Elevated temperature but not elevated CO₂ affects long-term patterns of stem diameter and height of Douglas-fir seedlings

Abstract

Global climatic change may impact forest productivity, but data are lacking on potential effects of elevated CO2 and temperature on tree growth. We determined changes in shoot growth for Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedlings exposed to ambient or elevated CO2 ( µmol·mol-1), and ambient or elevated temperature . Seedings were grown for 4 years (three complete growing seasons) in outdoor, sunlit chambers. In each season, height growth was initiated earlier and, in two seasons, ceased earlier for elevated compared with ambient temperature trees. Elevated temperature reduced intermediate and final plant heights. Stem diameter growth began earlier each season at the elevated compared with the ambient temperature, but temperature had no affect on final stem diameter. Elevated temperature tended to reduce leaf (p = 0.07) but not woody biomass. Elevated CO2 had no significant effects on stem diameter, height, and leaf or woody biomass, and there were no significant CO2 × temperature interactions. Thus, elevated temperatures (but not elevated CO2) associated with climate change may decrease seedling canopy growth as indicated by reduced height and leaf biomass but have little or no effect on overall woody growth as indicated by stem diameter and woody biomass.

Density-dependent responses of Picea purpurea seedlings for plant growth and resource allocation under elevated temperature

“…This discrepancy might be caused by the different research conditions and plant species used. In the experiment with Douglas-fir (Olszyk et al 1998;Olszyk et al 2003), seedlings were exposed to warming for 4 years under non-controlled light conditions, whereas in the present study, P. purpurea seedlings were exposed for 4 years under controlled light conditions. Low-light conditions could potentially influence more resource allocation to the shoot to increase the ability of light competition (Marfo and Dang 2009).…”

“…The results presented here are in disagreement with the previous reports on effects of elevated temperature on plant in the presence of competition. For example, Olszyk et al (1998) showed that elevated temperature reduced height growth but increased diameter in Douglas-fir seedlings grown in a stand (Olszyk et al 1998). Olszyk et al (2003) found elevated temperature decreased allocation of biomass from leaves and increased allocation to stems for Douglas-fir seedlings grown in the presence of competition.…”

Effects of experimental warming on growth, biomass allocation, and needle chemistry of Abies faxoniana in even-aged monospecific stands

“…The effects of warming on tree or seedling growth have been previously studied on Scots pine (Pinus sylvestris; Domisch et al 2002;Kilpeläinen et al 2005), Douglas-fir (Pseudotsuga menziesii; Olszyk et al 1998Olszyk et al , 2003 (2001) found that warming had no significant effect on height growth but increased ring width by 19% in Scots pines during an experimental treatment spanning 6 years. In A. faxoniana seedlings, short-term warming increased height growth but had no effect on diameter (Hou et al 2011).…”

“…Yet, these findings were obtained from experiments with young seedlings grown without competition. In addition, elevated temperature reduced height growth but increased diameter in Douglas-fir seedlings when grown in competition under non-controlled light conditions (Olszyk et al 1998). However, we used seedlings grown in even-aged monospecific stands with controlled light.…”

“…To predict the changes in forest community dynamics caused by warming, a number of temperature manipulation studies have been conducted, focusing on comparative physiological and developmental responses of individually grown tree seedlings and saplings (Olszyk et al 1998;Zha et al 2001Zha et al , 2005Kilpeläinen et al 2003Kilpeläinen et al , 2005Wu et al 2011). However, in nature, tree seedlings and saplings rarely become established and grow in isolation.…”