Effects of elevated CO2 concentration and nutrition on net photosynthesis, stomatal conductance and needle respiration of field-grown Norway spruce trees

Abstract

To study the effects of elevated CO(2) on gas exchange, nonstructural carbohydrate and nutrient concentrations in current-year foliage of 30-year-old Norway spruce (Picea abies (L.) Karst.) trees, branches were enclosed in ventilated, transparent plastic bags and flushed with ambient air (mean 370 &mgr;mol CO(2) mol(-1); control) or ambient air + 340 &mgr;mol CO(2) mol(-1) (elevated CO(2)) during two growing seasons. One branch bag was installed on each of 24 selected trees from control and fertilized plots. To reduce the effect of variation among trees, results from each treated branch were compared with those from a control branch on the same whorl of the same tree. Elevated CO(2) increased rates of light-saturated photosynthesis on average by 55% when measured at the treatment CO(2) concentration. The increase was larger in shoots with high needle nitrogen concentrations than in shoots with low needle nitrogen concentrations. However, shoots grown in elevated CO(2) showed a decrease in photosynthetic capacity compared with shoots grown in ambient CO(2). When measured at the internal CO(2) concentration of 200 &mgr;mol CO(2) mol(-1), photosynthetic rates of branches in the elevated CO(2) treatments were reduced by 8 to 32%. The elevated CO(2) treatment caused a 9 to 20% reduction in carboxylation efficiency and an 18% increase in respiration rates. In response to elevated CO(2), starch, fructose and glucose concentrations in the needles increased on average 33%, whereas concentrations of potassium, nitrogen, phosphorus, magnesium and boron decreased. Needle nitrogen concentrations explained 50-60% of the variation in photosynthesis and CO(2) acclimation was greater at low nitrogen concentrations than at high nitrogen concentrations. We conclude that the enhanced photosynthetic rates found in shoots exposed to elevated CO(2) increased carbohydrate concentrations, which may have a negative feedback on the photosynthetic apparatus and stimulate cyanide-resistant respiration. We also infer that the decrease in nutrient concentrations of needles exposed to elevated CO(2) was the result of retranslocation of nutrients to other parts of the branch or tree.

Isoprenoid emission response to changing light conditions of English oak, European beech and Norway spruce

“…The average A n rates for early spruce and late spruce were between 4.3 and 12.1 and between 3.6 and 12 µmol CO 2 m −2 s −1 respectively, whilst the G S rates ranged between 400 and 1200 mmol H 2 O m −2 s −1 for early spruce and between 300 and 1000 mmol H 2 O m −2 s −1 for late spruce. These values are in range or slightly higher than reported in other studies (Le Thiec et al, 1994;Roberntz and Stockfors, 1998;Špunda et al, 2005). Early spruce 1 and late spruce 2 behaved in a similar fashion as European beech with a tendency to stabilize their A n and G S rates at a light level of 500 µmol m −2 s −1 , indicating some shade adaptation of the selected needle twigs.…”

Genetic Variation of Ecophysiological Responses to CO2 in Picea glauca Seedlings

“…In a meta-analysis of 48 studies, Curtis and Wang [6] reported an insignificant 11% reduction in g s in response to elevated [CO 2 ]. Similarly, Roberntz and Stockfors [41] reported that elevated [CO 2 ] had no significant effect on g s in current year growth of 30-year-old Picea abies (L.) Karst. However, tree and leaf age has been reported to affect the degree of reduction in g s , with responses from younger conifer seedlings and foliage being more prominent than those shown by older trees [38,42].…”

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

“…(1) for each 30-min period. Light response of GPP was modelled from measured irradiance by a light response curve (Roberntz and Stockfors, 1998):…”