UV-B增强下施硅对稻田CH4和N2O排放及其增温潜势的影响

大气平流层臭氧损耗导致的地表紫外辐射增强作为全球变化重要问题之一,受到广泛关注。硅是水稻生长有益元素,但施硅是否影响稻田CH_4和 N_2O排放,迄今相关报道尚不多见。通过大田试验,研究UV-B增强下施硅对水稻生长、稻田甲烷(CH_4)和氧化亚氮( N_2O)排放及其增温潜势的影响。UV-B辐照设2水平,即对照(A,自然光)和增强20%(E);施硅量设2水平,即对照(Si0,0 kg SiO_2/hm2)和施硅(Si1,200 kg SiO_2/hm2)。结果表明,UV-B增强降低了成熟期水稻地上部和地下部生物量,而施硅能缓解UV-B增强对水稻生长的抑制作用,使水稻地上部和地下部生物量增加。UV-B增强可显著提高稻田CH_4和 N_2O排放通量和累积排放量,增加稻田CH_4和 N_2O排放的综合增温潜势。施硅能明显降低稻田CH_4排放,促进 N_2O排放,降低稻田CH_4和 N_2O排放的综合增温潜势。研究表明,施硅显著降低稻田CH_4和 N_2O的全球增温潜势,缓解UV-B增强对稻田CH_4和 N_2O的全球增温潜势的促进作用。     

UV-B辐射增强对小麦秸秆化学成分及其施用后土壤N2O排放的影响

在室外试验的基础上,研究了地表UV-B辐射增强条件下小麦秸秆成分的变化,及在室内不同培养条件下施用UV-B辐射处理后小麦秸秆对土壤N₂O排放的影响.室外试验结果表明：地表UV-B辐射增强减少了小麦地上部分生物量,显著增加了小麦秸秆木质素和全氮含量,增幅分别达94.2%和12.3%,降低了其C/N.室内培养试验结果表明：与常规小麦秸秆相比,UV-B辐射处理后的小麦秸秆显著提高了旱地和淹水条件下N₂O的排放量;施用秸秆同时伴施硝态氮条件下,经过UV-B辐射处理的小麦秸秆显著促进了旱地条件下N₂O的排放,其排放量为常规秸秆处理的3.2倍,但在淹水条件下对N₂O排放无显著影响;无论何种培养条件下,经过UV-B辐射处理的小麦秸秆对土壤呼吸都未产生显著影响.     

UV-B辐射增强对小麦秸秆化学成分及其施用后土壤N2O排放的影响

在室外试验的基础上,研究了地表UV-B辐射增强条件下小麦秸秆成分的变化,及在室内不同培养条件下施用UV-B辐射处理后小麦秸秆对土壤N₂O排放的影响.室外试验结果表明：地表UV-B辐射增强减少了小麦地上部分生物量,显著增加了小麦秸秆木质素和全氮含量,增幅分别达94.2%和12.3%,降低了其C/N.室内培养试验结果表明：与常规小麦秸秆相比,UV-B辐射处理后的小麦秸秆显著提高了旱地和淹水条件下N₂O的排放量;施用秸秆同时伴施硝态氮条件下,经过UV-B辐射处理的小麦秸秆显著促进了旱地条件下N₂O的排放,其排放量为常规秸秆处理的3.2倍,但在淹水条件下对N₂O排放无显著影响;无论何种培养条件下,经过UV-B辐射处理的小麦秸秆对土壤呼吸都未产生显著影响.     

UV-B辐射增强对抗除草剂转基因水稻 CH4排放的影响

在大田条件下,研究了UV-B(ultraviolet-B)辐射增强对抗除草剂转基因水稻及亲本常规水稻甲烷(CH4)排放的影响。UV-B辐射设2水平,即对照(CK,自然光),增强(Elevated,14.4 kJ·m-·2d-1),相当于南京地区大气臭氧耗损25%的辐射剂量。结果表明,UV-B辐射增强并没有改变稻田CH4排放通量的季节性变化规律。与对照相比,UV-B辐射增强显著提高CH4排放通量和累积排放量。水稻分蘖期CH4累积排放量最高,占全生育累积排放量的51.55%—61.01%;其次是拔节至孕穗期,占20.00%—26.64%。抗除草剂转基因水稻的CH4排放通量和累积排放量显著低于亲本常规水稻。研究说明,UV-B辐射增强下种植抗除草剂转基因水稻对于减缓稻田甲烷排放有积极意义。     

氮素类型和剂量对寒温带针叶林土壤N2O排放的影响

大气氮沉降输入会增加森林生态系统氮素有效性,进而改变土壤N_2O产生与排放,然而有关不同氮素离子(氧化态NO_3~--N与还原态NH_4~+-N)沉降对土壤N_2O排放的影响知之甚少。以大兴安岭寒温带针叶林为研究对象,构建了3种类型(NH_4Cl、KNO_3、NH_4NO_3)和4个施氮水平(0、10、20、40 kg N hm~(-2)a~(-1))的增氮控制试验,利用流动化学分析仪和静态箱-气相色谱法4次/月测定凋落物层和矿质层土壤无机氮含量、土壤-大气界面N_2O净交换通量以及相关环境因子,分析施氮类型和剂量对土壤氮素有效性、土壤N_2O通量的影响探讨氮素富集条件下土壤N_2O通量的环境驱动机制。结果表明:施氮类型和剂量均显著影响土壤无机氮含量,土壤NH_4~+-N的积累效应显著高于NO_3~--N。施氮一致增加寒温带针叶林土壤N_2O排放,NH_4NO_3促进效应最为明显,增幅为442%-677%,高于全球平均水平(134%)。土壤N_2O通量与土壤温度、凋落物层NH_4~+-N含量正相关,且随着施氮水平增加而增加。结果表明大气氮沉降短期内不会导致寒温带针叶林土壤NO_3~--N大量流失,但会显著促进土壤N_2O的排放。此外,外源性NH_4~+和NO_3~-输入对土壤N_2O排放的促进作用具有协同效应,在未来森林生态系统氮循环和氮平衡研究中应该区分对待。     

水肥一体化条件下设施菜地的N2O排放

在保证作物产量的前提下,研究减少农田土壤N_2O排放的水肥统筹管理措施对全球温室气体减排具有重要意义。以京郊典型设施菜地为例,设置了农民习惯(FP)、水肥一体化(FPD)、优化水肥一体化(OPTD)和对照(CK)4个处理,采用静态箱-气相色谱法,对果菜-叶菜(黄瓜-芹菜)轮作周期内土壤N_2O排放进行了观测,并分析了氮肥施用量、灌溉方式、土壤温度和湿度等因素对土壤N_2O排放的影响。结果表明:在黄瓜-芹菜种植模式中,各施氮处理除基肥施用后N_2O排放峰持续10—15d外,一般施肥、施肥+灌溉事件后土壤N_2O排放峰均呈现3—5d短而急促的情形。黄瓜生长季N_2O排放通量与土壤湿度(WFPS)之间呈现显著相关的关系;芹菜生长季N_2O排放通量与土壤温度之间呈现显著相关的关系。观测期内FP处理N_2O排放量为(31.00±2.15)kg N/hm~2,FPD处理与之相比N_2O排放量减少了4.2%,而OPTD处理在减少40%化肥氮量的情况下,N_2O累积排放量比FP处理减少了42.7%,且达到显著水平。说明在水肥一体化条件下,合理改变施肥体系是减少N_2O排放的前提,在此基础上进行水肥优化是设施菜地保持产量、减少N_2O排放的重要技术措施。     

UV-B辐射增强对元阳哈尼梯田稻田CH4排放规律的影响

在大田条件下,原位种植传统水稻品种白脚老粳,采用静态箱-气相色谱法研究了UV-B(ultraviolet-B)辐射增强(7.5 kJ m-2d-1)对元阳哈尼梯田海拔1600 m处稻田CH4排放量的影响,同时观测UV-B辐射增强对水稻生长的影响。结果表明:(1)UV-B辐射增强显著降低了水稻植株分蘖末期、拔节孕穗期、抽穗扬花期、成熟期地上部和地下部生物量(P0.05)。(2)UV-B辐射改变了稻田CH4的季节和日排放(成熟期)规律:对照组在拔节孕穗期出现1个排放峰,处理组在拔节孕穗期和成熟期出现2个排放峰;与对照相比,UV-B辐射增强改变了水稻成熟期CH4日排放第2个峰值出现的时间。(3)处理组CH4的季节排放通量与箱内温度的季节变化有显著的正相关性(R=0.789,P0.05)。(4)UV-B辐射增强在分蘖末期、拔节孕穗期、成熟期都极显著提高了CH4的累计排放量(P0.01),分别提高了47.2%,293.8%和74.4%。总之,UV-B辐射增强促进了元阳哈尼梯田传统水稻田CH4的排放。     

施用生物炭和秸秆还田对华北农田CO2、N2O排放的影响

以华北农田冬小麦-夏玉米轮作体系连续6a施用生物炭和秸秆还田的土壤为研究对象,于2013年10月—2014年9月,采用静态暗箱-气相色谱法,对CO_2、N_2O通量进行了整个轮作周期的连续观测,探究施用生物炭与秸秆还田对其排放通量的影响。试验共设4个处理:CK(对照)、C1(低量生物炭4.5 t hm~(-2)a~(-1))、C2(高量生物炭9.0 t hm~(-2)a~(-1))和SR(秸秆还田straw return)。结果表明:在整个轮作周期内,各处理CO_2、N_2O通量随时间的变化趋势基本一致。随着生物炭施用量的增加,CO_2排放通量分别增加了0.3%—90.3%(C1)、1.0%—334.2%(C2)和0.4%—156.3%(SR)。其中,C2处理对CO_2累积排放量影响最大,增幅为42.9%。对N_2O而言,C2处理显著降低了N_2O累积排放量,但增加了CO_2和N_2O排放的综合增温潜势,C1和SR处理对N_2O累积排放量及综合增温潜势均没有显著影响。相关分析表明,土壤温度和土壤含水量是影响CO_2通量最主要的因素,两者之间呈极显著的正相关关系;N_2O通量与土壤温度、土壤含水量、NO_3~--N和NH_4~+-N均表现出极显著的正相关关系,而与土壤p H值表现出极显著的负相关关系。由此可见,添加生物炭对于减少氮素的气体损失具有较大的潜力。     

增强UV-B辐射和氮素互作对植物生长代谢影响的研究进展

不同氮源条件下,UV-B辐射增强能改变植株对氮的吸收利用以及植株叶片的碳氢比和碳氮比,增加氨基酸的生物合成.缺氮条件下, UV-B辐射增强使植物叶片中SOD、POD活性增强,MDA含量增加;氮素过量时,UV-B辐射增强会降低植物对UV-B辐射的耐性.UV-B辐射增强和氮缺乏相互作用会降低叶片的光合速率、叶绿素含量、可溶性糖及淀粉含量,从而抑制植物的生长,降低生物量.该文对近年来国内外有关UV-B辐射增强与氮素相互作用对植物抗氧化系统、氮代谢、光合作用、生物量和形态结构的影响进行综述.     

不同种植年限人工苜蓿地土壤N_2O排放通量

以半干旱区不同种植年限人工苜蓿地(1、3、4、5和8年)为研究对象,利用静态箱-气相色谱法研究不同种植年限人工苜蓿地土壤系统、土壤-植被系统的N2O排放通量规律,探讨影响土壤N2O排放通量的主要因素。结果表明:(1)苜蓿种植年限影响苜蓿地土壤-植被系统、土壤系统的N2O排放通量,不同种植年限苜蓿地N2O排放通量规律为:4年5年3年8年1年。不同种植年限苜蓿地土壤-植被系统、土壤系统的N2O排放通量季节趋势均呈"春夏季高、秋季低",在5月和8月中旬各出现了N2O排放峰值,表现出N2O的源效应。土壤-植被系统的N2O排放通量大于土壤系统的N2O排放通量。(2)苜蓿地土壤系统N2O排放通量与土壤有机碳、C∶N、铵态氮、全氮、硝态氮含量及0~5 cm土层的土壤温度呈显著正相关,与0~10 cm土壤含水量呈极显著二次负相关。土壤-植被系统N2O排放通量与地上生物量呈极显著正相关。因此,土壤全氮、硝态氮含量、0~10 cm土壤含水量及地上生物量是制约N2O排放通量的关键因子。     

剔除林下灌草和添加翅荚决明对尾叶桉林土壤温室气体排放的影响

森林土壤是CO₂、CH₄和N₂O等温室气体的重要排放源。采用静态箱/色谱分析技术对中国科学院鹤山丘陵综合开放试验站的尾叶桉(Eucalyptus urophylla)林土壤CO₂、CH₄和N₂O排放通量进行了原位测定, 研究剔除林下灌草和添加翅荚决明(Cassia alata)对尾叶桉林土壤温室气体排放的影响。结果表明: 尾叶桉林土壤CO₂排放通量在湿季维持在较高水平, 在旱季则明显降低。CH₄和N₂O在湿季波动幅度较大, 在旱季则相对稳定。土壤CO₂和CH₄通量峰值均出现在湿季, 但N₂O峰值出现在旱季的12月。尾叶桉林土壤在不同处理下可能是CH₄的源, 也可能是CH₄的汇, 而对于CO₂和N₂O则主要是源。尾叶桉林下剔除灌草及添加翅荚决明能显著增大土壤CO₂和N₂O的排放, 但林下灌草剔除后有利于CH₄的吸收, 添加翅荚决明有利于CH₄的排放。表层土壤温度和湿度是影响土壤温室气体排放的首要因子。呼吸底物(氮源)和土壤微生物量也是影响土壤温室气体排放的重要因子。     

增强的UV-B辐射对麦田生态系统中种群数量动态的影响

研究了大田栽培和自然光条件下,模拟UV-B辐射(UV-B,280～315nm)增强对麦田生态系统杂草、大型土壤动物和麦蚜种群数量动态的影响。在UV-B辐射下,杂草和大型土壤动物的种类和数量降低,物种多样性改变,杂草总生物量也降低。UV-B辐射降低麦蚜复合种群数量,并与麦叶粗纤维、可溶性蛋白、可溶性糖、Mg和Zn含量有显著的相关性。UV-B辐射还导致麦蚜与麦叶Mg、Fe和Zn含量均显著增加。     

Reaction of savanna plants from Botswana on UV-B radiation

The annual savanna grasses Chloris virgata (C₄) and Tragus berteronianus (C₃) and the tree Acacia tortilis were exposed in a greenhouse to elevated UV-B radiation (16.8 kJ m^-2 d^-1 UV-B_Be) and to no UV-B and grown on a poor and a rich soil for one life-cycle (grasses) and one growing season (Acacia). UV-B radiation had no effect on biomass production and caryopses mass of both annual grasses. The longevity of the cotyledons of A. tortilis was shortened by 4 to 10 days under enhanced UV-B radiation, which also hampered the translocation of Fe, Mg and Mn from the cotyledons to the seedling and the retranslocation of Mn on both soil types and that of P on fertile soil out of senescent leaves. At the end of the growth period (190 days after germination), photosynthesis of UV-B radiated leaves of A. tortilis was significantly decreased and supported the tendency of decreased biomass of UV-B radiated plants. It is concluded that from the investigated savanna species the grasses are relatively well adapted to increased UV-B due to their actual exposure to high UV-B radiation under Botswana conditions, whereas saplings of A. tortilis are more sensitive to UV-B radiation.     

免耕施肥对稻田甲烷与氧化亚氮排放及其温室效应的影响

2008年采用静态箱-气相色谱法对鄂东南免耕不施肥(NT₀)、翻耕不施肥(CT₀)、免耕施肥(NTC)和翻耕施肥(CTC) 4种处理下稻田CH₄和N₂O的排放进行测定.结果表明：各处理CH₄排放均呈先升高后降低的季节性规律,而N₂O排放的季节性规律不明显;施肥显著提高了稻田CH₄和N₂O的排放.与翻耕不施肥相比,免耕不施肥显著提高了CH₄的排放量,并显著降低了N₂O的排放量;与翻耕施肥相比,免耕施肥仅略降低了CH₄的排放量和略提高了N₂O的排放量.对稻田CH₄和N₂O两种气体的综合温室效应分析表明,与翻耕不施肥相比,免耕不施肥的综合温室效应提高了25.9%,与翻耕施肥相比,免耕施肥的综合温室效应降低了10.1%.因此,合理的肥料运筹和稻田免耕技术可降低两种气体的综合温室效应.     

Effects of ultraviolet-B irradiance on soybean. VI. Influence of phosphorus nutrition on growth and flavonoid content

Soybeans Glycine max (L.) cv. Essex were hydroponically grown in a greenhouse at 2 levels of ultraviolet-B (UV-B) radiation (0 and 2 500 J m⁻¹ day⁻¹ biologically effective UV-B radiation) and 4 levels of P (6.5, 13, 26 and 52 μ M ). Plants were grown in each treatment combination to the complete expansion of the 4th trifoliolate leaf. UV-B radiation and reduced P supply generally decreased plant height, leaf area and total biomass, but increased specific leaf weight and flavonoid content (measured as absorbance of methanolic extracts). Although both UV-B radiation and low P supply produced deleterious effects on plant biomass, the effects were non-additive. The combination of UV-B and the lowest P level (6.5 μ M ) had no effect on total biomass or leaf area. This was at least partially due to the accumulation of flavonoids and leaf thickening. The results show that the sensitivity of soybean to UV-B radiation is dependent upon plant P supply. Plants experiencing P deficiency are less sensitive to UV-B than plants at optimum P levels.     

Effects of Enhanced UV-B Radiation on the Activity and Expression of Alternative Oxidase in Red Kidney Bean Leaves

An increase in ultraviolet （UV） B radiation on the earth＇s surface is a feature of current global climate changes. It has been reported that alternative oxidase （AOX） may have a protective role against oxidative stress induced by environmental stresses, such as UV-B. To better understand the characteristic tolerance of plants to UV-B radiation, the effects of enhanced UV-B radiation on the activity and expression of AOX in red kidney bean （Phaseolus vulgaris） leaves were investigated in the present study. The results show that the total respiration rate and AOX activity in red kidney bean leaves increased significantly during treatment with enhanced UV-B. However, cytochrome oxidase （COX） activity did not change significantly. The H2O2 content was also markedly increased and reached a maximum of 4.45 mmol·L^-1·g^-1 DW （dry weight） at 24 h of UV-B treatment, before dropping rapidly. Both alternative pathway content and alternative pathway activity were increased in the presence of exogenous H2O2. Immunoblotting analysis with anti-AOX monoclonal antibody revealed that expression of the AOX protein increased in red kidney bean leaves under enhanced UV-B radiation, reaching a peak at 72 h. In addition, AOX expression in red kidney bean leaves was induced by exogenous H2O2. These data indicate that the increase in AOX activity in red kidney bean leaves under enhanced UV-B radiation was mainly due to H2O2-induced AOX expression.     

Antioxidant Capacity of Flavonoid in Soybean Seedlings under the Joint Actions of Rare Earth Element La(III) and Ultraviolet-B Stress

The dynamic state of antioxidant capacity of flavonoid was investigated for a further demonstration of alleviating the damage of the ultraviolet (UV)-B radiation in the La-treated soybean seedlings under UV-B stress. Using hydroponics culture, the effects of lanthanum on the contents of flavonoid and its ability of antioxidant under elevated ultraviolet-B radiation (280–320 nm) was studied. The results showed flavonoid content in soybean seedlings with UV-B treatment during the stress and convalescent period was increased initially and then decreased, compared with control. Membrane permeability and MDA contents increase at first (first to fifth day) and then decrease (6th–11th day). A similar change of flavonoid content and clearance of flavonoid scavenging and ·OH in soybean seedlings occurred. Flavonoid content and ability of flavonoid scavenging and ·OH in soybean seedlings with La(III) + UV-B treatment were higher than those of UV-B treatment. Meanwhile, membrane permeability and MDA contents in soybean seedlings were lower than those of UV-B treatment. Compared with control, phenylalanine content in soybean seedlings with UV-B treatment is depressed, phenylalanine content in soybean seedlings with La(III) treatment was enhanced. However, phenylalanine content in La(III) + UV-B treatment is not decreased but slightly increased, compared with UV-B treatment. It suggested that the regulative effect of La(III) of the optimum concentration on flavonoid improved the metabolism of ROS, diminished the concentration of MDA and maintained normal plasma membrane permeability, and that its protective effect against low UV-B radiation is superior to that of high UV-B radiation. The defensive effect of La(III) on soybean seedlings under UV-B stress is carried out on the layer of defense system.     

镉和增强紫外线-B辐射复合作用对大豆生长的影响

研究了Cd^2+和增强紫外线-B(UV-B)辐射以及二者复合胁迫(Cd+UV-B)对大豆生长、光合作用、抗氧化酶活性和吲哚乙酸(IAA)氧化酶活性的影响,结果表明,UV-B辐射对大豆生长较CA^2+有更明显的抑制作用,主要是降低了光合作用,生物量减小;抑制节间的分化和伸长,节间减少,株高降低。UV-B辐射对POD、SOD活性有显著诱导作用,而Cd^2+明显颉颃UV-B对POD活性的诱导并抑制IAA氧化酶活性．在复合作用下,植物体内IAA氧化酶和POD活性较UV-B单独作用下显著降低,这两种酶活性降低会引起植物体内IAA含量升高,同时光合作用略有升高,这是株高和生物量较UV-B作用下有所增加的重要原因,复合胁迫还增强了对根伸长生长的抑制作用,根长度较对照显著降低(P<0．05)。IAA氧化酶和POD活性变化以及光合强度变化与大豆株高和生物量变化密切相关,这也是复合胁迫影响大豆生长状况的重要因素。