氮素分期优化管理对冬小麦产量和籽粒品质的影响

采用田间试验,对氮素分期优化管理方法对小麦籽粒品质的影响进行了研究,以期为高产、优质、资源高效、环境保护等多重目标并重的养分资源优化管理提供理论依据.结果表明:氮素供应量最优的处理(冬小麦返青期氮素供应量即0～60 cm土壤Nmin+肥料氮为90 kg/hm2,拔节期追氮量即施用肥料氮30 kg/hm2)的冬小麦籽粒产量和其他氮素供应量处理没有显著差异;氮素供应量最优的处理冬小麦籽粒的粗蛋白和面筋含量显著低于在返青期和拔节期供氮量都高的处理(冬小麦返青期氮素供应量即0～60 cm土壤Nmin+肥料氮为150kg/hm2、拔节期追氮量即施用肥料氮90kg/hm2),但与其他处理相比差异不显著;以高产、资源高效和环境保护为前提的冬小麦氮肥分期优化施用量获得了最高产量的同时兼具较好的小麦籽粒品质.     

城市绿地生态系统碳交换动态及其与环境控制因子的关系

随着城市的不断发展,城市绿地面积逐年增加,绿地生态系统潜在的碳汇和碳源功能显得非常重要。2014年1月至2016年1月,基于涡度技术对福州市绿地生态系统进行了碳通量连续两年的定位观测,并探讨了城市绿地生态系统碳交换年际动态特征及其环境调控因子。结果表明,城市绿地生态系统年总生态系统生产力(GEP)、生态系统净生产力(NEP)和生态系统呼吸(R_e)呈现出一致的变化规律,其中生态系统碳交换特征表现为生长季(4月-11月)以吸收CO_2为主,非生长季以释放CO_2为主。城市绿地R_e均与GPP、GEP呈正比关系,并且拟合线性斜率1,受生长季的降水量影响较大。采用指数方程对碳交换和土壤温度(T_a)进行模拟,生态系统日平均净碳交换量(NEE_(day))随T_a的增加呈指数增长模型,T_a可解释80%以上的变异;GEP随着T_a的增加逐渐增加,当T_a达到最高时,并未对GEP产生抑制作用;当气温低于5℃时,城市绿地生态系统以呼吸作用为主导,当气温高于5℃,城市绿地生态系统净吸收大气CO_2为主导。光合有效辐射(PAR)与NEE呈直角双曲线关系,当光补偿点PAR小于350μmol·(m~2·d)~(-1)时,NEE为正值,此时生态系统呼吸大于光合生产;当PAR大于500μmol·(m~2·d)~(-1)时,生态系统呼吸与光合生产持平,其碳吸收量基本达到饱和。生态系统最大光合速率、白天平均生态系统呼吸强度、表观量子效率(α)与温度和PAR的季节变化趋势相一致,均在7月最大和5月最小。相关性分析可知,不同月份NEE残差均与降水量呈负相关关系,与饱和水汽压差(VPD)呈正相关关系。上述研究结果为估算、模拟和预测城市绿地生态系统碳交换提供了基础数据支持和理论基础。     

梯度增温对青藏高原高寒草甸生态系统碳交换的影响

高寒草甸是青藏高原主要的草地生态系统类型,对气候变化非常敏感,研究高寒草甸生态系统碳交换对升温的响应具有重要的理论和现实意义。在青藏高原中部地区的高寒草甸,使用开顶箱法(open-top chambers,OTCs)设置不增温对照(T_0)以及4个不同程度的增温处理(T_1、T_2、T_3、T_4),采用CO_2红外分析仪对生长季期间的碳交换进行连续3年的观测。结果表明,4个增温处理的5cm土壤温度较之于不增温对照分别增加1.73(T_1)、1.83(T_2)、3.03(T_3)以及3.53℃(T_4);土壤水分没有发生梯度变化。观测期间,净生态系统碳交换(net ecosystem carbon exchange,NEE)基本为负值,因此高寒草甸表现为碳汇。增温小于2℃促进总生态系统生产力(gross ecosystem productivity,GEP),但对生态系统呼吸(ecosystem respiration,ER)影响较小,因而促进NEE,即促进高寒草甸的碳吸收;但增温大于3℃则抑制GEP,对ER影响较小,因而总体上对NEE产生抑制作用。综上所述,在高寒草甸生态系统,适度增温促进碳吸收,增温过度则降低碳吸收。     

11个能源林杨柳无性系热值季节及年度变化

测定了5个乔灌木柳树无性系和6个杨树无性系夏季、冬季不同组分的干质量热值,研究了1年生杨、柳无性系皮部和干部在夏季和冬季的干质量热值的变化情况,以及随着平茬次数的增加1年生柳树无性系全株热值的变化规律。结果表明:杨、柳树无性系不同组分在不同季节干质量热值的变化不完全一样,但是在冬季皮部、干部和全株热值均比在夏季时高;5个柳树无性系不同季节年份的干质量热值变化规律基本一致,冬季热值为1年生根1年生干＞2年生根1年生干＞3年生根1年生干,柳树无性系间的1年生根1年生干冬季热值与2年生根1年生干冬季热值的差异极显著,与3年生根1年生干冬季热值的差异显著,灌木柳的热值比乔木柳的高;6个杨树无性系(1年生根1年生干)的冬季全株干质量热值＞夏季全株干质量热值,但无性系间差异均不显著;1年生柳树全株冬季干质量热值普遍高于杨树。     

Persistence of external signs in Pacific herring Clupea pallasii Valenciennes with ichthyophoniasis

The progression of external signs of Ichthyophonus infection in Pacific herring Clupea pallasii Valenciennes was highly variable and asynchronous after intraperitoneal injection with pure parasite preparations; however, external signs generally persisted through the end of the study (429 days post‐exposure). Observed signs included papules, erosions and ulcers. The prevalence of external signs plateaued 35 days post‐exposure and persisted in 73–79% of exposed individuals through the end of the first experiment (147 days post‐exposure). Among a second group of infected herring, external signs completely resolved in only 10% of the fish after 429 days. The onset of mortality preceded the appearance of external signs. Histological examination of infected skin and skeletal muscle tissues indicated an apparent affinity of the parasite for host red muscle. Host responses consisted primarily of granulomatous inflammation, fibrosis and necrosis in the skeletal muscle and other tissues. The persistence and asynchrony of external signs and host response indicated that they were neither a precursor to host mortality nor did they provide reliable metrics for hindcasting on the date of exposure. However, the long‐term persistence of clinical signs in Pacific herring may be useful in ascertaining the population‐level impacts of ichthyophoniasis in regularly observed populations.     

铅镉铜锌复合污染对鹅毛竹生理生化特性的影响

采用盆栽试验的方法研究重金属Cd、Pb、Cu、Zn复合污染对鹅毛竹生理生化特性的影响,结果表明：在一定的重金属浓度范围内,随着各种重金属浓度的增加,鹅毛竹的叶绿素合成受到抑制,细胞膜的透性增加,MDA含量增加;2种保护酶对不同处理水平的重金属响应不同,其中APX表现出强的自我调节能力,随着重金属浓度的升高,APX的活性不断升高,但是GR活性呈现下降趋势且总体低于对照。     

Microbial activity and community structure in degraded soils on the Loess Plateau of China

Soil erosion is the main process leading to soil degradation on the Loess Plateau of China. The effects of soil‐erosion intensity (sheet, rill, and gully erosion) and different land use (140 y–old secondary forest site, 16 y–old bare site, 6 y–old succession site, and 43 y–old arable site) on gross and net N mineralization, soil organic‐carbon (SOC) turnover, the size and structure of the soil microbial community (phospholipid fatty acid analysis) were assessed. Erosion intensity in the bare plot increased from top slope (sheet erosion) to down slope (gully erosion). The more severe the soil erosion the stronger was the decline of SOC, total N, and microbial biomass (MB). The MBC/SOC ratio decreased whereas the metabolic quotient (qCO₂) increased. Differences in nutrient turnover in the different erosion zones of the bare plot were not significant. The microbial community changed towards less Gram negative bacteria and relative more fungi in the gully‐erosion zone. In forest soils, qCO₂ and the MBC/SOC ratio demonstrate a higher substrate‐use efficiency of the microbial biomass than in bare soils. Gross N mineralization and gross NH consumption clearly indicated a higher microbial activity in forest than in bare soils. Arable land use shifted the soil microbial community towards a higher relative abundance of fungi and a lower one of actinomycetes. During 6 y of natural succession on former bare plots, soil nutrient content and turnover as well as microbial biomass and structure developed towards forest conditions.     

2000-2013年中国植被碳利用效率(CUE)时空变化及其与气象因素的关系

植被碳利用效率（CUE）是评估陆地碳循环的重要指标,探讨其动态特征对气候变化的响应对于陆地生态系统碳循环研究具有重要的指示意义。基于MOD17数据计算中国植被CUE,辅以地统计学理论,利用趋势分析、变异系数及相关性分析等方法,研究了2000—2013年中国植被CUE的时空变化特征,并结合气象要素数据剖析植被CUE对气候变化的响应。结果表明:全国植被年CUE在研究年限内总体上表现为轻微的增长趋势,具体表现为在2000—2007年以0.000 6的变化率呈现波动下降的趋势,而2007—2013年植被CUE呈现显著上升的变化趋势,该变化特征可归因于2007年气温及降水格局的改变;植被CUE空间分布具有明显的空间异质性,大体呈现西部高东部低的状态。CUE增加较明显的区域主要分布在内蒙古呼伦贝尔地区,青藏高原大部分地区,东部沿海地区以及台湾岛。而CUE呈减少趋势的区域分布范围较广,其中减少趋势较为明显的地区主要包括东北平原及华北华中的大部分地区,另江南地区及新疆部分地区也有零星分布。草地及森林区域植被CUE波动变化较小,表明该部分地区生态系统处于良性循环。不同植被类型的CUE均值表现为:草地（0.21） > 农田（0.14） > 森林（0.09） > 灌丛（0.06）。全国大多数地区植被CUE与降水呈正相关,而与气温则呈负相关,而这种相关性会随着区域气候格局及植被类型的变化而变化。总体上,全国植被CUE的增加主要归因于降水量的增加,而气温的升高则造成植被CUE的降低。     

Impact of BSE on Livestock Production System

A total of 240 unvaccinated day-old broiler chicks, which had been found to be negative for antibodies against FAV-4, were divided into four groups of 60 chicks each. Group A was fed aflatoxin at 1 ppm from 7 days to 7 weeks of age. Group V was infected intra-abdominally at 14 days of age with 0.2 ml of FAV-4, having a titre of 10^5.5 TCID₅₀ per 0.2 ml. The combined group AV was given the aflatoxin and infected with FAV-4. The fourth group C served as the control. More pronounced clinical signs, a higher mortality rate (56.7%), and reductions in body weight gain and in the organ to body weight ratios of the bursa and spleen were recorded in group AV. A significant (p<0.01) reduction in the HI antibody titre following vaccination against Newcastle disease, and of skin thickness in the delayed hypersensitivity test following sensitization with DNCB, indicated an additive immunosuppressive effect from aflatoxin and FAV-4 on the humoral and cell-mediated immune responses in group AV compared to groups A and V. Microscopically, marked depletion and degeneration of lymphocytes in the thymus, bursa, spleen and caecal tonsils were observed in group AV up to 5 weeks PI.     

温度对农田黑土氮初级转化速率的影响

为探讨不同温度下土壤氮素的供应、固持和消耗损失过程,从而为农田土壤合理施用氮肥提供科学依据,以黑龙江省农田黑土为对象开展室内培养试验(15、25、35℃,60%WHC),采用15N同位素成对标记技术(~(15)NH_4NO_3和NH415NO3,15N标记丰度为5atom%,氮浓度为60 mg N·kg~(-1))及FLUAZ数值优化模型研究土壤氮初级矿化速率、初级固定速率和初级硝化速率对温度变化的响应。结果表明:在15～35℃范围内,土壤氮初级矿化速率随培养温度的增加显著增加,但25～35℃范围内的增幅小于15～25℃。在15～25℃范围内,土壤氮初级固定速率和初级硝化速率随培养温度的增加显著增加,而在25～35℃范围内土壤氮初级固定速率和初级硝化速率随培养温度的增加显著降低,但仍然显著高于15℃处理。15℃和25℃处理土壤氮初级矿化速率与初级固定速率比值(gm/gi)以及初级硝化速率与初级铵态氮固定速率比值(gn/ia)均稍大于1,两处理间没有显著差异,而35℃处理的gm/gi值和gn/ia值均远大于1。研究表明,温度在15～25℃范围内,土壤有机氮的矿化与固定过程耦联相对紧密,硝态氮累积及淋溶风险较小;而35℃高温条件下土壤有机氮矿化速率和硝化速率均显著大于铵态氮的生物固定速率,表明硝化作用是铵态氮的主要消耗过程,可能会增加硝态氮的累积、反硝化和淋溶风险。