大气CO2浓度上升对植物地下竞争的影响

植物地下竞争是影响农业生态系统和自然生态系统中植物群落结构变化的重要因素,而大气CO2浓度升高直接或间接影响了植物的生长及其地下环境,可能需重新评估植物地下竞争的状况。本文从大气CO2浓度升高对植物根系形态结构、生理吸收能力、根系共生真菌、叶片蒸腾速率的影响以及对地下竞争因子的土壤环境方面的影响,探讨未来CO2浓度升高条件下地下竞争的变化。     

CO2浓度升高对三江平原湿地土壤碳氮含量的影响

利用开顶箱薰气室(open-top chamber,OTC),设置正常大气CO2浓度(ambient CO2)和高CO2浓度(elevated CO2,700μmol/mol)2个水平和不施氮(NN,0g/m2),常氮(MN,5g/m2)和高氮(HN,15g/m2)3个氮素水平,研究了CO2浓度升高对三江平原草甸小叶章湿地(Calamagrostis angustifolia)土壤碳氮含量的影响。结果表明,CO2浓度升高连续运行两个生长季后,湿地土壤总有机碳含量没有显著变化,不同N处理增加了0.5%～1.8%。CO2浓度升高,土壤总氮含量总体呈下降趋势。就各生长期平均值而言,CO2浓度升高使土壤NH4+—N的含量分别降低了8.2%(NN),8.9%(MN)和9.7%(HN)。CO2浓度升高使不同N处理的土壤NO3-—N含量也呈降低趋势,其中高氮水平(HN)降低最多,降幅为9.6%。土壤有效态氮是控制植物对高CO2浓度响应的关键因素。     

大气CO2浓度升高对植物根系形态的影响及其调控机理

大气CO2浓度升高会对植物根系形态产生明显的影响,尤其是根的长度、分枝、产量、周转以及根与枝的分配模式等方面,从而有助于植物从土壤中摄取更多的养分及水分,更好地适应大气CO2浓度升高后的环境。目前,该领域研究,如在CO2浓度升高条件下,根系形态变化的内部调控机制,以及由其引起的物质分配和能量流动等仍存在较大争议。本文综述了近年来关于CO2浓度升高及与外界环境因素的共同作用对根系形态影响的研究,以期为阐明CO2浓度升高对植物根系生长发育带来的影响及其机制提供理论指导。     

大气CO2浓度升高对温带森林土壤微生物活性的影响

Microorganisms play a key role in the response of soil ecosystems to the rising atmospheric carbon dioxide (CO2) as they mineralize organic matter and drive nutrient cycling. To assess the effects of elevated CO2 on soil microbial C and N immobilization and on soil enzyme activities, in years 8 (2006) and 9 (2007) of an open-top chamber experiment that begun in spring of 1999, soil was sampled in summer, and microbial biomass and enzyme activity related to the carbon (C), nitrogen (N) and phosphorus (P) cycling were measured. Although no effects on microbial biomass C were detected, changes in microbial biomass N and metabolic activity involving C, N and P were observed under elevated CO2. Invertase and dehydrogenase activities were significantly enhanced by different degrees of elevated CO2. Nitrifying enzyme activity was significantly (P < 0.01) increased in the August 2006 samples that received the elevated CO2 treatment, as compared to the samples that received the ambient treatment. Denitrifying enzyme activity was significantly (P < 0.04) decreased by elevated CO2 treatments in the August 2006 and June 2007 (P < 0.09) samples. β-N-acetylglucosaminidase activity was increased under elevated CO2 by 7% and 25% in June and August 2006, respectively, compared to those under ambient CO2. The results of June 2006 samples showed that acid phosphatase activity was significantly enhanced under elevated CO2. Overall, these results suggested that elevated CO2 might cause changes in the belowground C, N and P cycling in temperate forest soils.     

大气CO2浓度升高对谷子生长发育及玉米螟发生的影响

人类活动导致全球大气CO_2浓度持续升高,研究大气CO_2浓度升高对C4作物谷子(Setaria italica)生长发育及虫害发生的影响,可以为谷子等C4作物制订应对气候变化栽培措施提供理论依据。本研究利用OTC(Open Top Chamber)系统,设两个CO_2浓度梯度(正常大气CO_2浓度、正常CO_2浓度+200μmol·mol-1)模拟CO_2浓度升高对谷子生长发育的影响。结果表明:大气CO_2浓度升高后,谷子净光合速率(Pn)、气孔导度(gs)、叶片蒸腾速率(Tr)和水分利用率(WUE)分别增加38.73%、27.53%、6.93%和40.56%;谷子叶片光系统Ⅱ最大光化学量子产量(Fv/Fm)和非光化学淬灭系数(NPQ)显著下降,光系统Ⅱ实际光化学量子产量(ΦPSII)和表观电子传递效率(ETR)显著增加,而对光化学淬灭系数(q P)无显著影响;此外,谷子株高、茎粗和小穗数分别增加3.41%、13.28%和13.11%;而叶重、茎重、千粒重、单株粒数和产量无显著变化,穗重和地上部分生物量分别显著下降12.8%和7.44%;大气CO_2浓度升高后,谷子灌浆期和收获期玉米螟(Ostrinia furnacalis)发生数量显著增加。大气CO_2浓度升高将有利于谷子的生长发育,但会增加玉米螟危害。     

土壤酶活性对温度和CO2浓度升高的响应研究

作为土壤生态系统中的重要组成部分及生物元素循环的积极参与者,土壤酶在陆地生态系统地下生态过程中扮演着十分重要的角色。升高温度和(或)大气CO2浓度可能直接或者间接影响其活性。但目前对温度和(或)大气CO2浓度升高对土壤酶的影响机理、过程及土壤酶对其的响应机制研究相对薄弱。本文初步总结了国内外关于温度和(或)大气CO2浓度升高对土壤酶活性影响研究的现状,并指出了目前研究中存在的不足。     

CO2浓度升高对三江平原湿地小叶章碳氮含量的影响

利用开顶箱薰气室(open-top chamber),设置正常大气CO2浓度和高CO2浓度(700 μmol/mol)2个水平和不施氮(NN,0 g/m2)、常氮(MN,5 g/m2)和高氮(HN,15 g/m2)3个氮素水平,研究CO2浓度升高对三江平原草甸小叶章碳氮积累的影响.结果表明,CO2浓度升高条件下小叶章植株总固碳量增加,不同氮水平下小叶章总固碳量分别增加19.3％(NN),24.4％(MN)和24.6％(HN),且根固定碳量占植株总体碳库比例均有不同程度的提高.CO2浓度升高降低了小叶章各器官氮含量,其中叶、茎氮含量以抽穗期降幅最大(14.4％和19.5％),根氮含量以腊熟期降幅最大(17.4％).小叶章各器官N含量的降低是由于CO2浓度升高条件下植株生长加快引起的稀释效应所致.     

稻田CH4和N2O排放对大气CO2浓度升高响应的研究进展

大气CO₂浓度升高是全球气候变化的主要驱动力,可直接或间接影响陆地生态系统碳氮循环。阐明稻田生态系统CH₄和N₂O排放对大气CO₂浓度升高的响应及其机制,是农业生产应对全球气候变化的重要组成部分。本文综述了国内外不同大气CO₂浓度升高模拟技术平台条件下稻田CH₄和N₂O排放的响应规律,进一步讨论分析了大气CO₂浓度升高影响CH₄和N₂O排放的相关机制,并展望了今后稻田CH₄和N₂O排放对大气CO₂浓度升高响应的主要研究方向,以期为应对全球气候变化提供理论依据和技术支撑。     

大气CO2和O3浓度升高对水稻'汕优63'叶片光合作用的影响

大气CO2浓度升高使水稻光合作用增强,而地表O3浓度增加则相反,但人们对大气CO2和O3浓度同时升高情景下水稻光合作用的响应和适应知之甚少。本文利用新型的自然光气体熏蒸平台,以杂交籼稻‘汕优63’为供试材料,设置室内对照(CK,大气本底浓度,实时模拟室外环境)、高浓度CO2(CO2本底浓度+200μmol·mol-1)、高浓度O3(O3本底浓度的1.6倍)、高浓度CO2+O3 4个处理,于拔节期、抽穗期和灌浆期测定稻叶的主要光合参数。整个布气期间,CO2和O3浓度平均的控制目标完成比(TAR)分别为1.04和1.00。与CK相比,CO2处理使拔节、抽穗和灌浆期净光合速率(Pn)分别增加15%、11%和28%,O3处理使对应生育期Pn分别降低32%、32%和88%,CO2+O3处理对拔节期和抽穗期Pn无显著影响,但成熟期Pn平均下降48%。CO2处理使拔节和抽穗期叶片气孔导度(Gs)和蒸腾速率(Tr)显著下降,但灌浆期无显著变化;O3处理对各期Gs和Tr的影响明显大于CO2处理,且以灌浆期的降幅最大;CO2+O3处理叶片Gs和Tr的降幅总体上明显低于单独的O3处理。CO2处理或CO2+O3处理叶片胞间CO2浓度(Ci)明显增加,而O3处理叶片Ci的变化相对较小。CO2处理使各期水分利用效率(WUE)增加,而O3处理则呈相反趋势,特别是生长后期。CO2+O3处理叶片拔节期和抽穗期WUE平均增加约15%,但灌浆期因O3的累积伤害,WUE不升反降。以上结果表明,大气CO2浓度升高将使杂交稻‘汕优63’叶片光合能力增强,但地表同步升高的O3浓度则使光合能力削弱并表现出明显的累积伤害,大气CO2和O3浓度同时升高可缓解O3胁迫对‘汕优63’光合作用的负效应。     

大气CO2浓度升高对植物 土壤系统地下过程影响的研究

综述了大气CO2浓度升高对根系、根际、根系分泌物、土壤呼吸和土壤物质转化和C、N循环影响的研究进展,阐述了有关实验的研究情况,以及它们在整个生态系统响应大气CO2浓度升高中的重要作用、目前研究中存在的争论、以及还需要研究的领域和方向及其研究的重要性。     

Seasonality of soil biological properties in a poplar plantation growing under elevated atmospheric CO2

Microorganisms are the regulators of decomposition processes occurring in soil, they also constitute a labile fraction of potentially available N. Microbial mineralization and nutrient cycling could be affected through altered plant inputs at elevated CO_2. An understanding of microbial biomass and microbial activity in response to belowground processes induced by elevated CO₂ is thus crucial in order to predict the long-term response of ecosystems to climatic changes. Microbial biomass, microbial respiration, inorganic N, extractable P and six enzymatic activities related to C, N, P and S cycling (β-glucosidase, cellulase, chitinase, protease, acid phosphatase and arylsulphatase) were investigated in soils of a poplar plantation exposed to elevated CO_2. Clones of Populus alba, Populus nigra and Populus x euramericana were grown in six 314 m² plots treated either with atmospheric (control) or enriched (550 μmol mol⁻¹ CO₂) CO₂ concentration with FACE technology (free-air CO₂ enrichment). Chemical and biochemical parameters were monitored throughout a year in soil samples collected at five sampling dates starting from Autumn 2000 to Autumn 2001.

The aim of the present work was: (1) to determine if CO₂ enrichment induces modifications to soil microbial pool size and metabolism, (2) to test how the seasonal fluctuations of soil biochemical properties and CO₂ level interact, (3) to evaluate if microbial nutrient acquisition activity is changed under elevated CO₂.

CO₂ enrichment significantly affected soil nutrient content and three enzyme activities: acid phosphatase, chitinase and arylsulphatase, indicators of nutrient acquisition activity. Microbial biomass increased by a 16% under elevated CO₂. All soil biochemical properties were significantly affected by the temporal variability and the interaction between time and CO₂ level significantly influenced β-glucosidase activity and microbial respiration. Data on arylsulphatase and chitinase activity suggest a possible shift of microbial population in favour of fungi induced by the FACE treatment.     

年际环境温度变化驱动水稻产量及其构成对CO2浓度和温度升高的响应差异

大气CO₂浓度([CO₂])和温度升高是未来气候变化的主要情境，阐明水稻产量及其构成对[CO₂]和温度升高的响应，是助力农业生产应对气候变化的重要组成部分。本文基于开放式[CO₂]和温度升高(elevated temperature and CO₂-free air controlled enrichment,T-FACE)试验平台的多年水稻生产数据，探讨了未来[CO₂]和温度升高对水稻产量和产量构成的影响。结果表明：与对照(CT)相比，高[CO₂](C+T)处理提高了水稻有效穗数和结实率，使水稻增产11.1%左右(5年平均)；增温(CT+)1～2℃减少了有效穗数和穗粒数，使水稻产量下降10%～25%；高[CO₂]和增温互作(C+T+)处理使水稻产量下降约10%，即高[CO₂]并未完全抵消温度升高带来的负效应。多年试验数据比较发现，相同处理对产量的影响趋势较为一致，但年际差异明显。随着年际生...     

CO2浓度与氮磷供应水平对黄瓜根系生长及各组织矿质养分含量的影响

在开顶式生长箱内，以黄瓜为试验材料，采用营养液培养方法，研究了不同氮水平、磷水平条件下大气CO2浓度对黄瓜植株内矿质养分含量以及根系形态的影响。结果表明：黄瓜植株各部位氮素含量随供氮水平提高而增加，磷水平提高，也能促进各部位氮含量的提高。植株各部位磷含量随供磷水平的提高而升高，在相同磷水平下，缺氮会使各部位磷含量升高。大气CO2浓度升高会使黄瓜植株各部位氮及特定部位的磷含量降低。黄瓜根部的Ca含量随CO2浓度的升高而显著降低，氮和磷水平的升高极显著地增加了其含量，且CO2浓度与供磷水平、供氮与供磷水平以及这三者之间存在明显的交互作用。供氮、供磷水平的升高极显著的提高了黄瓜叶片Ca的含量以及茎部Mg的含量，且两者存在明显的交互作用。黄瓜总根长和总根表面积随CO2浓度的增加有增大的趋势；在缺磷条件下，总根长和总根表面积随氮水平的提高而增大；而同一氮水平和CO2浓度下，磷水平的降低会增加总根长和总根表面积。总体看来，大气CO2浓度的升高能促进黄瓜根系的生长，但会使得黄瓜植株某些部位氮、磷、钙、镁等矿质元素含量降低，而供氮、供磷水平的提高可以通过增强黄瓜的生长与活力促进黄瓜根系对矿质养分的吸收，从而缓解由于CO2浓度升高带来的矿质元素含量降低的风险。这启示我们在对设施蔬菜CO2施肥的同时，也要注重适量提高合理配比下矿质元素的供应。     

温度和湿度对高寒湿地土壤碳矿化和氮矿化的影响

Relationships between carbon (C) production and nitrogen (N) mineralization were investigated in two alpine wetland soils of the Tibetan Plateau using laboratory incubation under different temperatures (5, 15, 25, and 35 ℃) and water saturation (noninundation and inundation). A significant positive relationship was found between CO2 production and N mineralization under increasing temperatures from 5 to 35 ℃ with the same water saturation condition in the marsh soil (r2 ＞ 0.49, P ＜ 0.0001) and the peat soil (r2 ＞ 0.38, P ＜ 0.002), and a negative relationship with water saturation increasing at the same temperature, especially 25 and 35 ℃, in the marsh soil (r2 ＞ 0.70, P ＜ 0.009) and the peat soil (r2 ＞ 0.61, P ＜ 0.013). In conclusion, temperatures and water saturation could regulate the relationship between CO2 production and net N mineralization in the Tibetan alpine marsh and peat soils.     

Effects of elevated CO2 concentration on rhizodeposition from Lolium perenne grown on soil exposed to 9 years of CO2 enrichment

The effects of enriched CO₂ atmosphere on partitioning of recently assimilated carbon were investigated in a plant-soil-microorganism system in which Lolium perenne seedlings were planted into cores inserted into the resident soil within a sward that had been treated with elevated CO₂ for 9 consecutive years, under two N fertilisation levels (Swiss FACE experiment). The planted cores were excavated from the ambient (35 Pa pCO₂) and enriched (60 Pa pCO₂) rings at two dates, in spring and autumn, during the growing season. The cores were brought back to the laboratory for ¹⁴C labelling of shoots in order to trace the transfer of recently assimilated C both within the plant and to the soil and microbial biomass. At the spring sampling, high N supply stimulated shoot and total dry matter production. Consistently, high N enhanced the allocation of recently fixed C to shoots, and reduced it to belowground compartments. Elevated CO₂ had no consequences for DM or the pattern of C allocation. At the autumn sampling, at high N plot, yield of L. perenne was stimulated by elevated CO₂. Consistently, ¹⁴C was preferentially allocated aboveground and, consequently belowground recent C allocation was depressed and rhizodeposition reduced. At both experimental periods, total soil C content was similar in all treatments, providing no evidence for soil carbon sequestration in the Swiss Free Air CO₂ Enrichment experiment (FACE) after 9 years of enrichment. Recently assimilated C and soil C were mineralised faster in soils from enriched rings, suggesting a CO₂-induced shift in the microbial biomass characteristics (structure, diversity, activity) and/or in the quality of the root-released organic compounds.     

CO2浓度升高对小麦秸秆性质、数量及其分解的影响

在江都FACE平台上观测了常N水平下大气CO2浓度升高对小麦秸秆数量和性质的影响,并利用稻季淹水培养试验研究了CO2浓度升高引起的小麦秸秆量和质的改变对其腐解和土壤微生物量碳的影响,结果表明:CO2浓度升高显著降低了麦秸中N含量,导致麦秸C/N和木质素/N比显著增加,但对麦秸其他生化组成——可溶物、半纤维素、纤维素、木质素和酚含量均无影响;CO2浓度升高引起的小麦秸秆性质改变对麦秸及其含C物质的分解均无显著影响,但显著减缓了含N物质的分解;若将收获的麦秸全部还田,CO2浓度升高引起的小麦秸秆量的增加也没有显著影响麦秸及其含C、N物质的分解。由于高CO2浓度导致的麦秸性质改变对土壤微生物量碳无显著影响,这也是CO2浓度升高引起麦秸性质变化幅度太小不足以影响麦秸及其含C物质分解的主要原因。     

大气CO2浓度升高和温升对水稻纹枯病侵染后的相关蛋白和防御酶的影响

纹枯病（sheath blight）作为一种土传病害,其发生和发展严重威胁到水稻（Oryza sativa L.）的生产。目前,大气CO2浓度（[CO2]）和温度升高如何影响感病植株内病程相关蛋白（pathogenesis related proteins, PR蛋白）和防御酶尚不清楚。本研究以纹枯病易感品种（Lemont）和抗性品种（YSBR1）为实验材料,利用田间开放式自由大气[CO2]和温度升高（T-FACE）平台设置四个处理：对照、[CO2]升高（[CO2]升高至590 μmol·mol-1）、温升（冠层温度升高2 ℃）及[CO2]升高和温升交互,通过人工接种R. solani,探究不同抗性品种叶片和茎鞘PR蛋白与防御酶活性,以及土壤基本理化性状的响应。研究结果表明：高[CO2]和温升下耕作土制成的土壤浸提液培养基中R. solani生长速率无显著差异,接种R. solani后病斑发展速率与土壤基本理化性状无关。水稻植株感病后,两个品种叶片和茎鞘中PR蛋白和相关防御酶表现出明显差异,且在高[CO2]和温升条件下,该差异进一步增大。对于茎鞘中的PR蛋白和防御酶,高[CO2]和温升交互处理明显增加Lemont和YSBR1茎鞘中过氧化氢酶（CAT）、苯丙氨酸解氨酶（PAL）、β-1,3-葡聚糖酶（GLU）和超氧化物歧化酶（SOD）活性。对于两个水稻品种,当R. solani入侵后,在各处理下,YSBR1叶片中PR蛋白和相关防御酶以及茎鞘中SOD和CAT活性均显著高于Lemont,且YSBR1病斑发展速率显著低于Lemont。在整个发病过程中,温升处理及其与高[CO2]互作处理均显著增加易感品种Lemont的病斑发展速率（增加了21% ~ 45%）,而对抗性品种YSBR1的病斑发展速率无显著影响。相关性分析结果表明,各处理下Lemont和YSBR1植株纹枯病病斑的发展速率均与其茎鞘中GLU活性存在显著正相关。因而,在R. solani侵染后,抗病品种中较高的PR蛋白和防御酶活形成的防卫反应,能够有效减轻未来高[CO2]和温升条件对纹枯病病斑发展速度的影响。研究结果对选育纹枯病抗性品种来适应未来气候变化背景下的水稻生产提供重要的借鉴意义。     

Crop rotation and nitrogen fertilization effect on soil CO2 emissions in central Iowa

Depending upon how soil is managed, it can serve as a source or sink for atmospheric carbon dioxide (CO₂). As the atmospheric CO₂ concentration continues to increase, more attention is being focused on the soil as a possible sink for atmospheric CO₂. This study was conducted to examine the short-term effects of crop rotation and N fertilization on soil CO₂ emissions in Central Iowa. Soil CO₂ emissions were measured during the growing seasons of 2003 and 2004 from plots fertilized with three N rates (0, 135, and 270 kg N ha⁻¹) in continuous corn and a corn–soybean rotation in a split-plot design. Soil samples were collected in the spring of 2004 from the 0–15 cm soil depth to determine soil organic C content. Crop residue input was estimated using a harvest index based on the measured crop yield. The results show that increasing N fertilization generally decreased soil CO₂ emissions and the continuous corn cropping system had higher soil CO₂ emissions than the corn–soybean rotation. Soil CO₂ emission rate at the peak time during the growing season and cumulative CO₂ under continuous corn increased by 24 and 18%, respectively compared to that from corn–soybean rotation. During this period, the soil fertilized with 270 kg N ha⁻¹ emitted, on average, 23% less CO₂ than the soil fertilized with the other two N rates. The greatest difference in CO₂ emission rate was observed in 2004; where plots that received 0 N rate had 31% greater CO₂ emission rate than plots fertilized with 270 kg N ha⁻¹. The findings of this research indicate that changes in cropping systems can have immediate impact on both rate and cumulative soil CO₂ emissions, where continuous corn caused greater soil CO₂ emissions than corn soybean rotation.