Whole-seedling biomass allocation, leaf area, and tissue chemistry for Douglas-fir exposed to elevated CO₂ and temperature for 4 years

Abstract

Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedlings were grown under ambient or elevated (ambient + 180 µmol·mol -1 ) CO 2 and ambient or elevated (ambient + 3.5°C) temperature in outdoor, sunlit chambers with a field soil. After 4 years, seedlings were harvested and measured for leaf area, leaf, fine root (<1 mm diameter), and structural (buds, branches, stems, main root, and lateral roots >1 mm in diameter) dry masses, and leaf and fine root C/N ratio, percent sugar, and percent cellulose. Elevated CO 2 did not affect biomass production or allocation for any plant organ but increased specific leaf mass, leaf C/N ratio, and percent sugar and decreased the ratio of leaf area to structural weight and leaf percent cellulose. Elevated temperature tended to reduce biomass allocation to leaves and leaf sugar concentration. Fine root percent sugar tended to increase with elevated temperature but only at elevated CO 2 . Therefore, for Douglas-fir seedlings growing under naturally limiting soil moisture and nutrition conditions, elevated CO 2 and temperature may have little impact on biomass or leaf area except for reduced specific leaf mass with elevated CO 2 and reduced biomass allocation to leaves with elevated temperature. However, both elevated CO 2 and temperature may alter leaf chemistry.Résumé : Des semis de douglas (Pseudotsuga menziesii (Mirb.) Franco) ont été exposés à une concentration ambiante ou élevée (ambiante + 180 µmol·mol -1 ) de CO 2 et à une température ambiante ou élevée (ambiante + 3,5°C) à l'extérieur, à la lumière du soleil, dans des chambres contenant un sol provenant du terrain. Après 4 ans, les semis ont été récoltés et les mesures suivantes ont été effectuées : la surface foliaire, la masse sèche du feuillage, des racines fines (<1 mm de diamètre) et des éléments structuraux (bourgeons, branches, tige, racine principale et racines secondaires >1 mm de diamètre), le rapport C/N du feuillage et des racines fines ainsi que le pourcentage de sucres et de cellulose. La concentration élevée de CO 2 n'a pas influencé la production de biomasse ni l'allocation dans aucune partie du plant. Elle a par contre augmenté la masse spécifique du feuillage, le rapport C/N et le pourcentage de sucres dans les feuilles et diminué le rapport entre la surface foliaire et la masse des éléments structuraux ainsi que le pourcentage de cellulose dans les feuilles. La température élevée a eu tendance à réduire l'allocation de la biomasse vers le feuillage ainsi que la concentration des sucres dans les feuilles. Le pourcentage de sucres dans les racines fines a eu tendance à augmenter à la température élevée mais seulement lorsque la concentration de CO 2 était élevée. Par consé-quent, pour les semis de douglas qui croissent dans des conditions naturelles où l'humidité du sol et les nutriments sont limités, une température et une concentration en CO 2 élevées auraient peu d'impact sur la biomasse ou la surface foliaire à l'exception d'une diminution de la masse spécifique du feuillage avec une concentration éle...

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

“…Lower N concentrations of needles resulted from a growth dilution. These results confirm literature reports (Hobbie et al 2001;Olszyk et al 2003). Similarly, N concentration was reduced in woody tissues and in roots of seedlings at LDET compared with LDAT.…”

“…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).…”

“…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. This discrepancy might be caused by the different research conditions and plant species used.…”

“…Numerous studies have showed that warming can lead to increased height and greater biomass production of tree seedlings, but there is considerable variation in biomass gain among species (Callaway et al 1994a, b;Olszyk et al 2003;Lin et al 2010;Wang et al 2012). Biomass allocation patterns between aboveground and belowground structures as well as among different aboveground parts may alter when plants are exposed to warming, although these changes are quite variable.…”

“…Biomass allocation patterns between aboveground and belowground structures as well as among different aboveground parts may alter when plants are exposed to warming, although these changes are quite variable. For example, researchers have found that warming has no effects on biomass allocation in some species (Zhao and Liu 2009), while other tree seedlings show decreased leaf area ratios (LAR) and produce more stem biomass at the expense of leaves (Callaway et al 1994a, b;Olszyk et al 2003). In addition, total chlorophyll concentrations per leaf area are often higher under increased temperature (Wang et al 2003;Zhao and Liu 2009).…”