Seasonal patterns of photosynthesis in Douglas fir seedlings during the third and fourth year of exposure to elevated CO₂ and temperature

Abstract

The interactive effects of elevated atmospheric CO 2 and temperature on seasonal patterns of photosynthesis in Douglas fir (Psuedotsuga menziesii (Mirb.) Franco) seedlings were examined. Seedlings were grown in sunlit chambers controlled to track either ambient (~400 p.p.m.) CO 2 or ambient +200 p.p.m. CO 2 , and either ambient temperature or ambient +4°C. Light-saturated net photosynthetic rates were measured approximately monthly over a 21 month period. Elevated CO 2 increased net photosynthetic rates by an average of 21% across temperature treatments during both the 1996 hydrologic year, the third year of exposure, and the 1997 hydrologic year. Elevated mean annual temperature increased net photosynthetic rates by an average of 33% across CO 2 treatments during both years. Seasonal temperature changes also affected net photosynthetic rates. Across treatments, net photosynthetic rates were highest in the spring and autumn, and lowest in July, August and December-January. Seasonal increases in temperature were not correlated with increases in the relative photosynthetic response to elevated CO 2 . Seasonal shifts in the photosynthetic temperature optimum reduced temperature effects on the relative response to elevated CO 2 . These results suggest that the effects of elevated CO 2 on net photosynthetic rates in Douglas fir are largely independent of temperature.

Short-term effects of experimental warming and enhanced ultraviolet-B radiation on photosynthesis and antioxidant defense of Picea asperata seedlings

“…Warming increased A in the present study as elsewhere (Lewis et al 2001). However, biomass accumulation was not increased by warming in this study (Fig.…”

Xeromorphy increases in shoots of Pseudotsuga menziesii (Mirb.) Franco seedlings with exposure to elevated temperature but not elevated CO2

“…For an open canopy, as for our P. menziesii trees, the increased daily uptake of CO 2 on a unit area basis with elevated temperature during most of the year (except possibly summer; Lewis et al 2001Lewis et al , 1999, could more than compensate for any reduction in leaf area. Especially important may be the weeks in late spring and early summer because trees growing at an elevated temperature achieved full leaf expansion earlier than their counterparts at ambient temperature (Olszyk et al 1998b), and would therefore have attained the maximum benefits of the higher photosynthetic rate with elevated temperature.…”

Seed Germination and Seedling Survival Rate of Pinus densiflora and Abies holophylla in Open-field Experimental Warming Using the Infrared Lamp

“…특히, 온 도 변화는 식물의 호흡 및 증산량에 영향을 주어 광합성 률, 기공전도도, 수분이용효율 등의 광합성 기구에 변화를 가져와 다양한 생장 특성 결과가 나타난다 (Lewis et al, 2001). 온도 증가가 식물과 생태계에 어떤 영향을 주는지 에 대한 연구는 실내·외 실험을 통해 지속적으로 이루어 져 왔다.…”