Effects of tree size and temperature on relative growth rate and its components of Fagus sylvatica seedlings exposed to two partial pressures of atmospheric [CO₂]

Abstract

Growth responses of two provenances of European beech (Fagus sylvatica) were studied. The seedlings were grown in closed‐top chambers at four temperature regimes (−2.9 °C below ambient, ambient, +2.3 °C and +4.8 °C above ambient) in combination with two CO2 partial pressures (40 Pa and 74 Pa). Growth was followed by making destructive harvests c. every 25 d from germination in early June to senescence in late September. Allocation patterns were significantly affected by the temperature regimes. However, changes in dry matter allocation and morphology associated with the different treatments at a given time were mostly a result of differences in tree size. Temperature regimes only had a significant effect on the relative growth rate, RGR, at the beginning of the experiment. In contrast to temperature, high [CO2] increased RGR throughout the experiment when compared with plants of equal size. As the trees increased in size net assimilation rate, NAR, decreased but the effect of [CO2] on both NAR and RGR had a tendency to increase. Increases in NAR caused by elevated [CO2] were partly counteracted by reductions in the leaf area ratio, LAR. Reductions in LAR were caused by concomitant reductions in specific leaf area, SLA, whereas the level of [CO2] did not significantly affect leaf weight ratio, LWR, nor other dry weight ratios. The interactions between temperature and [CO2] are highly dependent on whether they are expressed as instantaneous values for plants at a common age or instantaneous values at a common size (and thereby extracting the effects of ontogenetic drift). When comparing instantaneous values at common sizes, the positive effect of [CO2] on RGR increased with plant size in every temperature regime. This also occurred in every temperature regime when comparing plants of equal age but the response to [CO2] was less. The effect of [CO2] on RGR was dependent on growth temperature. The positive effects of elevated [CO2] on RGR were less than the positive effect on photosynthesis. The two provenances did not differ significantly in the response of RGR to [CO2] which is in agreement with measurements of photosynthesis.

Multiple environmental control of leaf area and its significance for productivity in beech saplings

“…Pronounced productivity stimulation by higher temperatures was found in various studies on beech (e.g. Piutti and Cescatti 1997;Bruhn et al 2000;Fotelli et al 2005;Saxe and Kerstiens 2005;Overdieck et al 2007). Our data show a productivity increase by about 60% with a 6°C-temperature increase (means of all treatments at 18 and 24°C) which matches well with the results of Overdieck et al (2007) who reported a 50% productivity increase in F. sylvatica saplings with a temperature increase by 4°C.…”

“…However, when both parameters were changed synchronously in the 24°C/500 Pa treatment, productivity was about 150% higher than in the 18°C/ 1,000 Pa treatment, which is substantially more than the added temperature and air humidity effects. In European beech, synergy effects were also observed for the combination of temperature and [CO 2 ] (Saxe and Kerstiens 2005;Bruhn et al 2000), temperature and light (Fotelli et al 2005) as well as for the light/soil fertility interaction (Johnson et al 1997). These results underline the importance of multi-factor studies when attempting to predict the response of trees to climatic changes.…”

“…Beech seedlings and saplings were studied in their response to elevated [CO 2 ] (e.g. Heath and Kerstiens 1997;Bruhn et al 2000;Kozovits et al 2005), elevated temperature (Leverenz et al 1999;Saxe and Kerstiens 2005;Overdieck et al 2007), low soil moisture (Madsen 1995;García-Plazaola and Becerril 2000;Fotelli et al 2001;Nielsen and Jørgensen 2003;Löf et al 2005) and increased N availability (Flückiger and Braun 1999;Finzi and Canham 2000;Thomas et al 2006). Most studies found significant growth responses to these factors.…”

Growth of Populus tremula on CO2-enriched soil at a natural mofette site

“…Our findings cannot easily be compared with the results of experiments in controlled-environment chambers which commonly, from the very beginning, show large positive effect of CO 2 on tree growth (e.g. Druart et al, 2006;Bruhn et al, 2000;Tjoelker et al, 1998). In these experiments the potted tree seedlings grew under optimal fertilized condition and were furthermore not affected by competition.…”

“…Druart et al, 2006;Bruhn et al, 2000;Tjoelker et al, 1998), in situ experiments using freeair CO 2 enrichment -FACE (Dawes et al, 2011;Eguchi et al, 2005;Pepin & Körner, 2002;Norby et al, 2001), and in situ studies at naturally CO 2 -enriched sites (Tognetti et al, 2000;Hättenschwiler et al, 1997;Paoletti et al, 2005). Working in mofette areas enables the study of long-term tree-growth response under authentic natural conditions.…”