Temporal changes in wetland plant communities with decades of cumulative water pollution in two plateau lakes in China’s Yunnan Province

Wetland plant communities in the plateau lakes of Yunnan Province, China, have decreased significantly over the past decades. To better understand this degradation, we analyzed the processes and characteristics of changes in wetland plant communities in two of the largest lakes in Yunnan Province, Dianchi and Erhai lakes. We collected records of native and alien plant communities in the two lakes from literature published from the 1950s to current period. We calculated plant community types and their area in some historical periods when related data were reported, and analyzed the relationship between changes in plant communities and water pollution. In Dianchi Lake, 12 community types of native plant communities, covering over 80% of the surface in the 1950s and 1960s, were reduced to four types covering 2.4% by the late 2000s. Alien plant communities started to appear in the lake in the late 1970s, and have since come to cover 4.9% of the lake surface, thereby becoming dominant. In Erhai Lake, 16 community types of native plant communities, covering 47.1% of the lake surface in the late 1970s, declined to 10 community types, covering 9.3% of the surface, by the late 2000s. Alien plant communities appeared in the middle 1980s, and at present cover 0.7% of the surface area. It was indicated that changes in plant communities were significant related to water eutrophication. The area occupied by native and alien plant communities was, respectively, negatively and positively related to the content of nutrients in water. This showed lacustrine pollution played an important role in native plant loss and alien plant invasion in the two plateau lakes.     

Effects of temperature and salinity on survival,growth and DNA methylation of juvenile Pacific abalone,Haliotis discus hannai Ino

Temperature and salinity are two of the most potent abiotic factors infl uencing marine mollusks.In this study,we investigated the individual and combined ef fects of temperature and salinity on the survival and growth of juvenile Pacifi c abalone,Haliotis discus hannai Ino,and also examined the DNA methylation alteration that may underpin the phenotypic variation of abalone exposed to dif ferent rearing conditions.The single-factor data showed that the suitable ranges of temperature and salinity were 16–28°C at a constant salinity of 32,and 24–40 at a constant temperature of 20°C,respectively.The two-factor data indicated that both survival and growth were signifi cantly af fected by temperature,salinity and their interaction.The optimal temperature-salinity combination for juveniles was 23–25°C and 30–36.To explore environment-induced DNA methylation alteration,the methylation-sensitive amplifi ed polymorphism(MSAP)technique was used to analyze the genomic methylation profi les of abalone reared in optimal and adverse conditions.Neither temperature nor salinity induced evident changes in the global methylation level,but 67 and 63 dif ferentially methylated loci were identifi ed in temperature and salinity treatments,respectively.The between-group eigen analysis also showed that both temperature and salinity could induce epigenetic dif ferentiation in H.discus hannai Ino.The results of our study provide optimal rearing conditions for juvenile H.discus hannai Ino,and represent the fi rst step toward revealing the epigenetic regulatory mechanism of abalone in response to thermal and salt stresses.     

建筑地基与基坑变形监测刍议

随着城市建设的高速发展 ,高层、超高层建筑在原建筑物稠密区大量兴建 ,加之过量超采城市地下水 ,带来的地基与基坑变形问题越来越突出。为了防治建筑地基与基坑变形灾害 ,必须建立操作性较强的变形监测系统 ,及时作好预警、预报工作 ,使变形监测的方法、技术更加完善。     

Capacities and failure modes of suction bucket foundation with internal bulkheads

Suction bucket foundations can be divided into four compartments by cruciform internal bulkheads, thereby yielding better capacity in certain conditions than those without internal bulkheads. As yet, no systematic study has been conducted regarding the effects of cruciform internal bulkheads on the capacities of suction bucket foundations. In this study, we established a large number of finite element models of suction bucket foundations with and without cruciform internal bulkheads and of solid embedded circular foundations. We found the uniaxial capacities and failure modes of suction bucket foundations with various depth ratios to remain basically unaffected by internal bulkheads in uniform clays. However, in inhomogeneous clay with high strength heterogeneity, we observed the uniaxial moment and horizontal capacities and corresponding failure modes of suction bucket foundations with a low depth ratio to be obviously affected by internal bulkheads. In this case, the uniaxial moment capacities, in particular, as well as the horizontal capacities of suction bucket foundations with cruciform internal bulkheads become obviously greater than those without internal bulkheads. Under combined loading, we found the failure envelopes of suction bucket foundations with and without cruciform internal bulkheads and of solid circular foundation to also be basically consistent in uniform clays. However, in inhomogeneous clay with high strength heterogeneity, cruciform internal bulkheads can obviously change the shapes of the failure envelopes of bucket foundations with a small depth ratio. We conclude that when the acting vertical load or foundation depth is relatively small, suction bucket foundations with cruciform internal bulkheads can be subjected to larger moment and horizontal loads in soft clays with high strength heterogeneity.     

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Interdecadal variations of surface winds over China marginal seas

Long term variability in the surface winds over the marginal seas of China is examined with a dominant-mode singular value decomposition method. Both interannual and interdecadal patterns are found to be seasonally and spatially dependent, with reanalyses and satellite remote sensing data yielding highly consistent results. The study reveals that summer monsoon winds over the East China Sea experienced an interdecadal weakening in the late 1960s and began a persistent recovery in 2005. The study also shows gradual weakening of the winter monsoon in the southern South China Sea by more than 2m/s since the 1960s, with corroboration from coastal climate stations in Borneo. This phenomenon has not been reported in previous monsoon studies.     

南昌地震台钻孔应变同震响应分析

通过总结2007年5月以来南昌地震台TJ-2钻孔应变仪的同震效应,并与同期中国地震台网(CSN)提供的全球大震目录中的数据进行对比分析,绘出了震级与震中距的对数关系图,得出南昌地震台体应变仪的映震能力的表达式近似为Ms=1.381gD+ 1.1.     

用高密度电法探测西安地区地裂缝的可行性研究

高密度电阻率法比常用的电阻率法有更多的优点,一次可以完成纵、横二维勘探过程,所以观测精度高,采集数据可靠,获得地质信息丰富。本文主要从高密度电法的工作方法、成果解释来说明用高密度电法探测西安地区地裂缝的可行性。     

DEVELOPMENT STRATEGIES OF WATER AND LAND RESOURCES IN THE HEXI REGION,CHINA

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一种使用正交调制互补码的新方法

本文提出一种新的方案,可以用正交调制的方法,同时发射两组互补码,从而使得该系统对目标信号相关时间的要求由历来的“必须远大于雷达重复周期”降低到”只要远大于码的总长”。本文给出了用计算机进行仿真的结果。