大气中O3与CO2浓度升高对植物影响研究进展

由于工业的快速发展,大气中的O₃和CO₂浓度有逐年上升的趋势,对植物产生了很大的影响。目前,植物对O₃和CO₂浓度变化的复合作用的响应机制研究已经成为生态学研究的热点问题。文中阐述了O₃和CO₂浓度升高及其复合作用对植物的形态特征、光合作用、抗氧化系统及生物量等生理生化机制的影响,指出目前研究中存在并有待进一步研究的问题,以期为进一步开展高浓度O₃和CO₂对植物生理生态学影响研究提供科学参考和理论依据。     

植物对气候变化生理响应研究进展

自工业革命以来, 人类活动尤其是发达国家在工业化过程中消耗大量资源、能源, 造成大气中温室气体浓度增加, 引起全球范围内的气候变化, 给人类的生存和发展带来严峻挑战, 也对植物的生理过程产生了影响。关于CO₂浓度升高及其与气候因子和环境胁迫因子对植物生理过程的影响已引起各国科学家广泛关注。文中就近年来气候变化对植物生理过程的影响国内外研究进行归类和分析, 介绍了植物对CO₂、温度、水分等因素变化的响应过程研究进展, 并提出对进一步研究的展望。     

稳定碳同位素在森林植物水分利用效率研究中的应用

介绍了植物水分利用效率与稳定碳同位素的相关性,以及影响植物碳同位素丰度值δ13C的主要因子,重点分析几种重要环境因子对林木δ13C的影响,表明降雨量、土壤水分状况、温度、光照和CO₂浓度等因素都会在不同程度上影响植物叶片气孔导度和CO₂的固定,导致植物δ13C发生变化;并从森林抚育间伐措施对δ13C的影响,水分胁迫条件下δ13C的变化,以及δ13C的替代测定方法等方面提出了研究展望。     

森林生态系统碳储量及碳通量遥感监测研究进展

在全球CO₂浓度持续增加导致气候变暖的背景下,森林生态系统碳储量及碳通量遥感大尺度监测成为关注热点。文中深入分析了当前国内外卫星遥感观测技术对森林碳循环评估的2种途径:1）基于遥感手段估算森林生物量并推算森林碳储量,通过碳储量变化确定森林生态系统的CO₂通量。归纳各类森林生物量遥感估算方法的原理及优缺点,系统评述各类方法在大区域森林碳储量估算中存在的不确定性。2）基于CO₂温室气体观测卫星遥感数据,定量监测森林生态系统与大气CO₂通量,基于交换的CO₂通量推算森林碳储量变化。归纳遥感手段观测森林生态系统与大气CO₂通量的主要数据、方法及优缺点,系统评述各类数据及方法在森林CO₂通量时空变化特征监测、森林碳储量估算等方面取得的进展,重点分析专用CO₂浓度监测卫星数据,尤其是我国自主碳卫星数据在CO₂柱浓度反演算法研究以及不同数据源之间的对比、验证和同化研究等方面取得的进展,总结专用温室气体遥感观测数据在森林碳储量及碳通量监测方面的优势。提出利用遥感手段进行森林生态系统碳循环定量监测的研究展望。     

全球[CO2]变化与植物水分关系

业已发现增加环境[CO₂]可以改善大多数植物的水分胁迫。许多研究结果表明,较低的蒸腾速率（Tr）与[CO₂]增加导致气孔关闭有关。由于[CO₂]增加引起蒸腾速率的下降和净光合速率（Pn）的提高,因此,生长在高于环境[CO₂]下的植物常常能够保持较高的水分利用效率（WUE）.也发现生长在高于环境[CO₂]下的植物能够保持较高的总水势（Ψ）,增加叶面积和生物量,有较大的根/茎比率（R/S）,因而通常比生长在正常环境[CO₂]下的植物更耐干旱。[CO₂]增加诱导产生的植物结构的变化（比如导管或管胞的解剖结构、叶比导度等）,可能与木质部空穴脆弱性的变化有关,也可能与栓塞逃逸的环境条件相联系。这些重要的问题需要进一步的研究。     

群众杨幼苗叶光合特性与碳氮分配对CO2浓度和气温升高的响应

【目的】研究杨树光合作用和碳氮分配对CO₂浓度和温度升高的响应，探讨气候变化下杨树的生理生态适应机制，以期为我国北方杨树人工林生产力和生态效益的长期提升提供理论依据。【方法】以盆栽群众杨当年生扦插幼苗为试验材料，在开顶式生长室内模拟研究了空气CO₂浓度和气温升高(分别比室外大气升高200μmol mol^-1和2℃)及其共同作用下的功能叶光合特性、叶解剖结构、器官间干物质和碳氮分配的响应，并探讨了苗期群众杨对CO₂浓度和气温升高的生理生态响应。【结果】1)在CO₂浓度升高处理下，群众杨叶片气孔密度降低，蒸腾速率减弱，瞬时水分利用效率显著提高；光合潜力和氮利用效率增加，并通过叶肉组织增厚、叶和根碳氮比增加、比叶重增大以及根冠比增加等途径维持单位叶面积氮含量、瞬时光合特性和叶绿素荧光特性不变，而单位质量暗呼吸速率降低，并使单株总干质量和总碳量显著增加。2)增温2℃下的群众杨叶气孔密度显著增加，但瞬时气体交换和荧光参数、光合特性变化不显著，株高和单株总氮量略低，器官间的干物质和碳氮分配...     

兴安落叶松生态系统CO2浓度及其δ13C动态对环境因子的响应

【目的】探明环境因子对兴安落叶松原始林生态系统CO₂浓度及其δ¹³C动态的影响,深入理解生态系统的碳交换过程,为模拟和预测全球变化与生态系统之间的互馈机制以及科学评估寒温带森林生态系统碳汇能力提供参考。【方法】采用离轴积分腔输出光谱技术对兴安落叶松生态系统不同物候期、不同高度的CO₂浓度及其δ¹³C进行连续高频观测,并分析环境因子与CO₂浓度变化的关系。【结果】1)兴安落叶松生态系统不同高度的CO₂浓度在生长季和日尺度上均呈单峰变化,峰值分别出现在展叶期(522.34μmol·mol^-1)和凌晨(782.81μmol·mol^-1),谷值分别出现在落叶期(406.07μmol·mol^-1)和中午(379.72μmol·mol^-1);δ¹³C变化趋势与CO₂浓度相反;2)CO₂浓度随垂直高度升高而减小,δ     

花叶假连翘3种叶色表型叶片的光合特性

以植物嵌合体花叶假连翘全绿叶、花叶、全白叶3种叶色表型叶片为试验材料,测定并比较了其光合色素含量、叶片解剖结构、光响应曲线和CO₂响应曲线,研究不同叶色表型叶片光合特性的差异,分析光照强度对叶片叶色表型变化的影响。结果表明:花叶假连翘3种叶色表型叶片的叶绿素a、叶绿素b、叶绿素a+b和类胡萝卜素含量差异显著,均表现为全绿叶>花叶>全白叶。叶片细胞层间叶绿体分布不均,是导致不同叶色表型叶片叶绿素含量和叶色存在差异的原因。全绿叶的最大净光合速率(Pn,max)、暗呼吸速率(Rd)和初始量子效率显著高于花叶;花叶的光补偿点(LCP)和光饱和点(LSP)显著高于全绿叶;全绿叶的光合能力(Amax)、光呼吸速率(Rp)和初始羧化效率(CE)显著高于花叶;花叶的CO₂补偿点(CCP)和CO₂饱和点(CSP)显著高于全绿叶。3种叶色表型叶片的气孔导度(Gs)、蒸腾速率(Tr)和水分利用效率(WUE)表现为全绿叶>花叶>全白叶,全绿叶和花叶的气孔导度、蒸腾速率和水分利用效率随着光合有效辐射(PAR)的增大而升高,到达最大值后趋于平缓,而全白叶变化不大;胞间CO₂浓度(Ci)表现为全白叶>花叶>全绿叶,全绿叶和花叶的胞间CO₂浓度随着光合有效辐射的增大呈现下降的趋势,而全白叶变化不大。3种叶色表型叶片的光合特性与叶绿素含量显著相关,全绿叶利用弱光的能力较强,而花叶利用强光的能力较强,因此,可将花叶假连翘栽种于光照强度较大的环境中,以此来保持花叶性状和诱导形成更多的花叶表型。     

氮沉降对凋落物分解的影响研究进展

过去几十年的人类活动增加了陆地生态系统的氮输入量,对凋落物分解的影响有促进、抑制和没有影响3种情况。凋落物的基质质量影响凋落物的分解,其中木质素、纤维素、酚类物质、N浓度、P浓度、C/N比、C/P比、木质素/N比具有重要作用。人类活动引起的全球变化,如CO₂增加、温度上升和降水变化,影响了氮沉降的速率和凋落物分解。未来氮沉降对凋落物分解的研究热点包括加强氮沉降对热带与亚热带森林凋落物和阔叶树种凋落物分解影响的研究,氮沉降对凋落物分解影响研究的长期化,采用13C同位素研究凋落物分解,注重凋落物分解对氮沉降与大气CO₂浓度升高、气候变暖、降水变化、紫外线辐射增强、P沉降交互作用响应的研究。     

CO2浓度增加对挪威云杉与赤松栎叶中P、Ca、K、Mg含量的影响

上个世纪以来,随着工业的发展,大气环境的污染越来越严重,致使大气中的CO₂浓度不断增加,估计这种增加的趋势还将继续.     

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.     

Separating effects of changes in atmospheric composition,climate and land-use on carbon sequestration of U.S. Mid-Atlantic temperate forests

Terrestrial carbon dynamics have been vastly modified because of changes in atmospheric composition, climate, and land-use. However, few studies provide a complete analysis of the factors and interactions that affect carbon dynamics over a large landscape. This study examines how changes in atmospheric composition (CO₂, O₃ and N deposition), climate and land-use affected carbon dynamics and sequestration in Mid-Atlantic temperate forests during the 20th century. We modified and applied the PnET-CN model, a well established process-based ecosystem model with a strong foundation of ecosystem knowledge from experimental studies. We validated the model results using the U.S. Forest Inventory and Analysis (FIA) data. Our results suggest that chronic changes in atmospheric chemistry over the past century markedly affected carbon dynamics and sequestration in Mid-Atlantic temperate forests, while climate change only had a minor impact although inter-annual climatic variability had a far more substantial effect. The NPP response to a century of chronic change in atmospheric composition at the regional scale was an increase of 29%, of which, 14% was from elevated CO₂, 17% from N deposition, 6% from the interaction between CO₂ and N deposition, and minus 8% from tropospheric ozone. Climate change increased NPP by only 4%. Disturbed forests had 6% lower NPP than undisturbed forests after seven decades. Regrowing forests after harvesting and natural disturbances had much greater capacity for sequestering carbon than undisturbed old-growth forests even though the newer forests had slightly lower net primary production (NPP). The modeling results indicated that N deposition was a stronger force than elevated CO₂ for increasing NPP and fast turnover tissues, while elevated CO₂ favored more sustainable carbon storage and sequestration. The model results are consistent with various experiments and observations and demonstrate a powerful approach to integrate and expand our knowledge of complex interactive effects of multiple environmental changes on forest carbon dynamics.     

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.     

Photosynthetic traits and growth of Quercus mongolica var. crispula sprouts attacked by powdery mildew under free-air CO2 enrichment

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 CO₂ enrichment. Elevated CO₂ 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 CO₂ concentration (i.e., 370 and 500 μmol mol^?1 for ambient and elevated CO₂ treatments, respectively) in both 1st and 2nd flush leaves of sprouts grown under elevated CO₂. On the other hand, no significant increase in net photosynthetic rate under elevated CO₂ 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 CO₂ condition. We conclude the growth enhancement in Japanese oak sprouts under elevated CO₂ in the present study was achieved not only by physiological response (i.e., photosynthetic stimulation) but also by disease interaction.     

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.     

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     

Effects of long-term elevated CO<Subscript>2</Subscript> on N<Subscript>2</Subscript>-fixing,denitrifying and nitrifying enzyme activities in forest soils under <Emphasis Type="Italic">Pinus sylvestriformis</Emphasis> in Changbai Mountain

A study was conducted to determine the effects of elevated CO₂ on soil N process at Changbai Mountain in Jilin Province, northeastern China (42°24′N, 128°06′E, and 738 m elevation). A randomized complete block design of ambient and elevated CO₂ was established in an open-top chamber facility in the spring of 1999. Changpai Scotch pine (Pinus sylvestris var. sylvestriformis seeds were sowed in May, 1999 and CO₂ fumigation treatments began after seeds germination. In each year, the exposure started at the end of April and stopped at the end of October. Soil samples were collected in June and August 2006 and in June 2007, and soil nitrifying, denitrifying and N₂-fixing enzyme activities were measured. Results show that soil nitrifying enzyme activities (NEA) in the 5–10 cm soil layer were significantly increased at elevated CO₂ by 30.3% in June 2006, by 30.9% in August 2006 and by 11.3% in June 2007. Soil denitrifying enzyme activities (DEA) were significantly decreased by elevated CO₂ treatment in June 2006 (P < 0.012) and August 2006 (P < 0.005) samplings in our study; no significant difference was detected in June 2007, and no significant changes in N₂-fixing enzyme activity were found. This study suggests that elevated CO₂ can alter soil nitrifying enzyme and denitrifying enzyme activities. Foundation project: This research was supported by the National Natural Science Foundation of China (No. 90411020) and Major State Basic Research Development Program of China (973 Program) (2002CB412502).     

Impacts of long-term elevation of atmospheric carbon dioxide concentration and temperature on the establishment,growth and mortality of boreal Scots pine branches

Abstract

The aim of this study was to investigate the impacts of elevated carbon dioxide (CO₂) 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 CO₂ and temperature. Measurements were carried out on the establishment of new branches, branch diameter growth and branch mortality. Elevated temperature and elevated CO₂ 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 CO₂ and temperature caused an increase in branch mortality.     

Effect of elevated ambient CO2 concentration on water use efficiency ofPinus sylvestriformis

Pinus sylvestriformis is an important species as an indicator of global climate changes in Changbai Mountain, China. The water use efficiency (WUE) of this species (11-year old) was studied on response to elevated CO₂ concentration at 500±100 μL·L⁻¹ by directly injecting CO₂ into the canopy under natural condition in 1998–1999. The results showed that the elevated CO₂ concentration reduced averagely stomatal opening, stomatal conductance and stomatal density to 78%, 80% and 87% respectively, as compared to normal ambient. The elevated CO₂ reduced the transpiration and enhances the water use efficiency (WUE) of plant. The project was supported by Chinese Academy of Sciences Responsible editor: Chai Ruihai     

Ten-year exposure to elevated CO2 increases stomatal number of Pinus koraiensis and P. sylvestriformis needles

Stomatal number and stomatal conductance are important structural and functional parameters for the assessment of carbon assimilation and water use under elevated CO₂. We studied stomatal density, number of stomatal rows and stomatal conductance of Pinus sylvestriformis and P. koraiensis needles exposed to elevated CO₂ (500 μmol mol^?1 CO₂) in open-top chambers for 10 years (1999–2009). Elevated CO₂ increased stomatal density on P. sylvestriformis by 10.8 % (13.5 % on abaxial surface and 8.0 % on adaxial surface) and the number of stomatal rows on P. koraiensis by 7.9 % (5.0 % in 1-year-old needles and 10.7 % in current-year needles). Increased stomatal density for P. sylvestriformis and number of stomatal rows for P. koraiensis indicate that elevated CO₂ increases stomatal number in both tree species. Needle age significantly influenced stomatal density and number of stomatal rows in P. koraiensis but not in P. sylvestriformis. For both species, elevated CO₂ did not significantly affect stomatal conductance but increased water use efficiency. The increase in stomatal number is not accompanied by significant changes in stomatal conductance at elevated CO₂ for both tree species suggesting that there may be no direct relationship between stomatal conductance and stomatal numbers.