Geomorphological Zones Research Articles

Marine algae from the oceanic atolls in the southwestern Caribbean (Albuquerque Cays, Courtown Cays, Serrana Bank, and Roncador Bank)

A total of 171 taxa of benthic marine algae are recorded from four oceanic atolls in the southwestern Caribbean Sea (Albuquerque Cays, Courtown Cays, Roncador Bank and Serrana Bank). The algae were collected in the different geomorphological zones and bottom habitats occurring in these reef-complexes, and within a depth range from intertidal to 40 m. Of the total taxa found, 6 are Cyanobacteria, 61 Chlorophyta, 22 Phaeophyta and 82 Rhodophyta. Twenty seven taxa are new records for the Colombian Caribbean. The marine flora of these atolls is closely related with that of the northern Caribbean phytogeographical region.

Iron age occupation in the Méma region, Mali

The recent archaeological campaign (regional site survey and excavations at the mound complex of Akumbu) has demonstrated that the Mema, a dry Sahelian region with a scattered population, was intensively occupied during the Iron Age. This intense occupation, certainly associated with better environmental conditions, extends back to the Late Stone Age. During the regional survey more than 100 Iron Age sites and nearly 30 Late Stone Age sites were identified; their size, surface material and features, and location on geomorphological zones were recorded. A series of radiocarbon dates spanning the fourth to fourteenth centuries ad obtained from the excavations at the Iron Age mound complex of Akumbu and a preliminary analysis of the pottery from both the excavations and the survey permitted the determination of a broad chronology of occupation. Numerous slag heaps (associated with smelting furnace remains) found during the survey and imported goods uncovered during the excavations at Akumbu indicate that both iron production and long-distance trade played an important role in the Mema economy.

Dynamics of fish communities on Reunion fringing reefs, Indian Ocean. II. Patterns of temporal fluctuations

Temporal fluctuations in fish communities on fringing reefs on Reunion Island (south-western Indian Ocean) were studied on three different scales: (1) within months, (2) within year and (3) between years. Greatest species richness and abundance of individuals were found during the full moon periods. This variation may be related to reproductive and/or trophic migrations of fishes inside or outside the reef, or to similar variations of prey populations. Seasonal fluctuations of fish abundance and species richness occurred in the three geomorphological zones and on the four reefs studied, but patterns differed among zones and reefs. Despite the increase in food availability during the austral summer, recruitment processes probably accounted for most of the seasonal fluctuations of fish communities, although it was not clearly evidenced. A decrease in fish abundance was observed in all zones during the 2 yr studied, although the magnitude of this decline differed between reefs. Coral degradation caused by hurricane Firinga impact and/or eutrophication of coral reef waters, may provide partial explanation for these patterns. Nevertheless, large interannual variation in recruitment of young individuals (especially for schooling species) may be the most valuable hypothesis causing the decrease in fish abundance on Reunion Island reefs.

Mitigative Design for Colluvial Slope Instability, Wadi Es-Sir Sewage Treatment Plant, Jordan

Lagoons were constructed within colluvial deposits in an area of 140,000 m2 as part of Wadi Es-Sir Sewage Treatment Plant Project in Jordan. The site has been excavated into steps and risers to construct the lagoons. A major noncircular slope failure occurred in October 1993 on the upper slope of the middle lagoon, resulting in an interruption of construction. Field and laboratory investigations were conducted to identify various geomorphologic zones, stratigraphy and geotechnical properties of all materials encountered at the site. Slope stability back analysis of failed slope was carried out using the 2-D limiting equilibrium Simplified Janbu method. Also, stability analysis was carried out for existing and improved conditions for all lagoons. Dry, partially saturated and fully saturated conditions were considered in the analysis. Pseudostatic stability analysis of the slopes was carried out considering a horizontal bedrock Peak Ground Acceleration (PGA) value of 0.2 g, evaluated at the site using a line source probabilistic seismic hazard assessment model incorporated in the computer program FRISK (McGuire, 1978). The study showed that the failure occurred through colluvial material due to the removal of a large amount of such materials near the toe of the slope during construction of the lagoon. The location of the slip surface was between 8 to 12 m in depth. Effective residual shear strength parameters along the failure plane were found to be: angle of friction (ϕ′) = 17°, and cohesion (c′) = 0.05 kg/cm2. Stability conditions for slopes at all lagoon sites were found to be unacceptable. Recommended measures to stabilize the slopes include replacing (partially or fully) the existing colluvial materials with free-drained rockfill to reach acceptable factors of safety under design conditions. These measures were implemented at the site.

Effect of soil fertility on host response to black leaf streak of plantain (Musaspp., AAB group) under traditional farming systems in Southeastern Nigeria

Abstract Plantain (Musa spp., AAB group) is a staple food crop in the humid forest regions of West and Central Africa. Its cultivation is threatened by black leaf streak (BLS), an air‐borne fungal leaf spot disease, caused by Mycosphaerella fijiensis Morelet. An on‐farm survey for BLS severity in relation to soil fertility was conducted in two different geomorphological zones, the main plantain‐growing areas of Rivers State where plantain is mostly cultivated in compound gardens and in outlying fields mixed with other food crops. Plantain in the Meander belts zone (the Central Niger Delta area) was less infected by BLS than in the Coastal plain sands (the east of the Niger delta). In addition, plantain grown in homestead gardens had a much lower BLS severity than that planted in field‐plots. The host plant response is attributable to the difference in soil fertility both between the two geomorphological zones and between the two farming systems. Therefore, the success of a system would depend on managing ...

Notes on the role of potassium in soil erosion in mountain pastures: Basis for a hypothesis

Soil erosion in mountain pastures has often been described in terms of rising or falling geomorphological gradients of erosion along slope. In some locations, however, small sectors of eroded soil coexist in any geomorphological zone alongside intact sectors. This has inspired some authors to explain the underlying factors in other forms of erosion, including those which are manifested in mosaics of rhexistasis-biostasis, lobules of solifluction, small tiers, etc. Geomorphological anomalies such as those related to cracks and vertical movements in small rocky blocks, melting snow or animal activity, have helped to describe the coexistence of these sectors. This paper considers that the variation of potassium in soil can permit an explanation of the frequent intact-eroded soil mosaics in siliceous substrata highlighted by herbaceous vegetation.

Orographical Zoning of West Bohemia

The paper treats of a concise survey of the development of orographical and geomorphological zoning of West Bohemia. The author proposes certain principles to be used in zoning and determines orographical units in this way.

Application of infiltration equations to a catchment with large spatial variability in infiltration

The infiltration equations according to Horton and Philip are applied to 52 double-ring infiltrometer tests performed in a small semiarid catchment in northern Tunisia. Spatial variability in infiltration properties is analysed as regards the coefficients of the two equations. Different geomorphological zones display different infiltration characteristics even if there is large variability within each zone and no clear statistical difference between the zones. Statistical properties of the coefficients of Horton's and Philip's equations describing cumulative infiltration are presented and discussed. The statistical distribution of the coefficients seems to be well approximated by an exponential function.

Spatial variability of infiltration in a semi-arid environment

Fifty-two double-ring infiltrometer tests, performed in a small, partly urbanized catchment in northern Tunisia are analyzed. Spatial variability is characterized by use of cross-correlation functions. Spatial patterns of infiltration properties are shown to be governed by geomorphology and occurring vegetation. Different geomorphological zones and zones with equal density of vegetation tend to be oriented in a parallel pattern in relation to the wadi. Statistical properties of infiltration capacities depending on geomorphological zone are presented.

Glacial Geomorphological Map (1:200 000) of Mt. Tomur Region, Tianshan (Abstract)

The Glacial Geomorphological Map (1:200 000) of Mt, Tomur Region, Tianshan, covers 78°33′ – 81°10′E and 41° 08′ – 42° 44′N, with high mountains, deep valleys and many snow peaks, the highest being Mt. Tomur (7435.3 a.s.l.). There are many glaciers in this region with a total area of 4553.69 km2. The melt water from glaciers irrigates the large oasis of Aksu, in the piedmont region in southern Xingjiang and waters the valley plain of Teks River in the Yili area. From piedmont plain to highest mountain summit, the vertical zonality of geomorphology is quite clear, rich in various geomorphological types, representing alpine geomorphology of the arid desert in Central Asia.The author joined the glacial/geomorphological expedition to the Mt. Tomur Region in 1963, 1973 and 1974, and, in the process of mapping, cooperated closely with mapping engineers. This involved extensive use of aerial photographs, satellite images, large-scale topographic maps, geological maps, geomorphological maps and other data, and comprehensive analyses, comparisons, and judgements of data.Special emphasis was placed on existing glaciers and the geomorphology of Quaternary glaciers, according to form, composition and relative chronological periods. The geomorphology was divided into five great systems, i.e. glacial, fluvio-glacial, fluvial, arid and artificial. Twenty-four geomorphic types were defined as the basic elements of the geomorphological map and shown in different colours and by various marks, while old and Neozoic faults were shown by black line marks. There are representative heights on all geomorphological zones. Colour brush-shading added much to the stereo effect.Below the main map, the longitudinal and cross sections of Quaternary geology and geomorphology of the Tialan valley, the stratigraphical columnar profile of West Zamtia and the fluvial/lacustrine deposit profile of the Loska basin were attached, showing the stratigraphical relation between the glacial and non-glacial deposit and the basis for the divisions of the glacial and inter-glacial periods.

Glacial Geomorphological Map (1:200 000) of Mt. Tomur Region, Tianshan (Abstract)

The Glacial Geomorphological Map (1:200 000) of Mt, Tomur Region, Tianshan, covers 78°33′ – 81°10′E and 41° 08′ – 42° 44′N, with high mountains, deep valleys and many snow peaks, the highest being Mt. Tomur (7435.3 a.s.l.). There are many glaciers in this region with a total area of 4553.69 km2. The melt water from glaciers irrigates the large oasis of Aksu, in the piedmont region in southern Xingjiang and waters the valley plain of Teks River in the Yili area. From piedmont plain to highest mountain summit, the vertical zonality of geomorphology is quite clear, rich in various geomorphological types, representing alpine geomorphology of the arid desert in Central Asia. The author joined the glacial/geomorphological expedition to the Mt. Tomur Region in 1963, 1973 and 1974, and, in the process of mapping, cooperated closely with mapping engineers. This involved extensive use of aerial photographs, satellite images, large-scale topographic maps, geological maps, geomorphological maps and other data, and comprehensive analyses, comparisons, and judgements of data. Special emphasis was placed on existing glaciers and the geomorphology of Quaternary glaciers, according to form, composition and relative chronological periods. The geomorphology was divided into five great systems, i.e. glacial, fluvio-glacial, fluvial, arid and artificial. Twenty-four geomorphic types were defined as the basic elements of the geomorphological map and shown in different colours and by various marks, while old and Neozoic faults were shown by black line marks. There are representative heights on all geomorphological zones. Colour brush-shading added much to the stereo effect. Below the main map, the longitudinal and cross sections of Quaternary geology and geomorphology of the Tialan valley, the stratigraphical columnar profile of West Zamtia and the fluvial/lacustrine deposit profile of the Loska basin were attached, showing the stratigraphical relation between the glacial and non-glacial deposit and the basis for the divisions of the glacial and inter-glacial periods.

Space-time variability in mediterranean pastures analyzed with diversity parameters

Different parameters of diversity and spatial niche amplitude (Piclou, 1975, Pineda et al., 1981b) have been used to describe the spatial organization of mediterranean grasslands in Central Spain. A slope sampled by 480 contiguous 8×8 cm quadrats proved to have a homogeneous floristic distribution when it was divided into 160 parts and maximum heterogeneity when divided into 4 sectors. These sectors corresponded to different geomorphological zones of the slope. The complexity of vegetation distribution on the slope was reflected by differences in organization — measured by diversity parameter A=H(P/E)/log2 N (number of plots) between the parts obtained by division. The presence of low-entropy species — specialists - and high entropy species — generalists — was related to the different scales of slope organization. The spatial distribution of plants was compared for different successional stages. Multivariate analysis of sampling plots confirmed previously identified organizational characteristics and clarified the nature of transitions between communities of different floristic composition or structure.

Ecological landscape inventories and evaluation

Olschowy, G., 1975. Ecological landscape inventories and evaluation. Landscape Plann., 2: 37–44. Landscape ecology, as basis for landscape-related planning, can be divided into: (1) ecological landscape inventory (“landscape analysis”) (a) for large areas (e.g. area of a country) (b) for regional planning zones (2) ecological landscape evaluation (“landscape diagnosis”) (a) of landscape factors (b) of spatial units For the development, environment and landscape programmes such as are being elaborated by many countries at the present time, ecological inventories of large areas are necessary. To this end, as well as geological maps and soil, water and climate maps, the following must also be made available: vegetation maps (potential natural vegetation, distribution of woodlands and wild flora), maps of wild fauna, protected areas and extensive landscape damage. The regional ecological inventory as basis for regional, land-use, local and landscape plans, covers the same features; it must, however, go into more detail, and include single criteria. Ecological evaluation should be undertaken in relation to the utilization of the space, thus for purposes of nature conservation and recreation, for agriculture and forestry, for industrial, trade, settlement and traffic purposes. The evaluation must include, in the first instance, the landscape factors: relief, geology, soil, water, climate, vegetation and fauna. One should aim at a comprehensive ecological evaluation of landscape areas and planning zones, with the object of defining ecological spatial units. Possible aids for demarcating these units are, primarily, maps of geomorphological zones, vegetation maps, soil maps, and also a combination of these data. At the present time, the complete compilation by area of ecological bases for planning forms the point of main effort of the methodical development in Germany.