60Coγ射线辐照对花魔芋农艺性状的影响

本试验开展了^60Coγ射线辐照对花魔芋(Amorphophallus konjac)农艺性状影响的研究。结果表明：辐射诱发了大量有利的或损伤的数量性状变异。这些可观察或可检测的变异有形态异常,主要表现为植株矮小及叶片畸形(包括叶片黄化、缺刻、叶卷曲及主叶脉粘连不分离等);还有其它的性状变化,如生长期、根系、鞭状茎分化、耐寒性,球茎增重和产量等。观察发现,辐射效应的主要特征是抑制和损伤,并有一定程度的生理修复。通过分析,这些数量性状的变化符合统计规律,如植株叶片面积的变化与辐射剂量关系可拟合成三次曲线,其它的性状变化与剂量成二次曲线。在花魔芋生长期间发现了大叶片植株、耐寒植株、少鞭状茎分化植株和高球茎增重系数植株等有益突变。大叶片可增加光合作用面积,提高产量;少鞭状茎分化可减少球茎物质分流,使积累更加有效;耐寒抗寒既可延长生长期,也可扩大种植范围和向适宜地区推广。通过实验,得出花魔芋的辐射敏感性强,诱变效应显著,性状变异有可选择性,辐射诱变育种和种质改良可行。此外,魔芋种植多采用无性繁殖方式,有些有利的变异性状可直接作为育种和引种驯化的基础材料利用。     

传统稻鱼系统中“田鲤鱼”的形态特征

稻田养鱼是一种重要的传统农业系统,养殖在稻田中的鲤鱼,在长期的自然选择和人工选择下逐渐形成了适应于稻田浅水环境的“田鲤鱼”.本研究以具有千年历史的全球重要农业文化遗产系统“青田稻鱼共生系统”和“从江稻鱼鸭系统”的青田田鱼和从江田鱼为范例,通过采样对两种“田鲤鱼”进行传统形态学分析和地标几何形态学分析;采用线粒体基因构建系统发育树;通过数据库数据提取和采样测量对两种“田鲤鱼”和其他常见鲤鱼种群或品系进行传统形态学聚类分析.传统形态学分析和地标几何形态学分析表明,青田田鱼和从江田鱼在形态上存在差异,与青田田鱼相比,从江田鱼尾部长而窄,体型较细长,尾部长度占身体长度比例小.对这两种田鱼及养殖于其他水体的其他鲤鱼种群进行系统发育树分析表明,青田田鱼和从江田鱼在遗传上是独立的种群;但形态聚类分析表明,这两种田鱼归为一类,明显不同于其他鲤鱼种群或品系,与其他鲤鱼种群的差异主要表现在背鳍和尾鳍上.这些研究结果说明,长期生活在稻田环境的青田田鱼和从江田鱼在遗传和形态上均明显不同于其他水体养殖鲤鱼种群,且青田田鱼和从江田鱼之间形态上存在差异.     

崇义客家梯田生态系统服务功能

开展崇义客家梯田系统生态服务功能价值评估,有助于人们更好地了解梯田系统对崇义客家社会的重要贡献,为当地政府保护客家梯田系统提供重要依据.本研究基于崇义客家梯田系统及其所处区域的社会经济特征,构建了相应的生态服务功能价值评估指标体系;运用定性分析法对客家梯田系统的生态服务功能机理及其重要性作了识别;以2014年统计数据为基础,采用物质量和价值量相结合的定量评价方法,对客家梯田系统的9项生态服务指标进行评估.结果表明: 在评估的9项指标中,土壤保持的物质量和价值量同居各指标之首,分别为76457 kg·hm^-2和105033 元·hm^-2,相应地占梯田系统总物质量和总价质量的72.2%和30.0%.文化传承和景观体现了客家梯田系统独特的生态服务功能,价值量分别为100000和46333元·hm^-2,位居9项指标的2、3位.产品供给是客家梯田系统提供给崇义客家人的重要福祉,但其物质量和价值量只占梯田系统生态服务总物质量和总价值量的6.1%与10.4%,因此仅考虑产品供给将严重低估梯田系统的生态服务功能.直观的经济数字反映了客家梯田系统对社会的巨大贡献,不仅有利于提高管理者和公众保护农业文化遗产的意识,也为政府制定客家梯田系统生态补偿标准提供了数据支撑.     

Reduced abundance and earlier collection of bumble bee workers under intensive cultivation of a mass‐flowering prairie crop

One of the most commonly seeded crops in Canada is canola, a cultivar of oilseed rape (Brassica napus). As a mass‐flowering crop grown intensively throughout the Canadian Prairies, canola has the potential to influence pollinator success across tens of thousands of square kilometers of cropland. Bumble bees (Bombus sp.) are efficient pollinators of many types of native and crop plants. We measured the influence of this mass‐flowering crop on the abundance and phenology of bumble bees, and on another species of social bee (a sweat bee; Halictus rubicundus), by continuously deploying traps at different levels of canola cultivation intensity, spanning the start and end of canola bloom. Queen bumble bees were more abundant in areas with more canola cover, indicating that this crop is attractive to queens. However, bumble bee workers were significantly fewer in these locations later in the season, suggesting reduced colony success. The median collection dates of workers of three bumble bee species were earlier near canola fields, suggesting a dynamic response of colonies to the increased floral resources. Different species experienced this shift to different extents. The sweat bee was not affected by canola cultivation intensity. Our findings suggest that mass‐flowering crops such as canola are attractive to bumble bee queens and therefore may lead to higher rates of colony establishment, but also that colonies established near this crop may be less successful. We propose that the effect on bumble bees can be mitigated by spacing the crop more evenly with respect to alternate floral resources.     

Surface N balances and reactive N loss to the environment from global intensive agricultural production systems for the period 1970-2030

Data for the historical years 1970 and 1995 and the FAO-Agriculture Towards 2030 projection are used to calculate N inputs (N fertilizer, animal manure, biological N fixation and atmospheric deposition) and the N export from the field in harvested crops and grass and grass consumption by grazing animals. In most industrialized countries we see a gradual increase of the overall N recovery of the intensive agricultural production systems over the whole 1970-2030 period. In contrast, low N input systems in many developing countries sustained low crop yields for many years but at the cost of soil fertility by depleting soil nutrient pools. In most developing countries the N recovery will increase in the coming decades by increasing efficiencies of N use in both crop and livestock production systems. The surface balance surplus of N is lost from the agricultural system via different pathways, including NH3 volatilization, denitrification, N2O and NO emissions, and nitrate leaching from the root zone. Global NH3-N emissions from fertilizer and animal manure application and stored manure increased from 18 to 34 Tg·yr-1 between 1970 and 1995, and will further increase to 44 Tg·yr-1 in 2030. Similar developments are seen for N2O-N (2.0 Tg·yr-1 in 1970, 2.7 Tg·yr-1 in 1995 and 3.5 Tg·yr-1 in 2030) and NO-N emissions (1.1 Tg·yr-1 in 1970, 1.5Tg·yr-1 in 1995 and 2.0 Tg·yr-1 in 2030).     

Agricultural intensification increases deforestation fire activity in Amazonia

Fire-driven deforestation is the major source of carbon emissions from Amazonia. Recent expansion of mechanized agriculture in forested regions of Amazonia has increased the average size of deforested areas, but related changes in fire dynamics remain poorly characterized. We estimated the contribution of fires from the deforestation process to total fire activity based on the local frequency of active fire detections from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensors. High-confidence fire detections at the same ground location on 2 or more days per year are most common in areas of active deforestation, where trunks, branches, and stumps can be piled and burned many times before woody fuels are depleted. Across Amazonia, high-frequency fires typical of deforestation accounted for more than 40% of the MODIS fire detections during 2003–2007. Active deforestation frontiers in Bolivia and the Brazilian states of Mato Grosso, Pará, and Rondônia contributed 84% of these high-frequency fires during this period. Among deforested areas, the frequency and timing of fire activity vary according to postclearing land use. Fire usage for expansion of mechanized crop production in Mato Grosso is more intense and more evenly distributed throughout the dry season than forest clearing for cattle ranching (4.6 vs. 1.7 fire days per deforested area, respectively), even for clearings >200 ha in size. Fires for deforestation may continue for several years, increasing the combustion completeness of cropland deforestation to nearly 100% and pasture deforestation to 50–90% over 1–3-year timescales typical of forest conversion. Our results demonstrate that there is no uniform relation between satellite-based fire detections and carbon emissions. Improved understanding of deforestation carbon losses in Amazonia will require models that capture interannual variation in the deforested area that contributes to fire activity and variable combustion completeness of individual clearings as a function of fire frequency or other evidence of postclearing land use.     

Contemporary carbon accumulation in a boreal oligotrophic minerogenic mire – a significant sink after accounting for all C-fluxes

Based on theories of mire development and responses to a changing climate, the current role of mires as a net carbon sink has been questioned. A rigorous evaluation of the current net C-exchange in mires requires measurements of all relevant fluxes. Estimates of annual total carbon budgets in mires are still very limited. Here, we present a full carbon budget over 2 years for a boreal minerogenic oligotrophic mire in northern Sweden (64°11′N, 19°33′E). Data on the following fluxes were collected: land–atmosphere CO₂ exchange (continuous Eddy covariance measurements) and CH₄ exchange (static chambers during the snow free period); TOC (total organic carbon) in precipitation; loss of TOC, dissolved inorganic carbon (DIC) and CH₄ through stream water runoff (continuous discharge measurements and regular C-concentration measurements). The mire constituted a net sink of 27±3.4 (±SD) g C m⁻² yr⁻¹ during 2004 and 20±3.4 g C m⁻² yr⁻¹ during 2005. This could be partitioned into an annual surface–atmosphere CO₂ net uptake of 55±1.9 g C m⁻² yr⁻¹ during 2004 and 48±1.6 g C m⁻² yr⁻¹ during 2005. The annual NEE was further separated into a net uptake season, with an uptake of 92 g C m⁻² yr⁻¹ during 2004 and 86 g C m⁻² yr⁻¹ during 2005, and a net loss season with a loss of 37 g C m⁻² yr⁻¹ during 2004 and 38 g C m⁻² yr⁻¹ during 2005. Of the annual net CO₂-C uptake, 37% and 31% was lost through runoff (with runoff TOC>DIC≫CH₄) and 16% and 29% through methane emission during 2004 and 2005, respectively. This mire is still a significant C-sink, with carbon accumulation rates comparable to the long-term Holocene C-accumulation, and higher than the C-accumulation during the late Holocene in the region.     

Will climate change be beneficial or detrimental to the invasive swede midge in North America? Contrasting predictions using climate projections from different general circulation models

Climate change may dramatically affect the distribution and abundance of organisms. With the world's population size expected to increase significantly during the next 100 years, we need to know how climate change might impact our food production systems. In particular, we need estimates of how future climate might alter the distribution of agricultural pests. We used the climate projections from two general circulation models (GCMs) of global climate, the Canadian Centre for Climate Modelling and Analysis GCM (CGCM2) and the Hadley Centre model (HadCM3), for the A2 and B2 scenarios from the Special Report on Emissions Scenarios in conjunction with a previously published bioclimatic envelope model (BEM) to predict the potential changes in distribution and abundance of the swede midge, Contarinia nasturtii, in North America. The BEM in conjunction with either GCM predicted that C. nasturtii would spread from its current initial invasion in southern Ontario and northwestern New York State into the Canadian prairies, northern Canada, and midwestern United States, but the magnitude of risk depended strongly on the GCM and the scenario used. When the CGCM2 projections were used, the BEM predicted an extensive shift in the location of the midges' climatic envelope through most of Ontario, Quebec, and the maritime and prairie provinces by the 2080s. In the United States, C. nasturtii was predicted to spread to all the Great Lake states, into midwestern states as far south as Colorado, and west into Washington State. When the HadCM3 was applied, southern Ontario, Saskatchewan, and Washington State were not as favourable for C. nasturtii by the 2080s. Indeed, when used with the HadCM3 climate projections, the BEM predicted the virtual disappearance of ‘very favourable’ regions for C. nasturtii. The CGCM2 projections generally caused the BEM to predict a small increase in the mean number of midge generations throughout the course of the century, whereas, the HadCM3 projections resulted in roughly the same mean number of generations but decreased variance. Predictions of the likely potential of C. nasturtii spatial spread are thus strongly dependent on the source of climate projections. This study illustrates the importance of using multiple GCMs in combination with multiple scenarios when studying the potential for spatial spread of an organism in response to climate change.     

Carbon balance assessment of a Belgian winter wheat crop (Triticum aestivum L.)

The carbon balance of a winter wheat crop in Lonzée, Belgium, was assessed from measurements carried out at different spatial and temporal scales between November 2004 and August 2005. From eddy covariance measurements, the net ecosystem exchange was found to be ?0.63 kg C m^?2 and resulted from the difference between gross primary productivity (GPP) (?1.58 kg C m^?2) and total ecosystem respiration (TER) (0.95 kg C m^?2). The impact of the u_* threshold value on these fluxes was assessed and found to be very small. GPP assessment was partially validated by comparison with an estimation scaled up from leaf scale assimilation measurements. Soil respiration (SR), extrapolated from chamber measurements, was 0.52 kg C m^?2. Net primary productivity, assessed from crop sampling, was ?0.83 kg C m^?2. By combining these fluxes, the autotrophic and heterotrophic components of respiration were deduced. Autotrophic respiration dominated both TER and SR. The evolution of these fluxes was analysed in relation to wheat development.