establishment

“…Magnússon (1992) and Sigurdsson (2009) Falge et al, 2002;Sigurdsson et al, 2002;Bergh et al, 2003;Jónsson, 2007). Furthermore, some studies have been conducted in downy birch (Betula pubescens Ehrh.)…”

Photosynthetic responses of birch and alder saplings grown in a free air CO2 enrichment system in northern Japan

“…Some studies find no photosynthetic down-regulation (Sigurdsson et al 2002, Zotz et al 2005Liberloo et al 2007). A possible reason for these varying results is that physiological or anatomical responses under elevated [CO 2 ] differ between species (Sage et al 1989;Körner 2000;Eguchi et al 2004) or vary with environmental conditions such as soil fertility (Ceulemans and Mousseau 1994;Sigurdsson 2001).…”

Species-specific and needle age-related responses of photosynthesis in two Pinus species to long-term exposure to elevated CO2 concentration

“…1, 2, 3). Trees, due to their long life span, have potential to acclimate changes in environmental factors such as CO 2 enrichment (Sigurdsson et al 2002). The difference in responses of photosynthetic capacity to long-term elevated CO 2 concentration between P. sylvestriformis and P. koraiensis may be partly resulted from differences in their growth behavior.…”

“…The effects of elevated CO 2 concentration on photosynthesis were found to be dependent on plant species, environmental conditions, duration of CO 2 exposure, and growth stage of plants (Tissue et al 1997;Ainsworth et al 2002;Sigurdsson et al 2002;Aranjuelo et al 2009). After 3 years of CO 2 enrichment (704 lmol mol -1 CO 2 ), no change in photosynthetic capacity of Quercus myrtifolia and Q. chapmanii was found, but the co-dominant Q. geminata showed a photosynthetic down-regulation (Ainsworth et al 2002).…”

“…Herrick and Thomas (2001) found that the P Nsat in elevated CO 2 treated L. styraciflua increased (?48%), and V cmax and J max did not change with CO 2 treatments. Sigurdsson et al (2002) and Ainsworth et al (2003) stated that plants growing at elevated CO 2 had an increased P Nsat in spite of whether photosynthetic down-regulation occurred or not.…”