减量施氮对苦荞产量形成及氮代谢酶活性的影响

为明确减量施氮对苦荞强弱势粒及产量形成的影响,以苦荞品种晋荞2号为试验材料,研究在225 kg/hm²(N1)、135 kg/hm²(N2)、45 kg/hm²(N3)、0 kg/hm²(N4,对照)4个氮肥处理下苦荞强弱势粒的灌浆动态、根系形态生理、叶片中叶绿素含量及氮代谢相关酶活性、农艺性状和产量的差异.结果显示:减氮处理下,N2处理时晋荞2号籽粒的灌浆起始势(R0)、最大灌浆速率(Gmax)和平均灌浆速率(Gmean)最大,达最大灌浆速率的时间(Tmax.G)最小;强弱势粒间以强势粒的A值(生长终值量)、R0、Gmax和Gmean大于弱势粒,而N值(形状参数)和Tmax.G则低于弱势粒. 4个氮肥处理和强弱势粒均以灌浆中期对粒重的贡献率最大,灌浆后期次之,灌浆前期最小.随着施氮量的减少,晋荞2号的根系长度等形态指标及根系活力呈先增加后降低的趋势,以N2处理最大;随着施氮量的减少,晋荞2号叶片中的叶绿素含量及谷氨酰胺合成酶(GS)、谷氨酸脱氢酶(GDH)、谷氨酰胺合酶(GOGAT)、硝酸还原酶(NR)活性呈先增加后降低的趋势,N2处理最大,强弱势粒间以强势粒的叶绿素含量较高、氮代谢酶活性较大. N2处理时的株高等农艺性状及产量形成指标均大于其余3个氮肥处理.本研究表明适当减量施氮可延缓苦荞衰老、促进苦荞强弱势粒的灌浆和氮代谢酶活性的增加,提高粒重和最终产量,进而实现节肥和高产.(表7参31)     

sup>17O-核磁共振研究给水中常见离子对水缔合的影响

给水中通常含有少量的离子,如Na⁺,K⁺,Ca²⁺,Mg²⁺及Cl^-,SO₄^2-,CO₃^2-等.本文测量了不同温度(20～60℃)下的水及由上述离子组成的不同浓度盐溶液(0～1mol/L)的¹⁷O-核磁共振(¹⁷O-NMR)的化学位移和半峰宽根据化学位移和半峰宽的变化与水缔合的关系分析了离子对水缔合的影响结果表明,不同离子对水缔合的影响不同,阳离子促进液态水形成缔合结构,阴离子则破坏水的缔合结构;离子电荷越大,半径越大,对水缔合的影响越大,其中电荷的影响程度更大.     

太湖不同水域沉积物甲烷释放潜力及其途径分析

为明确太湖不同湖区CH₄释放特征与释放潜力差异,采用水-气界面甲烷排放通量测定和室内厌氧培养,结合沉积物理化因子对太湖沉积物CH₄释放特征及其释放潜力差异进行研究。结果表明,不同湖区水-气界面CH₄排放通量存在显著差异;不同湖区、不同深度沉积物中CH₄释放潜力也存在明显差异,且CH₄释放潜力与含水率和总有机碳呈正相关,与盐度呈负相关;太湖沉积物产CH₄潜力最大的途径为甲基途径,且主要集中在沉积物10~35cm深度。由此可知,太湖是CH₄排放的净产生源,含水率、有机质和盐度等环境因子的差异以及沉积物深度均会影响沉积物甲烷排放和释放潜力,从而对太湖沉积系统的碳循环以及局部气候变化产生重要影响。     

轮班制度对于地铁司机疲劳的影响

立足于轮班工作模式,阐述轮班制度对司机疲劳产生与积累的影响。介绍疲劳指数方法和池田公式的理论基础及模型构架,基于北京地铁13号线现行轮班表,分别应用上述两种研究方法进行地铁轮班司机疲劳程度的分析。两种方法的评估结果显著相关,均说明13号线现行轮班表的制定会导致司机疲劳的产生,存在安全运营风险。应用上述方法可实现对司机疲劳程度的非接触式测量,避免对司机驾驶作业的干扰,同时为地铁运营公司的安全管理人员制定合理的轮班方案,建立全面、量化的动态管理措施,提高行车安全保障提供了科学依据。     

Human disturbance and shifts in vertebrate community composition in a biodiversity hotspot

Understanding how human modification of the landscape shapes vertebrate community composition is vital to understanding the current status and future trajectory of wildlife. Using a participatory approach, we deployed the largest camera-trap network in Mesoamerica to date to investigate how anthropogenic disturbance shapes the occupancy and co-occurrence of terrestrial vertebrate species in a tropical biodiversity hotspot: the Osa Peninsula, Costa Rica. We estimated species richness in different categories of land protection with rarefaction analysis and estimated the expected occupancy with a joint species distribution model that included covariates for anthropogenic disturbance, land protection, habitat quality, and habitat availability. Areas with the most stringent land-use protections (e.g., Corcovado National Park, 24 species [95% CI 23–25]) harbored significantly more species than unprotected areas (20 species [19.7–20.3]), mainly due to a reduced presence of large-bodied species of conservation concern in unprotected areas (e.g., jaguar Panthera onca and white-lipped peccary Tayassu pecari). Small-bodied generalist species, such as opossums (Didelphidae) and armadillos (Dasypus novemcinctus), in contrast, were more common at disturbed sites, resulting in a significant difference in vertebrate community composition between sites with low and high disturbance. Co-occurrence of species was also mainly associated with response to disturbance. Similar responses to disturbance create two groups of species, those whose site-level occupancy usually increased as anthropogenic disturbance increased and those whose estimated occupancy decreased. The absence of large-bodied species entails an important loss of ecological function in disturbed areas and can hinder forest development and maintenance. Efforts to protect and restore forested landscapes are likely having a positive effect on the abundance of some threatened species. These efforts, however, must be sustained and expanded to increase connectivity and ensure the long-term viability of the wildlife community.