Branch CO<Subscript>2</Subscript> efflux in vertical profile of Norway spruce tree

Branch CO₂ efflux of Norway spruce tree [Picea abies (L.) Karst.] was measured in ten branches at five different whorls during the growing season 2004 (from June till October) in campaigns of 3–4 times per month at the Beskydy Mts., the Czech Republic. Branch CO₂ efflux was measured using a portable infrared gas analyzer (LI-6250, LI-COR, Inc., USA), operating as a closed system. Branch woody-tissue temperature was measured continuously in 10-min intervals for each sample position during the whole experiment period. On the basis of relation between CO₂ efflux rate and woody-tissue temperature, a value of Q₁₀ and of normalized CO₂ efflux rate (E₁₀–CO₂ efflux rate at 10°C) was calculated for each sampled position. Estimated Q₁₀ values ranged from 2.12 to 2.89, and E₁₀ ranged from 0.41 to 1.19 μmolCO₂m⁻²s⁻¹. Differences in branch CO₂ efflux were found between orientations, east-side branches presented higher efflux rate than west-side branches. The highest branch CO₂ efflux rate values were measured in August and the lowest in October, which corresponds with woody-tissue temperature and growth processes during these periods. Branch CO₂ efflux was significantly and positively correlated with branch position within canopy and woody-tissue temperature. Branches from the upper whorls showed higher CO₂ efflux activity and seasonal dynamics than branches from the lower whorls.     

Effects of elevated CO2 concentration on the respiratory behavior of the branches of field-grown hinoki cypress (Chamaecyparis obtusa)

The effects of elevated atmospheric CO₂ concentrations on the nighttime respiration were examined for two sample branches of a hinoki cypress tree (Chamaecyparis obtusa) growing in the field with an open gas exchange system for a one-year period from July 1994 to June 1995. The branches were of a similar size and located at a similar position within the crown. One branch was subjected to an elevated CO₂ concentration of 800 μmol mol⁻¹ and the other was subjected to ambient air which had a CO₂ concentration of about 370 μmol mol⁻¹. Nighttime respiration rate was higher in elevated CO₂ level than in ambient CO₂ level. The relationship between nighttime respiration and the corresponding nighttime air temperature was fitted by the exponential function in every month of the year. The segregation of regression lines between the two CO₂ treatments increased gradually as the seasons progressed during the treatment period. TheQ ₁₀ values for nighttime respiration were lower in elevated CO₂ (1.9 ≤Q ₁₀ ≤ 3.7) than in ambient CO₂ (2.4 ≤Q ₁₀ ≤ 4.5) in every month of the year. TheQ ₁₀ was inversely related to the monthly mean nighttime air temperature in both elevated and ambient CO₂. The estimated daily nighttime respiration rate under both CO₂ treatments had a similar seasonal pattern, which almost synchronized with the temperature change. The respiration ratio of elevated CO₂ to ambient CO₂ increased gradually from 1.1 to 1.6 until the end of the experiment. Our results indicate that the CO₂ level and the temperature have a strong interactive effect on respiration and suggest that a potential increase in respiration of branches will occur when ambient CO₂ increases.     

Effect of Nutrient Optimization on Branch Characteristics in Picea abies (L.) Karst

The number and size of branches are major determinants of log grading. To study the effect of fertilization on branch characteristics in Norway spruce, trees were sampled in a nutrient optimization experiment in northern Sweden. Data were collected from 24 40-yr-old trees from fertilized and control plots after 12 yrs of annual nutrient application. On the fertilized plots, all essential macronutrients and micronutrients were supplied in irrigation water every second day during the growing season. Fertilization increased the number of new branches, but its effect on branch angle and branch mortality was small. Fertilization increased the diameter of the branches that were formed after the initiation of the treatment, but also the diameter of the branches that were formed before the fertilization commenced. Fertilization enhanced the general growth of a tree, but there were no significant changes in the relationships between stem and branch characteristics. Improved growth rate of trees, as an effect of fertilization, may impair branching quality of logs. Such negative effects may, however, to some extent be counteracted by planting density at stand establishment and later thinning regimens.     

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.     

Species mixing effect on Norway spruce response to elevated CO2 and climatic variables: root and radial growth response

A 7-year study was conducted to examine the growth (diameter and root) response of Norway spruce (Picea abies (L.) Karst.) seedlings to elevated CO₂ (CO_2ELV, 770 μmol (CO₂) mol^?1) in different mixture types (monospecific (M): a Norway spruce seedling surrounded by six spruce seedlings, group-admixture (G): a spruce seedling surrounded by three spruce and three European beech seedlings, single-admixture (S): a spruce seedling surrounded by six beech seedlings). After seven years of treatments, no significant effect from elevated CO₂ was found on the root dry mass (p?=?0.90) and radial growth (p?=?0.98) of Norway spruce. Neither did we find a significant interaction between [CO₂]?×?mixing treatments (p?=?0.56), i.e. there was not a significant effect of CO₂ concentrations [CO₂] in all the admixture types. On the contrary, spruce responses to admixture treatments were significant under CO_2AMB (p?=?0.05), which demonstrated that spruce mainly increased its growth (diameter and root) in M and neighbouring with beech was not favourable for spruce seedlings. In particular, spruce growth diminished when growing beside high proportions/numbers of European beech (S). Here, we also evaluated the association between tree-ring formation and climatic variables (precipitation and air temperature) in different admixture types under elevated and ambient CO₂ (CO_2AMB, 385 μmol (CO₂) mol^?1). Overall, our result suggests that spruce responses to climate factors can be affected by tree species mixing and CO₂ concentrations, i.e. the interaction between climatic variables?×?admixture types?×?[CO₂] could alter the response of spruce to climatic variables.

     

Age and spatial structure of natural Pinus sylvestris stands in Latvia

Abstract

The age and spatial structure of six natural old growth Pinus sylvestris stands in Latvia were investigated, to attempt to identify retrospectively the past features of development. In each stand, one or two plots of size 200–900 m² were established. Tree locations were mapped, stem diameter was measured, and tree age was determined from cores or by counting branch whorls. Tree distribution was assessed by Ripley's K function. A clumped spatial pattern was shown for P. sylvestris younger than 100 years. The temporal patterns of establishment could be partly linked to favourable climatic periods. The major disturbance affecting pine stands along the coast was windblown sand, which partly buried some stems and probably affected the patterns of seedling recruitment and mortality. Disturbance caused by fire had a major role in determining the past regimens of mortality and establishment in dry stands located inland. The successful invasion during the last century of spruce in more mesic plots with a pine overstorey may be due to fire suppression.     

Response of five dry tropical tree seedlings to elevated CO2: Impact of seed size and successional status

The impact of seed size and successional status on seedling growth under elevated CO₂ was studied for five dry tropical tree species viz. Albizia procera, Acacia nilotica, Phyllanthus emblica, Terminalia arjuna and Terminalia chebula. Seedlings from large (LS) and small seeds (SS) were grown at two CO₂ levels (ambient and elevated, 700–750 ppm). CO₂ assimilation rate, stomatal conductance, water use efficiency and foliar N were determined after 30 d exposure to elevated CO₂. Seedlings were harvested after 30 d and 60 d exposure periods. Height, diameter, leaf area, biomass and other growth traits (RGR, NAR, SLA, R:S) were determined. Seedling biomass across species was positively related with seed mass. Within species, LS seedlings exhibited greater biomass than SS seedlings. Elevated CO₂ enhanced plant biomass for all the species. The relative growth rate (RGR), net assimilation rate (NAR), CO₂ assimilation rate, R:S ratio and water use efficiency increased under elevated CO₂. However, the positive impact of elevated CO₂ was down regulated beyond 30 d exposure. Specific leaf area (SLA), transpiration rate, stomatal conductance declined due to exposure to elevated CO₂. Fast growing, early successional species exhibited greater RGR, NAR and CO₂ assimilation rate. Per cent enhancement in such traits was greater for slow growing species. The responses of individual species did not follow functional types (viz. legumes, non-legumes). The enhancement in biomass and RGR was greater for large-seeded species and LS seedlings within species. This study revealed that elevated CO₂ could cause large seeded, slow growing and late successional species to grow more vigorously.     

Effect of pruning on branch production and water relations in widely spaced ponderosa pines

This study dealt with the effects of pruning on branch and leaf area (F _a) production of ponderosa pines growing in silvopastoral systems in Patagonia. We hypothesized that pruning positively influences the number of branches per whorl and their basal area growth rate, changing F _a production. In addition, we studied some water relations in order to explain potential differences in branch growth rates between treatments. Two mathematical models were developed to estimate branch and total F _a. The averaged diameter at the third year of pruning was, for high-pruned trees 3.1 and 3.6 cm at the bottom and middle of the crown, against 4 and 4.4 cm for low-pruned trees. Pruning did not produce changes in the number of branches per whorl (approximately 7.6 branches per whorl). Water stress may be responsible of this lower branch growth in pruned trees. Water potential, stomatal conductance and transpiration were lower in high- than in low-pruned trees.     

Atmospheric carbon dioxide enrichment reduces carbohydrate and nitrogen reserves in overwintering Picea mariana

Abstract

Elevated levels of atmospheric carbon dioxide (CO₂) can directly affect the cold hardening process in evergreens through their effect on the accumulation of carbon and nitrogen reserves. This study investigated the biochemical responses of black spruce [Picea mariana (Mill.) B.S.P.] seedlings to CO₂ enrichment during growth, cold hardening and dehardening. Seedlings were grown under 350 (ambient) or 710 (elevated) ppm of CO₂ for 12 months in eight mini-greenhouses. Photoperiod and temperature were gradually lowered in autumn to induce cold hardening, and the conditions were reversed in spring to promote dehardening. At regular intervals, cold tolerance was assessed and sugars, starch and amino acid concentrations were measured. The freezing tolerance differed between the two treatments only in early autumn, with seedlings growing under high CO₂ being more tolerant. The northern ecotype was more cold tolerant with concomitant higher concentrations of sucrose, fructose, pinitol, glucose and total soluble sugars. The concentration of soluble sugars increased in needles and roots of black spruce along with cold hardening, and the concentrations of the cryoprotective sugars sucrose and raffinose were lower under elevated CO₂. Amino acid concentrations were also lower under elevated than under ambient CO_2. The lower level of reserve did not translate into a lower level of freezing tolerance.     

Relation between length and diameter of Pinus radiata branches

Abstract

The purpose of this study was to construct a model for the architecture of branches in Pinus radiata D. Don and to use it as a part of a modelling effort to relate timber quality as a function of growth and development. Diameter of branches at the insertion point and their length were measured from two types of branches on 2127 normal, healthy and growing branches of different ages, on 15-year-old radiata pine growing in a good and medium productive site in Chile, in stands that either were left without management or had been thinned and pruned. Statistical analysis showed a simple linear relationship between length and diameter with a common proportionality coefficient (slope) in both types of branches, different sites and management regimens. The equation for order 2 branches differed from that of order 3 branches only in the intercept. The results suggest that the uniform linear relationship between branch length and branch diameter could be applied to radiata pine stands of different site fertility and management regimens.     

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     

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     

Crown and branch attributes of mid-aged Betula alnoides plantations in response to planting density

Both crown and branch characteristics greatly affect tree growth and timber quality, and their development is closely related to planting density (PD). Here crown and branch attributes of Betula alnoides were investigated in a 14-year-old experimental plantation in southern China with five planting densities ranging from 500 to 3333 stems per hectare (sph). The results showed that high PD significantly reduced crown and branch sizes. The ratios of crown diameter to stem diameter at breast height at the stand level and for dominant and co-dominant trees were almost constant regardless of PD. PD also had no significant influence on the number and angle of branches, and only planting with the highest density significantly increased branch density and mortality. Insertion angle (IA) of dead branches was greater than that of live branches and these differences were significant at the two low planting densities (833 and 500?sph). Linear mixed models revealed that branch diameter (BD) was negatively correlated with its relative height in the crown and IA. The binary-logistic regression model indicated that branch status (live or dead) was codetermined by BD and PD. These findings can help farmers cultivate high-quality wood of B. alnoides and obtain a higher economic return.     

长白赤松和红松土壤微生物活性对高浓度CO2的响应

Responses of soil microbial activities to elevated CO₂ in experiment sites ofPinus sylvestriformis andPinus koraiensis seedlings were studied in summer in 2003. The results indicated the number of bacteria decreased significantly (p<0.05) under elevated CO₂ forPinus sylvestriformis andPinus koraiensis. Amylase and invertase activities in soil increased forPinus sylvestriformis and decreased forPinus koraiensis with CO₂ enrichment compared with those at ambient (350 μmol·mol⁻¹). The size of microbial biomass C also decreased significantly at 700 μmol·mol⁻¹ CO₂. Bacterial community structure had some evident changes under elevated CO₂ by DGGE (Denaturing Gradient Gel Electrophoresis) analysis of bacterial 16S rDNA gene fragments amplified by PCR from DNA extracted directly from soil. The results suggested that responses of soil microorganisms to elevated CO₂ would be related to plant species exposed to elevated CO₂. Foundation item: The study was supported by Major State Basic Research Development Program of China (2002CB412502) and the Knowledge Innovation Project from Chinese Academy of Sciences (KZCX1-SW-01-03). Biography: JIA Xia (1975), female, Ph. D. candidate of Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, P. R. China. Responsible editor: Song Funan     

Black spruce family growth performance under ambient and elevated atmospheric CO2

Seedlings from 20 families of black spruce (Picea mariana (Mill.) B.S.P.), representing a large range in field productivity, were subjected to a greenhouse retrospective test under ambient (409 ppm – year 1, 384 ppm – year 2) and high (686 ppm – year 1, 711 ppm – year 2) atmospheric CO₂ environments. After one and two growth cycles, seedling height and diameter growth significantly increased under elevated CO₂. At the end of the experiment, seedlings grown under high CO₂ had a mean above-ground dry weight of 48.77 g as compared to 26.36 g for seedlings grown under ambient atmospheric CO₂. Families were a significant source of variation for all growth parameters. Although the family × CO₂ environment interaction was not a statistically significant source of variation in the analysis of variance, the correlation between greenhouse and 15-year field height growth was weaker (r = 0.29, p = 0.2177) under elevated CO₂ compared to ambient CO₂ (r = 0.51, p = 0.0223) following the first growth cycle. However, following the second growth cycle, greenhouse-field correlations were similar between the two CO₂ environments (ambient CO₂: r = 0.55, p = 0.0115; elevated CO₂: r = 0.56, p = 0.0101). Thus, with this set of families, growth performance ranking after two years appears relatively stable under ambient and elevated CO₂.     

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     

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.     

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     

Photosynthetic response ofPinus sylvestriformis to elevated carbon dioxide and its influential factor analysis

The photosynthetic response of 12-year oldPinus sylvestriformis to elevated CO₂ and its influential factors were tested and analyzed in the forest region of Changbai Mountain in 1999. Trees grown at the natural condition were controlled at three levels of CO₂ concentration (350 μL·L⁻¹, 500 μL·L⁻¹ and 700 μL·L⁻¹) by CO₂ rich settlement designed by us. Net photosynthetic rates (NPR), temperature, relative humidity, stomatal conductance, intercellular CO₂ concentration and photosynthetic active radiation (PAR) were measured at 6:00, 8:00, 10:00, 14:00, 16:00 and 18:00 hours a day. Experimental results showed that the NPR ofPinus sylvestriformis increased by 32.6% and 123.0% at 500 μL·L⁻¹ and 700 μL·L⁻¹ CO₂ concentration respectively, compared to ambient atmospheric CO₂ concentration (350 μL·L⁻¹). The relations between NPR and influential factors, including temperature, relative humidity, intercellular CO₂ concentration and photosynthetic active radiation, were analyzed respectively by regression analysis at different CO₂ concentrations. Foundation Item: This project was supported by Chinese Academy of Sciences. Biography: WANG Chen-rui (1970-), male, Assistant Research Fellow in Institute of Applied Ecology, Chinese Academy of Sciences. Responsible editor: Chai Ruihai     

Effects of Light Intensity and Regeneration Mode on Stem Form and Growth of Cunninghamia lanceolata Saplings

ABSTRACT

Regeneration plays an essential role in the restructuring of plant communities, with seedlings and sprouts representing two different regeneration strategies. As an important timber species, Cunninghamia lanceolata is widely distributed throughout southern and eastern China. However, the morphology and growth of its sprouts and seedlings under natural environments have not been examined in detail. Our study quantified the morphology and growth of Cunninghamia lanceolata during its early regeneration phase. We selected a secondary mixed coniferous forest in the Huangshan region of China as the research location, and examined sapling height, basal stem diameter, lateral branch length, as well as the relationships between main stem and lateral branch elongation, and between sapling basal stem diameter and height. The results showed that high light intensity promoted the extension growth of main stems and the elongation of lateral branches of seedlings. Meanwhile, sprouts generally had shorter height growth than seedlings with the same basal stem diameter, and the growth allocation of seedlings was generally more dependent on light intensity. Our findings suggest that the morphology and growth of C. lanceolata might vary depending on the interaction of regeneration mode (plants originating from sprouts or seedlings) and light intensity.