Mechanisms of ≡C---H bond activation in oxidative carbonylations of alkynes catalyzed by palladium complexes

Three types of catalytic system based on palladium complexes were studied in the synthesis of alkynylcarboxylic acid esters by oxidative carbonylation of monosubstituted alkynes. Three mechanisms were proposed for activation of the ≡C---H bond in alkynes and the formation of RC≡C[Pd]X, a key intermediate: (i) electrophilic substitution of H⁺ by Cu(I), (ii) electrophilic substitution of H⁺ by I⁺, and (iii) oxidative addition of the C---H bond in alkynes to palladium.     

Responses of ecosystem nitrogen cycle to nitrogen addition: a meta-analysis

? Anthropogenic nitrogen (N) addition may substantially alter the terrestrial N cycle. However, a comprehensive understanding of how the ecosystem N cycle responds to external N input remains elusive. ? Here, we evaluated the central tendencies of the responses of 15 variables associated with the ecosystem N cycle to N addition, using data extracted from 206 peer-reviewed papers. ? Our results showed that the largest changes in the ecosystem N cycle caused by N addition were increases in soil inorganic N leaching (461%), soil NO?? concentration (429%), nitrification (154%), nitrous oxide emission (134%), and denitrification (84%). N addition also substantially increased soil NH?+ concentration (47%), and the N content in belowground (53%) and aboveground (44%) plant pools, leaves (24%), litter (24%) and dissolved organic N (21%). Total N content in the organic horizon (6.1%) and mineral soil (6.2%) slightly increased in response to N addition. However, N addition induced a decrease in microbial biomass N by 5.8%. ? The increases in N effluxes caused by N addition were much greater than those in plant and soil pools except soil NO??, suggesting a leaky terrestrial N system.     

模拟氮沉降和降雨变化对贝加尔针茅草原土壤细菌群落结构的影响

研究氮沉降和降雨变化对土壤细菌群落结构的影响,对未来预测多个气候变化因子对草地生态系统影响的交互作用具有重要意义。以施氮和灌溉分别模拟氮沉降和降雨增加,采用高通量测序技术,研究8个氮添加水平(0、15、30、50、100、150、200、300kg N hm-2a-1)和2个水分添加水平(不灌溉、模拟夏季增雨100 mm灌溉)对土壤细菌群落结构的影响。结果表明,氮素和水分输入增加后,土壤细菌群落组成、丰度均显著变化(P0.05)。在群落中占主导的细菌门类有疣微菌门Verrucomicrobia(30.61%—48.51%)、变形菌门Proteobacteria(21.37%—29.97%)、酸杆菌门Acidobacteria(9.54%—20.67%)和拟杆菌门Bacteroidetes(4.96%—9.74%)。在常规降雨和水分添加两种条件下,随着氮添加水平的增加,占主导的细菌门类(相对丰度1%)表现出不同的变化趋势。疣微菌门相对丰度在常规降雨N100—N300条件下显著降低,但在氮素和水分同时添加条件下随氮添加水平升高而逐渐升高,在N200—N300时显著升高。变形菌门和拟杆菌门相对丰度在常规降雨高氮添加条件下呈升高趋势,但在水分添加时却无明显变化。酸杆菌门相对丰度在常规降雨高氮添加条件下升高,但在水分添加后呈明显下降趋势。放线菌门Actinobacteria相对丰度在常规降雨N100—N300条件下显著升高,但在水分添加后高氮添加时显著降低。厚壁菌门Firmicutes相对丰度在常规降雨条件下无显著变化,但在水分和高氮添加条件下降低。浮霉菌门Planctomycetes相对丰度在两种不同的水分添加条件下均呈先升高后降低的趋势。氮素和水分添加对土壤细菌群落结构的变化存在明显的互作效应(P0.0001)。在不同氮素和水分输入条件下共有19个土壤细菌门类相对丰度有显著差异。土壤细菌群落结构的变化主要来自于疣微菌门和酸杆菌门的相对丰度变化,两者可作为土壤细菌群落结构变化的指示种。综上,氮素和水分添加显著改变了土壤细菌群落结构,氮素和水分对土壤细菌不同门类相对丰度变化存在明显的互作效应。     

贝加尔针茅草原土壤真菌群落结构对氮素和水分添加的响应

研究氮沉降和降雨变化对土壤真菌群落结构的互作效应,对未来预测多个气候变化因子对草地生态系统的交互作用具有重要意义。以施氮和灌溉模拟氮沉降和降雨增加,采用裂区设计,应用高通量测序技术,研究8个氮添加水平(0、15、30、50、100、150、200、300 kg N hm~(-2)a~(-1))和2个水分添加水平(不灌溉、模拟夏季增雨100 mm灌溉)对土壤真菌群落结构的影响。结果表明,氮素和水分添加后,土壤真菌群落中占优势的门类分别为接合菌门Zygomycota(22.0%—48.9%)、担子菌门Basidiomycota(7.8%—18.5%)、子囊菌门Ascomycota(9.4%—20.1%)、球囊菌门Glomeromycota(0.7%—3.1%)、壶菌门Chytridiomycota(0.1%—1.3%)。常规降雨条件下,随着氮添加水平升高,接合菌门相对丰度呈现出先升高后降低的趋势,N50处理最高;子囊菌门相对丰度在高氮添加时(N100—N300)呈升高趋势。而在氮素和水分同时添加条件下,随着氮添加水平升高,接合菌门相对丰度呈降低趋势,子囊菌门相对丰度变化则不明显。在相同的氮添加水平下,水分添加使接合菌门相对丰度增加,而担子菌门、子囊菌门、球囊菌门和壶菌门的相对丰度降低。在不同氮素和水分添加条件下,有5个土壤真菌门类11个真菌纲相对丰度变化显著。接合菌门的Mortierella属,担子菌门的Entolomataceae科和Geastrum属相对丰度变化极显著,可作为土壤真菌群落结构变化的指示种。PCo A分析结果也表明氮素和水分添加改变了土壤真菌群落结构。植物-土壤-微生物系统的结构方程模型结果表明,植物群落组成及植物物种丰富度的变化是土壤真菌群落结构发生变化的主要影响因素,土壤无机氮及p H的变化主要通过影响植物群落间接影响真菌群落,其对真菌群落的直接影响则较小。综上,氮素和水分添加改变了土壤真菌群落结构,且两者存在明显的互作效应,水分添加可改变氮添加对土壤真菌群落的影响。     

Deuterium Raman imaging for lipid analysis

Raman microscopy has been used to deduce information about the distributions of endogenous biomolecules without exogenous labeling. Several functional groups, such as alkynes (CC), nitriles (CN), and carbon-deuterium (C–D) bonds, have been employed in recent years as Raman tags to detect target molecules in cells. In this article, we review some recent advances in applications using deuterated fatty acids for lipid analysis, such as investigation of tumor-selective cytotoxicity of γ-linolenic acid (GLA), simultaneous two-color imaging of stearate and oleate using deuterated and protonated alkynes, Raman hyperspectral imaging, and analyses of the physical properties of lipids through spectral unmixing of the C–D vibrational frequencies. In addition, we review some advanced methods for observing intracellular metabolic activities, such as de novo lipogenesis from deuterium-labeled precursors.     

A review of nitrogen enrichment effects on three biogenic GHGs: the CO2 sink may be largely offset by stimulated N2O and CH4 emission

Anthropogenic nitrogen (N) enrichment of ecosystems, mainly from fuel combustion and fertilizer application, alters biogeochemical cycling of ecosystems in a way that leads to altered flux of biogenic greenhouse gases (GHGs). Our meta-analysis of 313 observations across 109 studies evaluated the effect of N addition on the flux of three major GHGs: CO₂, CH₄ and N₂O. The objective was to quantitatively synthesize data from agricultural and non-agricultural terrestrial ecosystems across the globe and examine whether factors, such as ecosystem type, N addition level and chemical form of N addition influence the direction and magnitude of GHG fluxes. Results indicate that N addition increased ecosystem carbon content of forests by 6%, marginally increased soil organic carbon of agricultural systems by 2%, but had no significant effect on net ecosystem CO₂ exchange for non-forest natural ecosystems. Across all ecosystems, N addition increased CH₄ emission by 97%, reduced CH₄ uptake by 38% and increased N₂O emission by 216%. The net effect of N on the global GHG budget is calculated and this topic is reviewed. Most often N addition is considered to increase forest C sequestration without consideration of N stimulation of GHG production in other ecosystems. However, our study indicated that although N addition increased the global terrestrial C sink, the CO₂ reduction could be largely offset (53–76%) by N stimulation of global CH₄ and N₂O emission from multiple ecosystems.     

氮添加对湿地松林土壤水解酶和氧化酶活性的影响

通过3个水平野外氮添加控制试验(0、40、120 kg N·hm^-2·a^-1),研究氮添加对亚热带湿地松林土壤水解酶和氧化酶活性的影响.结果表明: 氮添加显著抑制了土壤有机质中碳、氮、磷水解酶和氧化酶的活性,导致β-1,4-葡糖苷酶(BG)、纤维素二糖水解酶(CBH)、β-1,4-乙酰基-葡糖胺糖苷酶(NAG)、过氧化物酶(PER)活性下降16.5%～51.1%,并且高水平氮添加对酶活性抑制效果更明显;氮添加导致α-1,4-葡糖苷酶(aG)、β-1,4-木糖苷酶(BX)、酸性磷酸酶(AP)、多酚氧化酶(PPO)活性降低14.5%～38.6%,不同水平氮添加处理间差异不显著.土壤酶活性存在明显的季节性差异,BG、NAG、BX、CBH、AP、PPO活性表现为3月>6月>10月,aG、PER活性表现为10月>3月>6月.多数土壤水解酶和氧化酶与pH呈显著正相关,与NO₃^--N含量呈显著负相关,表明氮添加导致pH降低和土壤中硝化作用增强,抑制了土壤水解酶和氧化酶活性.氮添加不利于亚热带土壤有机质的矿化和周转,并且随着氮添加量的增加,效果更明显.     

亚热带杉木林土壤有机碳及其活性组分对氮磷添加的响应

通过野外氮、磷添加,分析N₀(0 kg N·hm^-2·a^-1)、N₁(50 kg N·hm^-2·a^-1)、N₂(100 kg N·hm^-2·a^-1)、P(50 kg P·hm^-2·a^-1)、N₁P和N₂P等6种处理3年后对亚热带杉木人工林土壤有机碳(SOC)、颗粒有机碳(POC)和水溶性有机碳(WSOC)的影响.结果表明:氮、磷添加对0～20 cm土层SOC含量无显著影响.磷添加显著降低0～5 cm土层POC含量,与无磷处理相比,加磷处理POC含量降低26.1%.WSOC含量对氮、磷添加的响应主要表现在0～5 cm土层,低水平氮添加和磷添加显著提高WSOC含量.在0～5 cm土层,氮添加对POC/SOC值无显著影响,而与无磷添加相比,POC/SOC值在磷添加处理下显著降低15.9%.在5～10和10～20 cm土层,氮、磷添加处理对POC/SOC值无显著影响.在亚热带地区,森林土壤碳稳定性主要受磷含量的调控,短期磷添加易导致表层土壤活性有机碳分解,增加土壤碳稳定性.     

Nickel/zinc-catalyzed decarbonylative addition of anhydrides to alkynes: A DFT study

Density functional theory (DFT) was used to investigate the nickel- or nickel(0)/zinc- catalyzed decarbonylative addition of phthalic anhydrides to alkynes. All intermediates and transition states were optimized completely at the B3LYP/6-31+G(d,p) level. Calculated results indicated that the decarbonylative addition of phthalic anhydrides to alkynes was exergonic, and the total free energy released was ?87.6 kJ mol^?1. In the five-coordinated complexes M4a and M4b, the insertion reaction of alkynes into the Ni-C bond occurred prior to that into the Ni-O bond. The nickel(0)/zinc-catalyzed decarbonylative addition was much more dominant than the nickel-catalyzed one in whole catalytic decarbonylative addition. The reaction channel CA→M1'→T1'→M2'→T2'→M3a'→M4a'→T3a1'→M5a1' →T4a1'→M6a'→P was the most favorable among all reaction pathways of the nickel- or nickel(0)/zinc- catalyzed decarbonylative addition of phthalic anhydrides to alkynes. And the alkyne insertion reaction was the rate-determining step for this channel. The additive ZnCl₂ had a significant effect, and it might change greatly the electron and geometry structures of those intermediates and transition states. On the whole, the solvent effect decreased the free energy barriers.

Rhodium-catalyzed synthesis of 2(5H)-furanones from terminal alkynes and non-substituted alkynes under water-gas shift reaction conditions

Rhodium-catalyzed synthesis of 2(5H)-furanones from alkynes under water-gas shift reaction conditions was studied. By improving the reaction conditions for internal alkynes reported previously, the reaction could be extended to terminal alkynes. Terminal alkynes are selectively converted into 3- and 4-substituted 2(5H)-furanones (2 and 3). When acetylene itself is used, 2(5H)-furanone (2n) is obtained in a good yield. Examination of reaction solutions by IR spectroscopy and some other experimental findings suggest that the active species would be an alkyne-coordinated monomeric rhodium anion. A new reaction path is proposed.     

Root and hyphal interactions influence N transfer by arbuscular mycorrhizal fungi in soybean/maize intercropping systems

In maize-soybean intercropping systems, the transfer of N from soybean to maize gives the intercropping system the advantage of improved N utilization and higher yields. Mycorrhiza acts as an important pathway for N transfer, providing a constant supply of N to sustain the growth and development of maize in its early stages. However, it is not clear how arbuscular mycorrhizal fungi (AMF) drive the transfer of N from soybean to maize in the intercropping system. Therefore, we quantified the amount of N transferred from soybean to maize under low and high N levels in the intercropping system, and the abundance and diversity of AMF involved in N transfer (¹⁵N-AMF) under different conditions by ¹⁵N leaf marker and DNA-SIP technology. We found that the interaction between roots and reducing the application of N fertilizer increased the amount of N transfer from soybean to maize. Compared with plastic plate separation (PS), no separation (NS) and mesh separation (MS) significantly increased the N fixation rate (from 14.33% to 39.09%), and the amount of N transfer under NS was 1.95–3.48 times that under MS. N transfer from soybean to maize ranged from 9.7 to 43.42 mg per pot in the no N treatment, while the addition of N fertilizer reduced N transfer by 14.12–66.28%. This is due to root interaction and reduced N fertilization increased the abundance and diversity of the ¹⁵N-AMF community, thereby promoting AMF colonization of maize and soybean roots. AMF colonization in soybean and maize roots under NS treatment was 6.47–17.24% higher than under MS treatment in all three levels of N addition. The increase of mycorrhiza in root system increased the N transfer from soybean to maize significantly. These results suggest that reduced N fertilizer in maize-soybean intercropping systems can increase N transfer by the mycorrhizal pathway, meeting maize N requirements and reducing chemical N fertilizer, which is important for sustainable agricultural development.     

The impact of elevated CO2, increased nitrogen availability and biodiversity on plant tissue quality and decomposition

Elevated CO₂, increased nitrogen (N) deposition and increasing species richness can increase net primary productivity (NPP). However, unless there are comparable changes in decomposition, increases in productivity will most likely be unsustainable. Without comparable increases in decomposition nutrients would accumulate in dead organic matter leading to nutrient limitations that could eventually prohibit additional increases in productivity. To address this issue, we measured aboveground plant and litter quality and belowground root quality, as well as decomposition of aboveground litter for one and 2‐year periods using in situ litterbags in response to a three‐way factorial manipulation of CO₂ (ambient vs. 560 ppm), N deposition (ambient vs. the addition of 4 g N m⁻² yr⁻¹) and plant species richness (one, four, nine and 16 species) in experimental grassland plots. Litter chemistry responded to the CO₂, N and plant diversity treatments, but decomposition was much less responsive. Elevated CO₂ induced decreases in % N and % lignin in plant tissues. N addition led to increases in % N and decreases in % lignin. Increasing plant diversity led to decreases in % N and % lignin and an increase in % cellulose. In contrast to the litter chemistry changes, elevated CO₂ had a much lower impact on decomposition and resulted in only a 2.5% decrease in carbon (C) loss. Detectable responses were not observed either to N addition or to species richness. These results suggest that global change factors such as biodiversity loss, elevated CO₂ and N deposition lead to significant changes in tissue quality; however, the response of decomposition is modest. Thus, the observed increases in productivity at higher diversity levels and with elevated CO₂ and N fertilization are not matched by an increase in decomposition rates. This lack of coupled responses between production and decomposition is likely to result in an accumulation of nutrients in the litter pool which will dampen the response of NPP to these factors over time.     

模拟氮沉降增加对寒温带针叶林土壤 CO2排放的初期影响

研究大气氮沉降增加情景下北方森林土壤CO2排放通量及其相关控制因子至关重要。在大兴安岭寒温带针叶林区建立了大气氮沉降模拟控制试验,利用静态箱-气相色谱法测定土壤CO2排放通量,同时测定土壤温度、水分、无机氮和可溶性碳含量等相关变量,分析寒温带针叶林土壤CO2排放特征及其主要驱动因子。结果表明:氮素输入没有显著改变森林土壤含水量,但降低了有机层土壤溶解性无机碳(DIC)含量,并增加有机层和矿质层土壤溶解性有机碳(DOC)含量。增氮短期内不影响土壤NH+4-N含量,但促进了土壤NO-3-N的累积。增氮倾向于增加北方森林土壤CO2排放。土壤CO2通量主要受土壤温度驱动,其次为土壤水分和DIC含量。虽然土壤温度整体上控制着土壤CO2通量的季节变化格局,但在生长旺季土壤含水量对其影响更为明显。在分析增氮对土壤CO2通量的净效应时,除了土壤温度和水分外,还要考虑土壤有效碳、氮动态的影响。     

施氮对空心莲子草(Alternanthera philoxeroides)和莲子草(Alternanthera sessilis)种间关系的影响

自然界的氮素释放总是呈现出空间和时间上的异质性,但关于异质性氮释放对于入侵植物和本地植物种间关系影响的研究相对较少。将入侵植物空心莲子草(Alternanthera philoxeroides)和同属本地植物莲子草(Alternanthera sessilis)分别进行单种种植(12株,无种间竞争)和混种种植(每种6株,有种间竞争),模拟大气氮湿沉降设置由两种不同施氮总量(15g N m~(-2)a~(-1)和30g N m~(-2)a~(-1))和两种不同施氮频率(每5天1次和每15天1次)交叉组成的4种施氮处理,并以不施氮为对照。施氮总量的增加显著促进了两种植物的生长,但对两种植物的种间竞争关系没有显著影响。施氮频率对两种植物的生长以及种间竞争关系都没有显著影响。两种植物在面对竞争时表现出不同的生物量分配策略,空心莲子草将更多的生物量分配到茎,而莲子草将更多的生物量分配到根。在全球变化的背景下,大气氮湿沉降可能会改变两种植物的种群结构和动态,但可能对这两种植物的种间关系影响较小。     

整合分析氮磷添加对土壤酶活性的影响

本文通过整合分析(Meta-analysis)的方法分析了氮、磷添加对土壤碳、氮和磷素循环水解酶以及土壤氧化酶活性的影响.结果表明: 氮添加显著增加了碳、氮和磷循环水解酶的活性,增幅分别为6.9%、5.6%和10.7%;与氮添加相比,在氮磷同时添加下,3类土壤酶的活性增加更为显著,增幅分别达13.4%、37.4%和13.3%.然而,对于土壤氧化酶,氮以及氮磷的添加都使其活性降低,分别降低了6.1%和0.4%.不同生态系统类型、氮肥类型、施肥速率和施肥试验时间都对土壤酶活性具有影响.在全球大气氮沉降与磷添加逐渐增加的背景下,土壤微生物活性和酶的变化将会对土壤生物地球化学循环过程和土壤生态系统功能产生重要影响.     

Utilization of Dissolved Nitrogen by Heterotrophic Bacterioplankton: Effect of Substrate C/N Ratio

The significance of dissolved combined amino acids (DCAA), dissolved free amino acids (DFAA), and dissolved DNA (D-DNA) as sources of C and N for marine bacteria in batch cultures with variable substrate C/N ratios was studied. Glucose, ammonium, alanine, and phosphate were added to the cultures to produce C/N ratios of 5, 10, and 15 and to ensure that phosphorus was not limiting. Maximum bacterial particulate organic carbon production (after 25 h of incubation) was inversely correlated with the C/N ratio: with the addition of identical amounts of carbon, the levels of production were 9.0-, 10.0-, and 11.1-fold higher at C/N ratios of 15, 10, and 5, respectively, relative to an unamended control. The bacterial growth efficiency increased from 22% (control cultures) to 44 to 53% in the cultures with manipulated C/N ratios (C/N-manipulated cultures). Net carbon incorporation from DCAA, DFAA, and D-DNA supported on average 19, 4, and 3% (control cultures and cultures to which only phosphate was added [+P cultures]) and 5, 4, and 0.3% of the particulate organic carbon production (C/N-manipulated cultures), respectively. In the C/N-manipulated cultures, a 2.6- to 3.4-fold-higher level of incorporation of DCAA, relative to that in the control cultures, occurred. Incorporation of D-DNA increased with the substrate C/N ratio, suggesting that D-DNA mainly was a source of N to the bacteria. Organic N (DCAA, DFAA, and D-DNA) sustained 14 to 49% of the net bacterial N production. NH₄⁺ was the dominant N source and constituted 55 to 99% of the total N uptake. NO₃^- contributed up to 23% to the total N uptake but was released in two cultures. The studied N compounds sustained nearly all of the bacterial N demand. Our results show that the C/N ratio of dissolved organic matter available to bacteria has a significant influence on the incorporation of individual compounds like DCAA and D-DNA.     

Highly efficient synthesis of vinyl substituted triazoles by Au(I) catalyzed alkyne activation

Au(I) catalyzed 1,2,3-triazole addition to non-activated alkyne was reported. A large group of substituted NH-1,2,3-triazoles were suitable for this transformation along with both internal and terminal alkynes. The N-1 and N-2 vinyl substituted 1,2,3-triazoles were prepared in up to 98% yield with as low as 0.2% catalyst loading, thereby providing a new protocol for the synthesis of potentially biological-active vinyl-triazole building blocks.     

不同降水条件下荒漠草原植物的养分含量及回收对增温和氮素添加的响应

为了探讨荒漠草原植物养分回收特征对长期增温和氮素添加的响应以及自然降水变异对其的调控作用,该研究依托实施12年的模拟增温和氮素添加实验平台,在相对多雨的2016年(超过长期均值52%)和相对少雨的2017年(低于长期均值16%),以常见C_3植物银灰旋花(Convolvulus ammannii)和C_4植物木地肤(Kochia prostrata)为研究对象,测定分析绿叶和枯叶的氮磷含量及回收效率。结果表明:(1)在相对多雨年(2016年),增温使2种植物的绿叶氮、枯叶氮、绿叶磷、枯叶磷含量分别增加了14.32%、25.45%、17.97%和46.47%,氮、磷回收效率分别显著减小了9.41%和16.99%(P0.05);氮素添加使2种植物的绿叶氮、枯叶氮、绿叶磷、枯叶磷含量分别提高了17.32%、25.62%、20.21%和51.41%,而氮、磷回收效率显著降低了9.33%和18.89%(P0.05);增温+氮素添加共同处理显著增加了植物氮磷含量、降低了氮磷回收效率。(2)在相对少雨年(2017年),增温、氮素添加、增温+氮素添加处理对植物叶片氮磷含量、回收效率均无显著影响。(3)叶片氮磷含量在物种间差异极显著(P0.000 1),而氮磷回收效率在物种间无显著差异。(4)回归分析表明,植物叶片氮磷含量随着土壤无机氮、有效磷及含水量的增加而增加,植物氮磷回收效率则随着土壤养分和水分的可利用性的增加而降低。研究认为,荒漠草原植物养分回收对全球变化的响应受自然降水变异的调控。     

Evaluation of sludge reduction by an environmentally friendly chemical uncoupler in a pilot-scale anaerobic/anoxic/oxic process

An environmentally friendly chemical, tetrakis(hydroxymethyl)phosphonium sulfate (THPS), was used as a metabolic uncoupler to reduce sludge production in a pilot-scale anaerobic/anoxic/oxic process. The results show that the addition of THPS (1.08–1.86 mL/m³ influent) in the sludge return section could reduce waste activated sludge by about 22.5 %, and decrease the sludge yield by about 14.7 % at the end of a run. At the same time, the addition of THPS slightly lowered the removal of chemical oxygen demand (COD), soluble COD and NH₄ ⁺–N, and slightly improved removal of total nitrogen. The effects of THPS addition on two characteristics of activated sludge in oxic tank are discussed in detail and the results suggest that the settleability of sludge was reduced by addition of THPS, while the specific oxygen uptake rate was increased. Molecular biology analysis shows that the addition of THPS had little effect on the microbial communities of sludge.     

生物炭施用3年后对稻麦轮作系统CH4和N2O综合温室效应的影响

本试验对比观测研究了在稻田土壤中经3年陈化后的生物炭(B₃)和新施入生物炭(B₀)对稻麦轮作系统CH₄和N₂O综合温室效应和温室气体强度的影响,旨在明确生物炭对土壤温室气体排放的长期效应.田间试验设置4个处理,分别为对照(CK)、施用氮肥不施用生物炭(N)、施用氮肥和新生物炭(NB₀)以及施用氮肥和陈化生物炭(NB₃)处理.结果表明: NB₀和NB₃处理均显著提高了稻田土壤pH值、有机碳和全氮含量,并且显著影响与温室气体排放相关的微生物潜在活性.与N处理相比,NB₃处理显著增加了作物产量,增幅14.1%,并且显著降低了CH₄和N₂O排放,降幅分别为9.0%和34.0%;而NB₀处理显著增加作物产量,增幅9.3%,显著降低N₂O排放,降幅38.6%,但增加了CH₄排放,增幅4.7%;同时NB₀和NB₃处理均能降低稻麦轮作系统的综合温室效应和温室气体强度,且NB₃处理能更有效地减少温室气体的排放并提高作物产量.在土壤中经3年陈化后的生物炭仍然具有固碳减排能力,因此,施用生物炭对稻麦轮作系统固碳减排和改善作物生产具有长期效应.