Mucus Aggregates in the Adriatic Sea: An Overview of Stages and Occurrences

Abstract. The wide range of macroscopic mucus aggregates in the Adriatic Sea is documented. These structures arc considered to be initially produced by diatoms. A differentiation into five states or stages: macroflocs, stringers, clouds, creamy surface layers, and gelatinous surface layers is proposed. This classification is based not only on size and shape, but also takes relative position in the water, stability, behavior, and effect on benthos into consideration. An interrelationship between these aggregates - as different manifestations or phases of the same phenomenon - is postulated.
Macroflocs and stringers arc more common. Larger aggregates (clouds, creamy layers, gelatinous layers) arc less frequent. The general term "marine snow" is inadequate to describe the entire range of aggregate sizes and shapes, while the Italian designation "mare sporco" (dirty sea) is misleading. Two massive occurrences of dense clouds coupled with surface accumulations were recorded in the Adriatic in 1988 and 1989. The effect of the various stages on the shallow coastal ecosystem of the Northern Adriatic Sea is discussed.     

Marine biofouling in Hong Kong:a review

From 1980 to 1998, biofouling communities in Hong Kong waters, the Zhujiang RiverEstuary and the Mirs Bay were studied and a total of 610 samples. The samples were collected from ves-sels, buoys, piers and cages. Totally, 340 species (see Appendix Ⅰ ) have been recorded and identified,six of which are new. At the same time, research on the biology of the cirripede, bryozoan, polychaeteand mollusc communities were also conducted. Twenty-three related papers have been published. Thisreview summarizes works in Hong Kong over past twenty years, and some unpublished data are also re-ported.     

The Effects of Industrial Pollution on the Development and Succession of Marine Fouling Communities I. Analysis of Species Richness and Frequency Data

Abstract. The effects of industrial pollution were determined by comparing the pattern of development of marine fouling communities situated along a pollution gradient within Port Kembla Harbour (Australia) with those from nearby Wollongong Harbour, a relatively unpolluted area. Fifty-three fouling species were found in the communities from Wollongong Harbour compared to only 40 in those from Port Kembla Harbour. Twenty-eight species (including many bryozoans) occurred only in the former, while 15 species occurred solely in the latter. Ten of the 25 species common to both areas were more numerous in Port Kembla Harbour, probably because of the greater availability of free substratum and food in this area. The species richness of fouling communities in Port Kembla Harbour was found to decrease as pollutant concentrations increased. In both study areas, communities established in summer showed significantly higher species richness than those whose development was initiated in winter. This difference was less pronounced in Port Kembla Harbour and was attributed to the effects of pollution on larval settlement. Although species richness increased at all sites through time, Wollongong Harbour communities contained a greater number of species at the end of the experiment than communities from Port Kembla Harbour. Despite this, fewer species were found in the very early developmental stages of the communities from Wollongong Harbour. This result highlights the inherent problems associated with using species richness or diversity measures as a means of determining marine environmental quality.     

ISLANDS AS PLACES OF BEING AND BELONGING*

ABSTRACT. Islands, traditionally important units of research and analysis in ethnographic research, have come to be viewed as a problematic unit of analysis, as anthropologists have realized the close integration of island societies within the wider world. This article argues that islands are still useful and fruitful foci of research, if their particular character is explored from an islandic point of view. Through life‐story interviews conducted in three large, dispersed families of Caribbean origin, the article demonstrates that islands may be usefully conceptualized as sociocultural constructs that constitute important anchoring points as well as sources of identification for migrants and their descendants.     

低覆盖度不同配置灌丛内风流结构与防风效果的风洞实验

 低覆盖度灌木群丛是干旱、半干旱区广泛分布且具有重要意义的植被，也是人工修复沙地应遵从的植被。通过风洞试验模拟了覆盖度在20%左右的三种水平配置格局的灌木群丛内风流结构与防风固沙效果。结果表明：①水平配置格局不同，低覆盖度灌木群丛的防风效果差异显著，行带式模式具有非常显著的阻碍和降低风速的作用（风速降低36%~43%）;等株行距模式次之，风速降低7%~28%;随机不均匀配置模式内局部有风速抬升现象，② 行带式模式内形成规整的随灌丛带波动的流场结构，而随机不均匀配置模式内形成由多个风影区和风速加速区组合的非常复杂的流场结构，等株行距模式居于二者之间。③ 带间宽度在56 cm和64 cm时的防风效果较带宽为32 cm和40 cm好。说明覆盖度降低到11%~13%，行带式模式的防风效果仍然不会降低。④两行一带配置均表现防风效果优于单行配置，且随试验风速的增大防风效果更好。     

PROPRIETARY RESIDENTIAL COMMUNITIES IN THE UNITED STATES

ABSTRACT. Proprietary residential communities constitute a major component in the evolving geography of urban America. In many metropolitan regions, proprietary residential communities or common‐interest developments, and associated forms of urban management, have emerged as the dominant form of residential development. Critical discourse on these communities and their residential community/homeowner associations has focused principally on the negative consequences for urban social and political life. It is argued here that many critical assessments are grounded in an idealistic view of contemporary society and an outdated conceptualization of citizenship. This article is intended to reenergize debate on these developments through a realist interpretation of the benefits and disbenefits of a form of residential development destined to exercise a major influence on the sociospatial structure of U.S. metropolitan areas in the early twenty‐first century.     

Rural Restructuring and the Changing Geography of Competitive Sport

The geography of sport has received relatively little attention from those interested in processes of rural social and economic change. This is despite the important role that sport plays in the structure of rural communities and regions. In addition to the obvious health benefits associated with physical activity, sport contributes to community identity and provides opportunities for social interaction. There is, however, considerable evidence to suggest that processes of restructuring are having direct impacts on sport in rural areas. Drawing on a case study from rural Western Australia, this paper argues that economic adjustment in the farming and business sectors, service withdrawal, and population decline are just some of the changes undermining the viability of sporting clubs in rural areas. We suggest that while sporting clubs have tended to be resilient in the face of restructuring, it is also clear that one of the outcomes is a changing geography of sport in declining rural areas.     

Plant functional types and climate along a precipitation gradient in temperate grasslands, north-east China and south-east Mongolia

Using data from three field surveys along a precipitation gradient of temperate grasslands in north-east China (the Northeast China Transect, NECT) and south-east Mongolia, the spatial distribution of six plant functional types (PFTs): C₃ species, C₄ species, grasses, shrubs, forbs and succulents and their relationships with climate were analysed. The spatial distribution of different PFTs varies in different regions and in different grassland types of the study area. The species richness in each PFT also has different relationships with climate (significantly or not). Generally, the number of C₃ species, C₄ species, grasses and forbs have positive relationships with precipitation and aridity. Shrubs have negative relationship with precipitation and aridity. Succulents were found to have no relationship with precipitation and aridity. Shrubs, grasses and forbs have stronger relationships with precipitation than C₃ and C₄ species. The relationships between C₃ species, forbs and aridity are more significant than with precipitation. On a regional basis, the combined effect of precipitation and temperature, the aridity, is more significantly correlated with the distribution of C₃ species and forbs, which are more dominant in the study area, than with C₄ species, grasses and succulents.     

High-resolution images reveal rate and pattern of shrub encroachment over six decades in New Mexico, U.S.A.

Encroachment of the shrub Prosopis glandulosa Torr. (honey mesquite) into semi-arid grasslands is a serious concern in the south-western United States, yet little is known about the long-term dynamics of the invasion process. We used ten high-resolution aerial and satellite images taken from 1936 to 1996 to track the population dynamics and spatial pattern of all P. glandulosa greater than 2 m in diameter on a 75 ha area in southern New Mexico.Shrub cover and patch numbers increased from 1936 to the 1970s, then stabilized at 43% cover and 83 patches ha⁻¹. Individual patches were extremely persistent: 95% of the area occupied by shrub patches in 1936 was still occupied in 1996. Recruitment into the 2 m size class was more variable: 0·6–5·2% year⁻¹ (mean 0·8% year⁻¹). Patch-shape complexity increased from 1936 to 1983 as adjacent shrubs merged, and then declined as those clusters filled in and became rounder. Spatial pattern of shrubs showed a distinct trend over time: strongly clustered in 1936 at lag distances up to 250 m, then random arrangement at all scales, and by 1983 pattern was regular at lag distances greater than 100 m. There was no clear relationship with precipitation.The use of remote sensing imagery allowed us to examine one site over time, and revealed patterns in population dynamics and spatial pattern that would not have been visible otherwise. Comparison of field estimates collected in 2001 with 1996 image data suggest that the canopy cover estimates were accurate, but shrub densities were seriously underestimated in the satellite photographs, which do not show shrubs smaller than 2 m diameter. As long as limitations of the imagery are understood, these methods can be applied over a larger and more heterogeneous area to examine environmental correlates of invasion success.     

Forest‐Cover Change from Labor‐ and Capital‐Intensive Commercial Logging in the Southern Chocó Rainforests*

This article examines two key aspects of land‐cover change in the south of the Chocó region. First, it assesses and compares the local impact on forest condition of labor‐intensive and capital‐intensive commercial logging. Second, it assesses the regional significance and permanency of these changes. Studies of land‐cover change associated with commercial logging have focused almost exclusively on capital‐intensive extraction and have assumed that after logging, degraded forests are transformed into agricultural cover. This study shows that both capital‐ and labor‐intensive logging result in similar land‐cover changes (i.e., forest degradation) if the timber sought is the same. However, labor‐intensive loggers also seek timber species not sought by capital‐intensive loggers, and this impact is statistically different from the impact of the extraction of the first group of species. Results also show that only a small fraction (20–30 percent) of the area logged is later converted to agricultural cover types. The persistence of logged forests means that up to 20 percent of the remaining forest cover could correspond to forests with significant and lasting levels of degradation. Furthermore, the different production requirements for each group of species also mean that there is a spatial differentiation in the impact of logging in the region. Logged forests are arranged into two consecutive corridors on each side of access routes (e.g., rivers). The first corridor corresponds to a narrow (approximately 1‐km) band of high‐intensity degradation. The second, broader (approximately 2‐km) forest band, with lower levels of degradation, extends inland along first‐tier corridors. A key factor determining the permanency of this land‐cover pattern is the strong control local communities have over the land in the region. This limits the spread of patterns observed in other frontier areas, especially the conversion of logged forests into agricultural cover.