Summit Areas Research Articles

Effects of Interannual Climate Variation on Aboveground Phytomass in Alpine Vegetation

Relationships between peak annual vascular aboveground phytomass and annual climate variation in alpine plant communities located on Niwot Ridge, Colorado, were analyzed using path analysis. The five community types, fellfield, dry meadow, moist meadow, wet meadow, and snowbed, represent a snow depth—soil moisture gradient and broadly represent the most common vegetation types on east—facing slopes of the Front Range alpine zone. Using nine successive years of data, this is the first longer term analysis of alpine phytomass and climate and one of the longest nonagricultural production records available. Live phytomass ranged from 97 g/m2 (snowbed) to 237 g/m2 (fellfield). Among—community differences in phytomass were greater than differences among years, but there was also significant phytomass variation among years. Path analysis indicated that climate accounted for 15—40% of the variation in phytomass. The dry communities, fellfield (exposed rocky summit areas dominated by cushion and mat plants) and dry meadow, were most sensitive to previous year precipitation, the moist and wet meadow communities were most sensitive to current growth season soil moisture, and the snowbed community was most sensitive to date of snow release. Because of the relatively high amount of variation attributable to variables related to precipitation, changes in precipitation regimes that may occur in alpine ecosystems will likely result in changes in phytomass that are detectable with clip—harvest methods.

Formation of stacked insulation films on rough metal surfaces

Insulation films with a stacked structure were formed on metal surfaces via a combination of the sol-gel and sputtering processes. Thin films of Ta 2O 5 prepared by the sol-gel process were effective in planarization of rough metal surfaces. Sputtered SiO 2 films were deposited on the sol-gel Ta 2O 5 films thus formed, and the insulation properties were evaluated by resistance measurements. It was found that the insulation properties of stacked films of the sputtered SiO 2 and sol-gel Ta 2O 5 films were much better than those of only sputtered or sol-gel films. It can be concluded from this result that sol-gel films were effective in planarization of concave regions, and that sputtered films were mainly formed on convex or summit areas of rough metal surfaces.

Unusual geochemistry of hydrothermal vents on submarine arc volcanoes: Kasuga Seamounts, Northern Mariana Arc

DSRV Alvin dives in the Northern Mariana island arc recovered warm hydrothermal fluids from the summit areas of seamounts Kasuga 2 and Kasuga 3, as well as hydrothermal deposits of elemental sulfur, Fe- and Mn-oxides, and nontronite. The composition of a gas-rich ∼ 39°C vent fluid sampled from Kasuga 2 Seamount is unusual compared to other submarine hydrothermal fluids in that it is enriched by 27% in Mg 2+ and 17% in SO 4 2−, and depleted by 64% in Ca 2+, relative to ambient seawater. The elevated concentrations of dissolved CO 2 (calculated from pH and A T), HCO 3 − and SO 4 2+, and near absence of H 2S, suggest that the unusual composition of this sample may result from the sub-seafloor addition of volcanic CO 2 and SO 2 to a seawater-derived hydrothermal fluid, resulting in: (1) ‘chemical weathering’ reactions, whereby igneous minerals or alteration phases are attacked by CO 2, adding Mg 2+ and other cations, Si, and HCO 3 − into solution; and (2) hydrolysis of SO 2 to SO 4 2− and S(0), adding excess SO 4 2− with a light δ 34S signature to the fluid and causing deposition of elemental sulfur at the seafloor vents. Saturation-state calculations suggest that the concentrations of Si and Ca 2+ in the fluid may be controlled at saturation with amorphous silica and dolomite respectively. The origin of the 9.3°C fluid collected from Kasuga 3 is difficult to determine because it is compositionally close to ambient seawater and shows possible evidence of both high- and low-temperature seawater-rock reaction. Banded and interlayered deposits of nontronite and Fe- and Mn-oxides were recovered from the Kasuga 3 summit, with oxygen-isotope geothermometry suggesting a formation temperature of ∼ 22°C for the nontronite.

GUAYANA HIGHLANDS VERSUS GUAYANA LOWLANDS, A REAPPRAISAL

SummaryDuring the last 40 years, an impressive amount of biological, especially botanical, information concerning the Venezuelan Guayana region has been accumulated. Both the lowlands, as well as the distinctive highland mountains (‘tepuis’), evidence an outstandingly rich and diversified flora and vegetation. It has been postulated that this biological richness and the high degree of endemism are the result of long‐term and highly effective isolation suffered by the flat summit areas during extremely long geologic epochs. This static view is being challenged presently by the results of recent intensive fieldwork made in the Venezuelan Guayana. A detailed analysis of two highly evolved Guayana taxa, Stegolepis (Rapateaceae) and Bonnetia (Theaceae s.l.) shows a rather uniform distribution not only in summit habitats, but also in intermediate and lowland habitats. As a whole, both genera and several related taxa prove to have occupied successfully not only the ancient summit regions of the tepuis, but also the surrounding lowlands of much more recent geomorphological origin. Palaeoecological research also supports the hypothesis that the entire Guayana Shield area has been affected by climatic oscillations during the recent past as have the nearby Andes. This implies significant past fluctuations of the altitudinal vegetation belts in the tepui area and could well explain the wide altitudinal gradient of most of the Guayana Highland taxa. Also, the presence of convergent ‘paramoid’ vegetation types on the summits of the Chimantá Massif, indicates active speciation not only at the systematic level, but especially at the ecologic level. Thus, it is proposed that the Guayana highland and lowland biota have been and still are dynamically and genetically interdependent, not only within the Guayana region itself, but also with the adjacent complex of lowland and mountain biota.

Erosion processes in a dune landscape along the Dutch coast

The landscape of the dunes along the Dutch coast is the result of the interaction of biological and geomorphological processes. Where the latter prevail, new landforms are created: blowouts by wind erosion, and rills and accumulation footslopes by overland flow. Spatial extent and rate of the erosion processes have been assessed by mapping and by measuring. It appears that dune sand is either sensitive to erosion by wind, or erosion by water, depending on the presence of organic material. Clean (yellow) sand is cohesionless and easily blown away, but has no surface runoff. Grey sand containing organic matter on the other hand will resist wind erosion, but it is waterrepellent and will be washed from slopes when rain follows a period of dry weather. Once the grey surface sand is removed from the surfaces by water erosion, wind erosion begins in the underlying yellow sand. Present-day geomorphological processes reshape the slopes of the original parabolic dunes. Wind is particularly active in summit areas where new blowouts are formed, whereas overland flow creates concave south-exposed slopes. The stepped surface of the north-exposed slopes is due to mass movements following rabbit activity.

Factors Controlling Stability of Mountain Ecosystems in Northern Mongolia

Factors Controlling Stability of Mountain Ecosystems in Northern Mongolia

Co-fluxes and growth rates in ferromanganese deposits from central Pacific seamount areas

Recent geochemical studies on ferromanganese deep-sea nodules have shown that the relationship between Mn and Fe allows us to differentiate between a diagenetic type (Mn/Fe ≥ 2.5) and a hydrogenetic type (Mn/Fe ≤ 2.5)1–7. Diagenetic and the lower parts of mixed type nodules are mainly supplied by an early diagenetic pore water source; hydrogenetic type nodules grow by very slow accumulation of inorganic colloidal particles of hydrated metal oxides from near-bottom seawater. Growth rates of hydrogenetic nodules generally do not exceed 5 mm Myr−1 (refs 8–11), whereas diagenetic nodules were found to grow much faster: an extreme example is the rate of 168 mm M yr−1 that was recently reported for a Mn-rich diagenetic type of nodule from the Peru Basin6. A different inter-element relationship of Co to the main metals Mn and Fe in different type of nodules has also been observed. We show here that the flux of Co into ferromanganese seamount crusts from the central Pacific is similar to the flux into pelagic nodules: the amount of Co supplied per unit of time and area is nearly constant in the oceanic water column. The most important factor governing the Co-enrichment is the growth rate; no local source is needed to explain the observed Co concentrations up to 2% in ore samples from summit areas.

The deposition of stony colluvium on clay soil as a cause of gully formation in the Rif Mountains, Morocco

AbstractV‐shaped gullies are formed on slopes in the Rif Mountains where stony colluvium covers a truncated Luvisol in finegrained, early pleistocene slope deposits. The colluvium resulted from large‐scale deforestation of summit areas in recent times. A number of properties related to the response of soil material to rainfall were investigated. Colluvium has a high infiltration capacity compared to the Luvisol. Consequently, the deposition of colluvium reduced overland flow and erosion by surface wash. Gully‐forming processes on the other hand were activated by the superposition of permeable over impermeable material.

Bedrock Weathering Features in a Portion of Eastern High Arctic Canada: Their Nature and Significance

Highly-weathered Pre-Cambrian bedrock has been reported from scattered localities across Arctic Canada during the past decade. As part of a study on weathering processes under arid conditions, field studies are reported on-similar terrain in the Alexandra Fjord-Cape Herschel area of east-central Ellesmere Island. Features examined and sampled in both near-coastal and upland positions include grus, tor-like forms, weathering pits, and tafoni. Factors influencing their development and preservation are reviewed. Particular emphasis is placed on the influence of bedrock lithology and mineralogy (in this case, hornblende content) on the intensity of physical disintegration under cold arid conditions. Chemical analyses and petrographic data are presented in support of this observation. Preservation of certain remnant weathering features in upland summit areas under cold-based glacial ice is postulated.

Quaternary piedmont plains on weakly resistant rocks in the Lower Saxonian mountains (W. Germany)

Summary The two piedmont plain levels of the investigated area are of Old Quaternary respective Middle to Young Quaternary age. Most of the proximal parts of these Quaternary piedmont plains are erosional piedmont plains on weakly resistant rocks of the Keuper and Lias. The central and distal parts of the piedmont plains are underlain by a variably thick cover of Middle to Young Quaternary sediments. Therefore the piedmont plains are partly a genuine erosional feature, the result of a combination of erosion and accumulation forms, or a genuine feature of accumulation. The loose Quaternary sediments underlying the piedmont plains consist mainly of loess which very often overlies solifluction layers and colluvial sediments, and which partly lies on the gravel body of the Middle Terrace, and, marginally on the gravel body of the Lower Terrace. Consequently, piedmont plains that appear morphographically uniform, have been formed here polygenetically and in several phases. The Young Wuermian phase, for example, resulted in a predominantly eolian sedimentary infilling of the dissected parts of the older piedmont plains so that their surfaces partly exceeded that of the original erosion piedmont plains; by the accumulation of very thick loess layers this sedimentation partly lead to an enlargement of the plains at their eastern margins. Especially in the lower and middle sections the thick loesses are interspersed with colluvial debris layers and sporadical debris stones thus proving a frequent interruption of the eolian sedimentation by extensive wash processes. These wash processes brought about a planation of an originally pronounced eolian micro relief; it obviously caused the wide distribution of almost level summit areas that are especially characteristic of the pure accumulation piedmont plains. In spite of the temporary predominance of accumulation processes in the course of the Quaternary formation of the piedmont plains the existance of two piedmont levels verifies the denudational reduction of the surface which was favoured by the minor resistance of the predominant clay and silt rocks. A favouring of the denudational reduction by the easy weathering readiness of these rocks becomes obvious at the outcrop of the occasionally embedded sandstone layers of the Lias which have been formed to small hogbacks out of a piedmont plain during the Middle and Young Quaternary degradation of the piedmont plains. On the margins of the basin the reduction of the surface was essentially influenced by the surrounding hogbacks and other mountains: on the one hand there was a (relatively small) reduction and widening of the piedmont plains by predominant formation of the slope feet which lead to a greater inclination of the back slopes of the hogbacks; on the other hand near the mouth of the valleys into the basin rock fans were formed. These elevated parts of the proximal parts of the piedmont plains the reduction of which lagged behind that of the adjacent parts of the piedmont plain were the initiating centres of the denudational wash of the piedmont plains. Besides this, they determined the position of the valleys of the central parts of the basin, the initial troughs of which always are situated in the contact area of two rock fans. This pattern therefore proves the intense connection of the piedmont plains to the adjacent slopes and valleys of the hogbacks and mountains that are surrounding the basin. The reduction phases of the local base levels and the piedmont plains correspond to an inset of differently old fans. By this the higher portions of the fans are often starting points of younger accumulation piedmont plains. The piedmont plains of the investigated area exhibit regional differences as to their extension and dissection which are in accordance with the different distance of the base level of both areas.

Some observations on rock weathering, Cumberland Peninsula, Baffin Island

A variety of bedrock weathering features—both modern and remnant—including surface grus, polygonal cracks, siliceous glaze, tors, weathering pits, and tafoni typify upland outcrops on the Cumberland Peninsula. Tor ridges are particularly prevalent and at lower elevations they show significant modification and streamlining by flowing ice. On summit areas at elevations above 750 m, however, remnant corestones are preserved in situ, suggesting selective preservation of upland surfaces. Bedrock structure and composition, topographic position, and intensity of process strongly influence tor development. Weathering pits are common on high level, open summit surfaces where weathering occurs in response to both climate and continued removal of derived debris. Pit enlargement through lateral undercutting has been favoured by accumulation of protective bottom residua, mechanical weathering, and the presence of exfoliation crusts. It is postulated that salt crystallization plays a role in outcrop microweathering under present upland arctic conditions.

Variations in Plant Communities With Topography Over Tropical Limestone Soils

Four line transects were investigated passing through primary and secondary forest near Belmopan, Belize, Central America. The transects ranged from 174 to 2012 m in length and are located in karstic topography with well-developed conical hills and depressions. Detailed quadrat and profile observations were made in order to interpret the vegetation pattern. Topo- graphy and drainage play a major part in determining this pattern, and summit areas are clearly distinguishable from hill slope, depressional and footslope areas. Plant succession following a major hurricane in 1961 can also be related to topography. An increased development of the accessible footslope areas is forecast in view of their better nutrient status, moisture levels and potential for rapid plant growth.

On the Tree Line Composed of Beech (Fagus crenata) on Funakata Mountains, Miyagi Prefecture

A boreal coniferous forest belt is underlain by a cool temperate summer green broad leaved forets belt in japanese mountains as usual. The latter, composed mainly of beech (Fagus crenate), however, has no overlying belt with arboric forest belt but has one with scrubs, herbaceous vegetations, Sasa communities and other treeless vegetations on mountains rising along the coast of the Sea of Japan. It is said that this results from heavy snow of the region. Such treeless vegetations are found also on summit areas of some mountains of backbone range in northeast Japan.In the above cases a tree line or an upper limit of arbors lies within an altitudinal range in which beech can survive. Across this line the growthform of beech shifts from arbor to sub-tree or shrub. Such an upper limit was studied in Funakata Mts. (Figs. 1 and 2) rising in a midst of the backbone range of noutheast Japan.The upper limit in this area runs higher in gullies and ravines than on spurs and ridges in elevation (Fig. 3 and Table 1). There is not so much differrence in the elevation of the limit between the east facing slope and the west facing. These tendencies are opposite to that observed on the mountains of the Sea of Japan side.This suggests that the zone of treeless vegetation of this area is not under the same condition as on the mountains of the Sea of Japan side. It is more probable that the treeless vegetations of Funakata Mts. result not from the heavy snow but from the strong wind. Heavily deformed Pinus parviflora var, pentaphylla scattered on the treeless vegetation belt of these mouttains supports this estimation, too.

THE PEDOGENESIS OF SOME GIBBSITIC SOILS FROM THE SOUTHERN UPLANDS OF SCOTLAND

SummaryThe mineralogy of ten profiles developed from hornfelsic rocks on the summit areas of the Merrick and Kells Hills has been investigated by X‐ray powder diffraction, thermal, infra‐red, and optical methods.The soil clays of the C horizons of all profiles contain 6 to 37 per cent of gibbsite but this mineral is not found in the A horizons. Optical observations reveal that gibbsite is associated with hematitic rock fragments which are considered to represent older soil material–i.e. are pedorelicts. It is suggested that the Merrick soils are polygenetic and consist of two soil stratigraphic units, recent pedogenic effects being superimposed on a basal horizon that has been strongly influenced by preglacial or interglacial weathering.

Dredged Basalt from Giacomini Seamount

DURING the cruise in July 1965 of the RV Acona of the University of Alaska Institute of Marine Science, two angular blocks of basalt (15×12×5 cm3 and 20×15×9 cm3) were dredged from the summit area of Giacomini Seamount (56° 24′ N, 146° 34′ W), at a depth of 790 m (Fig. 1). Several hundred igneous, metamorphic and sedimentary pebbles, cobbles and boulders were also recovered in the dredge haul; they showed a wide range of rounding and a very thin coating of manganese oxide, and were very similar to those recovered from the summit areas of Gilbert, Miller, Pratt and Ga-3 Seamounts in the Gulf of Alaska Seamount Province, as previously reported by Menard1 and others. Menard concluded that these gravels were ice-rafted glacial drift, an interpretation which is strongly supported by the presence of faceted and striated rocks among the Giacomini erratics.

On the nature of the summit areas of severe storms in Oklahoma

On the nature of the summit areas of severe storms in Oklahoma

On the nature of the summit areas of severe storms in Oklahoma

AbstractPhotographic and radiometric records of the summit areas of severe storms in Oklahoma obtained from a U‐2 aircraft flying at an altitude of 65,000 ft (20 Km) are combined with relevant synoptic data to make some tentative deductions on the nature of the flow and temperature fields in the outflow regions of the small fraction of giant storm cells which appear to have attained some form of quasi‐steady state.The summit area of a giant cell sometimes appears to consist of a rather smooth ‘gasometer‐shaped’ dome 5–8 nautical miles (10–15 Km) in diameter and reaching up to 20,000 ft (6 Km) above its environmental tropopause. It is suggested this dome consists mainly of air which has risen nearly adiabatically from the surface layers (after Ludlam 1963) contained within a rather thin shell of very stable air in which there is mixing between updraught air and environmental (stratospheric) air.A general description of the distribution and heights of storm tops along a developed squall‐line is also given.

On the Geomorphology of the Northern Part of the Tachov Basin and the Bohemian Forest

In 1960 the author carried out a quarternary and engineering-geological investigation of the area that is represented on sheets M-33-73-B-b, d and M-33-74-A-a, b, c, d of the new state map of Czechoslovakia compiled in scale of 1 : 25.000 The present paper treats of the geomorphological results of this investigation carried out in the northern part of the Tachov Basin and the Bohemian Forest. The maped area measures 330 km2. The field work was started with the investigation of the peneplain of the Bohemian Forest which lies at an approximate altitude of 650-750 m. Individually preserved dominants, composed of quartzitic migmatitic gneiss protrude above the peneplain surface (Tišina, Ve skalkách, Štokovský vrch etc.). The basic structural lines of the peneplain body of the Bohemian Forest were formed as early as the Varisian Orogene. After the Varisian faults, movements were resumed at the time of the saxonian tectonic disturbance which made the whole mountain range assume its present character. Towards the end of the Varisian Orogene, old fault lines were filled with hydrothermal quartz or blocked with clastic material. The quartz filling of the faults has the character of morphologically prominant veins or grabens, stretching from the northern environs of Tachov over Tři Sekery (Three Axes) towards Dolní Žandov and over Hazlov to Saxony. Selective stream erosion affected before all healed-up fault lines of the Upper-Rhine (longitudinal) direction as places rendering the least resistance. Valleys of the consequent streams heading for the subsided Tachov Basin are younger. Along the young Marienbad fault line valleys were founded tectonically (sections of the Hamerský and Kosový Brooks). The author consideres the sedimentation depression of the Tachov Basin - filled in its northern part with Tertiary sediments (gravel, sand, clay) - to belong to the accumulation phenomena. Pleistocene terraces have been ascertained along the Hamerský and Kosový Brooks. Two levels could be distinguished (12-18 m and 7-12 m), the thickness of the terrace accumulations reachins 2-4 m. Chronologically they are most probably older than Würm. On their surface they are covered with loeses. The unique occurrence of volcanic pyroclastic rocks of Železná hůrka in the vicinity of Boden is also considered an accumulation phenomenon. The next chapter treats of wheathering processes. Pleistocene weathering asserted itself most strongly in the summit areas of the Bohemian Forest where it formed extensive stone seas. In the Borský Mass it deeply affected the surface granite. Besides the Pleistocene weathering also Tertiary weathering (Chotěnov, Chodová Planá, Hamrníky) took active part especially in chemical decomposition of the alumosilicates in the rocks, Decomposed rocks occur in the form of whitish clayey eluvium along the whole course of the Marienbad fault. They also occur in the vicinity of mineral water springs with exhalations of CO2. The last chapter is reserved for periglacial phenomena. It describes solifluction and cryoturbation which deforms the upper layers of the weathered mantle. Periglacial phenomena are rather scarce in the area under investigation.

Striated Surfaces on the Upper Parts of Cirque Head Walls

In the Coeur d'Alene Mining District of northern Idaho the presence of glacially striated bedrock surfaces high on cirque headwalls and on very narrow divides behind and beside the cirques cannot be explained by commonly accepted theories of cirque origin. It is suggested that during the waxing phase of a glacial age the developing cirques are brim full or overfull of snow, neve, and ice and that during the maximum phase of glaciation a carapace of ice may cap summit areas above the cirques.

Edwards Plateau, a Combination Ranching Region

E ODWARDS PLATEAU is one of the most distinctive cultural and physiographic regions of Texas. It is popularly known as the sheep and goat country of Texas, and is the seat of one of the best developed and most prosperous ranching industries in the United States. The underlying limestone rocks (the Edwards and other formations of Comanchean age) resist erosion so that relatively great elevation and scanty stone-littered soil distinguish it from adjoining plain and hill areas on the southeast, east, and north; and the undulating, scrub-tree and thorn-bush summit areas present a marked contrast to the barren, rugged mountain ranges which border the region on the west. The plateau is separated from adjoining parts of the Gulf Coastal Plain on the southeast and east by sheer precipices and dissected areas (Balcones Escarpment) which are so rugged that they are locally designated as mountains. Lower escarpments separate the plateau from adjoining plain and hill land to the north, and the gorge of the Rio Grande is on the southern boundary of the region. Only on the northwest where Edwards Plateau merges with the Great Plains (Llano Estacado) is the boundary transitional in character. Conditions of the natural environment combine to make Edwards Plateau adaptable to a combination ranching industry. The average annual precipitation varies from about 30 inches in the eastern part of the region to 17 or 18 inches west of the Pecos River. This would probably enable the widespread development of dry-farming notwithstanding the rather high insolation and rapid rate of evaporation of the region if other conditions were favorable, but the residual soil cover of the limestone bed rock is so thin and cluttered with stones that all the slope and hill land and most upland districts are permanently non-agricultural. The drought-resistant vegetation is well suited to pastoral utilization since it contains turf forming and bunch grasses, a variety of herbaceous plants which may be designated as weeds, and many kinds of shrubs and small trees-most of which are thorny. Indeed the vegetation is so varied that its thorough utilization necessitates the maintenance of many goats and sheep as well as cattle upon practically every ranch. This plateau has been a pastoral land throughout the period of American occupation, and is now devoted almost exclusively to ranching. After the Indians were expelled (about 1880), sheepmen residing farther east and northeast began to enter the region with their flocks during periods after heavy rains when succulent forage was abundant. The scarcity of flowing streams and other permanent watering places made the range inhospitable to cattle, but sheep throve since they were able to subsist for weeks or even months without access to a water supply other than dew and moisture obtained by feeding upon succulent grasses and weeds. Permanent settlement began about 1890 when wells were bored and equipped with windmills and tanks