共查询到20条相似文献，搜索用时 15 毫秒
1.
Susan E. Ward Nicholas J. Ostle Simon Oakley Helen Quirk Peter A. Henrys Richard D. Bardgett 《Ecology letters》2013,16(10):1285-1293
Understanding the effects of warming on greenhouse gas feedbacks to climate change represents a major global challenge. Most research has focused on direct effects of warming, without considering how concurrent changes in plant communities may alter such effects. Here, we combined vegetation manipulations with warming to investigate their interactive effects on greenhouse gas emissions from peatland. We found that although warming consistently increased respiration, the effect on net ecosystem CO2 exchange depended on vegetation composition. The greatest increase in CO2 sink strength after warming was when shrubs were present, and the greatest decrease when graminoids were present. CH4 was more strongly controlled by vegetation composition than by warming, with largest emissions from graminoid communities. Our results show that plant community composition is a significant modulator of greenhouse gas emissions and their response to warming, and suggest that vegetation change could alter peatland carbon sink strength under future climate change. 相似文献
2.
碳足迹是指由企业、组织或个人引起的碳排放的集合。参照PAS2050规范并结合生命周期评价方法对上海市水稻生产进行了碳足迹评估。结果表明:(1)目前上海市水稻生产的碳排放为11.8114 t CO2e/hm2,折合每吨水稻生产周期的碳足迹为1.2321 t CO2e;(2)稻田温室气体排放是水稻生产最主要的碳排放源,每吨水稻生产的总排放量为0.9507 t CO2e,占水稻生产全部碳排放的77.1%,其中甲烷(CH4)又是最主要的温室气体,对稻田温室气体碳排放的贡献率高达96.6%;(3)化学肥料的施用是第二大碳排放源,每吨水稻生产的总排放量为0.2044 t CO2e,占水稻生产总碳排放的16.5%,其中N最高,排放量为0.1159 t CO2e。因此,上海低碳水稻生产的关键在降低稻田甲烷的排放,另外可通过提高氮肥利用效率,减少氮肥施用等方法减少种植过程中碳排放。 相似文献
3.
Soil carbon cycling processes potentially play a large role in biotic feedbacks to climate change, but little agreement exists at present on what the core of numerical soil C cycling models should look like. In contrast, most canopy models of photosynthesis and leaf gas exchange share a common ‘Farquhaur‐model’ core structure. Here, we explore why a similar core model structure for heterotrophic soil respiration remains elusive and how a pathway to that goal might be envisioned. The spatial and temporal variation in soil microsite conditions greatly complicates modeling efforts, but we believe it is possible to develop a tractable number of parameterizable equations that are organized into a coherent, modular, numerical model structure. First, we show parallels in insights gleaned from linking Arrhenius and Michaelis–Menten kinetics for both photosynthesis and soil respiration. Additional equations and layers of complexity are then added to simulate substrate supply. For soils, model modules that simulate carbon stabilization processes will be key to estimating the fraction of soil C that is accessible to enzymes. Potential modules for dynamic photosynthate input, wetting‐event inputs, freeze–thaw impacts on substrate diffusion, aggregate turnover, soluble‐C sorption, gas transport, methane respiration, and microbial dynamics are described for conceptually and numerically linking our understanding of fast‐response processes of soil gas exchange with longer‐term dynamics of soil carbon and nitrogen stocks. 相似文献
4.
南方稻作区是我国重要的粮食生产区,在国家粮食安全保障中起着至关重要的作用,探明南方不同省份双季稻生产的碳足迹差异,对促进低碳稻作农业发展具有重要意义.本研究采用2004—2014年农作物种植面积、农资投入等统计数据,运用碳足迹理论和生命周期法系统评价我国南方双季稻生产碳足迹时空分布状况及其构成.结果表明: 南方稻区各个省份早晚稻生产碳足迹大部分表现为增加趋势,早稻生产碳足迹较晚稻大.2004—2014年,安徽省双季稻平均碳足迹最高(1000 kg CO2-eq·hm-2),而福建、湖北和湖南省相对较小(750 kg CO2-eq·hm-2).碳足迹构成中以肥料的生产、运输及使用占比最大,占水稻生产总碳足迹的60%;柴油投入碳足迹贡献量次之,为26%左右.逐步回归分析表明,双季稻生产碳足迹大小与柴油、复混肥和钾肥的投入呈正相关.净利润收益纳入分析表明,湖北省为低排放-高收益省份,有利于农业低碳可持续性发展.随着农村劳动力非农化和作物生产机械化的快速递增,未来水稻生产中柴油等机械化碳投入将快速增长.因此,提升化肥利用效率、灌溉效率和机械化作业效率将是发展南方稻作区低碳农业的关键途径. 相似文献
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6.
Release of greenhouse gases from thawing permafrost is potentially the largest terrestrial feedback to climate change and one of the most likely to occur; however, estimates of its strength vary by a factor of thirty. Some of this uncertainty stems from abrupt thaw processes known as thermokarst (permafrost collapse due to ground ice melt), which alter controls on carbon and nitrogen cycling and expose organic matter from meters below the surface. Thermokarst may affect 20–50% of tundra uplands by the end of the century; however, little is known about the effect of different thermokarst morphologies on carbon and nitrogen release. We measured soil organic matter displacement, ecosystem respiration, and soil gas concentrations at 26 upland thermokarst features on the North Slope of Alaska. Features included the three most common upland thermokarst morphologies: active‐layer detachment slides, thermo‐erosion gullies, and retrogressive thaw slumps. We found that thermokarst morphology interacted with landscape parameters to determine both the initial displacement of organic matter and subsequent carbon and nitrogen cycling. The large proportion of ecosystem carbon exported off‐site by slumps and slides resulted in decreased ecosystem respiration postfailure, while gullies removed a smaller portion of ecosystem carbon but strongly increased respiration and N2O concentration. Elevated N2O in gully soils persisted through most of the growing season, indicating sustained nitrification and denitrification in disturbed soils, representing a potential noncarbon permafrost climate feedback. While upland thermokarst formation did not substantially alter redox conditions within features, it redistributed organic matter into both oxic and anoxic environments. Across morphologies, residual organic matter cover, and predisturbance respiration explained 83% of the variation in respiration response. Consistent differences between upland thermokarst types may contribute to the incorporation of this nonlinear process into projections of carbon and nitrogen release from degrading permafrost. 相似文献
7.
Drained peatlands are hotspots for greenhouse gas (GHG) emissions, which could be mitigated by rewetting and land use change. We performed an ecological/economic analysis of rewetting drained fertile peatlands in a hemiboreal climate using different land use strategies over 80 years. Vegetation, soil processes, and total GHG emissions were modeled using the CoupModel for four scenarios: (1) business as usual—Norway spruce with average soil water table of ?40 cm; (2) willow with groundwater at ?20 cm; (3) reed canary grass with groundwater at ?10 cm; and (4) a fully rewetted peatland. The predictions were based on previous model calibrations with several high‐resolution datasets consisting of water, heat, carbon, and nitrogen cycling. Spruce growth was calibrated by tree‐ring data that extended the time period covered. The GHG balance of four scenarios, including vegetation and soil, were 4.7, 7.1, 9.1, and 6.2 Mg CO2eq ha?1 year?1, respectively. The total soil emissions (including litter and peat respiration CO2 + N2O + CH4) were 33.1, 19.3, 15.3, and 11.0 Mg CO2eq ha?1 year?1, respectively, of which the peat loss contributed 35%, 24%, and 7% of the soil emissions for the three drained scenarios, respectively. No peat was lost for the wet peatland. It was also found that draining increases vegetation growth, but not as drastically as peat respiration does. The cost–benefit analysis (CBA) is sensitive to time frame, discount rate, and carbon price. Our results indicate that the net benefit was greater with a somewhat higher soil water table and when the peatland was vegetated with willow and reed canary grass (Scenarios 2 and 3). We conclude that saving peat and avoiding methane release using fairly wet conditions can significantly reduce GHG emissions, and that this strategy should be considered for land use planning and policy‐making. 相似文献
8.
从生命周期角度看,建筑碳足迹与能源和建材生产系统具有密切关系。随着技术的进步和节能政策的推进,中国能源的生产和使用,以及建材生产过程中的环境排放都随着时间在持续降低,这将间接地影响到建筑的环境表现。依据1990—2010年期间每5a的中国能源与建材生命周期清单数据,对北京市20年间住宅建筑系统开展生命周期评价和碳足迹核算,以揭示北京市住宅建筑系统的环境负荷变化特征。结果表明,北京市住宅建筑生命周期碳足迹随时间推移呈现降低趋势,主要来自能源系统和建材生产系统的碳减排贡献。不同结构建筑的碳足迹尽管有差异,但也呈现了相似的下降趋势。从生命周期阶段看,建筑碳足迹主要体现在建筑使用阶段和建材生产阶段。尽管建筑使用阶段的节能对于降低建筑生命周期碳足迹具有重要贡献,但节能在经济成本及环境成本方面而言是有限度的。在可持续的环境政策管理制定中,应从生命周期角度,统筹考虑协调各行业减碳的协调发展。论文同时也验证了在生命周期评价中考虑时间变量将有助于更好地利用生命周期评价结果支持环境可持续管理。结论对于城市规划的政策制定、量化环境表现是有益的。 相似文献
9.
Nuria Gomez‐Casanovas Tara W. Hudiburg Carl J. Bernacchi William J. Parton Evan H. DeLucia 《Global Change Biology》2016,22(4):1348-1360
Increases in atmospheric nitrogen deposition (Ndep) can strongly affect the greenhouse gas (GHG; CO2, CH4, and N2O) sink capacity of grasslands as well as other terrestrial ecosystems. Robust predictions of the net GHG sink strength of grasslands depend on how experimental N loads compare to projected Ndep rates, and how accurately the relationship between GHG fluxes and Ndep is characterized. A literature review revealed that the vast majority of experimental N loads were higher than levels these ecosystems are predicted to experience in the future. Using a process‐based biogeochemical model, we predicted that low levels of Ndep either enhanced or reduced the net GHG sink strength of most grasslands, but as experimental N loads continued to increase, grasslands transitioned to a N saturation‐decline stage, where the sensitivity of GHG exchange to further increases in Ndep declined. Most published studies represented treatments well into the N saturation‐decline stage. Our model results predict that the responses of GHG fluxes to N are highly nonlinear and that the N saturation thresholds for GHGs varied greatly among grasslands and with fire management. We predict that during the 21st century some grasslands will be in the N limitation stage where others will transition into the N saturation‐decline stage. The linear relationship between GHG sink strength and N load assumed by most studies can overestimate or underestimate predictions of the net GHG sink strength of grasslands depending on their N baseline status. The next generation of global change experiments should be designed at multiple N loads consistent with future Ndep rates to improve our empirical understanding and predictive ability. 相似文献
10.
Cameron M. Pittelkow Maria A. Adviento‐Borbe Chris van Kessel James E. Hill Bruce A. Linquist 《Global Change Biology》2014,20(5):1382-1393
To meet growing global food demand with limited land and reduced environmental impact, agricultural greenhouse gas (GHG) emissions are increasingly evaluated with respect to crop productivity, i.e., on a yield‐scaled as opposed to area basis. Here, we compiled available field data on CH4 and N2O emissions from rice production systems to test the hypothesis that in response to fertilizer nitrogen (N) addition, yield‐scaled global warming potential (GWP) will be minimized at N rates that maximize yields. Within each study, yield N surplus was calculated to estimate deficit or excess N application rates with respect to the optimal N rate (defined as the N rate at which maximum yield was achieved). Relationships between yield N surplus and GHG emissions were assessed using linear and nonlinear mixed‐effects models. Results indicate that yields increased in response to increasing N surplus when moving from deficit to optimal N rates. At N rates contributing to a yield N surplus, N2O and yield‐scaled N2O emissions increased exponentially. In contrast, CH4 emissions were not impacted by N inputs. Accordingly, yield‐scaled CH4 emissions decreased with N addition. Overall, yield‐scaled GWP was minimized at optimal N rates, decreasing by 21% compared to treatments without N addition. These results are unique compared to aerobic cropping systems in which N2O emissions are the primary contributor to GWP, meaning yield‐scaled GWP may not necessarily decrease for aerobic crops when yields are optimized by N fertilizer addition. Balancing gains in agricultural productivity with climate change concerns, this work supports the concept that high rice yields can be achieved with minimal yield‐scaled GWP through optimal N application rates. Moreover, additional improvements in N use efficiency may further reduce yield‐scaled GWP, thereby strengthening the economic and environmental sustainability of rice systems. 相似文献
11.
We investigated the effects of elevated ozone concentration (E‐O3) on CH4 and N2O emission from paddies with two rice cultivars: an inbred Indica cultivar Yangdao 6 (YD6) and a hybrid one II‐you 084 (IIY084), under fully open‐air field conditions in China. A mean 26.7% enhancement of ozone concentration above the ambient level (A‐O3) significantly reduced CH4 emission at tillering and flowering stages leading to a reduction of seasonal integral CH4 emission by 29.6% on average across the two cultivars. The reduced CH4 emission is associated with O3‐induced reduction in the whole‐plant biomass (?13.2%), root biomass (?34.7%), and maximum tiller number (?10.3%), all of which curbed the carbon supply for belowground CH4 production and its release from submerged soil to atmosphere. Although no significant difference was detected between the cultivars in the CH4 emission response to E‐O3, a larger decrease in CH4 emission with IIY084 (?33.2%) than that with YD6 (?7.0%) was observed at tillering stage, which may be due to the larger reduction in tiller number in IIY084 by E‐O3. Additionally, E‐O3 reduced seasonal mean NOx flux by 5.7% and 11.8% with IIY084 and YD6, respectively, but the effects were not significant statistically. We found that the relative response of CH4 emission to E‐O3 was not significantly different from those reported in open‐top chamber experiments. This study has thus confirmed that increasing ozone concentration would mitigate the global warming potential of CH4 and suggested consideration of the feedback mechanism between ozone and its precursor emission into the projection of future ozone effects on terrestrial ecosystem. 相似文献
12.
Amanda J. Holder John Clifton‐Brown Rebecca Rowe Paul Robson Dafydd Elias Marta Dondini Niall P. McNamara Iain S. Donnison Jon P. McCalmont 《Global Change Biology Bioenergy》2019,11(10):1173-1186
Soil organic carbon (SOC) is an important carbon pool susceptible to land‐use change (LUC). There are concerns that converting grasslands into the C4 bioenergy crop Miscanthus (to meet demands for renewable energy) could negatively impact SOC, resulting in reductions of greenhouse gas mitigation benefits gained from using Miscanthus as a fuel. This work addresses these concerns by sampling soils (0–30 cm) from a site 12 years (T12) after conversion from marginal agricultural grassland into Miscanthus x giganteus and four other novel Miscanthus hybrids. Soil samples were analysed for changes in below‐ground biomass, SOC and Miscanthus contribution to SOC (using a 13C natural abundance approach). Findings are compared to ECOSSE soil carbon model results (run for a LUC from grassland to Miscanthus scenario and continued grassland counterfactual), and wider implications are considered in the context of life cycle assessments based on the heating value of the dry matter (DM) feedstock. The mean T12 SOC stock at the site was 8 (±1 standard error) Mg C/ha lower than baseline time zero stocks (T0), with assessment of the five individual hybrids showing that while all had lower SOC stock than at T0 the difference was only significant for a single hybrid. Over the longer term, new Miscanthus C4 carbon replaces pre‐existing C3 carbon, though not at a high enough rate to completely offset losses by the end of year 12. At the end of simulated crop lifetime (15 years), the difference in SOC stocks between the two scenarios was 4 Mg C/ha (5 g CO2‐eq/MJ). Including modelled LUC‐induced SOC loss, along with carbon costs relating to soil nitrous oxide emissions, doubled the greenhouse gas intensity of Miscanthus to give a total global warming potential of 10 g CO2‐eq/MJ (180 kg CO2‐eq/Mg DM). 相似文献
13.
《应用生态学报》2025,36(4)
新疆是我国棉花的主产区和粮食作物的重要生产基地,如今正面临着保障国家粮食安全和实现低碳农业发展的双重压力。全面核算该地区主要农作物生产碳足迹,可从碳减排的视角为新疆主要农作物种植结构调整和生产体系全过程环境管理提供决策依据。本研究基于2005—2021年新疆小麦、玉米和棉花的种植面积、产量和农资生产投入量等数据,采用生命周期评价法核算该区域上述3大主要农作物的生产碳足迹,并采用灰色关联度分析其影响因素。结果表明: 2005—2021年间,新疆小麦、玉米的种植面积主要随棉花种植面积的变动而变动。小麦、玉米和棉花的年均单位面积碳足迹分别为2.21、2.67、3.61 t CE·hm-2;年均单位产量碳足迹分别为0.41、0.35、1.91 t CE·t-1。在碳效率上,3种作物的碳生态效率表现为:小麦(10.99 t CE·t CE-1)>玉米(9.68 t CE·t CE-1)>棉花(2.96 t CE·t CE-1);碳生产效率表现为:玉米(2.88 t·t CE-1)>小麦(2.48 t·t CE-1)>棉花(0.53 t·t CE-1);碳经济效率表现为:棉花(7148.74×103 yuan·t CE-1)>玉米(6094.32×103 yuan·t CE-1)>小麦(5904.23×103 yuan·t CE-1)。在碳投入结构上,农田N2O排放和化肥投入是3种作物生产碳足迹的主要来源;机械总动力、作物种植面积、有效灌溉面积、农膜用量、复合肥和氮肥投入的变化是作物碳足迹年际变化的主要驱动因素。由2022、2023年新疆小麦、玉米和棉花的生产碳足迹分析可知,未来新疆需要适度调整3大主要农作物的种植结构,并通过科技进步提高化肥利用效率、农膜利用率、灌溉和机械作业效率,在深入实施国家粮食安全战略的同时实现农作物的低碳生产。 相似文献
14.
各种层面上的碳足迹核算在全球气候变化控制领域得到了越来越多的关注。但是,这些关于碳足迹核算的相关国际标准繁多,彼此之间的关系复杂,不利于研究领域和工业界对这些标准进行应用与交流,限制了碳足迹核算的发展进度与深度。对目前已有的国际主要碳足迹核算标准及生命周期评价标准进行了整理,梳理出这些国际标准的一些基本特征,绘制了国际标准之间的关系图;并进一步从生命周期评价步骤的角度出发,解析了各种国际标准在这些阶段上的相关内容,以及每一个阶段上各标准相关规定中的不同特点及逻辑关系。对促进我国碳足迹核算相关研究与实践工作具有一定的理论与现实参考意义。 相似文献
15.
Junji Yuan Weixin Ding Deyan Liu Hojeong Kang Chris Freeman Jian Xiang Yongxin Lin 《Global Change Biology》2015,21(4):1567-1580
Coastal salt marshes are sensitive to global climate change and may play an important role in mitigating global warming. To evaluate the impacts of Spartina alterniflora invasion on global warming potential (GWP) in Chinese coastal areas, we measured CH4 and N2O fluxes and soil organic carbon sequestration rates along a transect of coastal wetlands in Jiangsu province, China, including open water; bare tidal flat; and invasive S. alterniflora, native Suaeda salsa, and Phragmites australis marshes. Annual CH4 emissions were estimated as 2.81, 4.16, 4.88, 10.79, and 16.98 kg CH4 ha?1 for open water, bare tidal flat, and P. australis, S. salsa, and S. alterniflora marshes, respectively, indicating that S. alterniflora invasion increased CH4 emissions by 57–505%. In contrast, negative N2O fluxes were found to be significantly and negatively correlated (P < 0.001) with net ecosystem CO2 exchange during the growing season in S. alterniflora and P. australis marshes. Annual N2O emissions were 0.24, 0.38, and 0.56 kg N2O ha?1 in open water, bare tidal flat and S. salsa marsh, respectively, compared with ‐0.51 kg N2O ha?1 for S. alterniflora marsh and ?0.25 kg N2O ha?1 for P. australis marsh. The carbon sequestration rate of S. alterniflora marsh amounted to 3.16 Mg C ha?1 yr?1 in the top 100 cm soil profile, a value that was 2.63‐ to 8.78‐fold higher than in native plant marshes. The estimated GWP was 1.78, ?0.60, ?4.09, and ?1.14 Mg CO2eq ha?1 yr?1 in open water, bare tidal flat, P. australis marsh and S. salsa marsh, respectively, but dropped to ?11.30 Mg CO2eq ha?1 yr?1 in S. alterniflora marsh. Our results indicate that although S. alterniflora invasion stimulates CH4 emissions, it can efficiently mitigate increases in atmospheric CO2 and N2O along the coast of China. 相似文献
16.
Alan Gray Peter E. Levy Mark D. A. Cooper Timothy Jones Jenny Gaiawyn Sarah R. Leeson Susan E. Ward Kerry J. Dinsmore Julia Drewer Lucy J. Sheppard Nick J. Ostle Chris D. Evans Annette Burden Piotr Zieliński 《Global Change Biology》2013,19(4):1141-1150
Previous studies have shown a correspondence between the abundance of particular plant species and methane flux. Here, we apply multivariate analyses, and weighted averaging, to assess the suitability of vegetation composition as a predictor of methane flux. We developed a functional classification of the vegetation, in terms of a number of plant traits expected to influence methane production and transport, and compared this with a purely taxonomic classification at species level and higher. We applied weighted averaging and indirect and direct ordination approaches to six sites in the United Kingdom, and found good relationships between methane flux and vegetation composition (classified both taxonomically and functionally). Plant species and functional groups also showed meaningful responses to management and experimental treatments. In addition to the United Kingdom, we applied the functional group classification across different geographical regions (Canada and the Netherlands) to assess the generality of the method. Again, the relationship appeared good at the site level, suggesting some general applicability of the functional classification. The method seems to have the potential for incorporation into large‐scale (national) greenhouse gas accounting programmes (in relation to peatland condition/management) using vegetation mapping schemes. The results presented here strongly suggest that robust predictive models can be derived using plant species data (for use in national‐scale studies). For trans‐national‐scale studies, where the taxonomic assemblage of vegetation differs widely between study sites, a functional classification of plant species data provides an appropriate basis for predictive models of methane flux. 相似文献
17.
D. Bruhn T. N. Mikkelsen M. M. M. Rolsted H. Egsgaard P. Ambus 《Plant biology (Stuttgart, Germany)》2014,16(2):512-516
The terrestrial vegetation is a source of UV radiation‐induced aerobic methane (CH4) release to the atmosphere. Hitherto pectin, a plant structural component, has been considered as the most likely precursor for this CH4 release. However, most of the leaf pectin is situated below the surface wax layer, and UV transmittance of the cuticle differs among plant species. In some species, the cuticle effectively absorbs and/or reflects UV radiation. Thus, pectin may not necessarily contribute substantially to the UV radiation‐induced CH4 emission measured at surface level in all species. Here, we investigated the potential of the leaf surface wax itself as a source of UV radiation‐induced leaf aerobic CH4 formation. Isolated leaf surface wax emitted CH4 at substantial rates in response to UV radiation. This discovery has implications for how the phenomenon should be scaled to global levels. In relation to this, we demonstrated that the UV radiation‐induced CH4 emission is independent of leaf area index above unity. Further, we observed that the presence of O2 in the atmosphere was necessary for achieving the highest rates of CH4 emission. Methane formation from leaf surface wax is supposedly a two‐step process initiated by a photolytic rearrangement reaction of the major component followed by an α‐cleavage of the generated ketone. 相似文献
18.
MARCELO VALADARES GALDOS CARLOS CLEMENTE CERRI RATTAN LAL† MARTIAL BERNOUX‡ BRIGITTE FEIGL CARLOS EDUARDO P. CERRI§ 《Global Change Biology Bioenergy》2010,2(1):37-44
Biofuels are both a promising solution to global warming mitigation and a potential contributor to the problem. Several life cycle assessments of bioethanol have been conducted to address these questions. We performed a synthesis of the available data on Brazilian ethanol production focusing on greenhouse gas (GHG) emissions and carbon (C) sinks in the agricultural and industrial phases. Emissions of carbon dioxide (CO2) from fossil fuels, methane (CH4) and nitrous oxide (N2O) from sources commonly included in C footprints, such as fossil fuel usage, biomass burning, nitrogen fertilizer application, liming and litter decomposition were accounted for. In addition, black carbon (BC) emissions from burning biomass and soil C sequestration were included in the balance. Most of the annual emissions per hectare are in the agricultural phase, both in the burned system (2209 out of a total of 2398 kg Ceq), and in the unburned system (559 out of 748 kg Ceq). Although nitrogen fertilizer emissions are large, 111 kg Ceq ha?1 yr?1, the largest single source of emissions is biomass burning in the manual harvest system, with a large amount of both GHG (196 kg Ceq ha?1 yr?1). and BC (1536 kg Ceq ha?1 yr?1). Besides avoiding emissions from biomass burning, harvesting sugarcane mechanically without burning tends to increase soil C stocks, providing a C sink of 1500 kg C ha?1 yr?1 in the 30 cm layer. The data show a C output: input ratio of 1.4 for ethanol produced under the conventionally burned and manual harvest compared with 6.5 for the mechanized harvest without burning, signifying the importance of conservation agricultural systems in bioethanol feedstock production. 相似文献
19.
Henrique O. Sawakuchi David Bastviken André O. Sawakuchi Alex V. Krusche Maria V. R. Ballester Jeffrey E. Richey 《Global Change Biology》2014,20(9):2829-2840
Methane (CH4) fluxes from world rivers are still poorly constrained, with measurements restricted mainly to temperate climates. Additional river flux measurements, including spatio‐temporal studies, are important to refine extrapolations. Here we assess the spatio‐temporal variability of CH4 fluxes from the Amazon and its main tributaries, the Negro, Solimões, Madeira, Tapajós, Xingu, and Pará Rivers, based on direct measurements using floating chambers. Sixteen of 34 sites were measured during low and high water seasons. Significant differences were observed within sites in the same river and among different rivers, types of rivers, and seasons. Ebullition contributed to more than 50% of total emissions for some rivers. Considering only river channels, our data indicate that large rivers in the Amazon Basin release between 0.40 and 0.58 Tg CH4 yr?1. Thus, our estimates of CH4 flux from all tropical rivers and rivers globally were, respectively, 19–51% to 31–84% higher than previous estimates, with large rivers of the Amazon accounting for 22–28% of global river CH4 emissions. 相似文献
20.
In several hazel (Corylus avellana L.) groves in the area of Langhe (Piedmont, Northwest Italy), many hazel branches suddenly withered, and in some cases, the whole tree died, with heavy economic losses for the farmers. Symptoms of jewel beetle attacks were detected on the trees. Eight Agrilus species were caught by traps from 2007 to 2009 in the surveyed hazel groves; among them, only four species have been known to develop on hazel. On the traps, Agrilus olivicolor Kiesenwetter was the most abundant species, while almost only Agrilus viridis (L.) was sampled by plant beating from 2008 to 2010. Moreover, almost all adults emerged from field‐collected hazel wood belonged to this latter species that proved to be the main responsible for the severe attacks on the hazel trees. Agrilus viridis adults emerged from late May to late June, and generally lived until the end of August, while egg masses were observed from late May to late July. The egg parasitoid Oobius zahaikevitshi Trjapitzin was found in all of the investigated groves; adults emerged already from the first egg masses collected on hazel trees in late May‐early June. O. zahaikevitshi was able to largely reduce A. viridis populations, with a parasitism rate of more than 50% in some groves. Recent attacks of A. viridis were related to a long period of drought; however, appropriate agronomic practices to minimize the effects of water stress and to conserve natural enemies, such as O. zahaikevitshi, could be more effective to protect hazel groves against boring beetle attacks. 相似文献