Repeated physical disturbances and the stability of sub‐tropical coral communities in Hong Kong,China

• 1. This paper reports on the dynamics of the coral community structure at A Ma Wan (AMW) and A Ye Wan (AYW) in Tung Ping Chau, Hong Kong, focusing on data collected before and after the summer typhoon seasons in 1997 to 1999. This period (1999) experienced the highest frequency of severe tropical cyclones to hit Hong Kong with one cyclone being the strongest to hit in the last 23 years (1984 to 2006).
• 2. This is part of a long‐term monitoring programme of subtropical coral communities that has been set up in AMW since May 1997 and AYW since May 1998 with nine fixed position 40 m long transects and 0.5 m × 0.5 m permanent quadrats laid at 5 m intervals along each transect. A total of 45 scleractinian coral species from 21 genera (12 families) was recorded, with 40 species in AMW and 32 species in AYW recorded at the beginning of the study.
• 3. Multidimensional scaling ordinations showed distinct spatial variations in the coral communities within and between sites. These variations were probably a result of the differential effects of the repeated cyclone impacts on the communities. Cyphastrea serailia, Goniopora lobata, Montipora peltiformis and Pavona decussata were the dominant species most strongly affected by cyclone impacts at AMW, experiencing a 6.2–16.2% loss of mean area cover during the study period. Some dominant species (e.g. P. decussata) in AYW also experienced a 6.5–14.3% loss of mean area cover within the same period.
• 4. Overall, these coral community structures appeared relatively stable and resistant to repeated physical disturbances. However, they may have low resilience towards more severe disturbances in the future. Preserving the resilience of coral communities/species in Tung Ping Chau should be one of the main goals of coral conservation strategies for the island.

Copyright © 2008 John Wiley & Sons, Ltd.     

预氧丝原位炭化无粘结剂C/C复合材料氧化动力学研究

采用恒温热重法测定了在空气中，０．１ＭＰａ，６７３Ｋ到９７３Ｋ下预氧丝（即预氧化聚丙烯腈纤维）原位炭化无粘结剂Ｃ／Ｃ复合的氧化失重率；并利用扫描电镜分析了这种复合材料氧化前后的结构，氧化动力学测定结果表明：该材料在氧化开始时，其氧化速率随时间的增长而增大，然后随时间的延长而减小，并趋向恒定，研究表明：该材料中预氧丝与基体炭界面结合处是空气中氧的扩散通道，杂质为空气中氧的吸附起到了有附活性中心的催化     

基于Lefkovitch矩阵模型的山酢浆草种群动态分析

依据林下多年生草本植物山酢浆草Oxalis griffithii的形态学特征,将其生活史划分为4个阶段,并根据3种生境下山酢浆草种群的野外调查资料建立了不同种群的Lefkovitch结构矩阵模型,在此基础上预测了山酢浆草种群的动态及其阶段结构的变化;同时,运用敏感度、贡献率指标分析了影响种群动态的关键生活史阶段。结果表明：不同生境下山酢浆草种群的动态发展趋势不尽相同,常绿阔叶林下的种群（MD）呈稳定发展状态,其他2种生境下种群表现出衰退的发展趋势;种群的动态变化过程受个体的生长、残存、萎缩和繁殖等的综合影响;不同生活史阶段对种群动态的影响差异显著,种群动态过程及其发展趋势主要受种群内较大阶段个体的影响。图2表5参19     

基于特征线方程N—S方程非增量型分离算法

为克服传统有限元方法求解流场时由于对流项占优而引起的求解振荡和基函数选择困难的问题,推导了基于特征线方程的粘性不可压N-S方程的增量型和非增量型分离算法的公式及求解步骤,并讨论了两者的Babuska-Brezzi条件.沿着特征线方向,N-S方程的对流项消失,方程矩阵是自伴随矩阵,可以自动满足有限单元法中能量泛函最小的要求,并可以给出合理的粘性耗散项.动量方程的求解采用非增量型分离算法,压力和速度可以采用任意阶次的插值函数,离散后的方程自动满足Babuska-Brezzi条件.为验证算法的可靠性,采用T3P3空间等阶次U-p单元计算了方柱绕流.结果表明：基于特征线方程的非增量型分离算法可以很好地应用于粘性不可压流场的计算,与目前流行的其它方法相比,该算法有明显的优势.     

Effects of intensive fishing on the perch population in a large oligotrophic lake in eastern Finland

The perch population in Lake Höytiäinen was intensively fished to reduce the density of the population and hence also the predation pressure by perch on vendace larvae. A hypothesis suggests that this predation can prevent recovery of commercially important vendace stock from a state of low-density. In the 1990s the density of the perch population in Lake Höytiäinen has increased, while the vendace stock has been sparse. Intensive fishing was conducted by professional fishermen with a paired bottom trawl, seine net, hoop net and small fish traps and by recreational fishermen with small fish traps. The size of perch population during the intensive fishing period was studied by test fishing with multi-mesh gillnets and the Leslie method in which trawl YPUE was regressed on the cumulative yield. The results suggest that the population size clearly diminished in the area where the fishing pressure was strongest. YPUE of test fishing decreased ca. 30% whereas the Leslie method gave almost a decrease twice as large as that of the former. Mean weight of perch increased in the trawl and test fishing catches during the intensive fishing period. The most effective fishing gear was trawl (62% of the total yield), but importance of trap net fishing by recreational fishermen was also high as they caught 22% of the total yield.     

Relative importance of habitat area and isolation for bird occurrence patterns in a naturally patchy landscape

There is debate among ecologists about whether total habitat area or patch arrangement contributes most to population and/or community responses to fragmented or patchy landscapes. We tested the relative effects of patch area and isolation for predicting bird occurrence in a naturally patchy landscape in the Bear River Mountains of Northern Utah, USA. We selected focal patches (mountain meadows) ranging in elevation from 1,920 to 2,860 m and in size from 0.6 to 182 ha. Breeding birds were sampled in each focal meadow during the summers of 2003 and 2004 using variable-distance point transects. Logistic regression and likelihood-based model selection were used to determine the relationship between likelihood of occurrence of three bird species (Brewer’s sparrow, vesper sparrow, and white-crowned sparrow) and area, isolation, and proximity metrics. We used model weights and model-averaged confidence intervals to assess the importance of each predictor variable. Plots of area versus isolation were used to evaluate complex relationships between the variables. We found that meadow area was the most important variable for explaining occurrence for two species, and that isolation was the most important for the other. We also found that the absolute distance was more appropriate for evaluating isolation responses than was the species-specific proximity metric. Our findings add clarity to the debate between ecologists regarding the relative importance of area and isolation in species responses to patchy landscapes.     

施肥量对水稻准两优527产量和营养动态的影响

贵州省黔南苗族布依族自治州属于中国西部丘原山地，平均海拔1100m，岩溶地貌发育典型，土壤贫瘠且宜耕作性较差，耕作粗放，作物的产量一直不高。农民为了提高作物的产量，大量施用无机肥料，肥料利用效率逐步降低，而且肥料的大量施用已经引起了严重的环境问题，因此合理运筹肥料是提高肥料利用率、减少污染的重要措施。     

麦套春棉麦棉共生期水分变化动态研究

１９９２～１９９３年对麦套春棉麦棉共生期水分变化动态进行了研究。两年试验结果表明，４种套种方式共生期田间持水量变化动态均表现为：棉行间＞棉株间＞麦棉行间＞麦行间；在试验范围内麦棉间距≥０３０ｍ时，无论麦收前有无自然降雨，棉行间、棉株间持水量与纯作棉田（ＣＫ）差异不显著，而麦棉行间、麦行间持水量显著低于ＣＫ；３—２式和４—２式用水较为经济；套种田与ＣＫ持水量等同点分布区集中在距小麦边行０３０～０４０ｍ处，各套种方式麦棉间距以０３０ｍ为宜。     

礼貌的顺应性

从语境关系顺应、语言结构顺应、动态顺应、意识程度四个方面对礼貌现象的考察说明礼貌具有顺应性。礼貌的顺应性是指在交际活动中, 处于不同心理状态的交际者根据语境变化选择适宜的礼貌策略来表达自己的思想。忽视礼貌的顺应性是礼貌原则存在不足之处的根本原因。     

浑善达克沙地飞播区不同恢复阶段植物群落结构动态变化

为研究浑善达克沙地飞播区不同恢复阶段植物群落结构动态变化,揭示飞播后浑善达克沙地植被恢复的特点和变化规律,于2013—2017年在浑善达克沙地11个飞播区进行了植被调查试验,并从功能型角度出发,结合对应分析、关联度分析以及Mann-Kendall趋势分析等数据分析方法探讨了飞播区植被恢复的阶段性以及各功能型植物在群落中的地位和作用。结果显示:浑善达克沙地飞播区19 a恢复时间共分为3个恢复阶段,且飞播后,伴随恢复时间的推移,乔木、灌木半灌木、多年生杂类草、一/二年生杂类草、多年生豆科牧草、多年生禾草、一/二年生禾草7个功能型植物间的相互依赖程度逐渐减弱;随着恢复年限的增加,群落的稳定性逐渐增大。不同恢复阶段,植被恢复的主导功能型并不唯一,可在不同阶段进行适时管理,从而使植物群落的演替阶段和整体发展趋势更有利于退化沙地的植被恢复与重建。