To examine spatial patterns and heterogeneities in greenhouse gas (GHG) sequestration, mitigation and emission of different afforestation types (i.e., ecological, economic, timber and firewood forest) in the “Grain for Green” project (GGP), we estimated the GHG budgets of 30 typical tree species in afforested areas, established a carbon accounting and net mitigation (CANM-GGP) assessment framework, and determined the net carbon sequestration and mitigation rates of the four afforestation types in the GGP. From 2000 to 2020, total carbon sequestration and mitigation in GGP amounted to 5097 TgCO2, with 26.84% offset by emissions (1368 TgCO2-eqv). Economic forest had the greatest emissions at 1035 TgCO2, offsetting carbon sequestration by 281.2%. GHG emissions offset carbon sequestration and mitigation by 3.00%, 6.78%, and 11.89% in firewood, ecological, and timber forest, respectively. GGP net carbon sequestration and mitigation rate was 6.21 tCO2/ha/yr, highest in firewood forest (18.68 tCO2/ha/yr), followed by ecological forest (9.65 tCO2/ha/yr) and timber forest (3.52 tCO2/ha/yr). Economic forest showed a net GHG increase (6.67 tCO2/ha/yr). Overall, GGP achieved significant net carbon sequestration and mitigation benefits except economic forest. Ecological forest contributed most to net carbon sequestration due to the largest afforestation area and the second highest net carbon sequestration rate. Firewood forest had the highest net carbon sequestration and mitigation rate, and their potential mitigation benefits could be substantial. Our work provides a new approach for assessing afforestation as an important and promising nature-based climate solution and suggests multiple afforestation options for GHG mitigation.

Tropospheric ozone (O3) is a potent oxidant that can harm plants, making it a key focus of research in ecology and agriculture. However, comprehensive reviews about the developmental history of O3 research on plants are lacking. This review utilized Citespace software to unveil the evolution of the main research themes over time, which correlated with three distinct developmental periods. During the first period, researchers primarily focused on the impact of O3 on photosynthesis and plant defense responses. As time progressed, more in-depth investigations were undertaken including determining the critical levels at which O3 damage to plants occurred, analyzing the source-sink carbon balance and carbon allocation, assessing food security based on risk evaluation, identifying quantitative trait loci (QTL) associated with O3 tolerance, conducting transgenic research, and exploring the combined effect of multiple stressors on vegetation within the context of climate change. Despite these insights, several gaps and challenges remain, that merit future considerations. Greater research efforts should focus on 1) insufficient studies on the combined effects of O3, CO2, and drought in the context of global warming; 2) intermittent elevated O3 events and plant recovery mechanisms under low O3 concentration; 3) reproductive and renewal capacity of species, and t O3 effects on community stability or composition; 4) updating O3 flux measurements to reflect effective O3 flux when O3 index is applied, and challenges in determining species-specific phytotoxicity threshold; and 5) O3-tolerance gene screening and breeding.

Urban areas are the major anthropogenic source of atmospheric CO2, thus making long-term and continuous observations of their carbon emission dynamics extremely important. The COVID-19 lockdown served as a natural experiment that provided a unique opportunity to analyse the contribution of human activities to CO2 emissions from urban areas. In 2020, Beijing experienced COVID-19 confinement with different levels of restrictions on social mobility and economic activity, resulting in reductions in CO2 emissions. To investigate the response mechanisms of CO2 flux to restriction measures, we analysed CO2 flux data obtained using the eddy covariance technique from 2015 to 2020, and compared CO2 flux during the COVID-19 confinement period in 2020 with the preceding years (2015-2019) and across various levels of confinement. The results showed that: (1) the annual CO2 flux was 2.1 ± 0.2 kg C/(m2·yr) in 2020, which showed a significant reduction of 31.8 % compared to the adjacent 2019; (2) the reduction in CO2 flux was closely related to the level of restrictions on human activities; (3) most reductions occurred during the morning (85.7 %) and evening (32.7 %) peak traffic times, indicating that commuting-related transportation is a primary contributor to urban CO2 emissions. It is suggested that measures that reduce transportation-related CO2 sources should be considered as priorities for reducing urban CO2 emissions. The dynamic variation of urban CO2 flux captured by the eddy covariance technology is conductive to strengthening the supervision of the implementation of urban carbon emission reduction policies, promoting the achievement of dual carbon goals.

To limit global warming to below 1.5 °C–2 °C, more than 140 countries have pledged carbon neutrality. However, many less-developed countries and regions face economic constraints and often suffer from severe ecosystem degradation, which jointly hinder their ability to meet these commitments. Here, we use the Qinghai–Tibet Plateau (QTP), a less-developed region that has experienced ecosystem degradation, as a case study. We use a novel multi-scenario modeling framework to assess the impact of different combinations of natural climate solutions (NCS) and carbon emission reduction policies (CERPs) on carbon neutrality and associated costs. Our findings show that carbon neutrality was achieved on the QTP by 2020, with a surplus of 18.16 MtCO _2 yr ^−1 . However, without CERPs, carbon emissions on the QTP are projected to increase fivefold by 2060 compared with 2020 levels. Even with stringent NCS, a shortfall of nearly 375.34 ± 99.05 MtCO _2 yr ^−1 in maintaining carbon neutrality remains in 2060. If CERPs are implemented without NCS, the cost of maintaining carbon neutrality in 2060 is estimated at USD 199.07 ± 25.96 billion during 2020–2060. Notably, integrating NCS with CERPs reduces costs by nearly half (USD 111.51 ± 21.48 billion). Furthermore, the integration of aggressive CERPs and NCS on the QTP could contribute a further additional surplus by 2060 toward national carbon neutrality goals at a pretty low carbon price. Our research highlights that combining NCS with CERPs yields greater climate benefits at significantly lower costs, providing potential pathways for financially constrained regions to enhance climate mitigation, especially when supported by international climate finance and cooperative mechanisms.

O3 (ozone) is an environmental pollutant that can exacerbate inflammatory damage and contribute to respiratory diseases. However, the molecular mechanisms and potential targets for intervention in ozone-induced lung inflammatory injury are not yet known. To address this, our study exposed mice to 0.6 ppm and 1.0 ppm of O3 (3 h/d, 14 d), evaluating lung inflammation through histopathological examinations, lung function assessments, and analyses of white blood cells and inflammatory factors in BALF. Furthermore, we employed transcriptomic and non-targeted metabolomic approaches to decipher differentially expressed genes (DEGs) and metabolites in mouse lung tissue from the 1.0 ppm O3 exposure group. A comprehensive integration analysis of these omics data was conducted using Pearson correlation analysis. Finally, our findings show that ozone exposure indeed elicits pulmonary inflammation. Transcriptomic analysis identified 311 differentially expressed genes, predominantly implicated in circadian rhythm, IL-17 signaling pathway, and PPAR signaling. Meanwhile, metabolomic profiling revealed 41 differentially regulated metabolites, mainly associated with riboflavin metabolism, glutathione metabolism, and ABC transporter pathways. Integrated multi-omics analysis through Pearson correlation identified three key components (Pla2g10, O-phosphoethanolamine, and phosphorylcholine) showing significant enrichment in glycerophospholipid metabolism. Collectively, our findings suggest that glycerophospholipid metabolism may serve as potential therapeutic targets and diagnostic biomarkers for ozone-induced pulmonary inflammatory injury.

(1) Background: Urban tree species mapping is crucial for ecosystem service evaluation and sustainable urban strategy development. However, due to the spectral similarity among dominant urban tree species, spectral data alone are insufficient for high-accuracy classification. (2) Methods: We present an approach that integrates the high-precision Canopy Height Model (CHM), generated from Ziyuan-3 (ZY3) stereo images, with multi-temporal Sentinel-2 data, for mapping 23 dominant urban tree species in Shenzhen. We primarily employed a random forest classifier using combinations of spectral bands, vegetation indices, and structural features, with subsets refined through Variance Inflation Factor (VIF) screening. We compared different models with different combinations of features, with or without the inclusion of CHM data. (3) Results: This study found that integrating VIF-screened seasonal Sentinel-2 spectral data with vegetation indices and structural metrics (Cop_DEM and ZY3_Cop_CHM) yielded an overall accuracy of 89.2%. Notably, ZY3_Cop_CHM emerged as the most influential predictor in the model. Additionally, the incorporation of ZY3_CHM data enhanced the classification accuracy by 7.1% and improved the accuracy by 4.8% compared with the use of ALOS_CHM. The species-specific F1 accuracy of a tree varies under different models and feature combinations, which underscores the need for tailored model tuning and an increase in overall model performance. Conclusions: These results indicate that integrating the ZY3_CHM data with multi-temporal Sentinel-2 data can accurately map the dominant urban tree species, suggesting its potential applicability in other urban environments.

Ground-level ozone (O3) pollution has been a severe environmental and health problem for decades. The importance of biogenic volatile organic compounds (BVOCs) in the formation of tropospheric photochemistry O3 has been highlighted, especially in areas of rapid urbanization. We conducted simultaneous measurements of trace gases, including NO, NOX, O3, and BVOCs (i.e., isoprene and α-pinene), in the urban and rural forest areas of Beijing to determine the relationships between them. The results highlight the differences between the urban and rural forest areas of Beijing in terms of ambient air concentrations of BVOCs and O3, and the interrelationships between BVOCs, NOX, and ozone were quantified. Moreover, the isoprene concentration was found to be higher in the atmosphere of the urban site than of the rural site, which had higher α-pinene concentrations and higher O3 concentrations. The NOX concentration was higher at the urban site than at the rural site, and there was a significant exponential relationship between NOX and O3 at the urban site, indicating that the impact of NOx on O3 at the urban site was greater than that at the rural site. The O3 concentration increased with rising isoprene and α-pinene in both sites. In the case of substantially increased BVOC concentrations, declining NOX concentrations strongly promote the formation of O3. Consideration should be given to planting tree species with low-BVOC emissions, as they are crucial for mitigating O3 pollution in urban areas. Additionally, the relationships between BVOCs, NOX, and O3 should be considered in policymaking related to O3 control.

The particle size distributions of polychlorinated and polybrominated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs and PBDD/Fs, respectively; together labeled PXDD/Fs) in ambient air in a suburban area in Beijing, China, were determined. The sums of the concentrations of the 17 2,3,7,8-PCDD/Fs and the sums of the concentrations of the 13 2,3,7,8-PBDD/Fs that were analyzed were 1499-2799 fg m(-3) (95.4-175.4 fg I-TEQ m(-3)) and 1171-2424 fg m(-3) (42.2-109.3 fg TEQ m(-3)), respectively. The PXDD/Fs were mainly (similar to 90%) in the particulate phase. Significant linear correlations were found between the gas/particle partition coefficients (K-p) and subcooled liquid vapor pressures (P-L(0)) of the PXDD/Fs. The regression coefficients indicated that the PCDD/Fs were mainly adsorbed to the particles and that the PBDD/Fs were mainly absorbed by the particles. The concentrations of the PXDD/Fs increased as the particle size decreased. The highest PXDD/F concentrations were found in the d(ae) < 1.0 mu m particles and more than 80% of the PXDD/Fs were found to be in the dae < 2.5 mu m particles. Similar regression coefficients were found for the K-P against P-L(0) for the different particle size fractions in the air. The PXDD/F distribution profiles in particles of different sizes were also studied. The lower chlorinated PCDD/Fs were found at higher concentrations in the coarser particles, and the higher chlorinated PCDD/Fs were mainly found in the finer particles. Polybrominated dibenzofurans, particularly the higher brominated dibenzofurans, were the dominant PBDD/F congeners. The contributions of the higher brominated dibenzofurans to the total PBDD/F concentrations decreased as the particle size increased, but that was not the case for the polybrominated dibenzo-p-dioxins.

Dwarf bamboo (Indocalamus decorus) is an O3-tolerant plant species. To identify the possible mechanism and response of leaf morphological, antioxidant, and anatomical characteristics to elevated atmospheric O3 (EO3) concentrations, we exposed three-year-old I. decorus seedlings to three O3 levels (low O3-LO: ambient air; medium O3-MO: Ambient air+70ppb high O3-HO: Ambient air+140ppb O3) over a growing season using open-top chambers. Leaf shape and stomatal characteristics, and leaf microscopic structure of I. decorus were examined. The results indicated that 1) the stomata O3 flux (Fst) of HO decreased more rapidly under EO3 as the exposure time increased. The foliar O3 injury of HO and MO occurred when AOT40 was 26.62 ppm·h and 33.20 ppm·h, respectively, 2) under EO3, leaf number, leaf mass per area, leaf area, and stomata length/width all decreased, while leaf thickness, stomatal density, width, and area increased compared to the control, 3) MDA and total soluble protein contents all showed significantly increase under HO (36.57% and 32.77%) and MO(31.91% and 19.52%) while proline contents only increased under HO(33.27%). 4) MO and HO increased bulliform cells numbers in the leaves by 6.28% and 23.01%, respectively. HO reduced the transverse area of bulliform cells by 13.73%, while MO treatments had no effect, and 5) the number of fusoid cells interspace, the transverse area of fusoid cells interspace, and mesophyll thickness of HO significantly increased by 11.16%, 28.58%, and 13.42%, respectively. In conclusion, I. decorus exhibits strong O3 tolerance characteristics, which stem from adaptions in the leaf's morphological, structural, antioxidant, and anatomical features. One critical attribute was the enlargement of the bulliform cell transverse area and the transverse area of fusoid cells interspace that drove this resistance to O3. Local bamboo species with high resistance to O3 pollution thus need to be promoted for sustained productivity and ecosystem services in areas with high O3 pollution.

Ambient ozone (O3) concentrations generally increase in episodic but constant patterns. However, information on the response of plants to episodic exposure to O3 is limited. Maize is a C4 crop planted extensively around the world. In this study, maize plants were exposed to two different durations (30 days and 45 days) of elevated O3 concentration (eO3, +80 ppb above ambient) at the early and late growth stages for assessing the effects of the developmental stage of maize and recovery after exposure to eO3 on the photosynthetic parameters. The results showed that (1) eO3 significantly decreased the leaf chlorophyll (Chl) content, saturated photosynthetic rate (Asat), stomatal conductance (Cond), transpiration (Tr), maximum and saturated light photochemical efficiencies of PSII (Fv/Fm, Fv’/Fm’), non-photochemical quenching coefficient (qN), the quantum yield of non-cyclic electron transport (ΦPS2), and quantum yield of CO2 assimilation (ΦCO2); (2) significant differences were recorded between early and late exposure to eO3 in Asat, Cond, Tr, Fv/Fm, Fv’/Fm’, qN, ΦPS2, ΦCO2, etc.; (3) 30 days after O3 exposure was stopped, Chl, Fv/Fm, Fv’/Fm’, qN, Asat, qP, and ΦCO2 recovered fully or partially. The recovery was better when the plants were exposed to eO3 for 30 days than for 45 days. In conclusion, the developmental stage at which exposure occurred and the post-exposure recovery significantly influenced the photosynthetic response of maize to eO3 exposure. Thus, it is necessary to consider the developmental stage and recovery after exposure to eO3 while assessing the risk of O3 to crops.

Abstract Climate change leads to permafrost thawing, accelerating carbon emissions increases, challenges the goal of climate change mitigation. However, it remains unknown whether implementing ecological restoration projects in Alpine areas can offset the adverse effects of permafrost thawing locally. Here we took the Qinghai‒Tibet Plateau as an example to explore this issue based on the improved Biome-BGCMuSo model. We found future climate change-induced permafrost thawing will decrease carbon sink. Projects’ carbon sink enhancement could fully counteract the permafrost thawing-induced carbon loss. Additionally, future warmer and wetter climates will enlarge the suitable area for restoration. If these areas are taken into account, carbon sink attributable to Projects will further increase. These results indicate that ERPs have the potential to combat future permafrost thawing-induced carbon loss, and their contribution will be further amplified by future climate change.

Nitrous oxide (N2O) emissions from livestock manure contribute significantly to the growth of atmospheric N2O, a powerful greenhouse gas and dominant ozone-depleting substance. Here, we estimate global N2O emissions from livestock manure during 1890-2020 using the tier 2 approach of the 2019 Refinement to the 2006 IPCC Guidelines. Global N2O emissions from livestock manure increased by ~350% from 451 [368-556] Gg N year-1 in 1890 to 2042 [1677-2514] Gg N year-1 in 2020. These emissions contributed ~30% to the global anthropogenic N2O emissions in the decade 2010-2019. Cattle contributed the most (60%) to the increase, followed by poultry (19%), pigs (15%), and sheep and goats (6%). Regionally, South Asia, Africa, and Latin America dominated the growth in global emissions since the 1990s. Nationally, the largest emissions were found in India (329 Gg N year-1), followed by China (267 Gg N year-1), the United States (163 Gg N year-1), Brazil (129 Gg N year-1) and Pakistan (102 Gg N year-1) in the 2010s. We found a substantial impact of livestock productivity, specifically animal body weight and milk yield, on the emission trends. Furthermore, a large spread existed among different methodologies in estimates of global N2O emission from livestock manure, with our results 20%-25% lower than those based on the 2006 IPCC Guidelines. This study highlights the need for robust time-variant model parameterization and continuous improvement of emissions factors to enhance the precision of emission inventories. Additionally, urgent mitigation is required, as all available inventories indicate a rapid increase in global N2O emissions from livestock manure in recent decades.

In this work, we assessed the effects of increasing ozone (O3) on four petunia varieties with different floral pigmentation (pink, red, rose-red, and white). Plants were exposed, in open-top chambers located in China, to three O3 concentrations, i.e., (i) ambient air (AA), (ii) AA + 60 ppb O3 (AA + 60), and (iii) AA + 120 ppb O3 (AA + 120), for 85 days (9 h day−1). Flower diameter and duration were assessed, together with leaf chlorophyll and flavonoid contents. White petunia showed a reduced flower diameter and longevity under AA + 60 (−7 and −6%, respectively, in comparison to AA), whereas pink and red petunias only showed this under AA + 120 (−8 and −7%, on average, respectively). Chlorophyll loss occurred in all varieties under AA + 60 (−30%, on average), and at AA + 120 in white and red petunias (−54%, on average). The total flavonoid content in the pink and white varieties increased only under AA + 120 (around +85%), while it grew at both AA + 60 and AA + 120 (+92% and two-fold higher, respectively) in the red variety. Increasing O3 concentrations did not affect particularly the red-rose variety. The white variety showed the strongest correlations among flower and leaf properties, confirming a variety-related O3 response, as well as demonstrating that it had the highest O3 sensitivity.

The intermittent ozone (O3) exposure of crops to alternating high and low concentrations is common in fields, but its impact on crop production has not been thoroughly investigated. In this study, two widely planted and O3-sensitive crops, winter wheat and soybean, were intermittently exposed to elevated O3 concentrations in open-top chambers. The results showed that the winter wheat and soybean yields significantly decreased with O3 exposure (AOT40, cumulative hourly O3 concentration above 40 ppb) (p < 0.001). The relative yield losses were 0.99% per AOT40 for winter wheat and 1.2% per AOT40 for soybean, respectively. The responses of the crop biomasses to elevated O3 concentrations were lower than that of crop yield. Although the O3-induced crop yield and biomass losses under continuous O3 exposure were greater than those under intermittent O3 exposure, the differences were not statistically significant. Therefore, we can conclude that the effects of elevated O3 concentrations on crops are closely related to the exposure dose but not significantly related to the temporal distribution of elevated O3 concentrations. This study improves our understanding of how crop production responds to intermittent O3 exposure.

生态产品价值实现是指在维持生态系统稳定性和完整性的前提下,通过合理开发利用生态产品,将其生态价值转化为经济效益的过程.生态产品价值实现机制包含了促进生态产品价值实现的政策、市场和技术机制.生态产品通过各种途径实现的经济价值总和称为生态产品价值实现量.生态产品价值实现量与生态产品总值(GEP)的比值为生态产品价值实现率.评估生态产品价值实现率是评判生态产品价值实现状况的基础,是评估生态产品价值实现机制是否有效运转的重要前提.提出生态产品价值实现率的概念和核算方法,以浙江省丽水市为例,在核算GEP的基础上,评估生态产品价值实现量与实现率来分析丽水市生态产品价值实现状况、问题及影响因素,提出提高生态产品价值实现率的对策建议.研究表明,丽水市2019年GEP为4110.21亿元,生态产品价值实现量为1017.49亿元,生态产品价值实现率为24.76％.丽水生态产品价值实现模式主要有市场交易和政府补偿两种模式.市场交易模式贡献了95.84％的生态产品价值实现量,是目前丽水市最有效的生态产品价值实现模式,但存在价值实现效率不均衡、对于缺乏市场或是市场机制不成熟的生态产品不适用等问题.政府补偿模式贡献了4.16％的生态产品价值实现量,可广泛适用于各类产品价值实现,但存在价值实现效率低下、价值实现机制不成熟、价值实现资金来源单一、单项产品价值实现量小等问题.针对以上问题,研究建议通过完善生态产品市场交易机制、丰富生态补偿模式及资金来源、建立完整的生态产品产业链等途径促进丽水市生态产品价值实现.

城市是人类居住和活动最集中地区,其CO2排放量占世界总排放量的 71％,城市碳排放规律研究对全球碳减排工作具有重要意义.利用涡动相关技术观测了北京市某街区 2015 年至 2016 年的CO2通量,重点研究了不同时间尺度和气象条件下的CO2通量的日变化规律,分析了影响城市CO2通量的社会及自然因素.结果表明,CO2通量日变化特征具有(1)明显的早晚"双峰型"特征,早晚高峰分别出现在早上 7:30-9:30 和晚上 17:30-20:30;(2)周末特征:周末早高峰时间延迟,晚于工作日约1.5h,且峰值低了约 10.8％,但晚高峰时间提前,且峰值高于工作日约 10.6％;(3)季节特征:冬季CO2通量均值和早高峰值明显高于其他季节,夏季中午具有明显低峰区;(4)风向特征:在不同来风方向上,CO2通量的日变化峰值差异很大;(5)天气特征:阴天双峰特征比晴天明显.研究表明CO2通量日变化主要与交通流量动态变化关系最为密切,其次要受到植被的影响.因此,交通减排和植被增汇对于控制城市碳排放具有重要意义.

臭氧(O3)已经成为我国许多大中城市夏季的首要污染物,其具有较强的植物毒性,严重威胁农业安全.O3污染常发生于高温晴天,具有间歇性和累积性的特点,但现有研究多集中于在叶片尺度上探究长期O3暴露对植物生理过程的影响,而间歇性暴露对植物整株生长和光合生理特性的影响鲜有报道.以大豆为实验对象,依托开顶式气室(OTC)进行间歇性臭氧暴露,探究大豆叶片群体光合作用及产量对间歇性O3暴露的响应.结果发现(1)间歇性O3暴露具有累积性和恢复性,在低O3暴露剂量(AOT40≤2.47μL L_1 h_1)处理下,大豆植株的净光合速率降低,但与对照组无显著差异.当AOT40较高时(AOT40≤5.35μL L-1 h-1),大豆植株的净光合速率显著降低,而随着O3胁迫的消失,大豆植株的净光合速率逐渐回升,并最终恢复.(2)不同的光合参数对间歇性臭氧暴露敏感性不同,其中最大净光合速率最为敏感.在低AOT40下最大净光合速率显著降低,且恢复时间更长.(3)O3二次暴露后,净光合速率降低幅度较低,且恢复更快,说明间歇性O3暴露可能会提高大豆的耐受阈值.(4)当AOT40低于5.35μL L-1 h-1时,对大豆产量无显著影响,说明间歇性臭氧暴露条件下,大豆减产阈值更高.

The effects of volatile organic compounds on urban air quality and the ozone have been widely acknowledged, and the contributions of relevant biogenic sources are currently receiving rising attentions. However, inventories of biogenic volatile organic compounds (BVOCs) are in fact limited for the environmental management of megacities. In this study, we provided an estimation of BVOC emissions and their spatial characteristics in a typical urbanized area, Shenzhen megacity, China, based on an in-depth vegetation investigation and using remote sensing data. The total BVOC emission in Shenzhen in 2019 was estimated to be 3.84 × 109 g C, of which isoprene contributed to about 24.4%, monoterpenes about 44.4%, sesquiterpenes about 1.9%, and other VOCs (OVOCs) about 29.3%. Metropolitan BVOC emissions exhibited a seasonal pattern with a peak in July and a decline in January. They were mainly derived from the less built-up areas (88.9% of BVOC emissions). Estimated BVOCs comprised around 5.2% of the total municipal VOC emissions in 2019. This percentage may increase as more green spaces emerge and anthropogenic emissions decrease in built-up areas. Furthermore, synergistic effects existed between BVOC emissions and relevant vegetation-based ecosystem services (e.g., air purification, carbon fixation). Greening during urban sprawl should be based on a trade-off between BVOC emissions and ecosystem benefits of urban green spaces. The results suggested that urban greening in Shenzhen, and like other cities as well, need to account for BVOC contributions to ozone. Meanwhile, greening cites should adopt proactive environmental management by using plant species with low BVOC emissions to maintain urban ecosystem services while avoid further degradation to ozone pollution.

Urbanization-induced phenological changes have received considerable attention owing to their implications for determining urban ecosystem productivity and predicting the response of plants and ecosystem carbon cycles to future climate change. However, inconsistent rural-urban gradients in plant phenology remain, and phenological drivers other than temperature are poorly understood. In this study, we simultaneously observed the micro-climate and spring leaf phenology of seven woody plant species at 13 parks along a rural-urban gradient in Beijing, China. The minimum (Tmin) and mean (Tmean) air temperature and the minimum (VPDmin) and mean (VPDmean) vapor pressure deficit increased significantly along the rural-urban gradient, but the maximum air temperature (Tmax) and maximum vapor pressure deficit (VPDmax) did not. All observed leaf phenological phases for the seven species were significantly advanced along the rural-urban gradient by 0.20 to 1.02 days/km. Advances in the occurrence of leaf phenological events were significantly correlated with increases in Tmean (accounting for 57-59% variation), Tmin (21-26%), VPDmin (12-16%), and VPDmean (3-5%), but not with changes in Tmax or VPDmax. Advances in spring leaf phenology along the rural-urban gradient differed between non-native species and native species and between shrubs and trees. The reason may be mainly that the sensitivities of spring leaf phenology to micro-climate differ with species origin and growth form. This study highlights that urbanization-induced increases in Tmean and Tmin are the major contributors to advances in spring leaf phenology along the rural-urban gradient, exerting less influence on native species than on non-native species.

为探究近地面臭氧(O3)浓度升高对植物的不良影响随暴露时间延长的变化情况,本研究以小白菜(Brassica pekinensis)为研究对象,采用开顶式气室(OTC),设置4种O3浓度水平,即环境浓度(NF),环境浓度+40 nmol·mol-1(NF40),环境浓度+80 nmol·mol-1(NF80),环境浓度+120 nmol·mol-1(NF120).根据小白菜叶绿素(Chl)、类胡萝卜素(Car)、可溶性蛋白(SP)、可溶性糖(SS)、磷酸烯醇式丙酮酸羧化酶活性(PEPC)、丙二醛(MDA)、抗坏血酸(AsA)、谷胱甘肽(GSH)、总抗氧化能力(T-AOC)与O3暴露剂量(AOT40)的线性模型截距与模型斜率在不同测定时间的关系,明确O3浓度升高对小白菜叶片生理特征的影响随暴露时间的变化规律.研究发现,累积熏蒸28d时,随着O3浓度升高,与NF组相比,NF40、NF80、NF120组小白菜叶片Chl,Car和SP含量分别减少19.09%、30.45%、33.66%,12.85%、24.69%、27.78%和26.30%、37.89%、38.16%(P<0.05),而叶片MDA,SS,GSH,AsA,T-AOC含量分别增加 31.11%、33.42%、75.23%,165.61%、207.08%、306.00%,78.30%、89.08%、162.09%,14.47%、15.11%、92.35%,27.87%、32.84%、42.61%.结果表明,O3浓度升高会造成小白菜叶片光合色素下降和生理伤害增加,并诱使小白菜抵御O3胁迫的抗氧化能力增强.随着O3暴露时间延长,叶片中Chl、Car、SP、MDA对O3的敏感性(即指标对单位O3暴露剂量变化的响应大小)减弱(P<0.05),而SS、GSH、AsA、T-AOC对O3敏感性无显著变化,说明随着暴露时间延长O3胁迫对小白菜叶片生理特征的影响强度呈下降趋势,小白菜对O3胁迫的敏感性降低.研究表明,长时间高浓度O3熏蒸降低了小白菜的光合作用,提高了抗氧化能力,最终导致生物量降低,同时降低了小白菜对O3胁迫的敏感性.