Class Distribution (class + distribution)

Distribution by Scientific Domains

Kinds of Class Distribution

  • size class distribution


  • Selected Abstracts


    Quantification of termite attack on lying dead wood by a line intersection method in the Kabili-Sepilok Forest Reserve, Sabah, Malaysia

    INSECT CONSERVATION AND DIVERSITY, Issue 2 2008
    LENE BERGE
    Abstract., 1A line intersection method was used to estimate abundance (technically linear abundance: m1 m,2), biovolume (m3 ha,1) and size class distribution (defined by diameter) of lying dead wood in tropical forest. Additional semi-quantitative protocols assessed decay state (4 classes), termite attack (5 classes) and live termite occupancy (3 classes). 2Three forest types (kerangas, alluvial and sandstone) were sampled in the Kabili-Sepilok Forest Reserve of Eastern Sabah, using plots of 30 × 30 m. Approximately 50 man-hours were required per site, at a replication of three plots per site and three well-separated sites per forest type. 3Mean biovolume of lying dead wood exceeded 8 × 103 m3 ha,1 in kerangas (= heath) forest, with lower values in other types. Large items (> 19 cm diameter) were less than 10% of total abundance, but represented the largest biovolume, exceeding (alluvial) or equalling (kerangas) the total biovolumes of smaller categories combined. Most items (not less than 75%) were present as small wood (< 10 cm diameter). Items in the highest decay class had the highest biovolume. 4Termite attack was greater in the kerangas, where nearly 90% of items showed evidence of consumption, compared with 58% in the alluvial and 40% in the sandstone forests. Over 40% of items in the kerangas contained live termites compared with 25% in the alluvial and 15% in the sandstone. Items in the highest attack class (= almost total internal destruction) represented about one-half of the total biovolume available in the alluvial and kerangas forest types, and about one-third in the sandstone. [source]


    Diversity and composition of trees and shrubs in Kasagala forest: a semiarid savannah woodland in central Uganda

    AFRICAN JOURNAL OF ECOLOGY, Issue 1 2010
    Samson Gwali
    Abstract The diversity and composition of trees and shrubs of ,5 cm diameter at breast height (DBH) were investigated in Kasagala woodland in central Uganda using 1 ha permanent sample plots. A total of 2745 trees and shrubs with a mean stem density of 686 ha,1 were recorded. These included 69 tree species belonging to 28 families and 47 genera. There was a larger number of small stems compared with that of larger stems. There was significant variation in stem size class distribution between the plots (F = 3.14, P = 0.027). The variation in stem densities (counts) across different size classes was significant (F = 8.31, P < 0.001). Species diversity was higher in the low lands compared with that in the elevated sites in the woodland. The species encountered were unevenly distributed across the plots. Species abundance was not significantly different across the sample plots (F = 2.63, P = 0.053). We suggest that the structure of the forest is typical of any regenerating forest, but other human influences may have played a part in the dominance of size classes <10 cm DBH. The causes of the present status and composition of the woodland require further investigation. Résumé La diversité et la composition des arbres et arbustes de plus de 5 cm dbh ont étéétudiées dans la forêt de Kasagala, au centre de l'Ouganda, en utilisant des parcelles échantillons permanentes d'un hectare. On a relevé la présence de 2745 arbres et arbustes, avec une densité moyenne de 686 troncs ha,1. Ceux-ci comprenaient 69 espèces d'arbres appartenant à 28 familles et à 47 genres. Il y avait un plus grand nombre de petits troncs que de gros. Il y avait une variation significative de la distribution des classes de taille entre les parcelles (F = 3.14, P = 0.027). La variation de la densité des troncs (comptages) entre les différentes classes de taille était significative (F = 8.31, P < 0.001). La diversité des espèces était plus grande dans les terres basses que dans les sites plus élevés dans la forêt. Les espèces rencontrées étaient distribuées de façon inégale entre les parcelles. L'abondance des espèces n'était pas significativement différente selon les parcelles échantillons (F = 2.63, P = 0.053). Nous suggérons que la structure de la forêt est typique de toute forêt en voie de régénération, mais que d'autres influences humaines peuvent avoir joué un rôle dans la dominance des classes de taille <10 cm dbh. Les raisons du statut et de la composition actuels de la forêt requièrent de nouvelles investigations. [source]


    Natural regeneration and population dynamics of the tree Afzelia quanzensis in woodlands in Southern Africa

    AFRICAN JOURNAL OF ECOLOGY, Issue 4 2009
    Karin Gerhardt
    Abstract The logging of tree species of high commercial value is increasing throughout the African continent, yet the ecology of these species is generally poorly known. We studied the regeneration pattern and size class distribution of Afzelia quanzensis populations in northern South Africa over a 5-year period. Recruitment was low as the annual seedling mortality was >65%. Seedlings were located under the canopy and were affected by drought and browsing. The adults were scattered or were in a clump-dispersed pattern, which would result in higher recruitment of offspring near parents. Individuals of 0,10 cm diameter at breast height (DBH) were few, while there were 32 trees ha,1 at >10 cm DBH with an annual mortality of 0.8%. Annual diameter increments varied between 0.06 and 0.28 cm. It appears that the transition from the sapling into the juvenile stage could be a bottleneck in the regeneration of the species. A longer study, including more rainfall cycles, may reveal other patterns as dry and wet years have different impacts on dynamics. Résumé La coupe d'espèces d'arbres de grande valeur commerciale augmente dans tout le continent africain, pourtant l'écologie de ces espèces est généralement mal connue. Nous avons étudié le schéma de régénération et la distribution des classes d'âge des populations d'Afzelia quanzensis dans le nord de l'Afrique du Sud pendant cinq ans. Le recrutement était faible car la mortalité annuelle des jeunes plants était de plus de 65%. Les jeunes plans se trouvaient sous la canopée et étaient affectés par la sécheresse et par le broutage des animaux. Les adultes étaient dispersés ou se trouvaient en un schéma en bosquet, qui résulte en un plus fort recrutement de la progéniture près des parents. Les individus de 0,10 cm DBH étaient rares, alors qu'il y avait32 arbres ha,1à >10 cm DBH, avec une mortalité annuelle de 0,8%. L'incrément annuel du diamètre variait entre 0,06 et 0,28 cm. Il semble que la transition entre le stade de jeune arbre et celui de juvénile pourrait bien constituer un étranglement dans la régénération de l'espèce. Une étude plus longue, comprenant plus de cycles de pluies, pourrait révéler un autre schéma étant donné que les années sèches et humides ont des impacts différents sur cette dynamique. [source]


    Baobabs and elephants in Kruger National Park: nowhere to hide

    AFRICAN JOURNAL OF ECOLOGY, Issue 2 2008
    M. T. Edkins
    Abstract Baobab size class distributions were surveyed in the Limpopo National Park (LNP), Mozambique, and the Kruger National Park (KNP), South Africa. There are very few elephants in the LNP and the baobab population there had a reverse J-shaped size class distribution with many small baobabs. In contrast, the elephant-impacted baobab population of KNP displayed a mono-modal size-class distribution, with a lack in recruitment. Within KNP, elephant impact (percentage bark stripped up to the height of 3 m) decreased with increasing rockiness and slope steepness. We interpret this to suggest that steep rocky slopes are inaccessible to elephants and therefore these sites may act as a refuge for baobabs. In such inaccessible areas, the baobab population has a similar size-class distribution to that of the populations in the LNP. However, these baobab refugia are restricted in the northern KNP landscape and are therefore probably not large enough to sustain a viable baobab population. Résumé On a étudié la distribution des classes de taille des baobabs dans le Parc National de Limpopo (LNP), au Mozambique et au Parc National Kruger (KNP), en Afrique du Sud. Il y a très peu d'éléphants dans le LNP, et la population de baobabs y connaît une distribution de classes de taille en J inversé, avec de nombreux petits baobabs. Par contre, la population de baobabs du KNP est influencée par les éléphants et présente une distribution monomodale, avec un manque de recrutement. Au sein du KNP, l'impact des éléphants (le pourcentage d'écorces arrachées jusqu'à une hauteur de 3 mètres) diminuait quand augmentait le caractère rocailleux et abrupt des pentes. Nous interprétons cela et suggérons que les pentes abruptes et rocailleuses sont inaccessibles aux éléphants et que ces endroits peuvent donc servir de refuges pour les baobabs. Dans ces endroits inaccessibles, la population de baobabs a une distribution de classes semblable à celles des populations du LNP. Cependant, ces refuges pour baobabs se limitent au paysage nord du KNP et ne sont donc probablement pas suffisants pour accueillir une population de baobabs viable. [source]


    2D-Fractal Based Algorithms for Fine and Ultrafine Particulate Solids Systems Characterization

    PARTICLE & PARTICLE SYSTEMS CHARACTERIZATION, Issue 4-5 2007
    Giuseppe Bonifazi
    Abstract Fractal geometry concerns the study of non-Euclidean geometrical figures generated by a recursive sequence of mathematical operations. The proposed 2D-fractal approach was applied to characterise the image structure and texture generated by fine and ultrafine particles when impacting on a flat surface. The work was developed with reference to particles usually produced in the ornamental stone sector during the different working phases carried out in dry conditions. Specific milling actions have been performed at a laboratoty scale on different ornamental stone products, in order to generate different particle populations to utilize in the study. The aim of the work was to develop a simple, reliable and low cost analytical set of procedures with the ability to establish correlations between particles detected by fractal characteristics and their classical attributes, e.g., i) size class distribution, ii) shape, iii) composition, etc. Such a logic should constitute the core of a control engine with the ability to optimize dust capture abatement strategies, according to produced dusts characteristics. [source]


    Effects of Logging on the Diversity of Lianas in a Lowland Tropical Rain Forest in Hainan Island, South China

    BIOTROPICA, Issue 5 2009
    Yi Ding
    ABSTRACT Lianas are an integral part of tropical forest ecosystems, which usually respond strongly to severe disturbances, such as logging. To compare the effect of different logging systems on the lianas diversity in tropical rain forest, we recorded all lianas and trees ,1 cm dbh in two 40-year-old forest sites after clear cutting (CC) and selective cutting (SC) as well as in an old-growth (OG) lowland tropical rain forest on Hainan Island in south China. Results showed that OG contained fewer liana stems and lower species richness (stems: 261, richness: 42 in 1 ha) than CC (606, 52) and SC (727, 50). However, OG had the highest Fisher's , diversity index (17.3) and species richness per stem (0.184). Species composition and dbh class distribution of lianas varied significantly with different logging systems. The mean liana dbh in OG (22.1 cm) were higher than those in CC (7.0 cm) and SC (10.4 cm). Stem twining was the most frequent climbing mechanism represented in the forest, as shown by the greatest species richness, abundance, basal area, and host tree number with this mechanism. The percent of host tree stems ,4 cm dbh hosting at least one liana individual in SC (39%) was higher than CC (23%) and OG (19.5%). Large host trees (dbh,60 cm) were more likely to be infested by lianas in SC and OG. Our study demonstrated that logging disturbance could significantly change the composition and structure of liana communities in the lowland tropical rain forest of south China. [source]


    Baobabs and elephants in Kruger National Park: nowhere to hide

    AFRICAN JOURNAL OF ECOLOGY, Issue 2 2008
    M. T. Edkins
    Abstract Baobab size class distributions were surveyed in the Limpopo National Park (LNP), Mozambique, and the Kruger National Park (KNP), South Africa. There are very few elephants in the LNP and the baobab population there had a reverse J-shaped size class distribution with many small baobabs. In contrast, the elephant-impacted baobab population of KNP displayed a mono-modal size-class distribution, with a lack in recruitment. Within KNP, elephant impact (percentage bark stripped up to the height of 3 m) decreased with increasing rockiness and slope steepness. We interpret this to suggest that steep rocky slopes are inaccessible to elephants and therefore these sites may act as a refuge for baobabs. In such inaccessible areas, the baobab population has a similar size-class distribution to that of the populations in the LNP. However, these baobab refugia are restricted in the northern KNP landscape and are therefore probably not large enough to sustain a viable baobab population. Résumé On a étudié la distribution des classes de taille des baobabs dans le Parc National de Limpopo (LNP), au Mozambique et au Parc National Kruger (KNP), en Afrique du Sud. Il y a très peu d'éléphants dans le LNP, et la population de baobabs y connaît une distribution de classes de taille en J inversé, avec de nombreux petits baobabs. Par contre, la population de baobabs du KNP est influencée par les éléphants et présente une distribution monomodale, avec un manque de recrutement. Au sein du KNP, l'impact des éléphants (le pourcentage d'écorces arrachées jusqu'à une hauteur de 3 mètres) diminuait quand augmentait le caractère rocailleux et abrupt des pentes. Nous interprétons cela et suggérons que les pentes abruptes et rocailleuses sont inaccessibles aux éléphants et que ces endroits peuvent donc servir de refuges pour les baobabs. Dans ces endroits inaccessibles, la population de baobabs a une distribution de classes semblable à celles des populations du LNP. Cependant, ces refuges pour baobabs se limitent au paysage nord du KNP et ne sont donc probablement pas suffisants pour accueillir une population de baobabs viable. [source]


    Long-term canopy dynamics in a large area of temperate old-growth beech (Fagus crenata) forest: analysis by aerial photographs and digital elevation models

    JOURNAL OF ECOLOGY, Issue 6 2004
    YUKO HENBO
    Summary 1Long-term canopy dynamics in a large area of temperate old-growth beech forest in the Daisen Forest Reserve, south-western Japan (11.56 ha studied over 43 years), were investigated using digital elevation models (DEMs) of the canopy surface, constructed from aerial photographs taken in the growing season (i.e. with foliage) in 1958, 1978, 1992 and 2001. A ground surface DEM at the same resolution (a 2.5 × 2.5 m grid) was constructed using aerial photographs taken when foliage was absent (winter 2002). Canopy height data were obtained by calculating differences in elevation between the canopy and the ground surface, and a canopy height profile was constructed. 2Topographic data for a 4-ha plot, located within the 11.56-ha area, were obtained via a ground survey and used to validate the ground surface DEM derived from aerial photographs. 3Canopy height class distributions changed significantly over the 43 years. The total number of gaps, defined as areas where canopy height was , 15 m, decreased but total gap area increased over time. Total gap area in 2001 was twice that of 1958. The density of gaps decreased as gap size increased. 4Gap formation rates increased from 0.47% year,1 (1958,78) to 1.30% year,1 (1992,2001), with a mean of 0.77% year,1, and substantially exceeded closure rates, which fluctuated from 0.28% year,1 (1958,78) to 0.54% year,1 (1978,92), with a mean of 0.39% year,1. Gaps generally expanded and became connected to each other. 5Temporal variation in gap formation and closure might be correlated with the frequency and severity of typhoon disturbances but, if the observed trends continue, this old-growth beech stand may become an open stand. The long-term dynamics of this forest type appear to be far from equilibrium. [source]


    Women and class structure in contemporary Japan1

    THE BRITISH JOURNAL OF SOCIOLOGY, Issue 3 2001
    Sawako Shirahase
    ABSTRACT The main purpose of this study is to examine how to determine the class position of women, especially married women, in Japan. This study examines three different approaches to conceptualizing women's position in the class structure: the conventional approach, the individual approach, and the dominance approach. Since 1975, the overall rate of female labour force participation in Japan has increased, and given this growth, particularly of employees working outside home, I discuss whether the increased entry of women, particularly married women, into the labour market challenges the conventional way of assigning class positions to women by simply deriving them from their husband's class positions. The data set used in this study is derived from the 1995 Japanese Social Stratification and Mobility Survey. An examination of class distributions suggests that the pictures of macro-class structure provided by the conventional approach and the dominance approach show very little difference. Married women who belong to the female-dominant family still form a very small minority of all married women in the society. Furthermore, the male-dominant family shows the greatest stability over the life course whereas the female-dominant family, where the wife experiences with-drawal from the labour market, is least stable. The increasing number of married women in the labour market, thus, has not yet become a major threat to the conventional way of assigning women to a class position in contemporary Japan. Women, even among those working on a full-time basis, perceive their position in the stratification system using not only their own work, but also their husband's. In contrast, men's perception is determined by their own education and employment, not by their wives'. This asymmetry in the effect of the husband's class and of the wife's class on class identification is related not only to gender inequality within the labour market but also to the division of labour by gender within the household. [source]


    Herbivorous fishes and the potential of Caribbean marine reserves to preserve coral reef ecosystems

    AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 5 2010
    Dorothée Kopp
    Abstract 1.The development of macroalgae to the detriment of corals is now one of the major threats to coral reefs. Herbivorous fishes are partly responsible for algal regulation on coral reefs and their overexploitation favours the shift from scleractinian coral-dominated systems towards macroalgae-dominated systems. 2.Marine protected areas (MPAs) that have been established worldwide may benefit coral reefs through the maintenance of high densities of herbivorous fishes which regulate algal growth. 3.The paper assesses whether small MPAs in the Caribbean are able to enhance herbivorous fish stock and by controlling macroalgae help to maintain reef ecosystems. A visual census using band-transects was undertaken around Guadeloupe island where marine reserves have been in place since 1979. The effects of MPAs on both benthic communities and herbivorous fishes are examined. 4.Inside MPAs, herbivorous fish biomass was almost twice as high as outside MPAs and macroalgal cover was significantly lower. Fish size class distributions revealed that large individuals occurred mainly inside MPAs and that few male individuals were found outside MPAs. Copyright © 2010 John Wiley & Sons, Ltd. [source]