Ecophysiological responses and carbon distribution ofPinus koraiensis seedlings to elevated carbon dioxide

The net CO₂ assimilation rate, stomatal conductance, RuBPcase (ribulose 1,5-biphosphate carboxylose) activity, dry weight of aboveground and belowgroud part, plant height, the length and diameter of taproot ofPinus koraiensis seedlings were measured and analyzed after six-week exposure to elevated CO₂ in an open-top chamber in Changbai Mountain of China from May to Oct. 1999. Seedlings were planted in four different conditions: on an open site, control chamber, 500 μL·L⁻¹ and 700 μL·L⁻¹ CO₂ chambers. The results showed that the total biomass of the seedlings increased whereas stomatal conductance decreased. The physiological responses and growth to 500 μL·L⁻¹ and 700 μL·L⁻¹ CO₂ varied greatly. The acclimation of photosynthesis was downward to 700 μL·L⁻¹ CO₂ but upward to 500 μL·L⁻¹ CO₂. The RuBPcase activity, chlorophyll and soluble sugar contents of the seedlings grown at 500 μL·L⁻¹ CO₂ were higher than that at 700 μL·L⁻¹ CO₂. The concentration 500 μL·L⁻¹ CO₂ enhanced the growth of aboveground part whereas 700 μL·L⁻¹ CO₂ allocated more carbon to belowground part. Elevated CO₂ changed the carbon distribution pattern. The ecophysiological responses were significantly different between plants grown under 500 μL·L⁻¹ CO₂ and 700 μL·L⁻¹ CO₂. Foundation Item: This paper was supported by Chinese Academy of Sciences. Biography: HAN Shi-jie (1956-), male, Ph. Doctor, Professor in Laboratory of Ecological Process of Trace Substance in Terrestrial Ecosystem, Institute of Applied Ecology, Chinese Academy of Sciences. Responsible editor: Chai Ruihai     

Response of seedlings of different tree species to elevated C02 in Changbai Mountain

Eco-physiological responses of seedlings of eight species,Pinus koraiensis, Picea koraiensis, Larix olgensis, Populus ussuriensis, Betula platyphylla, Tilia amurensis, Traxinus mandshurica andAcer mono from broadleaved/Korean pine forest, to elevated CO₂ were studied by using open-top chambers under natural sunlight in Changbai Mountain, China in two growing seasons (1998–1999). Two concentrations of CO₂ were designed: elevated CO₂ (700 μmol·mol⁻¹) and ambient CO₂ (400 μmol·mol⁻¹). The study results showed that the height growth of the tree seedlings grown at elevated CO₂ increased by about 10%–40% compared to those grown at ambient CO₂. And the water using efficiency of seedlings also followed the same tendency. However, the responses of seedlings in transpiration and chlorophyll content to elevated CO₂ varied with tree species. The broad-leaf tree species were more sensitive to the elevated CO₂ than conifer tree species. All seedlings showed a photosynthetic acclimation to long-term elevated CO₂. Foundation item: The project was supported by National Key Basic Development of China (G1999043400) and the grant KZCX 406-4, KZCX1 SW-01 of the Chinese Academy of Sciences Biography: WANG Miao (1964-), maie, associate professor in Institute of applied Ecology, Chinese Academy of Sciences, Shenyang 110016, P. R. China. Responsible editor: Song Funan     

Responses of the seedlings of five dominant tree species in Changbai Mountain to soil water stress

Soil water stress was studied on the potted seedlings of five dominant tree species (Pinus koraienes Sieb.et Zucc.,Fraxinus mandshurica Rupr., Juglans mandshurica Maxim, Tilia amurensis Rupr. and Quercus mongolica Fisch.ex Turcz) from the broadleaved/Korean pine forest in Changbai Mountain. Leaf growth, water transpiration and photosynthesis were compared for each species under three soil moisture conditions: 85%-100% (high water, CK), 65%-85% (Medium water, MW) and 45%-65% (low water, LW) of 37.4% water-holding capacity in field. The results showed that the characteristic of typical drought-resistance of the leaves is significantly developed. The net photosynthetic rate and water use efficiency of Fraxinus mandshurica were higher in MW than those in CK. But for the other four species, the net photosynthetic rate and water use efficiency in CK were lower than those in MW and LW. The transpiration rate responding to soil moistures varied from species to soecies.     

Effect of elevated CO2 concentration on growth course of tree seedlings in Changbai Mountain

One-year-old seedlings ofPinus koraiensis, Pinus sylvestriformis, Phellodendron amurense were grown in open-top chambers (OTCs) with 700 and 500 ώmol/mol CO₂ concentrations, control chamber and on open site (ambient CO₂, about 350 ώmol/mol CO₂) respectively at the Open Research Station of Changbai Mountain Forest Ecosystems, Chinese Academy of Sciences, and the growth course responses of three species to elevated CO₂ and temperature during one growing season was studied from May to Oct. 1999. The results showed that increase in CO₂ concentration enhanced the growth of seedlings and the effect of 700 (ώmol/mol CO₂ was more remarkable than 500 ώmol/mol CO₂ on seedling growth. Under the condition of doubly elevated CO₂ concentration, the biomass increased by 38% in average for coniferous seedlings and 60% for broad-leaved seedlings. With continuous treatment of high CO₂ concentration, the monthly-accumulated biomass of shade-tolerantPinus koraiensis seedlings was bigger in July than in August and September, while those ofPinus sylvestriformis andPhellodendron amurense seedlings showed an increase in July and August, or did not decrese until September. During the hot August, high CO₂ concentration enhanced the growth ofPinus koraiensis seedlings by increasing temperature, but it did not show dominance in other two species. Foundation Item: This paper was supported by Chinese Academy of Sciences and the Open Research Station of Changbai Mountain Forest Ecosystem.     

Stomatal response ofPinus sylvestriformis to elevated CO2 concentrations during the four years of exposure

Four-year-oldPinus sylvestriformis were exposed for four growing seasons in open top chambers to ambient CO₂ concentration (approx. 350 μmol·mol⁻¹) and high CO₂ concentrations (500 and 700 μmol·mol⁻¹) at Research Station of Changbai Mountain Forest Ecosystems, Chinese Academy of Sciences at Antu Town, Jilin Province, China (42°N, 128°E). Stomatal response to elevated CO₂ concentrations was examined by stomatal conductance (g _s), ratio of intercellular to ambient CO₂ concentration (c _i/c _a) and stomatal number. Reciprocal transfer experiments of stomatal conductance showed that stomatal conductance in high-[CO₂]-grown plants increased in comparison with ambient-[CO₂]-grown plants when measured at their respective growth CO₂ concentration and at the same measurement CO₂ concentration (except a reduction in 700 μmol·mol⁻¹ CO₂. grown plants compared with plants on unchambered field when measured at growth CO₂ concentration and 350 μmol·mol⁻¹CO₂). High-[CO₂]-grown plants exhibited lowerc _i/c _a ratios than ambient-[CO₂]-grown plants when measured at their respective growth CO₂ concentration. However,c _i/c _a ratios increased for plants grown in high CO₂ concentrations compared with control plants when measured at the same CO₂ concentration. There was no significant difference in stomatal number per unit long needle between elevated and ambient CO₂. However, elevated CO₂ concentrations reduced the total stomatal number of whole needle by the decline of stomatal line and changed the allocation pattern of stomata between upper and lower surface of needle. Foundation Item: This research was supported by National Basic Research Program of China (2002CB412502), Project of Key program of the National Natural Science Foundation of China (90411020) and National Natural Science Foundation of China (30400051). Biography: ZHOU Yu-mei (1973-), female, Ph. Doctor, assistant research fellow, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, P. R. China. Responsible editor: Song Funan     

Effects of elevated CO2 on net photosynthetic rate of trees in Changbai Mountain

Net photosynthetic rates (NPRs) of four species seedlings,Pinus koraiensis, Pinus sylvestriformis, Fraxinus mandshurica andPhellodendron amurense, were measured at different CO₂ concentrations and time respectively in Changbai Mountain during the growing season in 1999. The seedlings were cultivated in open-top chambers (OTCs), located outdoors and exposed to natural sunlight. The experimental objects were divided into four groups by tree species. CO₂ concentrations in chambers were kept at 500 μL·L⁻¹ and 700 μL·L⁻¹ and contrast chamber and contrast field were set. The results showed that the effects of elevated CO₂ on NPR of the trees strongly depended on tree species and time. NPRs ofPinus koreainsis andPinus sylvestriformis seedlings increased with the rising of CO₂ concentration, while that ofPhellodendron amurense andFraxinus mandshurica increased at some time and decreased at another time. This project was supported by Chinese Academy of Sciences Responsible editor: Chai Ruihai     

Response of seedlings growth ofPinus sylvestriformis to atmospheric CO2 enrichment in Changbai Mountain

The biomass and ratio of root-shoot ofPinus sylvestriformis seedlings at CO₂ concentration of 700 μL·L⁻¹ and 500 μL·L⁻¹ were measured using open-top chambers (OTCs) in Changbai Mountain during Jun. to Oct. in 1999. The results showed that doubling CO₂ concentration was benefit to seedling growth of the species (500 μL·L⁻¹ was better than 700 μL·L⁻¹) and the biomass production was increased in both above-ground and underground parts of seedlings. Carbon transformation to roots was evident as rising of CO₂ concentration. This project is supported by Chinese Academy of Sciences Responsible editor: Chai Ruihai     

Simulating leaf net CO2 assimilation rate of C3 & C4 plants and its response to environmental factors

Basic structure and algorithm of leaf mechanism photosynthesis model were described in first part of this study based on former researcher results. Then, considering some environmental factors influencing on leaf photosynthesis, three numerical sensitivity experiments were carried out. We simulated the single leaf net CO₂ assimilation, which acts as a function of different light, carbon dioxide and temperature conditions. The relationships between leaf net photosynthetic rate of C₃ and C₄ plant with CO₂ concentration intercellular, leaf temperature, and photosynthetic active radiation (PAR) were presented, respectively. The results show the numerical experiment may indicate the main characteristic of plant photosynthesis in C₃ and C₄ plant, and further can be used to integrate with the regional climate model and act as land surface process scheme, and better understand the interaction between vegetation and atmosphere. Foundation Item: This paper was supported by Natural Science Foundation of China (Grant No. 39900084) Biography: ZHANG Jia-hua (1966-), male, Ph. Doctor, Associate professor in START, Institute of Atmospheric Physics. Chinese Academy of SciencesBeijing, 100029, P. R. China Responsible editor: Chai Ruihai     

Family Variation in the Morphology and Physiology of White Spruce (Picea glauca) Seedlings in Response to Elevated CO2 and Temperature

Tree improvement programs aim to develop families that are well-adapted to future growing conditions. To gain insight into the stability of the family genetic response to climate change, white spruce (Picea glauca) seedlings from 60 full-sib families were subjected to a combination of two temperature regimes and two levels of CO₂ over two growing seasons. There was positive effect of warmer temperatures and higher CO₂ on some growth variables but no significant family × treatment interactions. Instantaneous water use efficiency was the only physiological trait that was affected positively by the CO₂ treatment, showing a 51% increase that was consistent across families.     

Effects of elevated CO2 concentrations on photosynthesis, dark respiration and RuBPcase activity of three species seedlings in Changbai Mountain

Two-year-old seedlings ofPinus koraiensis, Pinus sylvestriformis andFraxinus mandshurica were treated in open-top chambers with elevated CO₂ concentrations (700 μL·L⁻¹, 500 μL·L⁻¹) and ambient CO₂ concentrations (350 μL·L⁻¹) in Changbai Mountain from June to Sept. in 1999 and 2001. The net photosynthetic rate, dark respiration rate, ribulose-1,5-bisphosphate carboxlase (RuBPcase) activity, and chlorophyll content were analyzed. The results indicated the RuBPcase activity of the three species seedlings increased at elevated CO₂ concentrations. The elevated CO₂ concentrations stimulated the net photosynthetic rates of three tree species exceptP. sylvestriformis grown under 500 μL·L⁻¹ CO₂ concentration. The dark respiration rates ofP. koraiensis andP. sylvestriformis increased under concentration of 700 μL·L⁻¹ CO₂, out that ofF. mandshurica decreased under both concentrations 700 μL·L⁻¹ and 500 μL·L⁻¹ CO₂. The seedlings ofF. mandshurica decreased in chlorophyll contents at elevated CO₂ concentrations. Foundation item: This paper was supported by the National Natural Science Foundation of China (No. 30070158). Knowledge Innovation Item of Chinese Academy of Sciences (KZCX2-406) and “Hundred Scientists” Project of Chinese Academy of Sciences. Biography: Zhou Yu-mei (1973-) Ph. Doctor, Assistant Research fellow Institute of Applied Ecology. Chinese Academy of Sciences. Shenyang 110016. P.R. China. Responsible editor: Song Funan     

Photosynthetic response to variation in CO2 concentrations and temperature of four broad-leaved trees in Beijing region

Responses of the photosynthetic characteristics to variation in CO₂ concentration and temperature of Ginkgo biloba, Eucommia ulmoides, Magnolia denudata and Tilia japonica were measured during the peak growing season. The results show that the ambient CO₂ concentration could not meet the requirements for photosynthesis of these four species. The optimal temperatures for photosynthesis were lower than the average daytime air temperature. Hence, the photosynthesis of these four species was restricted by the low CO₂ concentration and high daytime air temperature at the time of measurement. Marked enhancements in the net photosynthetic rate were found in all four species when the CO₂ concentration was doubled. When the dependency on CO₂ and temperature were examined simultaneously, it was seen that for increased CO₂ concentrations there was a shift in the optimum temperature for M. denudata and T. japonica towards higher temperatures. Due to their independence on CO₂ concentrations, this trend could not be found in the G. biloba and E. ulmoides data sets. The stomatal conductance (G _s) was sensitive to a vapor pressure deficit (VPD) which in turn was sensitive to temperature. An increase in temperature would cause the VPD to increase and plants might be assumed to react by reducing their stomatal apertures. The effect on stomatal resistance would be most significant at high temperatures. The restriction to stomatal conductance for these four species would increase if CO₂ concentrations were elevated at the same temperature. __________ Translated from Journal of Agricultural University of Hebei, 2006, 29 (6): 39–43 [译自: 河北农业大学学报]     

Propagation of trembling aspen and hybrid poplar for agroforestry: potential benefits of elevated CO2 in the greenhouse

We examined the usefulness of elevated CO₂ in the greenhouse to aid in early selection of genotypes and in the propagation of Populus tremuloides Michaux (aspen) and hybrid poplars for agroforestry, afforestation, or reclamation. Growth in elevated (800 ppm) vs ambient (375 ppm) CO₂ for 95 days resulted in greater height (14%), stem caliper (16%), overall biomass, and proportional allocation of biomass to roots as well as elevated net assimilation and water-use-efficiency. Aspen clones selected for superior growth (based on phenotypic selection) broke bud significantly earlier than unselected clones under both CO₂ levels; superior clones were also taller with greater stem caliper under both CO₂ treatments (but not significant). Under ambient CO₂ male aspen were taller than females while under elevated CO₂ female aspen were taller than males and also had greater caliper (but not significant). Hybrid poplar grown under elevated (vs ambient) CO₂ broke bud significantly earlier and had significantly greater net assimilation and water-use efficiency; they were also taller with greater caliper (but not significant). Differences in performance among the eight hybrid clones were enhanced by growth under elevated CO₂. Under ambient CO₂, P38P38 was the clone that broke bud earliest, was tallest with greater caliper and had a lower shoot:root biomass ratio. Sargentii, on the other hand, was the shortest with the smallest caliper. The implications of these results need to be considered in the context of using aspen and hybrid poplar for large-scale agroforestry, afforestation and reclamation across Canada. This revised version was published online in August 2006 with corrections to the Cover Date.     

Influence of woody and herbaceous vegetation control on leaf gas exchange,water status,and nutrient relations of eastern white pine (Pinus strobus L.) seedlings planted in a central Ontario clearcut

The influence of herbaceous and woody vegetation control, either singly or in combination, on leaf gas exchange, water status, and nutrient relations of planted eastern white pine (Pinus strobus L.) seedlings was examined in a central Ontario clearcut over four consecutive growing seasons (GSs). Net carbon assimilation (A_n), leaf conductance to water vapour (G_wv), water use efficiency (WUE), and midday leaf water potential (ψ_m) were measured periodically during the second to fourth GSs of vegetation control treatments, while leaf nutrient relations were examined in GS five. Leaf A_n and G_wv were reduced (p ≤ 0.05) in the presence of herbaceous vegetation in GS two, by both herbaceous and woody vegetation in GS three, and only by woody vegetation (largely trembling aspen (Populus tremuloides Michx.)) in GS four. Leaf WUE was increased (p ≤ 0.05) in all three GSs in which herbaceous vegetation control was applied and where woody vegetation provided partial shading of planted white pine. Leaf water status was comparatively less responsive to vegetation control treatments, but leaf ψ_m was increased (p ≤ 0.05) in the presence of woody vegetation in GSs two and four, likely due to shading and reduced atmospheric evaporative demand of the white pine seedling environment. Within a given GS, the effects of vegetation control on A_n, G_wv, and ψ_m were strongly linked to treatment-induced changes in total vegetative cover, and light and soil moisture availability. Seedling height, diameter, and volume growth rates were positively correlated with A_n and WUE in GSs two and three, but less so in GS four. Vector analysis suggested that herbaceous competition induced foliar N, P, and K deficiencies in five-year-old white pine seedlings while competition from aspen resulted in foliar Ca deficiency.     

Changes in root growth and relationships between plant organs and root hydraulic traits in American elm (Ulmus americana L.) and red oak (Quercus rubra L.) seedlings due to elevated CO2 level

The relationships between plant organs and root hydrological traits are not well known and the question arises whether elevated CO2 changes these relationships. This study attempted to answer this question. A pseudo-replicated experiment was conducted with two times 24 American elm (Ulmus americana L.) and 23 and 24 red oak (Quercus rubra L.) seedlings growing in ambient CO2 (around 360 μmol·L–1) and 540 ± 7.95 μmol·L–1 CO₂ in a greenhouse. After 71 days of treatment for American elm and 77 days for red oak, 14 American elm and 12 red oak seedlings from each of the two CO2 levels were randomly selected in order to examine the flow rate of root xylem sap, root hydraulic conductance, total root hydraulic conductivity, fine root and coarse root hydraulic conductivity. All seedlings were harvested to investigate total plant biomass, stem biomass and leaf biomass, leaf area, height, basal diameter, total root biomass, coarse root biomass and fine root biomass. The following conclusions are reached: 1) plant organs respond to the elevated CO2 level earlier than hydraulic traits of roots and may gradually lead to changes in hydraulic traits; 2) plant organs have different relationships with hydraulic traits of roots and elevated CO2 changes these relationships; the changes may be of importance for plants as means to acclimatize to changing environments; 3) biomass of coarse roots increased rather more than that of fine roots; 4) Lorentzian and Caussian models are better in estimating the biomass of seedlings than single-variable models.     

高CO2浓度和干旱胁迫对4种树苗光合特性的影响

在不同CO2浓度(380、720 μmol·mol-1)的密闭式生长箱内,对5年生油松和侧柏苗、3年生元宝枫和刺槐苗进行培养,研究CO2浓度升高与干旱胁迫对4种树苗光合特性和水分利用效率的影响.结果表明:高CO2浓度均能增加正常水分和重度干旱胁迫下4个树苗的光合速率(Pn)、胞间CO2浓度(Ci)和瞬时水分利用效率(WUE;),而降低蒸腾速率(Tr)和气孔导度(Cord);在轻度干旱和重度干旱条件下,Pn、Ci、Tr、Cond和WUEi增加,刺槐的WUEi却减少.CO2浓度增加,4个树种在同一干旱时期的碳稳定同位素比值(δ13C)减少.随着干旱胁迫加剧,不同CO2浓度下4个树种的Pn、Tr和Cond减少,而720 μmol·mol-1 CO2浓度下4个树种和380 μmol·mol-1CO2浓度下刺槐和元宝枫的WUEi和δ13C增加,而380μmol·mol-1CO2浓度下油松和侧柏的WUEi和δ13C先增加,到重度干旱时又下降.CO2浓度增加与干旱胁迫的交互作用减弱了干旱胁迫或者CO2浓度增加中的某一因子对气孔变化的敏感性,使得气孔变化缓慢,延迟了水分胁迫的发生.