Western Escarpment Research Articles

Woody Plant Species Composition, Population Structure and Carbon Sequestration Potential of the A. senegal (L.) Willd Woodland Along a Distance Gradient in North-Western Tigray, Ethiopia

In Ethiopia, dry land vegetation including the fairly intact lowland and western escarpment woodlands occupy the largest vegetation resource of the country. These forests play a central role in environmental regulation and socio-economic assets, yet they received less scientific attention than the moist forests. This study evaluated the woody plant species composition, population structure and carbon sequestration potential of the A. senegal woodland across three distance gradients from the settlements. A total of 45 sample quadrants were laid along a systematically established nine parallel transect lines to collect vegetation and soil data across distance gradients from settlement. Mature tree dry biomass with DBH＞2.5 cm was estimated using allometric equations. A total of 41 woody plant species that belong to 20 families were recorded and A. senegal was the dominant species with 56.4 IVI value. Woody plant species diversity, density and richness were significantly higher in the distant plots compared to the nearest plots to settlement (p＜0.05). The cumulative DBH class distribution of all individuals had showed an interrupted inverted J-shape population pattern. There were 19 species without seedlings, 15 species without saplings and 14 species without both seedlings and saplings. A significant above ground carbon (5.3 to 12.7 ton ha-1), root carbon (1.6 to 3.6 ton ha-1), soil organic carbon (35.6 to 44.5 ton ha-1), total carbon stock (42.5 to 60.7 ton ha-1) and total carbon dioxide equivalent (157.7 to 222.8 ton ha-1) was observed consistently with an increasing of distance from settlement (p＜0.05). Distance from settlement had significant and positive correlation with species diversity and carbon stock at 0.64** and 0.78**. Disturbance intensity may directly influence the variation of species composition, richness and density along the A. senegal woodland. The sustainability of the A. senegal woodland needs urgent protection, conservation and restoration.

Downscaling Last Glacial Maximum climate over southern Africa

We conducted the first dynamic downscaling of Last Glacial Maximum (LGM) climate over southern Africa using a regional climate model. Eight coupled global climate model (CGCM) projections of LGM climate were downscaled to 8 km resolution, and compared to a downscaling of present-day climate. It is projected that temperatures were significantly lower during the LGM compared to the present-day, with annual average temperatures 4–6 °C lower along the eastern escarpment, south-north aligned Cape Fold Mountains and western escarpment. Southern Africa is projected to have been generally wetter during the LGM, with a significant extension in the northward reach of frontal rainfall. The largest rainfall increases are projected for the south-north aligned Cape Fold Mountains and the western escarpment of South Africa, but with rainfall decreases projected for the Cape south coast region. Rainfall seasonality is projected to have been significantly different from that of the present-day, with an all-year rainfall region plausibly extending as far north and east as the present-day Free State and Gauteng provinces of South Africa. Evaluations of the downscalings against key published proxy records for the LGM from southern Africa suggest good agreement and few deviations.

The controlling factors of modern facies distributions in a half‐graben lacustrine rift basin: A case study from Hulun Lake, Northeastern China

Hulun Lake is located in Northeast China and is a well‐exposed modern lacustrine rift basin. In this study, recent fieldwork has demonstrated that it was mainly filled by alluvial fan and fan delta deposits along the western escarpment, which were controlled by the Eerguna Fault Zones. However, it was filled by river‐deltaic and eolian deposits along the eastern slope. The distributions of the depositional systems were found to be controlled by their positions within the basin. The western escarpment was determined to have influenced the distributions of the alluvial fan and fan delta deposits. In contrast, the river‐deltaic and eolian deposits were controlled by the sediment supply, paleogeomorphology, and wind forces. The asymmetric geometry of the basin was determined to have resulted in different facies associations. First, a region of maximum sediment thickness and high‐gradient escarpment was found to be located near a normal fault foot (Eerguna Fault). Second, a region of a shallower and low‐gradient slope was located near the margin of a river‐lake transition. The depositional characteristics obtained from the prospecting trench indicated that the coarse deposits on the western side were mainly derived from unexpected flooding, gravity, and episodic flooding in an ascending order. In contrast, the fine deposits on the eastern side were mainly sourced from a meandering river. A clear understanding of controlling factors on facies associations can potentially reveal the sedimentary process and evolution of the depositional systems, as well as provide an important methodology for the prediction of facies in other sedimentary basins with similar characteristics.

Chlorophytum asperum (Agavaceae), a new species from Northern Cape, South Africa

Chlorophytum asperum (Agavaceae) is a new species from the western escarpment of Namaqualand, Northern Cape, South Africa. It is a late-flowering species distinguished by its corm-like rhizome, and scabrid leaves with the hairs in clusters or fascicles, especially markedly so on the leaf underside towards the base, and relatively small flowers with tepals 8–10mm long.

A review of the Geissorhiza namaquensis (Iridaceae: Crocoideae) group with the new species G. namaquamontana from Northern Cape, South Africa

The Geissorhiza namaquensis (Iridaceae) group of species from Namaqualand, Northern Cape, South Africa, has until now included two species, the short-tubed G. namaquensis from the western escarpment of central and northern Namaqualand, and the long-tubed Geissorhiza kamiesmontana from high elevations in the Kamiesberg. Two collections of short-tubed plants from the Kamiesberg currently included in G. namaquensis are shorter than normal and have unusually small flowers for that species, and are now matched by a new collection from Grootberg, some 21km southwest of Kamieskroon. This has led us to revise the concept of G. namaquensis, which we now restrict to taller plants up to 300mm tall, with comparatively larger flowers with tepals 14–18×±4mm and anthers 4.5–5.5mm long. The shorter plants from the Kamiesberg and Grootberg, 80–160(–250) mm tall, with smaller flowers with tepals 8–10×±2mm and anthers 2–3mm long, are described as the new species Geissorhiza namaquamontana.

Understanding transient landscape of the Ethiopian Plateau in relation to mantle dynamics

The Ethiopian Plateau, situated on the Western Escarpment of the East African Rift System, constitutes a part of a large igneous province that has experienced extensive flood basalt volcanism around 30 Ma related to the outpouring of the Afar mantle plume. This non‐orogenic plateau with long‐wavelength dynamic topography has been deeply incised by the Blue Nile River and its numerous tributaries. The plateau represents an excellent natural laboratory to study the interplay between bedrock river incision and uplift. Our analysis of a total of 202 convex upward and double‐concave tributary longitudinal profiles reveals 244 knickpoints, the majority of which are not associated with lithologic boundaries or faults. The normalized steepness indices (ksn) of these profiles vary in upstream versus downstream from knickpoints indicating variable uplift within the plateau. Our investigation of integrating mantle seismic P‐wave velocity anomaly with ksn and knickpoints suggests ongoing incision of the plateau surface in response to Afar plume related mantle dynamics. Tributary reaches with higher ksn generally lie above the areas with negative velocity anomaly, thus hotter (than normal) mantle that are likely undergoing more uplift. Therefore, this study suggests that the transient landscape incision of the Ethiopian Plateau is largely controlled by the ongoing uplift of the plateau, indicating that the plateau physiography is dynamic, not stable.

Revised lithostratigraphy of the Upper Permian Balfour and Teekloof formations of the main Karoo Basin, South Africa

A new lithostratigraphic framework is introduced for the Permian Balfour and upper Teekloof formations (lower Beaufort Group) in the main Karoo Basin of South Africa. The Balfour Formation’s Barberskrans Member (BM) is identified as the Oudeberg Member at its current type location. Thus the BM requires renaming, and is here defined as the Ripplemead member (RM) after Ripplemead farm 20 km north of Nieu Bethesda. The upper Teekloof Formation is subdivided into the sandstone-poor Steenkampsvlakte Member and sandstone-rich Javanerskop member which occurs in the highest points of the western escarpment between Beaufort West and Fraserburg. The thickness of the Balfour Formation does not significantly change from east to west, but thins rapidly northwards to a point where the Oudeberg Member is not present, and other subdivisions are much attenuated. Recent biostratigraphic revisions of Lopingian tetrapod fauna show the Ripplemead and Javanerskop members are not contemporaneous. Therefore, no lithostratigraphic members in the Upper Permian Beaufort Group have basin wide distribution, and it is recommended that they be used as local markers only in conjunction with other proxies (e.g. biostratigraphic and chronostratigraphic markers). Patterns of biostratigraphic disappearance of tetrapods in the Balfour Formation at the same stratigraphic interval throughout the basin despite the thinning of strata northward, supports a temporally phased terrestrial Permo-Triassic mass extinction (PTME). The lack of basin wide lithostratigraphic markers highlights the variable aggradation rates during the deposition of the Beaufort Group caused by foreland tectonics and localised subsidence. A need for a full consideration of these complexities and their effects on the fossil records is therefore required in determining whether the terrestrial PTME is synchronous with the marine extinction.

Land cover changes as impacted by spatio-temporal rainfall variability along the Ethiopian Rift Valley escarpment

Magnitudes of land cover changes nowadays can be assessed properly, but their driving forces are subject to many discussions. Next to the accepted role of human influence, the impact of natural climate variability is often neglected. In this paper, the impact of rainfall variability on land cover changes (LCC) is investigated for the western escarpment of the Raya Graben along the northern Ethiopian Rift Valley. First, LCC between 2000 and 2014 were analysed at specific time steps using Landsat imagery. Based on the obtained LCC maps, the link was set with rainfall variability, obtained by means of the satellite-derived rainfall estimates (RFEs) from NOAA-CPC. After a correction by the incorporation of local meteorological station data, these estimates prove to be good estimators for the actual amount of precipitation (ρ RFE1.0 = 0.85, p = 0.00, n = 126; ρ RFE2.0 = 0.76, p = 0.00, n = 934). By performing several linear regression analyses, a significant positive relationship between the precipitation parameter DIFF 5Y (i.e. the at-RFE pixel scale difference in five-year average annual precipitation for the two periods preceding the land cover maps) and the changes in the woody vegetation cover was found (standardised regression coefficient β = 0.23, p = 0.02, n = 108). Despite the dominance of direct human impact, further greening of the study area can be expected for the future concomitantly to a wetter climate, if all other factors remain constant.

Remote Sensing for Characterisation and Kinematic Analysis of Large Slope Failures: Debre Sina Landslide, Main Ethiopian Rift Escarpment

Frequently occurring landslides in Ethiopia endanger rapidly expanding settlements and infrastructure. We investigated a large landslide on the western escarpment of the Main Ethiopian Rift close to Debre Sina. To understand the extent and amplitude of the movements, we derived vectors of horizontal displacements by feature matching of very high resolution satellite images (VHR). The major movements occurred in two phases, after the rainy seasons in 2005 and 2006 reaching magnitudes of 48 ± 10.1 m and 114 ± 7.2 m, respectively. The results for the first phase were supported by amplitude tracking using two Envisat/ASAR scenes from the 31 July 2004 and the 29 October 2005. Surface changes in vertical direction were analyzed by subtraction of a pre-event digital elevation model (DEM) from aerial photographs and post-event DEM from ALOS/PRISM triplet data. Furthermore, we derived elevation changes using satellite laser altimetry measurement acquired by the ICESat satellite. These analyses allowed us to delineate the main landslide, which covers an area of 6.5 km2, shallow landslides surrounding the main landslide body that increased the area to 8.5 km2, and the stable area in the lower part of the slope. We assume that the main triggering factor for such a large landslide was precipitation cumulated over several months and we suspect that the slope failure will progress towards the foot of the slope.

Changes in Ecological Landscape Pattern and Land Use from 1985 to 2014 in the Panshet Dam Catchment

The Sahyadri, the northern part of Western Ghats in the state of Maharashtra, India, are one of the most fragile ecosystems on Earth. There are major changes in the original ecosystem and land use in the Sahyadri over the past two centuries. A ground survey was conducted by Ecological Society, Pune in 1985 as well as in 2014 to assess current land use and status of biodiversity in the Panshet dam catchment situated in Sahyadri. This study probes to understand factors responsible for decline of biodiversity and changed land use. We highlight the extent and causes for change in land use. The study attempted to quantify this change by carrying out manual digitization of multispectral WV-2 satellite images by visual interpretation and ground truthing and compare with the study done by Ecological Society in 1985. The mapping of the catchment area shows that areas towards western escarpment i.e. away from the dam wall have retained better vegetation cover while degradation is evident in eastern parts of the catchment. Such studies will be useful for land use planning, understanding cost-benefits of nature conservation, assessing restoration potential, and developing conservation-restoration strategies on a regional scale. We recommend similar vegetation and land use class mappingfor all dam catchments in the Western Ghats.

A small Remarkable Bryophyte Collection from the Ibb Province (Yemen), with Eleven New Records for the Bryoflora of Yemen

Based on a recent small bryophyte collection from the western escarpment mountains of Yemen in the vicinity of Ibb (Ibb Governorate), 36 mosses are reported, among them 11 new to the bryoflora of the country. Gemmabryum nanoapiculatum (Ochi & Kürschner) Kürschner comb. nov. is collected for the first time since the type collection. Beside some hygrophytic taxa, growing in the vicinty of water pools and runnels, most of the recorded species belong to drought adapted, xerophytic taxa and fit into the expected bryophyte spectrum for the Arabian Peninsula. Together with pantropical and Afromontane species they indicate a common floral history and past and present migration routes.

The sub-Recent <i>Bradleytriebella lineata</i> (Ostracoda, Crustacea) in Israel

Abstract. Sub-Recent ostracod valves of Bradleytriebella lineata (Victor & Fernando, 1981) were recorded in Nahal Bokek only in 2008 but not during subsequent surveys in 2010 and 2013. Nahal Bokek, a stream entering the Dead Sea from its western escarpment, represents the species’ single record in Israel, far away from its main Afrotropical and South to East Asia distribution. The temporary colonization of Nahal Bokek by B. lineata probably resulted from the suitability of the thermal stream waters for occupation and the subsequent termination of the population only six days after the collection of the sub-Recent valves during a flood on 24 October 2008. The preceding flood on 30 February 2008 restricts the period of possible stream inhabitation by B. lineata to a duration of eight months. Thus, the record of sub-Recent valves of B. lineata in Nahal Bokek represents an exceptional example of short-term occupation of a hydrologically dynamic flood-controlled water body by a species far away from its main geographical distribution. The recognition of Nahal Bokek as a stream fed mainly by thermal waters shows that the documentation of the abiotic habitat characteristics is a prerequisite for the understanding of the occurrence of a species outside its proper range of distribution.

New Finding of Coal in Western Escarpment of Mainpat Plateau, Surguja District, Chhattisgarh

Abstract The Mainpat plateau (N22°41′00″ to 22°55’ 00″ and E 83°08′00″ to 83°25′00″) is a table-land, rising >400 m above foothills, consisting of Archaean rocks (granite-gneisses, phyllite etc), Gondwana formations and Deccan basalt. Archaean rocks occur at the foot hills of Mainpat and Gondwana formations are exposed in the western escarpment of Mainpat plateau in turn overlain by the basaltic rock of Deccan Traps at the top. Barakar Formation contains coal seams from few cm to ~9 m are exposed near Chitaghutri, Kodwari, Tirkela, Tekta etc. villages of Lakhanpur tehsil of Surguja district, covered in Survey of India, Toposheet 64 N/1. Coal present in the area contains high volatile matters and high ash in the different seams in different localities. Analysis shows that coal of this area ranges between C and E grade with useful heat value varying from 3461 to 5223 K Cal/kg. This recently discovered area is located between Hasdo –Arand and Mand-Raigarh coalfields. Coal bearing horizon seems to be persistent, beneath the Deccan Traps.

Thermal waters in the Lower Yarmouk Gorge and their relation to surrounding aquifers

Sources and mineralization of groundwaters from Cretaceous A7/B2 and B4 limestone aquifers in the Golan and Ajloun Heights are derived from conjoint discussion of stable isotopes of water and sulphate, major ion chemistry, rare earth distribution patterns and the (hydro)geological setting. Isotope fractionation of precipitation was used to derive elevation and continental influence of recharge areas. Positive shift of δ18O and δ2H occur due to evaporation before replenishment and the interaction with basalts. Major infiltration areas for Golan Heights are the limy foothills of the Mt. Hermon and for the Ajloun Heights the Plateau itself. To a less degree, precipitation infiltrates also the basaltic catchments. Groundwaters are mineralized by water/rock (i) variably altered limestones by diagenesis, (ii) evaporates and seawater brines enclosed in limestone matrix and (iii) locally occurring basaltic intrusiva. In the Yarmouk Gorge, a deep-seated brine of the Ha’on type ascends and mixes with the fresh shallow groundwater.Contrasting the macro chemical composition, REY distribution patterns indicate the lithology of the recharge areas. Infiltration over basalts results in REY patterns distinctly different to those derived from limy catchments.REY and isotope fingerprints prove that water from the Syrian Hauran Plateau is recharging springs and wells in the lowermost Yamouk gorge. The basaltic cover of the Golan Heights is of minor importance for recharge of the underlying A7/B2 aquifer, which becomes recharged at the foothills of Mt. Hermon and gets confined southwards. Even the wells in the basaltic cover receive water from the underlying limestone aquifer.Anomalous heat flux near the Yarmouk gorge and locally in the western escarpment of the Ajloun may be produced by ascending fluids from greater depth and/or by basaltic intrusions.

Paleo erosion rates and climate shifts recorded by Quaternary cut-and-fill sequences in the Pisco valley, central Peru

Fluvial cut-and-fill sequences have frequently been reported from various sites on Earth. Nevertheless, the information about the past erosional regime and hydrological conditions have not yet been adequately deciphered from these archives. The Quaternary terrace sequences in the Pisco valley, located at ca. 13°S, offer a manifestation of an orbitally-driven cyclicity in terrace construction where phases of sediment accumulation have been related to the Minchin (48–36 ka) and Tauca (26–15 ka) lake level highstands on the Altiplano. Here, we present a 10Be-based sediment budget for the cut-and-fill terrace sequences in this valley to quantify the orbitally forced changes in precipitation and erosion. We find that the Minchin period was characterized by an erosional pulse along the Pacific coast where denudation rates reached values as high as 600±80 mm/ka for a relatively short time span lasting a few thousands of years. This contrasts to the younger pluvial periods and the modern situation when 10Be-based sediment budgets register nearly zero erosion at the Pacific coast. We relate these contrasts to different erosional conditions between the modern and the Minchin time. First, the sediment budget infers a precipitation pattern that matches with the modern climate ca. 1000 km farther north, where highly erratic and extreme El Niño-related precipitation results in fast erosion and flooding along the coast. Second, the formation of a thick terrace sequence requires sufficient material on catchment hillslopes to be stripped off by erosion. This was most likely the case immediately before the start of the Minchin period, because this erosional epoch was preceded by a >50 ka-long time span with poorly erosive climate conditions, allowing for sufficient regolith to build up on the hillslopes. Finally, this study suggests a strong control of orbitally and ice sheet forced latitudinal shifts of the ITCZ on the erosional gradients and sediment production on the western escarpment of the Peruvian Andes at 13° during the Minchin period.

Rainfall and temperature estimation for a data sparse region

Abstract. Humanitarian and development agencies face difficult decisions about where and how to prioritise climate risk reduction measures. These tasks are especially challenging in regions with few meteorological stations, complex topography and extreme weather events. In this study, we blend surface meteorological observations, remotely sensed (TRMM and NDVI) data, physiographic indices, and regression techniques to produce gridded maps of annual mean precipitation and temperature, as well as parameters for site-specific, daily weather generation in Yemen. Maps of annual means were cross-validated and tested against independent observations. These replicated known features such as peak rainfall totals in the highlands and western escarpment, as well as maximum temperatures along the coastal plains and interior. The weather generator reproduced daily and annual diagnostics when run with parameters from observed meteorological series for a test site at Taiz. However, when run with interpolated parameters, the frequency of wet days, mean wet-day amount, annual totals and variability were underestimated. Stratification of sites for model calibration improved representation of the growing season's rainfall totals. Future work should focus on a wider range of model inputs to better discriminate controls exerted by different landscape units.

Diplasiolejeunea Mayaykuensis (Lejeuneaceae, Marchantiophyta), a New Liverwort Species from Southern Ecuador

Abstract A new epiphytic species of Diplasiolejeunea (Spruce) Schiffn. from the Amazonian region of southern Ecuador is described and illustrated. Diplasiolejeunea mayaykuensis Schäf.-Verw. & Heinrichs, sp. nov. is characterized by ascending to squarrose leaves, narrowly ovate(-lanceolate) underleaf lobes with acute to subobtuse apices, well developed lobule teeth and lobules with strongly involute free margins. Morphologically, D. mayaykuensis closely resembles D. brunnea Steph. and D. cavifolia Steph. The locality is situated in the western escarpment of the Cordillera del Condor.

Climatic imprint on landscape morphology in the western escarpment of the Andes

Because of competing forces and variations through time, the relative importance of geomorphic processes responsible for the long-term topographic evolution of a mountain range is not always obvious. Here we perform a space-for-time substitution with the western escarpment of the Andes between 10 and 20°S to identify the mechanisms of plateau destruction over geological timescales. We use this setting to propose that variations in the precipitation rate play a primary role in setting hillslope relief in uplifted mountainous landscapes. We find that in dry climates local topographic relief grows with increasing precipitation, independent of the underlying lithology and given an overall uniform rock uplift history. We proceed by differentiating Andean landscapes with generally low precipitation rates (80–500mma−1, Peruvian Andes 10–20°S) where local relief correlates positively with precipitation, from those with higher precipitation rates (400–1400mma−1, Chilean Andes 35–40°S) where increases in precipitation lead to topographic decay. We suggest that these trends result from dominant bottom-up control (channel incision is faster than hillslope response) giving way to an increasing top-down control (hillslope lowering is faster than channel incision). With low precipitation, relief growth is controlled by stream incision and knickzone retreat into a largely undissected plateau. With higher precipitation rates, relief is set by the steepness of graded streams and the rates of sediment production and transport on hillslopes.Trends of topography can also be interpreted in temporal terms in which the higher precipitation results in shorter response times, such that the Peruvian Andes between 10 and 20°S are still responding to Miocene uplift, while in the Chilean Andes between 35 and 40°S, these knickzones have already propagated through the entire fluvial network. We anticipate that such changes also operate during the formation and destruction of other mountainous plateau landscapes.

"This is the Right Place"

We welcome you to the 2013 Annual Meeting of the Seismological Society of America in Salt Lake City. On 24 July 1847, when Mormon pioneers first viewed the Salt Lake Valley, Brigham Young famously pronounced, is the right - the place of destiny and refuge they had been seeking. By the time of Young's death in 1877, Mormon pioneers had extensively colonized most of what we now recognize as Utah's main seismic belt, notably along the Wasatch Front, the western escarpment of the Wasatch Range that forms the eastern topographic boundary of the Basin and Range Province (Fig. 1). This contrast in geology and geography signals active tectonic forces inexorably at work.

A unique radiation of marine littorinid snails in the freshwater streams of the Western Ghats of India: the genusCremnoconchusW.T. Blanford, 1869 (Gastropoda: Littorinidae)

The caenogastropod family Littorinidae is almost exclusively marine, but a unique freshwater genus, Cremnoconchus, is known from India. Its members are restricted to montane streams on the western escarpment of the Western Ghats, at altitudes between 300 and 1400 m. Four species and several varieties were described in the 19th century, but no taxonomic study has been carried out for over 120 years and the last anatomical report was in 1935. Nevertheless, they are of unusual evolutionary interest and also of conservation concern as a genus endemic to the Western Ghats biodiversity hotspot. Based on anatomical study of newly collected material and examination of historical and type specimens, we present a systematic revision of Cremnoconchus, illustrating shells, radulae, and reproductive anatomy. The very large eggs, invaginated penial filament, and calcified operculum are unique among Littorinidae. Three valid, described species (C. syhadrensis, C. conicus, C. canaliculatus) are recognized in the northern Western Ghats in Maharashtra state, where all can occasionally be found sympatrically. We describe an additional six new species from the central Western Ghats in a small area (linear distance 80 km) of Karnataka state, over 500 km south of the previously known range of the genus. Here the species each appear to be restricted to a single drainage system. Because of their highly restricted distribution and fragile habitat, this radiation of nine species is judged to be endangered.