共查询到20条相似文献,搜索用时 62 毫秒
1.
The impact of seed size and successional status on seedling growth under elevated CO 2 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 CO 2 levels (ambient and elevated, 700–750 ppm). CO 2 assimilation rate, stomatal conductance, water use efficiency and foliar N were determined after 30 d exposure to elevated CO 2. 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 CO 2 enhanced plant biomass for all the species. The relative growth rate (RGR), net assimilation rate (NAR), CO 2 assimilation rate, R:S ratio and water use efficiency increased under elevated CO 2. However, the positive impact of elevated CO 2 was down regulated beyond 30 d exposure. Specific leaf area (SLA), transpiration rate, stomatal conductance declined due to exposure to elevated CO 2. Fast growing, early successional species exhibited greater RGR, NAR and CO 2 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 CO 2 could cause large seeded, slow growing and late successional species to grow more vigorously. 相似文献
2.
Abstract Elevated levels of atmospheric carbon dioxide (CO 2) 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 CO 2 enrichment during growth, cold hardening and dehardening. Seedlings were grown under 350 (ambient) or 710 (elevated) ppm of CO 2 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 CO 2 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 CO 2. 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. 相似文献
3.
Several studies have been conducted on the response of crops to greater concentrations of atmospheric CO 2 (CO 2 fertilization) as a result of climate change, but only few studies have evaluated this effect on multipurpose agroforestry tree species in tropical environments. The objectives of this study were to quantify differences in growth parameters and in leaf carbon (C) and nitrogen (N) concentrations of Cedrela odorata L. and Gliricidia sepium (Jacq.) Walp. seedlings under current ambient temperature (32°C daytime, 22°C night time) and CO 2 (360 ppm) (AMB); CO 2 fertilization (800 ppm, 32°C daytime, 22°C night time) ( fCO 2); elevated ambient temperature (360 ppm, 34°C daytime, 25°C night time) (TEMP); and a combination of elevated temperature (32°C daytime, 22°C night time) and CO 2 fertilization (800 ppm) (TEMPx fCO 2). Results showed significant differences ( P < 0.05) in seedling growth parameters (seedling height, number of stem leaves, leaf area ratio, shoot and root biomass, and shoot/root ratio) between treatments for both tree species. The greatest increases in growth parameters occurred in the TEMP and TEMPx fCO 2 treatments compared to the AMB treatment for both tree species. However, growth parameters were significantly lower ( P < 0.05) in the fCO 2 treatment compared to that of the AMB treatment. Leaf N concentration was 1.1 to 2.1 times lower ( P < 0.05) in all treatments when compared to current ambient conditions (AMB) in both tree species, but no significant changes in leaf C concentrations were observed. Results from our study suggested that fCO 2 had the greatest negative impact on tree growth parameters, and leaf N concentrations were affected negatively in all treatments compared to current ambient conditions. It is expected that such changes in growth parameters and plant N content may impact the long-term cycling of nutrients in agroforestry systems. 相似文献
4.
We examined the usefulness of elevated CO 2 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) CO 2 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 CO 2 levels; superior clones were also taller with greater stem caliper under both CO 2 treatments (but not significant). Under ambient CO 2 male aspen were taller than females while under elevated CO 2 female aspen were taller than males and also had greater caliper (but not significant). Hybrid poplar grown under elevated
( vs ambient) CO 2 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 CO 2. Under ambient CO 2, 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. 相似文献
5.
Research into the effects of rising atmospheric carbon dioxide (CO 2) on plant diseases remains limited despite the economic importance of this subject. Loblolly pine ( Pinus taeda) seedlings were exposed to ambient and twice ambient levels of atmospheric CO 2 prior to inoculation with the fusiform rust fungus (the obligate pathogen Cronartium quercuum f.sp. fusiforme, CQF) or the pitch canker fungus (the facultative pathogen Fusarium circinatum, FC). Additionally, northern red oak seedlings ( Quercus rubra; an alternate host of CQF) were exposed to ambient or elevated levels of atmospheric CO 2 prior to inoculation with CQF. In all cases, disease incidence (percent of plants infected) and disease severity (proportion
of each plant affected) were determined; with the oak seedlings, the latent period (time to sporulation) was also monitored.
In general, disease incidence was decreased by exposure to elevated CO 2. This exposure also increased the latent period for CQF on oak seedlings. In no instance did exposure to elevated CO 2 affect disease severity. This research demonstrated that plants may benefit from exposure to the increasing concentration
of CO 2 in the atmosphere through decreases in fungal disease incidence. 相似文献
6.
Eco-physiological responses of seedlings of eight species, Pinus koraiensis, Picea koraiensis, Larix olgensis, Populus ussuriensis, Betula platyphylla, Tilia amurensis, Traxinus mandshurica and Acer mono from broadleaved/Korean pine forest, to elevated CO 2 were studied by using open-top chambers under natural sunlight in Changbai Mountain, China in two growing seasons (1998–1999).
Two concentrations of CO 2 were designed: elevated CO 2 (700 μmol·mol −1) and ambient CO 2 (400 μmol·mol −1). The study results showed that the height growth of the tree seedlings grown at elevated CO 2 increased by about 10%–40% compared to those grown at ambient CO 2. And the water using efficiency of seedlings also followed the same tendency. However, the responses of seedlings in transpiration
and chlorophyll content to elevated CO 2 varied with tree species. The broad-leaf tree species were more sensitive to the elevated CO 2 than conifer tree species. All seedlings showed a photosynthetic acclimation to long-term elevated CO 2.
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 相似文献
7.
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 CO 2 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. 相似文献
8.
The effects of elevated atmospheric CO 2 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 CO 2 concentration of 800 μmol mol −1 and the other was subjected to ambient air which had a CO 2 concentration of about 370 μmol mol −1. Nighttime respiration rate was higher in elevated CO 2 level than in ambient CO 2 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 CO 2 treatments increased gradually as the seasons progressed during the treatment period. The Q
10 values for nighttime respiration were lower in elevated CO 2 (1.9 ≤ Q
10 ≤ 3.7) than in ambient CO 2 (2.4 ≤ Q
10 ≤ 4.5) in every month of the year. The Q
10 was inversely related to the monthly mean nighttime air temperature in both elevated and ambient CO 2. The estimated daily nighttime respiration rate under both CO 2 treatments had a similar seasonal pattern, which almost synchronized with the temperature change. The respiration ratio of
elevated CO 2 to ambient CO 2 increased gradually from 1.1 to 1.6 until the end of the experiment. Our results indicate that the CO 2 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 CO 2 increases. 相似文献
9.
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 (CO2ELV, 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 CO2AMB (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 (CO2AMB, 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. 相似文献
10.
One-year-old seedlings of Pinus koraiensis, Pinus sylvestriformis, Phellodendron amurense were grown in open-top chambers (OTCs) with 700 and 500 ώmol/mol CO 2 concentrations, control chamber and on open site (ambient CO 2, about 350 ώmol/mol CO 2) 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 CO 2 and temperature during one growing season was studied from May to Oct. 1999. The results showed that increase in CO 2 concentration enhanced the growth of seedlings and the effect of 700 (ώmol/mol CO 2 was more remarkable than 500 ώmol/mol CO 2 on seedling growth. Under the condition of doubly elevated CO 2 concentration, the biomass increased by 38% in average for coniferous seedlings and 60% for broad-leaved seedlings. With
continuous treatment of high CO 2 concentration, the monthly-accumulated biomass of shade-tolerant Pinus koraiensis seedlings was bigger in July than in August and September, while those of Pinus sylvestriformis and Phellodendron amurense seedlings showed an increase in July and August, or did not decrese until September. During the hot August, high CO 2 concentration enhanced the growth of Pinus 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. 相似文献
11.
To investigate the interactive effects of CO 2 concentration ([CO 2]) and nitrogen supply on the growth and biomass of boreal trees, white birch seedlings ( Betula papyrifera) were grown under ambient (360 μmol mol −1) and elevated [CO 2] (720 μmol mol −1) with five nitrogen supply regimes (10, 80, 150, 220, and 290 μmol mol −1) in greenhouses. After 90 days of treatment, seedling height, root-collar diameter, biomass of different organs, leaf N concentration, and specific leaf area (SLA) were measured. Significant interactive effects of [CO 2] and N supply were found on height, root-collar diameter, leaf biomass, stem biomass and total biomass, stem mass ratio (SMR), and root mass ratio (RMR), but not on root mass, leaf mass ratio (LMR), leaf to root ratio (LRR), or leaf N concentration. The CO 2 elevation generally increased all the growth and biomass parameters and the increases were generally greater at higher levels of N supply or higher leaf N concentration. However, the CO 2 elevation significantly reduced SLA (13.4%) and mass-based leaf N concentration but did not affect area-based leaf N concentration. Increases in N supply generally increased the growth and biomass parameters, but the relationships were generally curvilinear. Based on a second order polynomial model, the optimal leaf N concentration was 1.33 g m −2 for height growth under ambient [CO 2] and 1.52 g m −2 under doubled [CO 2]; 1.48 g m −2 for diameter under ambient [CO 2] and 1.64 g m −2 under doubled [CO 2]; 1.29 g m −2 for stem biomass under ambient [CO 2] and 1.43 g m −2 under doubled [CO 2]. The general trend is that the optimal leaf N was higher at doubled than ambient [CO 2]. However, [CO 2] did not affect the optimal leaf N for leaf and total biomass. The CO 2 elevation significantly increased RMR and SMR but decreased LMR and LRR. LMR increased and RMR decreased with the increasing N supply. SMR increased with increase N supply up to 80 μmol mol −1 and then leveled off (under elevated [CO 2]) or stated to decline (under ambient [CO 2]) with further increases in N supply. The results suggest that the CO 2 elevation increased biomass accumulation, particularly stem biomass and at higher N supply. The results also suggest that while modest N fertilization will increase seedling growth and biomass accumulation, excessive application of N may not stimulate further growth or even result in growth decline. 相似文献
12.
Interactive effects of elevated atmospheric CO 2 and soil N fertility on above- and below-ground growth, mycorrhizal colonization, and water relations of juvenile ponderosa pine ( Pinus ponderosa Dougl. ex Laws.) were investigated. One-year-old seedlings were planted in undisturbed field soil within open-top chambers which permitted creation of atmospheres with 700 μl l −1, 525 μl l −1, or ambient CO 2 concentrations. High and medium soil N treatments were imposed by incorporating sufficient (NH 4) 2SO 4 to increase total N by 200 μg g −1 and 100 μg g −1, respectively, while unamended soil, which had a total N concentration of approximately 900 μg g −1, constituted the low N treatment. Following each of two consecutive field growing seasons, whole seedlings of every combination of CO 2 and N treatment were harvested to permit assessment of shoot and root growth and quantification of ectomycorrhizal development. Late in the second growing season, a simulated drought episode was imposed by withholding irrigation during which predawn and midday xylem water potential and soil water potential were measured. The initial harvest revealed that coarse and fine root weights were increased by CO 2 enrichment during the first growing season. This result was most apparent in the 525 μl l −1 CO 2 treatment and high soil N, which produced the greatest root volume as well. Shoot/root ratio decreased with increasing CO 2 at the first harvest. After two growing seasons, elevated CO 2 increased seedling diameter, shoot and root volume, and shoot and coarse root weight, again most prominently in high N. Unlike the initial results, however, stimulation of seedling growth by the 700 μl l −1 CO 2 atmosphere exceeded that in 525 μl l −1 CO 2 after two growing seasons, and shoot/root ratio was unaffected by either CO 2 or N. At both harvests, seedlings grown in the enriched atmospheres generally had higher mycorrhizal counts and greater percentages of colonized root length, but differences among treatments in ectomycorrhizal development were nonsignficant regardless of quantification method. During the imposed drought episode, xylem water potential of seedlings grown in elevated CO 2 descended below that of seedlings grown in the ambient atmosphere as soil water potential decreased, most notably in the predawn measurements. These results suggest that CO 2 enrichment stimulates shoot and root growth of juvenile ponderosa pine under field conditions, a response somewhat dependent on soil N availability. However, below-ground growth is not increased proportionally more than that above ground, which may predispose this species to greater stress when soil water is limited. 相似文献
13.
We tested the effects of exponential nutrient loading and springtime carbon loading during nursery culture on the field performance
of black spruce ( Picea mariana (Mill.) B.S.P.). Seedlings were grown from seed with a conventional, fixed dose fertilizer (10 mg N seedling −1) or an exponential nutrient loading regime (75 mg N seedling −1). The following spring, seedlings were exposed for two weeks to either ambient (370 ppm) or elevated levels of CO 2 (800 ppm) and then planted in the field; seedling growth was followed for the next six years. Exponential nutrient loading
increased seedling height, stem diameter and leader growth, with the largest increases in height and leader length occurring
in the first three years after outplanting. Carbon loading increased seedling height and leader length, but only in seedlings
that had been exponentially nutrient loaded. A combination of carbon and nutrient loading increased shoot height 26%, stem
diameter 37% and leader length 40% over trees that received neither treatment. These results demonstrate that the growth enhancement
seen under exponential nutrient loading is maintained under field conditions for at least six years. Carbon loading just before
outplanting was a useful supplement to nutrient loading, but was ineffective in the absence of nutrient loading. 相似文献
14.
Two-year-old seedlings of Pinus koraiensis, Pinus sylvestriformis and Fraxinus mandshurica were treated in open-top chambers with elevated CO 2 concentrations (700 μL·L −1, 500 μL·L −1) and ambient CO 2 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 CO 2 concentrations. The elevated CO 2 concentrations stimulated the net photosynthetic rates of three tree species except P. sylvestriformis grown under 500 μL·L −1 CO 2 concentration. The dark respiration rates of P. koraiensis and P. sylvestriformis increased under concentration of 700 μL·L −1 CO 2, out that of F. mandshurica decreased under both concentrations 700 μL·L −1 and 500 μL·L −1 CO 2. The seedlings of F. mandshurica decreased in chlorophyll contents at elevated CO 2 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 相似文献
15.
To predict the performance of coppice forests with Japanese oak ( Quercus mongolica var. crispula) in future changing environment, we studied the growth, photosynthesis, and powdery mildew ( Erysiphe alphitoides) infection of sprouts of Japanese oak under free-air CO 2 enrichment. Elevated CO 2 reduced powdery mildew infection in both leaves of the shoot emerged in spring (1st flush) and the lammas and proleptic shoots (2nd flush) of sprouts. We observed significant increase in the net photosynthetic rate at growth CO 2 concentration (i.e., 370 and 500 μmol mol ?1 for ambient and elevated CO 2 treatments, respectively) in both 1st and 2nd flush leaves of sprouts grown under elevated CO 2. On the other hand, no significant increase in net photosynthetic rate under elevated CO 2 was found before cutting. The photosynthetic activity of 2nd flush leaves in the sprouts under ambient condition was greatly reduced by severe infection to powdery mildew. Growth of sprouts was enhanced in the elevated CO 2 condition. We conclude the growth enhancement in Japanese oak sprouts under elevated CO 2 in the present study was achieved not only by physiological response (i.e., photosynthetic stimulation) but also by disease interaction. 相似文献
16.
One-year-old interior spruce (Picea glauca (Moench) Voss × Picea engelmannii Parry) spring-stock and summer-stock were grown under two phosphorus (P) fertility regimes, with (+P) or without (–P), followed by a simulated winter, and a second growing period under an adequate fertility regime in a controlled environment room. The two stock-types differed in their response to low P availability. For spring-stock, morphological development, phosphorus-use efficiency (PUE) and P specific absorption rate (SAR) were similar between –P and +P seedlings. For summer-stock, –P seedlings compared to +P seedlings had lower (p 0.05) morphological development, but greater PUE and SAR. For both stock-types, P content increased in +P seedlings, remained low in –P seedlings, and P concentration decreased in nursery-needles (i.e., formed in the nursery) of –P seedlings. The difference in stock-type response to low phosphorus availability (–P) was attributed to internal supply of P and it's retranslocation. Assimilation (A) of CO 2 in nursery-needles was similar between –P and +P seedlings for both stock-types. For spring-stock, +P seedlings had greater A in new-needles (i.e., needles formed during the trial) than –P seedlings. It was recommended that the spring-stock be selected over summer-stock for sites low in P availability. 相似文献
17.
Responses of soil microbial activities to elevated CO 2 in experiment sites of Pinus sylvestriformis and Pinus koraiensis seedlings were studied in summer in 2003. The results indicated the number of bacteria decreased significantly ( p<0.05) under elevated CO 2 for Pinus sylvestriformis and Pinus koraiensis. Amylase and invertase activities in soil increased for Pinus sylvestriformis and decreased for Pinus koraiensis with CO 2 enrichment compared with those at ambient (350 μmol·mol −1). The size of microbial biomass C also decreased significantly at 700 μmol·mol −1 CO 2. Bacterial community structure had some evident changes under elevated CO 2 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 CO 2 would be related to plant species exposed to elevated CO 2.
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 相似文献
18.
Abstract The aim of this study was to investigate the impacts of elevated carbon dioxide (CO 2) and temperature on the establishment, growth and mortality of the branches of Scots pine ( Pinus sylvestris L). In 1997, 16 young trees were individually enclosed in chambers, in eastern Finland, for a period of 5 years (1997–2001), in an environment that simulated the future climate for the region. There were four replicates of each treatment, including combinations of ambient and elevated CO 2 and temperature. Measurements were carried out on the establishment of new branches, branch diameter growth and branch mortality. Elevated temperature and elevated CO 2 had no positive effect on the number of branches that established each year or branch diameter growth. They were, instead, related to tree height growth and stem diameter growth, respectively. However, elevated CO 2 and temperature caused an increase in branch mortality. 相似文献
19.
When spring frosts occur on recently planted forest sites, severe damage may occur to the seedlings. The aim of the present study was to test how different low levels of nutrient concentrations in Norway spruce ( Picea abies (L.) Karst.) seedlings affected spring frost hardiness and time of bud break. Seedlings were grown in a greenhouse for one season and supplied with fertiliser containing 22, 43 and 72 mg N l –1, respectively. The treatments resulted in needle nitrogen concentrations ranging from 0.9 to 1.8% in autumn. After winter storage at 0 °C, bud break was recorded on seedlings growing in the greenhouse, outdoors and in growth chambers at 12 °C and at 17 °C. Freezing tests were performed on seedlings directly removed from winter storage and following one week growth in the greenhouse. Seedlings receiving fertiliser with 43 mg N l –1 had less freezing injury than the two other fertilisation treatments in the present study. The earliest bud break occurred in seedlings receiving 72 mg N l –1. 相似文献
20.
? This review considers potential effects of atmospheric change and climate warming within the timberline ecotone of the Central European Alps. After focusing on the impacts of ozone (O3) and rising atmospheric CO2 concentration, effects of climate warming on the carbon and water balance of timberline trees and forests will be outlined towards conclusions about changes in tree growth and treeline dynamics. ? Presently, ambient ground-level O3 concentrations do not exert crucial stress on adult conifers at the timberline of the Central European Alps. In response to elevated atmospheric CO2 Larix decidua showed growth increase, whereas no such response was found in Pinus uncinata. Overall climate warming appears as the factor responsible for the observed growth stimulation of timberline trees. ? Increased seedling re-establishment in the Central European Alps however, resulted from invasion into potential habitats rather than upward migration due to climate change, although seedlings will only reach tree size upon successful coupling with the atmosphere and thus loosing the beneficial microclimate of low stature vegetation. ? In conclusion, future climate extremes are more likely than the gradual temperature increase to control treeline dynamics in the Central European Alps. 相似文献
|