中亚热带3种次生林生态系统服务权衡与协同

以中亚热带地区不同演替阶段次生林为对象,研究了马尾松+石栎针阔混交林(PM)、南酸枣落叶阔叶林(CA)及青冈+石栎常绿阔叶林(CG) 2种调节服务[土壤有机碳(SOC)调节、全氮(TN)调节]及1种支持服务(物种多样性)之间的权衡与协同关系及其影响因素。结果表明:CA的物种多样性显著高于PM、CG,CA与CG的土壤SOC、TN含量显著高于PM。3种次生林土壤SOC调节与TN调节为协同关系,物种多样性与土壤SOC、TN调节为权衡关系,PM、CA权衡表现为物种多样性具有相对较高的收益,CG权衡无固定的相对受益方。在演替前期,常绿阔叶树种比例、土壤p H分别与土壤TN调节-物种多样性、土壤SOC调节-土壤TN调节的权衡呈负相关,随着演替进行,地形因子、土壤因子及树种组成因子对生态系统服务权衡产生的影响较小。     

Extinction following intracranial reward: the effect of delay between acquisition and extinction

Rats trained to press a bar for intracranial reinforcement gave as many responses during extinction as did water-reinforced controls, when extinction came immediately after an acquisition session. However, the experimental animals gave fewer responses in extinction than water-reinforced animals when extinction was delayed for 1 hour after acquisition. The activity level of the experimental animals was high immediately after acquisition but declined markedly over the delay period, which suggests that resistance to extinction after intracranial reinforcement is primarily a function of activity level.     

足球技术和体能训练的关系

1　“体能测试”对提高足球运动水平的作用没有想象的那么大。媒体报道 ,国家体委有关部门对中国足球的战略决策是“抓体能测试”。中国足协 1997年 5周的春训期间每天进行一次高强度有氧耐力训练 ;戚务生带领国家队起到了表率作用 :“在亚洲杯之前先行一步 ,分 3阶段训练 ,每天先跑 10 0 0 0m至 130 0 0m ,进行有氧训练 ,再跑 6 0 0 0m至 80 0 0m进行无氧训练 ,最后进行对抗性训练。”中国足协推行体能测试已经多年了 ,其作用与效果不言而喻 :亚洲出线的目标节节败退 ,连亚洲杯也第一次被挤出四强。这是否是对中国足球敲响了最后的警钟 ?你…     

Behavioral sensitivity to purinergic drugs parallels ethanol sensitivity in selectively bred mice

Behavioral responses to an adenosine receptor agonist and antagonist were examined in mice genetically selected for differential sensitivity to the soporific effects of ethanol. Both ethanol and the adenosine receptor agonist L-phenylisopropyladenosine had greater sedative and hypothermic effects in ethanol-sensitive "long-sleep" mice than in ethanol-insensitive "short-sleep" mice. Long-sleep mice were also more sensitive to the excitatory behavioral effects of theophylline, an adenosine receptor antagonist. These data suggest that adenosine may be an endogenous mediator of responses to ethanol.     

传热过程中的场协同作用应用分析

简要介绍了传热过程中场协同作用的基本思想.分别从能量方程,图线,边界层理论和场协同原理的角度分析了流体流过恒温半无限大平板时壁面有喷吹或抽吸的现象和流体垂直流过两不等温的平行多孔平板的现象,讨论了冷却和加热壁面时流体速度的变化对壁面热流密度的影响,从不同角度分析所得结论是一致的,从而表明了场协同原理从一个新的角度揭示了对流传热的物理机制,其可以作为一种新的分析对流传热和各种传递现象的方法.     

黑龙江农田生态系统服务权衡与协同

为促进农田生态系统可持续发展,亟需探究旱改水背景下黑龙江省农田生态系统服务变化。本研究基于1995年、2005年、2015年、2020年4期遥感影像解译结果,分析黑龙江省农田分布、农田生态系统服务变化,评估其权衡与协同关系,识别热点区域并划分生态功能管理分区。结果表明:1)黑龙江省旱地改为水田趋势明显,全省水田面积增长162.45%,主要位于三江平原;2)研究区的粮食产量、碳固定量、土壤保持量呈上升趋势,水分亏缺量也随之增长;3)粮食供应和碳固定具有空间协同关系,而与水文调节、土壤保持存在显著的权衡关系。研究发现1995—2020年农田生态系统服务具有一致的权衡/协同关系,但相关程度存在差异。依次,全省可划分为农产品供给区、土壤保持区和生态保护区3类生态功能区,从而实现区域生态系统服务最大化。     

安庆都市圈生态系统服务权衡与协同

为厘清区域发展特征、优化区域布局、实现生态转型和绿色可持续发展,研究生态系统服务之间的权衡和协同关系是发展的基础.本研究以安庆都市圈为研究对象,运用空间计量法估算安庆都市圈的水源涵养、土壤保持、NPP服务和食物供给等4种生态系统服务,分析不同生态系统服务之间的权衡与协同关系,并运用CA-Markov模型预测203 0年...     

Abrupt climate change and extinction events in Earth history

Slowly changing boundary conditions can sometimes cause discontinuous responses in climate models and result in relatively rapid transitions between different climate states. Such terrestrially induced abrupt climate transitions could have contributed to biotic crises in earth history. Ancillary events associated with transitions could disperse unstable climate behavior over a longer but still geologically brief interval and account for the stepwise nature of some extinction events. There is a growing body of theoretical and empirical support for the concept of abrupt climate change, and a comparison of paleoclimate data with the Phanerozoic extinction record indicates that climate and biotic transitions often coincide. However, more stratigraphic information is needed to precisely assess phase relations between the two types of transitions. The climate-life comparison also suggests that, if climate change is significantly contributing to biotic turnover, ecosystems may be more sensitive to forcing during the early stages of evolution from an ice-free to a glaciated state. Our analysis suggests that a terrestrially induced climate instability is a viable mechanism for causing rapid environmental change and biotic turnover in earth history, but the relation is not so strong that other sources of variance can be excluded.     

Geomagnetic polarity change and faunal extinction in the southern ocean

Paleomnlagnietic polarity changes have been detected in nine deep-sea sedimentary cores (from the Pacific-Antarctic Basin) in which an extinction horizon of a radiolarian assemblage was previously independently determined. The depths of the polarity change 0.7 million years ago and the faunal boundary are closely correlated, confirming that the faunal extinction was locally virtually synchronous. Although the reason for the faunal extinction is unknown. the possibility of causal relationships between faunal extinction and factors directly involved with sedimentation rate, sedimentation rate variation, and sediment type appears to be excluded.     

Eyeball retraction: classical conditioning and extinction in the albino rabbit

A comparison of the percentage-performance curve of a classical conditioning group with those of three control groups provided unequivocal evidence of successful conditioning of the retractor bulbi response to an auditory conditioned stimulus.     

Ecosystem collapse in Pleistocene Australia and a human role in megafaunal extinction

Most of Australia's largest mammals became extinct 50,000 to 45,000 years ago, shortly after humans colonized the continent. Without exceptional climate change at that time, a human cause is inferred, but a mechanism remains elusive. A 140,000-year record of dietary delta(13)C documents a permanent reduction in food sources available to the Australian emu, beginning about the time of human colonization; a change replicated at three widely separated sites and in the marsupial wombat. We speculate that human firing of landscapes rapidly converted a drought-adapted mosaic of trees, shrubs, and nutritious grasslands to the modern fire-adapted desert scrub. Animals that could adapt survived; those that could not, became extinct.     

Cope's rule, hypercarnivory, and extinction in North American canids

Over the past 50 million years, successive clades of large carnivorous mammals diversified and then declined to extinction. In most instances, the cause of the decline remains a puzzle. Here we argue that energetic constraints and pervasive selection for larger size (Cope's rule) in carnivores lead to dietary specialization (hypercarnivory) and increased vulnerability to extinction. In two major clades of extinct North American canids, the evolution of large size was associated with a dietary shift to hypercarnivory and a decline in species durations. Thus, selection for attributes that promoted individual success resulted in progressive evolutionary failure of their clades.     

四氧嘧啶与链脲佐菌素诱导小鼠糖尿病模型的效果比较

用相同总剂量的四氧嘧啶1次给药和2次给药及较大剂量链脲佐菌素1次给药3种方法诱导小白鼠糖尿病模型,多次测定血糖,体重等糖尿病相关指标,以确定糖尿病模型建立的最佳方法。结果表明,四氧嘧啶建模率为91．94％,高于链脲佐菌素建模率(66．7％)(P<0．05);四氧嘧啶建模组的死亡率为15％及体重下降率为 18．1％,均高于链脲佐菌素建模组(死亡率3．3％,体重下降率12．0％)(P<0．05);四氧嘧啶连续2次小剂量给药的建模效果优于1次性大剂量给药。两种药物比较,虽然四氧嘧啶的建模率高于链脲佐菌素,但其对建模小鼠的损害亦明显大于链脲佐菌素,建模时连续小剂量给药,并于4．5～5 h后灌胃质量分数50％葡萄糖,可以降低死亡率, 提高建模率。     

中年ICR小鼠学习记忆损害与血清甲状腺素的关系

研究中年ICR小鼠在新物体再认任务和六臂辐射状水迷宫(RAWM)中的学习记忆能力变化及其与血清甲状腺素(TH)的相关性。结果表明,新物体再认试验中12月龄与6月龄ICR小鼠间的成绩无显著性差异;RAWM中,12月龄小鼠较6月龄小鼠空间学习记忆能力减退;12月龄小鼠血清TH水平(FT3,FT4)低于6月龄小鼠,且FT3水平既与小鼠的空间性学习能力相关,又与记忆能力相关,而FT4仅与空间性学习能力相关。这些结果提示血清TH水平下降可能参与了中年ICR小鼠空间学习记忆能力减退。     

不同土地利用情景下天津市生态系统服务及权衡与协同分析

  目的  土地利用变化是导致生态系统服务及其关系变化的重要影响因素,探讨土地利用变化对生态系统服务影响具有重要意义。  方法  本研究基于2000和2015年天津市土地利用数据,结合区域发展规划,采用GeoSOS-FLUS模型预测2030年3种不同情景下的土地利用格局,并利用InVEST模型评估生态系统服务及权衡/协同关系。  结果  （1）2015—2030年,自然发展情景下城市继续扩张,建设用地增加27.68%,耕地下降11.47%。生态规划情景下城市扩张减缓,建设用地增加7.97%,林地、草地、水域和灌丛共增加2.02%。城市快速发展情景下建设用地和耕地基本保持稳定,水域面积增加4.78%。（2）2015—2030年不同情景下天津市综合生态系统服务指数均呈现下降趋势,其中自然发展、生态规划和城市快速发展情景下综合生态系统服务指数分别为0.172、0.181、0.180。（3）2015—2030年不同情景下4种生态系统服务的权衡/协同关系方向未变,但强弱发生了复杂的变化,总体上生态规划情景下协同关系更强,自然发展情景下协同关系更弱。  结论  本研究建议天津市未来应控制城市扩张速度、优化当前土地利用结构、增强生态环境建设。研究结果可为天津市生态系统管理提供理论基础。