云南陡坡地优化利用若干问题研究—以滇西北地区为例

云南陡坡垦殖较为严重,滇西北地区尤为突出。主要原因有宜耕地缺乏、社会经济发展滞后、粮食单产低、人口增长较快、交通不便等。陡坡垦殖导致植被破坏、土壤侵蚀;环境变劣,部分地区失去生存条件;灾害频繁,威胁中下游地区生命和财产安全。退耕还林是一项系统工程。工作尚未大规模开展之前,应认真落实应退耕地面积和退耕还林地块,积极解决群众温饱,减轻土地压力。退耕还林规划应与区域发展规划协调一致;建立农林复合系统,实现陡坡地优化利用;组织技术培训,建立技术保障系统;发展交通事业,改善生产生活条件。     

Female circumcision and ethnic identification in Sudan with special reference to the Berti of Darfur1

This article assesses the state of female circumcision in the Sudan with the primary emphasis being placed on the Berti of Darfur. Among other things, the article examines the factors that have so far led to the perpetuation of the practice and the failure of the anti-circumcision campaign. The author suggests a renewal of the campaign through the use of a comprehensive approach which encompasses the social, aesthetic, medical, identificational and religious variables involved in the practice. This revised version was published online in July 2006 with corrections to the Cover Date.     

Islam and cultural identity among the Berti of Sudan1

Focusing on the Berti of Sudan, this article assesses the role of Islam and Arabism as important variables in the social construction of cultural identity of the studied people. In line with most relevant recent literature, the author looks at cultural identity as a social construct, a dynamic ideology of shifting borders and a historical process that is grounded on diachronic social formation. The article argues that the present Berti identity is a conscious reflection of their subordinate position vis-à-vis the kingdoms and states which have dominated Sudan over the past few centuries. This revised version was published online in July 2006 with corrections to the Cover Date.     

A note on nearshore wave features: Implications for wave generation

This paper analyses 10 years of wave data from the Mediterranean Spanish (Catalan) coast considering the mean wave climate and storm events from the standpoint of wind-wave momentum transfer and wave prediction. The data, registered by a buoy at about 12 km from the coastline, revealed two main groups of wave storms, with NW and E directions. NW storms correspond to a fetch-limited situation since the intense wind blows from land. Low-pressure centres located over the Mediterranean Sea produce easterly storms. Near the coast the eastern winds from the sea are replaced by NW winds coming from meteorological patterns over northern Spain and south-western France. Wave storms are classified and studied to obtain their main features (including spectral width, wave length, wave age and bimodality) and discussed in terms of wind-wave momentum transfer for operational wave predictions. Observations show a complex coastal wave climate. Fetch-limited storms presented smaller spectral widths while varying wind situations presented larger widths due to the presence of bimodal spectra. These wave features are highly relevant for wind–ocean momentum transfer and, thus, for current and wave predictions. The spectral width proved to be a good indicator of sea complexity and is thus applicable for improved wind drag estimations. A new drag coefficient formulation is proposed, based on existing wind dependent drag expressions, but including also spectral wave properties (a spectral width parameter) that highlights the characteristics of wind-wave generation under pre-existing swell. Such a formulation, once properly validated with field observations, is expected to improve wind-wave predictions.     

Hydrography and dynamics of the Ría de Ribadeo (NW Spain), a wave driven estuary

The Ría de Ribadeo, a small embayment in NW Spain, was observed for the first time using three months of ADCP (Acoustic Doppler Current Profiler) current meter records and three CTD (Conductivity Temperature Depth) surveys. A wave driven circulation pattern arises from the observations, instead of the shelf wind driven circulation of other Galician Rias. Based on ADCP records, a unidirectional flow in the horizontal velocity field coexists with the classic two-layer circulation (bidirectional flow). The proposed horizontal circulation pattern can then be explained as a wave driven inflow. This flow enters the ria through the west side, describes an anticlockwise gyre inside of it, and flows out through the east side. Numerical simulations run with the HAMSOM (Hamburg Shelf Ocean Model) agreed with observations, confirming the proposed pattern.     

Distributions of Calanus spp. and other mesozooplankton in the Labrador Sea in relation to hydrography in spring and summer (1995-2000)

We collected mesozooplankton samples in the upper 100 m in spring or early summer each year between 1995 and 2000 along a section from Hamilton Bank (Labrador) to Cape Desolation (Greenland), and along additional sections in spring 1997 and early summer 1995. The North Atlantic waters of the central basin were characterised by the presence of the copepods Calanus finmarchicus, Euchaeta norvegica and Scolecithrocella minor and euphausiids. Calanus glacialis, Calanus hyperboreus and Pseudocalanus spp. were associated with the Arctic waters over the shelves. Amongst the other enumerated groups larvaceans were concentrated over the shelves and around the margins. Amphipods, pteropods and the copepods Oithona spp. and Oncaea spp. showed no definable relationships with water masses or bathymetry, while the diel migrant ostracods and chaetognaths were confined to deep water. Metrida longa, also a strong diel migrant, and Microcalanus spp., a mainly deep water species and possible diel migrant, were both sometimes quite abundant on the shelves as well as in the central basin, consistent with their likely Arctic origins.Analysis of community structure along the section across the Labrador Sea indicated that stations could be grouped into five different zones corresponding to: the Labrador Shelf; the Labrador Slope; the western and central Labrador Sea; the eastern Labrador Sea and Greenland Slope; and, the Greenland Shelf. The boundaries between zones varied spatially between years, but community composition was relatively consistent within a given zone and a given season (spring versus early summer). The relationship between community composition and water masses was not entirely straightforward. For example, Labrador Shelf water was generally confined to the shelf, but in spring 2000 when it also dominated the adjacent slope zone, the community in the Labrador Slope zone was similar to those found in other years. Conversely, in spring 1997, when Arctic organisms were unusually abundant in the Labrador Slope zone, there was no increased contribution of shelf water. In addition, North Atlantic organisms were often found on the shelves when no slope or central basin water was present.Although other organisms were sometimes very abundant, the mesozooplankton preserved dry weight biomass was dominated everywhere by the three species of Calanus, which together always accounted for ≥70%. One species, C. finmarchicus, comprised >60% of the total mesozooplankton biomass and >80% of the abundance of large copepods in spring and summer throughout the central Labrador Sea. In western and central regions of the central basin average C. finmarchicus biomass was ca 4 g dry weight m⁻² and average abundance, ca 17?000 m⁻² over both seasons. Highest levels (ca 7 g dry weight m⁻², >100?000 m⁻²) occurred in the northern Labrador Sea in spring and in eastern and southwest regions in early summer. C. hyperboreus contributed ca 20% of the total mesozooplankton biomass in the central basin in spring and <5% in early summer, while C. glacialis accounted for <1%. Over the shelves, C. hyperboreus contributed a maximum of 54% and 3.6 g dry weight m⁻², and C. glacialis, a maximum of 29% and 1 g dry weight m⁻², to the total mesozooplankton biomass.     

Spatial variability of intertidal rocky shore assemblages in the northwest coast of Portugal

The spatial variability of rocky shore assemblages of the northwest Portuguese coast was studied in a total of 12 transects, visited twice between March and August 2003. Each transect was positioned from the upper to the lower shore and four replicate samples (50 × 50 cm) were taken at each visually identified assemblage. Multivariate analysis was used to test the null hypothesis of no significant differences among assemblages located on different heights along the transect and among assemblages located at the same height on different transects. The distribution pattern of organisms along the height was not consistent across transects and significant variability could be found in assemblages located at the same height on the shore. Globally, the variability from the lower to the upper shore (vertical axis) was larger than from transect to transect (horizontal axis) but the distribution pattern along height was clearer in sheltered transects than in exposed ones. The heterogeneity in composition between the visually identified assemblages, within the same transect, was, however, the major source of variability in the study area. In the rocky intertidal northwest coast of Portugal, where tidal amplitude is broad and extremely wave-exposed sites are scarce, height above chart datum was the most important factor determining the distribution and species composition of the assemblages. However, variability along the horizontal axis was also significant and should be considered in studies of spatial patterns of distribution of organisms within this area.     

Horizontal Transfer of Matter by a Cave-Dwelling Mysid

Abstract. The role of a cave-dwelling mysid population as a matter carrier was evaluated in a cave of the Medes Is. (NW Mediterranean) during 1988–89. Hemimysis spehmcola (Ledoyer , 1963) is a gregarious mysid whose swarms migrate daily from the inner end of the cave - where they remain during the day–to the exterior where they feed during the night. Fecal pellet composition, pellet egestion and pellet decomposition were measured in order to evaluate the transfer of matter by mysids. Based on the strong daily behavioural rhythms of these mysids. special importance was attached to the sampling frequency (every 2 h). In order to assess seasonal variability, four daily cycles were evaluated within a year. In situ incubations were carried out to determine changes on the egestion rates, morphology, weight and composition (AA. C: N ratios) of pellets in the course of a day. The number of pellets deposited inside the cave was estimated using containers distributed along the cave bottom by SCUBA divers. Fecal pellets showed an amorphous composition, whereby diatom frustules, dinoflagellate loricae and coccolithoporids were very scarce. About 25% of the body weight were estimated to be egested daily as fecal pellets, suggesting a detritivorous feeding habit. The population oscillated seasonally between 1 and 12 millions. Individuals egested between 1.6 and 3.5 pellets a day into the cave, each averaging from 9.4 to 11.9 μg DW, 0.5 to 1.0 μg C and 0.046 to 0.27 μg N. Therefore, the population carried daily about 20 407 g DW POM. 2–21 g C and 0.5 2.7 g N from outside to inside the cave. Pellets decomposed very quickly; between 20 to 50% of both C and N were released from pellets in less than 2 h after egestion. Oxidation of pellets theoretically consumes an amount of oxygen which agrees with the high BOD values previously reported for this cave. Marine caves are generally viewed as strictly oligotrophic systems; dense mysid populations, however, could strongly modify the trophic relationships in marine caves.