13 resultados para reasoning and rehabilitation

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植被恢复重建是遏制水土流失的有效措施之一,研究植被恢复重建过程、评价植物群落健康状况对加速植被建设具有重要的实践意义。本文根据黄土丘陵沟壑区的特点,建立了植物群落健康评价指标体系,对草地植被恢复重建过程中的不同阶段的植物群落的健康状况进行了评价。结果表明:植被群落活力变化过程呈抛物线型;群落组织力基本呈波动性变化;恢复力的变化则与活力变化过程相反,在群落活力达到最高水平时,群落的恢复力降至最低;土壤健康呈波动性上升的变化趋势。综合评价表明,植物群落健康水平随着演替过程的发展呈波动性且逐渐上升的变化过程。

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随着Web信息的与日俱增,使用机器处理这种信息成为一种必然的趋势。语义Web应运而生,成为当前研究的热点之一。它以本体为核心,为不同领域提供共享的词汇,以便机器处理Web信息。表达本体的标准语言OWL以描述逻辑为基础。OWL本体的推理可伸缩性差,难以适应规模较大的本体应用,因此推理可伸缩性问题是一个重要的实际问题。此外,OWL本体是一个逻辑系统,在生成、维护和集成等过程中,都很容易出现非一致现象,导致标准的推理机制不能正常运作。因此本体非一致问题是另一个重要的实际问题。针对上述两个实际问题,本文分别在实现可伸缩推理、修复非一致本体、以及进行非一致容忍推理三个方面提出了解决办法。 [可伸缩推理方面] 本文提出了一种本体断言公理集的划分方法,使本体推理能够在独立的划分子集中进行,以此提高本体推理的可伸缩性。 [本体修复方面] 本文提出了一种计算具有最小删除代价的本体子集的方法;通过删除这种本体子集,可以恢复本体的一致性。该方法将计算上述本体子集的问题归约为在命题逻辑程序中计算某种最优模型的问题,以调用现有的可满足性问题求解器来解决。 [非一致容忍推理方面] 本文将命题逻辑中字典序推理方法应用到描述逻辑中,以提供针对非一致本体的查询机制。本文还提出了一种在描述逻辑本体中进行字典序推理的方法。该方法将字典序结论的判定问题归约为命题可满足性判定问题,以调用现有的可满足性问题求解器来解决。

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该文以内蒙古霍林河露天煤矿为例,在国家九五攻关子专题“大型煤矿生态环境综合整治及其试验示范研究”的支持下对半干旱地区大型露天煤矿开采所造成的生态环境影响与生态恢复的理论与技术问题进行了深入研究.1.从生态环境影响、生态恢复理论与生态恢复技术等方面对露天煤矿区生态环境恢复与重建这一学科领域的发展历程、现状与趋势进行了系统的论述.2.建立了适用于半干旱草原矿区生态环境质量评价的指标体系与模糊数学综合评判模型.3.筛选了沙棘、草木樨等十余种适于半干旱地区矿山生态恢复的植物种类.

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人类向大气中排放的大量氮氧化合物和氟氯烃类化合物(CFC’s)引起臭氧分子的分解,导致到达地球表面的紫外辐射增加,特别是UV-B辐射增强。本项目以青杨组杨树为模式植物,从形态和生理方面研究了来自不同UV-B背景下的康定杨与青杨在增强UV-B下的反应及其反应差异,并探讨了干旱、施肥对它们抗UV-B能力的影响。杨树具有分布广、适应性强、在生态环境治理和解决木材短缺方面均占有重要位置,研究成果可为生态系统的恢复与重建提供理论依据和科学指导。主要研究结果有以下: 1. 在温室中经过增强UV-B处理,杨树的外部形态及生理活动受到了一定程度的影响。增强UV-B导致康定杨、青杨的生物量、叶面积及节间长度降低,叶片增厚,SOD活性升高,膜伤害增加,而对叶片数目、R/S、叶绿素A、叶绿素B及整个叶绿素含量没有影响。两种杨树对UV-B胁迫的响应存在差异:在增强UV-B条件下,青杨的植株高度、生物量、叶面积、脯氨酸含量、长期用水效率受到的影响大于康定杨,相比而言,康定杨在比叶面积、叶片厚度、可溶性糖含量、UV-B吸收物质的含量及SOD和GPX活性方面增加的程度大于青杨。这些区别说明,来自于高海拔的康定杨比来自于低海拔的青杨对增强UV-B 具有更强的耐性。我们认为二者在叶片厚度、比叶面积、UV-B吸收物质含量及SOD、GPX活性差异是导致对增强UV-B耐性不同的原因。 2. 干旱与增强UV-B对杨树的生长和生理特性均产生了影响,而且两种胁迫共同作用时干旱表现减弱或加剧了UV-B对杨树某些形态和生理特性的影响。 据试验结果,干旱显著地降低了杨树的株高、叶片数目、叶面积,增加了叶片厚度,促进ABA的积累,提高了CAT活性。对于干旱,两种杨树之间也表现出了一定的差异性。可溶性蛋白质和脯氨酸在青杨叶片中得到显著积累,而在康定杨中没有变化。此外,CAT、长期用水效率在康定杨中受到的影响更加明显。长期用水效率的不同变化趋势说明两种杨树对水分胁迫采用了不同的用水策略,康定杨采用的是节水用水策略,提高用水效率,而青杨采用的是耗水的用水策略。根据干旱对叶面积、脯氨酸、ABA含量、CAT活性及长期用水效率等方面的影响,我们认为来自高海拔地区的康定杨比来自低海拔的青杨有更大的耐旱性,这是对生长环境长期适应的结果。在高海拔地区,因霜冻常带来土壤水分不可利用,降低了根系对水分的吸收,树木容易受到的生理性干旱。另外,高海拔的地区低的气温使植株对严寒有较强的耐性,减少了水分的需要。 生长于增强UV-B下的康定杨和青杨植株表现为高度降低,叶面积缩小,比叶面积增加;叶片栅栏组织、海绵组织均受到增强UV-B的影响,其厚度的增加导致整个叶片变厚。增强UV-B还显著提高了杨树的APX活性、UV-B吸收物质含量,而对叶片数目、ABA、可溶性蛋白质含量及CAT活性没有产生影响。试验中也观察到了两种杨树对增强UV-B响应的差异:与康定杨相比,在增强UV-B下青杨株高、叶面积降低的程度更大一些,SOD活性显著提高。另外UV-B吸收物质受到的影响不同。根据这些差别,高海拔的康定杨(3500 m)比来自低海拔的青杨(1500 m)增强UV-B有较强的耐性。 与水分充足情况下UV-B对植株的影响相比,干旱对杨树抗增强UV-B产生了一定的影响,表现为加剧或减弱UV-B对植物的影响,但这种影响与形态、生理指标有关。当干旱与增强UV-B共同作用时,杨树植株的株高、叶面积进一步降低、叶片进一步增厚。就脯氨酸的积累的而言,在没有水分胁迫时,增强UV-B促使它显著增加,而在干旱处理下这种效果变得不明显。干旱对增强UV-B的影响还与杨树的种类有一定的关系。在康定杨中,干旱减弱了增强UV-B对栅栏组织与海绵组织的影响,且在植株高度、叶面积上表现出累加效应,而在CAT上交互作用显著;但在青杨中干旱则加剧增强UV-B对栅栏组织与海绵组织的影响,在植株高度、叶面积及比叶面积上表现出显著的交互作用。据碳同素分析,在水分充足的条件下,无论是康定杨,还是青杨,增强UV-B均导致其长期用水效率的提高,然而当两种胁迫共同作用时,长期用水效率则表现出差异,在青杨中,长期用水效率得到进一步增高,而康定杨中干旱的效应被增强UV-B所减轻。 3. 田间试验表明,杨树的生长、生理特征都受到养分和增强UV-B的影响。施肥对杨树的影响表现为:提高了叶面积、生物量及SOD的活性,降低了抗坏血酸含量。对于施肥作用,两种杨树的反应也有区别:在康定杨中施肥显著增加了的叶片长度、宽度及光合色素的含量,降低了净光合速率、气孔导度及胞间CO2浓度;在青杨中,则SOD、GPX、APX活性表现增加。从试验看出,施肥对来自于高海拔地区的康定杨(3500 m)的影响较大,对来自低海拔的青杨(1500 m)影响较小,这与它们对原产地的生境适应有一定关系。在康定杨生长的高海拔地区,低温度和湿度不能为地上凋落物或土壤中的根分解提供理想的条件,造成当地土壤的低养分状况,所以当肥料施用以后,效果显著。 经过增强UV-B处理,杨树叶片中UV-B吸收物质含量、GPX的活性得到提高,而脯氨酸、丙二醛、可溶性蛋白质、叶绿素及类胡萝卜素含量没有受到影响。对于增强UV-B两种杨树受到的影响也有所不同:在青杨中增强UV-B导致叶面积缩小,生物量、净光合速率降低,APX的活性及长期用水效率的提高,而对康定杨的这些指标没有产生显著影响,相反抗氧化酶的活性明显高于青杨。这些差异性是由于两种杨树对原产地不同UV-B背景的长期适应结果。康定杨长期生长在较高UV-B环境中,对UV-B有较强的耐性。而青杨适应于较低的UV-B环境,对增强UV-B较为敏感。 试验中施肥也影响了植株对增强UV-B的反应,不过这种影响与杨树的种类及测定指标有一定的相关性。例如,在缺肥的情况下,青杨的长期用水效率和康定杨的叶绿素含量都受到增强UV-B的显著影响,而施肥以后这种影响变得不显著。在缺肥的条件下,GPX、APX在青杨中的活性、GPX在康定杨中的活性对增加UV-B反应不敏感;而施肥以后则变化显著,同样胞间CO2浓度在康定杨也有类似的变化。 For past decades, Ultraviolet radiation, especially UV-B reaching the Earth’s surface increased because of depletion of ozone layer resulted from emission of NxO and CFC’s from human activities. In this experiment, different species of Populus section Tacamahaca Spach from different UV-B background were selected as a model plant to assess the effects of enhanced UV-B radiation. Morphological and physiological traits induced by enhanced UV-B were observed and the different responses between P. kangdingensis and P. cathayana were discussed, furthermore the influences of drought and fertilizer on responses induced by enhanced UV-B were studied. Since poplars play an important role in lumber supply, and are important component of ecosystems due to their fast growth and wide adaptation, the study could provide a strong theoretical evidence and scientific direction for the afforestation, and rehabilitation of ecosystem. The results are as follows: 1. The experiment conducted in a greenhouse indicated that morphological and physiological traits of two poplars were affected by enhanced UV-B radiation. Enhanced UV-B radiation not only reduced biomass, leave area and internode length, but also increased leaf thickness and SOD activity as well as MDA concentration and electrolyte rate. However, no significant changes in leaf numbers, root shoot ratio, and total chlorophyll and chlorophyll component were observed. There were different responses to enhanced UV-B radiation between two species. Compared with P. kangdingensis, cuttings of P. cathayana, exhibited lower height increment and smaller leaf area. In addition, there were significant differences in free proline, soluble protein, and UV-B absorbing compounds, and the activity of SOD and GPX, long-term WUE between them. Differences in plant height, biomass, leaf area, free proline concentration, and long-termed WUE showed that P. cathayana were more affected by enhanced UV-B radiation than P. kangdingensis. In contrast, more increase of specific leaf mass, leaf thickness, and soluble sugar, and UV-B absorbing compounds, and activity of SOD and GPX were observed in P. kangdingensis. According to these results, we suggested that P. kangdingensis from high elevation, which adapted to higher UV-B environments, had more tolerance to enhanced UV-B than P. cathayana from low elevation, which adapted to lower UV-B environment. We believe it was the difference of leaf thickness, specific leaf mass, and UV-B absorbing compounds as well as the activity of SOD and GPX resulted in lower adaptation of P. cathayana to enhanced UV-B radiation. 2. Growth and physiological traits of two poplars were affected by both drought and enhanced UV-B radiation. Moreover, it was observed that when two stresses applied together drought could exacerbate UV-B effects or decrease sensitivity to UV-B. In the experiment, drought significantly decreased plant height, leaf numbers, leaf area, and increased leaf thickness, and ABA, and CAT activity of two poplars. There were significant interspecific differences to drought stress. Exposed to drought, soluble protein and proline concentration were increased in P. cathayana but not in P. kangdingensis. However, more changes in CAT and long-term WUE were observed in kangdingensis. Different change in long-term WUE suggests that two poplars adapted different water-use strategies. P. kangdingensis employ a conservative water-use strategy, whereas P. cathayana employ a prodigal water-use strategy. Based on the differences in leaf area, accumulation of free proline and ABA, CAT activity as well as long-term WUE, we believed that P. kangdingensis from high elevation had a greater tolerance to drought than P. cathayana from low elevation,which is the result of adaptation to local environment. In high elevation area, trees are prone to suffer from physiological drought because of un-movable water caused by frost. Besides lower temperature enable the plants had greater adaptability to frost as a results the requirement of water is reduced Enhanced UV-B radiation decreased shoots height, leaf area, and increased specific leaf mass and thickness of palisade and sponge layer as well as APX activity and UV-B absorbing compounds in both species. Whereas, leaf numbers, ABA content, soluble protein and CAT activity showed no differences to enhanced UV-B radiation. Interspecific differences were also observed. Compared with P. kangdingensis, P. cathayana showed lower shoot height and smaller leaf area, higher SOD activity. Besides, variation in UV-B absorbing compounds was found. These differences suggested that P. kangdingensis from high elevation (3500 m) was more tolerant to enhanced UV-B radiation than P. cathayana from low elevation (1500 m). Compared with morphological and physiological changes induced by enhanced UV-B radiation under well-watered conditions, drought exacerbated or decreased these changes. However, these effects vary with parameters measured. When two stresses applied together, shoot height and leaf area further decreased while leaf thickness further increased. Under well-watered conditions, enhanced UV-B radiation significantly increased proline content, but such effect was not observed under drought conditions. The effect of drought on enhanced UV-B radiation was related to species. For example, drought reduced the effects of enhanced UV-B radiation on palisade parenchyma and sponge mesophyll in P. kangdingensis, and additive effects in shoot height and leaf area and interactive effect CAT activity were observed. In contrast, for P. cathayana drought significantly exacerbated the effects of enhanced UV-B radiation on palisade parenchyma and sponge mesophyll; there were noticeable interaction in shoot height, leaf area and specific leaf mass. As far as long-term WUE is concerned, it was increased by enhanced UV-B radiation under well-watered conditions in both species. While different effect was observed between two species in combination of two stresses. Long-term water use efficiency was further increased in P. cathayana whereas the effect was less significant in P. kangdingensis. 3. The field experiment showed that growth and physiological traits of poplars were affected by nutrition and enhanced UV-B radiation. Fertilization significantly increased leaf area, biomass and SOD activity, reduced Ascorbic acid concentration. There was interspecific difference in response to fertilization. For P. kangdingensis, fertilization significantly increased leaf width, leaf length and photosynthetic pigments content while net photosynthetic rate and stomatal conductance, intercellular CO2 concentration were significantly decreased. However, for P. cathayana, these parameters were unaffected except the increase of SOD, GPX and APX activity. From above, it could concluded that P. kangdingensis from high elevation was more affected by fertilization than P. cathayana, This difference was due to adaptation to local environment., The low temperature and moisture where P. kangdingensis was collected can not provided optimum to decompose roots and litter fall as a result the nutrition in soil was poor. Exposed to enhanced UV-B radiation, for both species UV-B absorbing compounds and GPX activity were significantly increased while proline, MDA, soluble protein, chlorophyll, carotenoids were not affected. Different responses were also observed between the two species. Enhanced UV-B radiation caused significant decreases in leaf area, biomass, net photosynthetic rate and increase in APX activity and long-term WUE in P. cathayana but not in P. kangdingensis. In addition, activity in antioxidant enzymes was much higher in P. kangdingensis than in P. cathayana. In the experiment fertilization affected responses of cuttings to enhanced UV-B radiation, but it concern species and parameters measured. Long-term WUE in P. cathayana and chlorophyll in P. kangdingensis were significantly increased by enhanced UV-B radiation under non-fertilization treatments while the increase was not found under fertilization treatment. In contrast, under no fertilization treatment enhanced UV-B radiation did not affected GPX and APX activity in P. cathayana and GPX in P. kangdingensis while significant increase appeared after application of fertilization. Similar effect of enhanced UV-B radiation on intercellular CO2 concentration in P. kangdingensis was observed.

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本研究通过粗枝云杉不同种群进行的温室半控制试验,采用植物生态学、生理学和生物化学的研究方法,系统地研究了粗枝云杉不同种群抗旱性的生长、形态、生理和生化机理,并结合有关研究进行综合分析,得出主要研究结论如下: 1.粗枝云杉对干旱胁迫的综合反应 粗枝云杉在干旱胁迫下的适应机制为:(1)相对生长速率及植株结构的调整:干旱胁迫下虽然植株相对生长速率显著降低,且有相对较多的生物量向根部分配,但并未发现细根/总根比增加。(2)粗枝云杉对干旱胁迫的光合作用表现为:干旱胁迫显著地降低了控制的理想条件下的气体交换,但干旱胁迫对PSII最大光化学效率(Fv/Fm)没有影响,表明干旱并未影响到光合机构。(3)干旱还影响了很多生理生化过程,包括渗透调解物质(游离脯氨酸)、膜脂过氧化产物、脱落酸(ABA)含量的增加,以及保护酶活性的升高。这些结果证明植物遭受干旱胁迫后发生了一系列的形态、生理和生化响应,这些变化能提高干旱时期植物的存活和生长能力。 2.粗枝云杉不同种群对干旱胁迫反应的种群差异 粗枝云杉三个种群-干旱种群(四川丹巴和甘肃迭部)和湿润种群(四川黑水)对干旱适应不同,这种不同应归因于它们采用的用水策略不同:在水分良好和干旱胁迫条件下,受试种群在相对生长速率和水分利用效率(WUE)方面都表现出显著的种群间差异。与湿润种群相比,干旱种群在两种水分条件下有更高的WUE。粗枝云杉不同种群的碳同位素组分(δ13C)只在干旱胁迫下有显著差异,并且这种差异在水分良好时比干旱胁迫条件下小,说明生理响应和干旱适应性之间的关系受植物内部抗旱机制和外部环境条件(如水分可利用性)或两者互作效应的影响。这些结果说明干旱种群和湿润种群所采用的用水策略不同。干旱种群有更强的抗旱能力,采用的是节水型的用水策略,而湿润种群抗旱能力较弱,采用的是耗水型的用水策略。 3. 遮荫对粗枝云杉不同种群抗旱性影响 干旱胁迫显著降低了全光条件下叶相对含水量(RWC)、相对生长速率、气体交换参数、PSII的有效量子产量(Y),提高了非光化学猝灭效率(qN)、水分利用效率、脯氨酸(PRO)积累、脱落酸(ABA)含量及保护酶活性。然而这种变化在遮荫条件下不明显。我们得出结论适度遮荫降低了干旱对植物的胁迫作用。另一方面,在干旱条件下,与湿润种群相比,干旱种群抗旱性更强,表现在干旱种群净光合速率与单位重量上叶氮含量(Nmass)降低较少。另外,干旱种群表现出更为敏感的气孔导度,更高的热耗散能力(qN)能力、用水效率、ABA积累、保护酶活性,以及更低的总用水量、相对生长速率。这一结果表明这两种群采用不同的生理策略对干旱和遮荫做出反应。许多生长和生理反应差异与这两个种群原产地气候条件相适应。 4. 外源脱落酸(ABA)喷施对粗枝云杉不同种群抗旱性影响 外源ABA喷施在干旱和水分良好条件下均不同程度地提高了根/茎比,表明根和茎对ABA敏感程度不同。实验结果还表明,外源ABA喷施对这两个种群在干旱胁迫期间影响不同。干旱胁迫期间,伴随着ABA喷施,湿润种群净光合速率(A)显著降低,而干旱种群净光合速率变化不明显。另一方面,外源ABA喷施显著提高了干旱条件下干旱种群的单位叶面积重(LMA)、根/茎比、细根/总根(Ft)比、水分利用效率(WUE)、ABA含量, 以及保护酶活性。然而,外源ABA喷施对湿润种群的上述测定指标没有显著影响。这一结果表明干旱种群对外源ABA喷施更为敏感, 反应在更大的气孔导度降低,更高的生物量可塑性,及更高的水分利用效率、ABA含量和保护酶活性。综上所述,我们得出结论,粗枝云杉对外源ABA敏感性因种群的不同而不同。该研究结果可为两个明显不同种群在适应分化方面提供强有力的证据。 Arid or semi-arid land covers more than half of China's land territory. In arid systems, severe shortages of soil water often coincide with periods of high temperatures and high solar radiation, producing multiple stresses on plant performance. Protection from high radiation loads in shaded microenvironments during drought may compensate for a loss of productivity due to reduced irradiance when water is available. Additionally, ABA, a well-known stress-inducible plant hormone, has long been studied as a potential mediator for induction of drought tolerance in plants. Picea asperata Mast., which is one of the most important tree species used for the production of pulp wood and timber, is a prime reforestation species in western China. In this experiment, different population of P. asperata were used as experiment material to study the adaptability to drought stress and population differences in adaptabiliy, and the effects of shade and exogenous abscisic acid (ABA) application on the drought tolerance. Our results cold provide a strong theoretical evidence and scientific direction for the afforestation, and rehabilitation of ecosystem in the arid and semi-arid area, and provide a strong evidence for adaptive differentiation of different populations, and so may be used as criteria for species selection and tree improvement. The results are as follows: 1. A large set of parallel response to drought stress Drought stress caused pronounced inhibition of the growth and increased relatively dry matter allocation into the root; drought stress also caused pronounced inhibition of photosynthesis, while drought showed no effects on the maximal quantum yield of PSII photochemistry (Fv/Fm) in dark-adapted leaves, indicating that drought had no effects on the primary photochemistry of PSII. However, in light-adapted leaves, drought reduced the quantum yield of PSII electron transport (Y) and increased the non-photochemical quenching (qN). Drought also affected many physiological and biochemical processes, including increases in superoxide dismutase (SOD), ascorbate peroxidase (APX) activities, malondialdehyde and ABA content. These results demonstrate that there are a large set of parallel changes in the morphological, physiological and biochemical responses when plants are exposed to drought stress; these changes may enhance the capability of plants to survive and grow during drought periods. 2. Difference in adaptation to drought stress between contrasting populations of Picea asperata There were significant population differences in growth, dry matter allocation and water use efficiency. Compared with the wet climate population (Heishui), the dry climate population (Dan ba and Jiebu) showed higher LMA, fine root/total root ratio and water use efficiency under drought-stressed treatments. The results suggested that there were different water-use strategies between the dry population and the wet population. The dry climate population with higher drought tolerance may employ a conservative water-use strategy, whereas the wet climate population with lower drought tolerance may employ a prodigal water-use strategy. These variations in drought responses may be used as criteria for species selection and tree improvement. 3. The effects of shade on the drought tolerance For both populations tested, drought resulted in lower needle relative water content (RWC), relative growth rate (RGR), gas exchange parameters and effective PSII quantum yield (Y), and higher non-photochemical quenching (qN), water use efficiency (WUE), proline (PRO) and abscisic acid (ABA) accumulation, superoxide dismutase (SOD), ascorbate peroxidase (APX) activities as well as malondialdehyde (MDA) levels and electrolyte leakage in sun plants, whereas these changes were not significant in shade plants. Our study results implied that shade, applied together with drought, ameliorated the detrimental effects of drought. On the other hand, compared with the wet climate population, the dry climate population was more tolerant to drought in the sun treatment, as indicated by less decreases in A and mass-based leaf nitrogen content (Nmass), more responsive stomata, greater capacity for non-radiative dissipation of excitation energy as heat (analysed by qN), and higher WUE,higher level of antioxidant enzyme activities,higher ABA accumulation as well as lower MDA content and electrolyte leakage. Many of the differences in growth and physiological responses reported here are consistent with the climatic differences between the locations of the populations of P. asperata. 4. The effects of exogenous abscisic acid (ABA) application on the drought tolerance For both populations tested, exogenous ABA application increased root/shoot ratio (Rs) under well-watered and drought-stressed conditions, indicating that there was differential sensitivity to ABA in the roots and shoots. However, it appeared that ABA application affected the two P. asperata populations very differently during drought. CO2 assimilation rate (A) was significantly decreased in the wet climate population, but only to a minor extent in the dry climate population following ABA application during soil drying. On the other hand, ABA application significantly decreased stomatal conductance (gs), transpiration rate (E) and malondialdehyde (MDA) content, and significantly increased leaf mass per area (LMA), Rs, fine root/total root ratio (Ft), water use efficiency (WUE), ABA contents, superoxide dismutase (SOD), ascorbate peroxidase (APX) and catalase (CAT) activities under drought condition in the dry climate population, whereas ABA application did not significantly affect these parameters in the wet population plants. The results clearly demonstrated that the dry climate population was more responsive to ABA application than the wet climate population, as indicated by the strong stomata closure and by greater plasticity of LMA and biomass allocation, as well as by higher WUE, ABA content and anti-oxidative capacity to defense against oxidative stress, possibly predominantly by APX. We concluded that sensitivity to exogenous ABA application is population dependent in P. asperata. Our results provide strong evidence for adaptive differentiation between populations of P. asperata.

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杨树具有分布广、适应性强的特征,在生态环境治理和解决木材短缺方面均占有重要位置。青杨(Populus cathayana Rehd.)是青杨派树种的重要成员之一,也是生长较迅速、易繁殖的重要杨树资源。本研究选取了来自不同气候地区的青杨两种群为材料,采用植物生态学、生理学和生物化学的研究方法,系统地研究了青杨对干旱与遮荫、干旱与外源脱落酸(ABA)喷施的生长、形态、生理和生化响应及种群间差异,研究成果可为我国干旱半干旱地区的造林以及生态恢复提供理论依据和科学指导。主要研究结论如下:1.青杨在干旱胁迫下的适应机制为:生长性状及生物量的分配变化:干旱胁迫下虽然植株生长受抑,株高、基茎及各部分生物量都显著减小,但有相对较多的生物量向根部分配,根/冠比以及细/粗根比增加。青杨对干旱胁迫的光合作用表现为:干旱胁迫降低了青杨的净光合速率、蒸腾速率、气孔导度以及光合氮利用效率,提高了瞬时用水效率。干旱还引起了活性氧的产生,使得膜脂过氧化产物丙二醛(MDA)增加,同时也增强了植物抗氧化酶系统(如超氧化物歧化酶(SOD)、过氧化氢酶(CAT)和抗坏血酸过氧化物酶(APX)活性的增加)及非酶系统的能力(如抗坏血酸(AsA)含量的增加)。干旱降低了植物叶片的相对含水量,而促进了渗透调节物质(游离脯氨酸及可溶性糖)的积累,增加了植物的渗调能力。干旱下青杨两种群的内源ABA含量显著增加,碳同位素组分(δ13C)也显著提高。这些结果证明植物遭受干旱胁迫后发生一系列的形态、生理和生化响应,这些变化能提高植物在干旱下的存活和生长能力。2.青杨两种群对干旱胁迫反应的种群差异:与来自湿润地区的汉源种群相比,来自干旱地区的乐都种群在干旱条件下生物量向根系分配的可塑性更强,同时具有更强的抗氧化系统能力,所受到活性氧的伤害也更少,并且累积更多的脯胺酸和ABA,具有更高的δ13C。这些都说明了乐都种群对干旱的适应性比汉源种群更强。两种群对干旱的响应差异应归于它们的用水策略的不同:汉源种群来自湿润地区,采用了耗水型的用水策略,抗旱能力较弱;而乐都种群,来自干旱地区,通常采用节水型的用水策略,有更强的抗旱能力。3.遮荫对青杨两种群抗旱性的影响:遮荫对青杨抗旱性的影响决定于遮荫程度的不同,我们的结果表明中度的遮荫可以有效的提高干旱下植物的生长,对干旱胁迫有明显的缓解作用,具体体现在中度遮荫下受旱植物的叶片相对含水量得到提高,使得植物体内水分状况得到了改善;光合速率并未降低,植物光合氮利用效率增加,说明中度的遮荫并未明显限制植物的碳获得;抗氧化酶活性与膜脂过氧化产物MDA含量的同时降低,说明中度遮荫下所受到的活性氧伤害减少;中度遮荫下的ABA及δ13C的变化也不如在全光下变化明显,这也说明中度遮荫缓解了干旱胁迫。但是重度的遮荫却对干旱胁迫有明显的加剧作用,主要表现在重度遮荫降低了植物的光合速率,严重抑制了植物的生长;同时重度遮荫下脯胺酸含量和抗氧化酶活性的急剧下降,导致了植物渗调能力的下降及膜脂过氧化产物MDA的显著升高;重度遮荫还显著降低了内源ABA的累积和δ13C,降低了植物的抗旱能力。此外,青杨两种群在对干旱和遮荫的响应中,也表现出种群差异。汉源种群,来自湿润且年日照辐射较少的地区,表现出相对更强的耐荫性和需水性。而乐都种群,来自干旱且年日照辐射丰富的地区,表现出相对更强的耐旱性和需光性。这说明了植物对环境胁迫的耐受性是其长期适应原生境的结果,并且来自不同气候地区的两种群在面临环境胁迫时会采取不同的生存策略。4. 外源ABA喷施对青杨两种群抗旱性的影响:外源ABA的喷施可以提高两种群的抗旱性,具体表现为外源ABA喷施促进了青杨根系的生长,显著提高了干旱下植物的根/冠比和细/粗根比,减少了比叶面积;在生理生化方面,外源ABA降低了干旱下植物叶片的气孔导度,降低了蒸腾速率和净光合速率,但提高了瞬时用水效率,提高了叶片的相对含水量,增加了干旱下植物的保水能力。外源ABA进一步增加了干旱下植物内源ABA的积累,促进了植物渗调物质如脯胺酸和可溶性糖的积累,增加了抗氧化酶系统(如SOD、APX、CAT)的活性和非酶系统AsA的含量,降低了活性氧(如超氧阴离子(O2和过氧化氢(H2O2))对植株的伤害。此外,外源ABA还进一步提高了干旱下植物的δ13C,提高了植物的长期用水效率,由此提高了植物的抗旱能力。另一方面,两种群对外源ABA和干旱的响应也有所差别。来自湿润地区的汉源种群,对干旱较为敏感,所受干旱的影响也较大,而外源ABA的喷施对汉源种群抗旱性的提高作用也更为突出。乐都种群,由于其长期适应干旱地区的生长,本身已具有较强的抗旱能力,因此外源ABA喷施对其抗旱性的提高不如对汉源种群的效果明显。由此我们可以得出对于一些抗性弱或干旱敏感的物种或者种群,可以采用外施ABA的方法来提高其抗性。Poplars play an important role in lumber supply, and are important component ofecosystems due to their wide distribution and well adaptation. Populus cathayana Rehd.,which belongs to Populus Sect. Tacamahaca Spach, is one of the most important resources ofpoplars for its fast growth and reproductive. In this study, different populations of P.cathayana were used as experiment material to investigate the adaptability to drought stressand population differences in adaptability, and the effects of shade and exogenous abscisicacid (ABA) application on the drought tolerance. Our results could provide a strongtheoretical evidence and scientific direction for the afforestation, and rehabilitation ofecosystem in the arid and semi-arid area, and provide a strong evidence for adaptivedifferentiation of different populations, and so may be used as criteria for species selectionand tree improvement. The results are as follows:1. A large set of parallel response to drought stress: Drought stress caused pronouncedinhibition of the growth and increased relatively dry matter allocation into the root. For thetwo populations, the shoot height, basal diameter and total biomass were decreased but theroot/shoot ratio and fine root/coarse root ratio were increased under drought conditions;Drought stress caused pronounced inhibition of photosynthesis, decreased the stomatalconductance, transpiration rate, and photosynthetic nitrogen-use efficiency (PNUE) butincreased the instantaneous water use efficiency. Drought significantly improved the levels ofreactive oxygen species and malondialdehyde (MDA) and to induce the entire set ofantioxidative systems including the increase of activities of superoxide dismutase (SOD),ascorbate peroxidase (APX), catalase (CAT) and ascorbate (AsA) content. Drought decreased the leaf relative water content (RWC) but improved the capability of osmotic adjustmentindicated by the higher proline accumulation. Drought also increased the ABA content andcarbon isotope composition (δ13C), which indicating the long period water use efficiency wasimproved under drought. These results demonstrate that there are a large set of parallelchanges in the morphological, physiological and biochemical responses when plants areexposed to drought stress; these changes may enhance the capability of plants to survive andgrow during drought periods.2. Difference in adaptation to drought stress between contrasting populations of P.cathayana: Compared with the Hanyuan population (wet climate), the Ledu population (dryclimate) showed higher root/shoot ratio and water use efficiency, exhibited higherantioxidative systems capability thus resulting in less oxidative damage, accumulated moreABA and free proline content under drought conditions. The results suggested that there weredifferent water-use strategies between the two populations. The Ledu population, whichcomes from dry climate region, with higher drought tolerance, may employ a conservativewater-use strategy, whereas the Hanyuan population, which comes from wet climate, withlower drought tolerance, may employ a prodigal water-use strategy. These variations indrought responses may be used as criteria for species selection and tree improvement.3. The effects of shade on the drought tolerance: The reduction in the availability of lightand water affected the morphological and physiological responses of the two P. cathayanapopulations. In addition, the light environment modified the growth responses of P.cathayana seedlings to varying water environments in different ways depending upon theintensity of the light levels considered. There is an apparent alleviation to drought effects bymoderate shade in P. cathayana seedlings, as indicated by the higher leaf RWC, and unchanged net photosynthesis and PNUE, as well as by the lower antioxditative enzymeactivity, MDA, ABA and δ13C levels, which implied moderate shade did not significantlylimited the carbon acquisition or inhibited the plant growth, but ameliorated the detrimentaleffects of drought. On the other hand, an apparent aggravation to drought effects by severeshade was also observed, as indicated by the pronounced decrease of plant growth and net photosynthesis, the lower total biomass, ABA level, δ13C, free proline content andantioxditative enzyme activity and higher MDA accumulation. By contrast, the twopopulations showed different responses to shade and drought. The Hanyuan population,which comes from a riparian basin having a relatively wet climate and less annual solarradiation, is more sensitive to drought but more tolerant to shade. The Ledu population, whichcomes from a mountainous plateau with less rainfall and with more annual solar radiation, ismore tolerant to drought but more sensitive to shade. The results demonstrated that theendurance of plants to stress is a result of long-term evolution and adaptation to theenvironment, as suggested by the different strategies employed by the P. cathayanapopulations originating from contrasting habitats when they were exposed to drought andshade.4. The effects of exogenous ABA application on the drought tolerance: For bothpopulations under drought conditions tested, exogenous ABA application significantlyimproved the root/shoot ratio, fine root/coarse root ratio, and decreased the specifical leaf area.On the physiological and biochemical traits, exogenous ABA application significantlydecreased stomatal conductance, transpiration rate and net photosythesis but increased theinstance water use efficiency and leaf RWC. On the other hand, exogenous ABA applicationsignificantly increased endogenous ABA, proline, solube sugar and AsA content, as well asSOD, APX and CAT activities, thus reduced the damage of reactive oxygen species. Moreover,the long period water use efficiency as indicated by δ13C was also improved by exogenousABA application. In additionally, there was different responsive between the two populationsto drought and exogenous ABA application. The Hanyuan population, which comes from wetclimate region, is more sensitive to drought, and the effect of exogenous ABA is moreobviously than that in the Ledu population, which comes from dry climate region and is moredrought-responsive. Therefore, we can use exogenous ABA application to improve theresistance of plants, especially for the drought- sensitive species or populations.

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光是植物赖以生存的重要环境因子,但是植物在获得光的同时不可避免的会受到紫外辐射的伤害。尤其是近年来,人类向大气中排放的大量氮氧化合物和氟氯烃类化合物(CFC’s)引起臭氧分子的分解,导致到达地球表面的紫外辐射增加,特别是UV-B辐射增强。而另一方面,植物对UV-B辐射反应的敏感性在种间和品种间存在差异,主要受植物基因型,生态型和生活型的控制。本项目分别以粗枝云杉和青杨组杨树为模式植物,从形态和生理生化方面分别研究了来自不同水分背景下的粗枝云杉种群和来自不同UV-B背景下的青杨种群在增强UV-B下的反应及其反应差异,并探讨了干旱、喷施外源脱落酸(ABA)对它们抗UV-B能力的影响。研究成果可为生态系统的恢复与重建提供理论依据和科学指导。主要研究结果如下: 1. 粗枝云杉的两个种群,湿润种群(来自四川黑水)和干旱种群(来自甘肃迭部)在水分良好和干旱状况下表现出对增强UV-B的不同响应。同时,干旱对粗枝云杉抗UV-B能力的影响也得到研究:两种胁迫共同作用时,干旱表现出在一定程度上减弱了增强UV-B对粗枝云杉的生理特性的影响。 干旱胁迫显著降低了两个粗枝云杉种群的光合同化速率(A), 气孔导度(gs)和PSII的有效光量子产量(Y), 同时,提高了非光化学猝灭效率(qN)和超氧化物歧化酶(SOD)的活性。与湿润种群相比,干旱种群抗旱性更强,表现为干旱种群拥有更高的SOD和干旱进一步加剧了UV-B的胁迫效应。 本研究中,干旱胁迫单独作用时,显著降低了青杨两个种群的生物量积累和气体交换,具体包括A、gs、蒸腾速率(E)和光合氮利用效率(PNUE),提高了两个种群的瞬时水分利用效率(WUEi)、长期水分利用效率(WUET)、碳同位素组分(δ13C)和氮含量(N)。同时,UV吸收物质和ABA含量也得到积累。另一方面,增强UV-B对青杨两个种群各个指标的影响,同干旱所引起的效应有着相似的趋势。同低海拔种群相比,高海拔种群有着更强的抗旱和抗UV-B能力,具体表现在高海拔种群有着更多的生物量积累,更强的气体交换和水分利用效率及更高水平的ABA和UV吸收物质含量。相比干旱诱导的生物量积累和气体交换的降低,在干旱和增强UV-B两个胁迫同时作用于青杨时,这种降低表现的更为明显。显著的干旱和UV-B的交互作用还表现在WUEi, WUET, δ13C, 可溶性蛋白含量, UV吸收物质含量, ABA, 叶片和茎中的N含量以及C/N比中。 3. 经过一个生长季的试验观察,增强UV-B、外源ABA及两因子共同作用对青杨的生物量积累、气体交换、内源ABA和UV吸收物质含量、抗氧化系统以及碳、氮含量和碳/氮比均产生显著影响。本试验中,青杨的两个种群分别来自中国西南部的不同海拔地区,高海拔种群来自青海大通而低海拔种群来自四川九寨。外源ABA的胁迫为直接喷施ABA到青杨叶片,而增强UV-B胁迫是利用平方波系统分别保证青杨苗暴露于外界UV-B强度和两倍于外界UV-B强度下。 研究结果显示,增强UV-B显著的降低了两个青杨种群的株高、基茎、总叶面积和总生物量等生长指标,同时也导致其A、gs、E和叶片中碳含量的减少。而显著增加了SOD和过氧化物酶(GPx)活性水平,诱导了过氧化氢(H2O2)和MDA的显著增加,促进了UV吸收物质和不同器官中内源ABA含量的显著积累。另一方面,外源ABA引起了青杨光合同化速率的下降,SOD和GPx酶活性的增强,H2O2 和 MDA含量也表现出显著增加,同时,内源ABA含量得到显著累积。同低海拔种群相比,高海拔种群具有更加抗UV-B和外源ABA的特性。显著的UV-B和ABA的交互作用表现在A, E, SOD和GPx活性,以及叶片和根部的内源ABA等一系列指标中。在所有胁迫下,叶片中的碳和氮含量同其在茎和根中的含量显著相关,另外,叶片和茎中的氮含量同茎中的碳含量显著相关。 Sunlight is an indispensable environment factor for plants survival and development. Meanwhile, photosynthetic organisms need sunlight and are thus, inevitably, exposed to UV radiation. Especially for recent years, ultraviolet radiation, especially UV-B reaching the Earth’s surface increased because of depletion of ozone layer resulted from emission of NxO and CFC’s from human activities. On the other hand, the sensitivity of plants to UV-B radiation depends on the species, developmental stage and experimental conditions. In this experiment, two populations of Picea asperata Mast from different water background and two populations of Populus cathayana Rehder from different altitude background were selected as model plants to assess the effects of enhanced UV-B radiation. Morphological and physiological traits induced by enhanced UV-B in each plant species were observed and the different responses were discussed, furthermore the influences of drought and exogenous ABA on responses induced by enhanced UV-B were studied. The study could provide a strong theoretical evidence and scientific direction for the afforestation and rehabilitation of ecosystem. The results are as follows: 1. Different responses of two contrasting Picea asperata Mast. populations to enhanced ultraviolet-B (UV-B) radiation under well-watered and drought conditions were investigated. And the effects of enhanced UV-B on tolerance of drought were also observed in our study that the UV-B exposure may have alleviated some of the damage induced by drought. Two contrasting populations, originating from a wet and dry climate region in China, respectively, were employed in our study. Drought significantly decreased CO2 assimilation rate (A), stomatal conductance (gs) and effective PSII quantum yield (Y), while it significantly increased non-photochemical quenching (qN) and the activity of superoxide dismutase (SOD) in both populations. Compared with the wet climate population, the dry climate population was more acclimated to drought stress and showed much higher activities of SOD and ascorbate peroxidase (APX), and much lower levels of malondialdehyde (MDA) and electrolyte leakage. On the other hand, enhanced UV-B radiation also induced a significant decrease in the chlorophyll (Chl) content in both populations under well-watered conditions, and a significant increase in UV-absorbing compounds in the wet climate population. After one growing season of exposure to different UV-B levels and watering regimes, the increases in MDA and electrolyte leakage, as induced by drought, were less pronounced under the combination of UV-B and drought. In addition, an additive effect of drought and UV-B on A and gs was observed in the wet climate population, and on the activity of APX and qN in the dry climate population. 2. The significant effects of drought, enhanced UV-B radiation and their combination on Populus cathayana Rehd. growth and physiological traits were investigated in two populations, originating from high and low altitudes in south-west China. Our results showed that UV-B acts as an important signal allowing P. cathayana seedlings to respond to drought and that the combination of drought and UV-B may cause synergistically detrimental effects on plant growth in both populations. In both populations, drought significantly decreased biomass accumulation and gas exchange parameters, including A, gs, E and photosynthetic nitrogen use efficiency (PNUE). However, instantaneous water use efficiency (WUEi), transpiration efficiency (WUET), carbon isotope composition (δ13C) and nitrogen (N) content, as well as the accumulation of soluble protein, UV-absorbing compounds and abscisic acid (ABA) were significantly increased by drought. On the other hand, cuttings from both populations, when kept under enhanced UV-B radiation conditions, showed very similar changes in all above-mentioned parameters, as induced by drought. Compared with the low altitude population, the high altitude population was more tolerant to drought and enhanced UV-B, as indicated by the higher level of biomass accumulation, gas exchange, water-use efficiency, ABA concentration and UV-absorbing compounds. After one growing season of exposure to different UV-B levels and watering regimes, the decrease in biomass accumulation and gas exchange, induced by drought, was more pronounced under the combination of UV-B and drought. Significant interactions between drought and UV-B were observed in WUEi, WUET, δ13C, soluble protein, UV-absorbing compounds, ABA and in the leaf and stem N, as well as in the leaf and stem C/N ratio. 3. During one growing season, significant effects induced by enhanced UV-B radiation, exogenous ABA and their combination on biomass accumulation, gas exchange, endogenous ABA and UV-absorbing compounds concentrations, antioxidant system as well as carbon (C) content, nitrogen (N) content and C/N ratio were investigated in two contrasting Populus cathayana populations, originating from high and low altitudes in south-west China. Exogenous ABA was sprayed to the leaves and enhanced UV-B treatment was using a square-wave system to make the seedlings under ambient (1×) or twice ambient (2×) doses of biologically effective UV-B radiation (UV-BBE). Enhanced UV-B radiation significantly decreased height, basal diameter, total leaf area, total biomass, A, gs, E and carbon (C) content in leaves, and significantly increased activities of SOD and guaiacol peroxidase (GPx), hydrogen peroxide (H2O2) and malonaldehyde (MDA) content as well as the accumulation of UV-absorbing compounds and endogenous ABA concentrations among different organs in both populations. In contrast, exogenous ABA showed significant decrease in A and significant increases in activities of SOD and GPx, H2O2, MDA content and the endogenous ABA concentrations. Compared with the low altitude population, the high altitude population was more tolerant to enhanced UV-B and exogenous ABA. Significant interactions between UV-B and ABA were observed in A, E, activities of SOD and GPx, as well as in endogenous ABA in leaves and roots of both populations. Across all treatments, C and N content in leaves was strongly correlated with those were in stems and roots, respectively. Additionally, leaf and stem N content were significant correlated with stem C content.

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语义Web是现有Web的一个语义延伸,目标是使Web的应用具有一定的智能,能够进行更准确的信息搜索和一定的决策支持,帮助用户自动完成一些任务。语义Web的实现需要人工智能、数据库等领域的技术支持,需要对已有的技术进行改进和扩展,也需要对现有技术本身如ECA规则进行更深入的研究从而进一步将其扩展到语义Web。自动推理技术是语义Web实现的基础之一,而ECA规则可以为系统增加反应性行为能力,本文围绕自动推理和ECA规则,主要进行了如下研究:(1) 一阶逻辑推理技术对语义Web的推理支持。分析了语义Web语言需要的表达能力,对现有描述逻辑工具、一阶逻辑工具的能力进行了考察。现有的描述逻辑工具不足以处理应用所需要的更丰富的语言成分、任意的一阶逻辑规则等,而一阶逻辑自动定理证明工具和有限模型查找工具有分别都有较好的研究成果。把语义Web的推理问题化成可满足性判定问题后,本文给出了一阶逻辑定理证明器和有限模型查找器形成的并发过程进行可满足性判定的方法。这样既可以解决描述逻辑工具的不足,并可弥补定理证明器对可满足的公式推理的不完备性。(2) ECA规则(主动规则)的终止性分析。终止性是主动规则最重要的行为性质,不终止是由于主动规则的级联触发造成的,意味着定义错误。终止性检查通常是不可判定的。有效的静态分析方法是主动规则得以实际应用的保证。静态分析的关键是合适的数据库状态描述,本文给出用约束表示数据库状态的方法,通过模拟规则执行,使用约束求解进行条件计算和重复状态检查,判断主动规则集合是否终止。用约束精确表示了数据库状态,在规则处理中考虑了执行语义,从而得到更精确的终止性结论。

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本文概述了时序推理的代表理论以及它们对本学科的未来研究,尤其是对AI的影响。

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本文简要地介绍了数控自动编程专家系统.其中包括:专家系统知识表示的形式;分层次的黑板结构;前向推理求解策略和相应的解释功能;系统针对不同类型的曲线组合,采用不同的独立的知识源(KS)进行处理.由于在知识的处理上采用编码技术,在前向推理求解策略中使用启发信息和“剪技”技术,提高了系统的时空效率.系统中的规划程序能自动规划切削路径.输出供数控车床使用的 NC 代码,并可在显示屏上进行图形显示和切削仿真.目前原型系统已经在 IBM-PC 和 Sun3/60计算机上利用FORTRAN 语言实现.

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Moral decision-making in business means the decisions involved in moral issues in business context. Moral intensity is a construct that captures the extent of issue-related moral imperative in a situation, which is one of the most important factors in the study of moral decision-making in business. Based on Issue-Contingent Model, the present study investigated the influence of moral intensity on moral decision-making in business (including moral recognition, moral judgment, and moral intent in the present study), and further focused on exploring the mechanism of moral intensity in moral decision-making in business. Recently, the studies in decision-making gave more emphasis to the role of emotions. The present study tried to include empathy into moral decision-making in business to explore the role of empathy in the relationship between moral intensity and moral decision-making in business, which would enrich and extend Issue-Contingent Model. The present study would also make up for a deficiency in the study of moral decision-making in business that overemphasized the rational reasoning and neglected the role of emotions. There were three parts in the present study. Firstly, study 1 replicated the former study and explored the relationship between perceived moral intensity and moral decision-making in business in China by questionnaire method. Secondly, study 2 focused on exploring the influence of the components of moral intensity on moral decision-making in business and empathic response by experimental method. Finally, study 3 explored the role of empathy in the relationship between moral intensity and moral decision-making in business. The results indicated that, 1.Perceived moral intensity was the significant predictor for moral decision- making in business. 2.Magnitude of consequence, social consensus, and probability of effect had significant effects on moral decision-making in business. Magnitude of consequence and probability of effect could influence empathic response significantly. 3.Empathic response played the role of mediator between moral intensity and moral decision-making in business. Empathic response completely mediated the relationship between moral intensity and moral recognition. Empathic response partly mediated the relationship between moral intensity and moral judgment, moral intent. Further analysis indicated that probability of effect and magnitude of consequence relied more on empathic response than social consensus to influence moral judgment and moral intent. Dispositional empathy could influence moral decision-making in business through perceived moral intensity and empathic response. 4.Controlled empathic levels could influence moral decision-making in business significantly. Empathic levels influenced the effect of probability of effect on moral decision-making in business, and did not influence the effect of magnitude of consequence and social consensus on moral decision-making in business. These findings not only contribute to enrich the models of moral decision- making in business, but also have significant practical applications in the training of moral decision-making in business.

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As the foundation of other human resource practices, job analysis plays an essential role in HR management. Exploring sources of variance in job analysis ratings given by incumbents from the same job is of much significance to HRM practices. It can also shed lights on employee motivation in organizations. But previous studies in job analysis field have usually been conducted at individual level and take variance in job analysis ratings given by incumbents of the same job as error or bias. This dissertation takes the position that the variance may be meaningful based on role theory and other relevant theories. It first reviewed pervious studies on factors which may influence job analysis ratings provided by incumbents of the same job, and then investigated individual, interpersonal and organizational level variables which may exert impacts on these job analysis ratings, using multilevel data from 8 jobs of 1124 incumbents. The major findings are as follows: 1) Level of job performance and job attitudes affect incumbents’ job analysis ratings by incumbents of the same job at individual level. Specifically, incumbents with high level of job performance rated their job require higher levels of technical skills (power plant designers), and regarded information processing activities as more important to their job (book editors). Regarding the effects of job attitudes, incumbents of the four jobs with high level of job satisfaction gave higher importance and level ratings on organizational and cognitive skills, as well as higher level ratings on technical skills. Further, incumbents with higher affective commitment provided higher importance and level ratings of cognitive skills. Lastly, more involved job incumbents perceived organizational skills and cognitive skills as more important, and required at higher levels, for their job. 2) Leader-Member Exchange and goal structure also have effects on job analysis ratings by incumbents of the same job at interpersonal level. In good quality LMX relationship, news reporters rated decision-making activities and interpersonal activities as more important to their job. On the other side, when book editors structured their goals as cooperative with others’, they provided higher importance ratings on reasoning and interpersonal skills, and related personality requirements, as well as higher level ratings on reasoning abilities. 3) Worker requirements for the identical job are distinct from one organization to another. Specifically, there were between-organization differences in achievement orientation and conscientiousness related personality requirements. In addition, two dimensions of organizational culture, achievement-oriented culture and integrity-oriented culture in particular, were significantly associated with importance ratings of achievement orientation and conscientiousness related personality requirements respectively. Furthermore, achievement-oriented culture both directly and indirect (through job involvement) influenced achievement orientation related personality requirements. The results indicate that variation in job analysis ratings provided by incumbents of the same job may be meaningful. Future job analysis studies and practices should consider the impacts of these individual, interpersonal and organizational level factors on job analysis information. The results also have important implications for employee motivation concerning how organizational demands can be transformed into specific job and worker requirements.