Soil Catena Research Articles

Soil Catenas on pinedale and Bull Lake moraines, Willow Lake, wind river mountains, Wyoming

Soils in coarse-grained tills on Pinedale (about 20,000 years old) and Bull Lake (about 140,000 years old) moraines show significant variaton with slope position and age. Soils on the Pinedale moraine are mostly non-calcareous Typic Cryoborolls with A/Bw/C profiles that thicken considerably downslope. These soils are weakly developed due to their youth and to the unstable, steep (up to 24°), highly convexo-concave slopes. Soils on the Bull Lake moraine are mostly Argic Cryoborolls with A/Bt/C profiles. These soils are more strongly developed than soils at similar positions on the Pinedale moraine because the Bull Lake moraine is older and has less steep (up to 16°), more gently curved slopes. The soils on the Bull Lake moraine contain more clay, a higher proportion of pedogenic clay, more weathered stones, and more free sesquioxides. Erosion and dry conditions at the convex summit and shoulder sites on the Bull Lake moraine have resulted in thin soils with minimal argillic horizons; these soils are only slightly more strongly developed than soils at analogous sites on the much younger Pinedale moraine. In contrast, at the concave sites in downslope positions the soils on the Bull Lake moraine are much more strongly developed than analogous soils on the Pinedale moraine; slow deposition of weathered material, probably transported by creep, has acted concurrently with pedogenesis to form soils with thick, homogeneous argillic horizons. The relationship between hillslope curvature and soil properties on both moraines is shown by significant correlations between soil properties and the second derivative of the hillslope profile. This relationship is probably due primarily to the interaction of soil formation and soil creep.

Soil catenas on pinedale and bull lake moraines, willow lake, wind river mountains, Wyoming

Abstract Soils in coarse-grained tills on Pinedale (about 20,000 years old) and Bull Lake (about 140,000 years old) moraines show significant variaton with slope position and age. Soils on the Pinedale moraine are mostly non-calcareous Typic Cryoborolls with A/Bw/C profiles that thicken considerably downslope. These soils are weakly developed due to their youth and to the unstable, steep (up to 24°), highly convexo-concave slopes. Soils on the Bull Lake moraine are mostly Argic Cryoborolls with A/Bt/C profiles. These soils are more strongly developed than soils at similar positions on the Pinedale moraine because the Bull Lake moraine is older and has less steep (up to 16°), more gently curved slopes. The soils on the Bull Lake moraine contain more clay, a higher proportion of pedogenic clay, more weathered stones, and more free sesquioxides. Erosion and dry conditions at the convex summit and shoulder sites on the Bull Lake moraine have resulted in thin soils with minimal argillic horizons; these soils are only slightly more strongly developed than soils at analogous sites on the much younger Pinedale moraine. In contrast, at the concave sites in downslope positions the soils on the Bull Lake moraine are much more strongly developed than analogous soils on the Pinedale moraine; slow deposition of weathered material, probably transported by creep, has acted concurrently with pedogenesis to form soils with thick, homogeneous argillic horizons. The relationship between hillslope curvature and soil properties on both moraines is shown by significant correlations between soil properties and the second derivative of the hillslope profile. This relationship is probably due primarily to the interaction of soil formation and soil creep.

SOIL-LANDSCAPE ANALYSIS IN RELATION TO SOIL DISTRIBUTION AND MAPPING AT A SITE WITHIN THE WEYBURN ASSOCIATION

Soil-landscape relationships were studied in detail at a site comprised of Dark Brown and related soils of the Weyburn Association in central Saskatchewan. Detailed soil observations along transects identified actual soil series and related their distribution to landscape parameters. A slope-profiling approach, involving division of slopes according to angular differences between measured lengths along the transects, revealed that while soil distribution varied in terms of slope position, slope length, slope gradient and sequence, the most significant relationship lies between soil distribution and shape of slopes. Most slopes could be subdivided readily into convex units, concave units, usually short rectilinear units joining them, and depressional units. Such divisions generally coincided with observable soil divisions, corresponding, respectively, with shallow, deep and gleyed soils. The convex units comprised Regosols and Rego, Calcareous and ’shallow Orthic’ Dark Brown Chernozemic soils. The concave units included ’deep Orthic,’ ’AB Orthic’ and Eluviated series. The depressional units were generally composed of Gleyed Orthic or Gleyed Eluviated series. Both field and laboratory analyses confirm that the soils within landscapes form a continuum, but that recognition of the soil groupings suggested provide a practical and feasible field separation in mapping soils. A combination of aerial photos, field examination of soils and an evaluation of slopes and particularly slope changes could be used to recognize and map these broad, landscape-related soil groupings. Key words: Soil association, soil catena, soil series, slope analysis, topography, map units

A Soil Catena in the Medicine Bow Mountains, Wyoming, U.S.A., with Reference to Paleoenvironmental Influences

Topography controls soil development and vegetation wherein well-drained Cryoboralfs, Cryochrepts, and Cryumbrepts under coniferous-aspen forest in higher parts of a catena in the Medicine Bow Mountains, Wyoming, merge with Cryaquepts and Cryofibrists in a poorly drained fen having grasses, sedges, rushes, and shrubs at the base of the chain. Soil development began in late Pleistocene time on Pinedale till, probably under forest. Calcium carbonate in some profiles implies former dry climates under grasses and possibly sagebrush during the Altithermal. An erosional unconformity separates late Pleistocene and Altithermal soil-forming events from those of the Neoglacial. Data suggest that the Neoglacial brought a return of forest, and podzolization is presently removing carbonates from soil profiles. The soils are in a state of disequilibrium in relation to the current environment because of changing paleoenvironments and oscillations of ecotones along the mountain front during the late Pleistocene and Holocene.

The effects of recent land use changes on red podzolic soils near Sydney, N.S.W., Australia

Summary The effects of changing land use on morphological, physical and chemical properties of red podzolic soils under pasture and forest are reported from four soil catenas north west of Sydney. The results indicate that the pasture soils have lower organic matter contents and porosities, higher bulk densities and reduced aggregate stability in the A horizons compared with their forest counterparts. Biological homogenisation (bioturbation) is particularly more marked in the forest topsoils compared with the pasture soils. The changes in soil properties can probably be attributed to differences in soil fauna and rates of faunal activity under the different vegetation types. Microclimatic differences may also influence faunal activity between the sites. The decrease in bioturbation and structural stability under pasture have apparently led to a slight increase in clay translocation from A to B horizons and the development of a clearer texture contrast. No major evidence or erosion of topsoils on convex sites nor downslope accumulation of eroded material was recorded.

Silcrete in Western Australia: geomorphological settings, textures, structures, and their genetic implications

Summary Tertiary silcrete and laterite are extensively preserved in Western Australia in low-relief landscapes. Silcrete is best developed on topographic highs developed on fluviatile sands which overly radiolarites or deeply kaolinised claystones. Laterite occurs topographically lower and is generally developed on fine-grained bed rock. Lateral transition of silcrete to laterite indicates that these duricrusts form a soil catena. Cone structures in the silcretes indicate strongly evaporitic, dry conditions, whereas solution pipes in duricrust profiles indicate humid conditions. The silcrete/laterite catena thus indicates a strongly seasonal, hot, and humid climate, with rainfall probably in excess of 1000 mm yr −1 .

Soil requirements of central Australian sandridge plants in relation to the duneswale soil catena

AbstractThe soil requirements of seven central Australian sandridge plant species were examined by comparing the soils associated with individuals of each species in their typical sandridge habitats and in anomalous habitats such as dry watercourses, grader banks on road verges, disturbed ground near boreholes, and sand‐filled rock crevices.The species studied were Zygochloa paradoxa, Chamaesyce wheeleri, Calotis erinacea, Helichrysum ambiguum, Dampiera cinerea, Triodia basedowii and Monachather paradoxa.The first two of these are characteristic of open dunecrests, the next three of crests and upper dune slopes, and the last two of lower slopes and swales. The first five species grow in a range of anomalous habitats with nutrient status comparable to swales and lowerslopes, but only if the soils are loosened or have enhanced moisture status. The deep wellsorted sands of dry watercourses form the only anomalous habitat for Zygochloa paradoxa and Chamaesyce wheeleri. Calotis erinacea, Helichrysum ambiguum and Dampiera cinerea also grow on poorly sorted graderbank and borehole soils in the swales, but not on unmodified swale soils. The only anomalous habitats in which the last two have been found are very similar to their typical sandridge habitats and so reveal little of soil requirements.

Estructura y funcionalismo de un encinar montano en el Montseny. I: planteamiento del estudio y descripción del área experimental

This paper is a preliminar one on objectives of a new project in terrestrial ecology and on the characteristics of selected study area. The project is being drived by Ecology departments of Universitat de Barcelona and Universitat Autonoma de Barcelona, and is embodied in a larger one on nutrient cycles in forest ecosystems. The parameters measured and their relationships are exposed and future developments briefly discussed. The La Castanya valley is included in the Montseny nature park, a Biosphere Reserve, in a Mediterranean mountain stage with relatively humid climate but with great interanual fluctuation. The bedrock is nearly all constituted by paleozoic shales and valley-side slopes are pronounced (30%) . There is a soil catena from litosols to rankers and brown acid soils that can be lixiviated in some places. Vegetation is a green oak mountain forest (Quercetum ilicis mediterraneo-montanum) in nearly all the valley. There are, however, some grasslands and a beech forest near the summits and also a little Taxus baccata trees clump. The green oak forest is a young one, in a regeneration stage, after a very intensive explotation period (wood for fuel and coal making) interrupted some years ago, and an early farming period. In the experimental plot direct insolation is lowered by topographic position and the soil is colluvial, deep but with loose rocks at surface. Herb and shrub layer are poor, being the young Quercus ilex also dominants. The experimental plot surface is 0,22 ha, including 450 trees (more than 5 cm dbh) between 7 and 12 m high. The branch system has a lowe layer level, with a few horizontal branches, and a higher one with near vertical branches. The major axis is not clearly defined, as it divides in two or three over 2,5-4 m.

Soil and Vegetation Catenas on the Forest-Savanna Boundary in Ghana

A study was carried out on two similar soil catenas and their associated vegetation from a locality on the forest-savanna boundary in west-central Ghana. Soil samples were analyzed for major plant nutrients and the values obtained related to the vegetation using principal components analysis and analysis of foliar nutrient levels. Vegetation types were found to occupy distinct catenary positions and to be associated with characteristic soil types. Levels of total phosphorus, exchangeable calcium and potassium, water content, and pH in the topsoil were all found to be higher under forest than under savanna, but total nitrogen was not different. The change from savanna woodland to open-tree savanna coincided with decreasing levels of nitrogen and potassium in foliage samples and of potassium in the topsoil. Differences in soil fertility are, however, probably secondary, and it is concluded that the primary factors separating vegetation types relate to effective soil depth, soil texture, and water supply. EXTENSIVE AREAS of Guinea Savanna vegetation bordering the forest zones in West Africa have been classically interpreted as representing a biotic climax, established and maintained by the periodic burning associated with traditional agriculture. Recent, more detailed studies have, however, indicated the importance of edaphic factors in determining the pattern of vegetation on the forest-savanna boundary; in particular, attention has been drawn to the relation of vegetation patterns to the catenary development of soils (Spichiger 1975), to soil texture as it affects soil moisture and nutrients (Askew, Moffatt, Montgomery, and Searl 1970, 1971), and to soil nutrients directly (de Rham 1970, Goodland and Pollard 1973). This paper reports the study of two soil catenas and their associated vegetation from a locality on the forest-savanna boundary near Degedege in westcentral Ghana (latitude 7?48.5'N, longitude 2?26.5' W). Field work was carried out in July and August 1976, during the short, summer dry season. A description and classification of the vegetation at Degedege has already been published (Swaine, Hall, and Lock 1977), and so in this study attention was concentrated on the soil catenas and levels of major nutrients in the topsoils. Floristic and physiognomic data were collected to distinguish the main vegetation units and to relate them to existing classifications. GEOGRAPHICAL CONTEXT In this region of Ghana, forest and savanna form a mosaic, with forest in narrow bands along streams and in patches on summits, and savanna on the slopes between (fig. 1). The description of 'forest-interfluve' has been proposed for this pattern (Swaine et al. 1977), contrasting it with the 'savanna-interfluve' pattern, more widespread in West Africa, in which forest is confined to the valleys. Climatic data are not available for the immediate vicinity of Degedege, but from those of the nearest stations annual rainfall can be estimated at ca. 1200 mm. This is distributed in a two-peak pattern with maxima in May-June and September, separated by a comparatively cool, dry period; the main dry season from November to April includes at least five 'arid' months (sensu Mohr, i.e., less than 10 cm in a month). As noted by Swaine et al. (1977), the forest savanna boundary in this region of Ghana runs approximately east-west, apparently cutting across the local trend in annual rainfall. The underlying rocks are mainly metamorphics of the Lower Birrimian formation, part of the Precambian basement. Country rock was not exposed in the study area, but fragments of phyllite and quartz (the latter from intruded veins) were found in soil pits. Topography is very gentle, with slopes of less than 3? in the study area, resulting from dissection of a Tertiary peneplain surface (Brash 1962). Hilltop cappings of hardened ironpan seem widespread, though seldom exposed at the surface. Cultivation in the study area, approximately 1.5 km from the nearest village, appears to be sporadic, rather than on a regular rotation and is entirely confined to the hilltop forests and their margins. Savanna trees in the area showed moderate to severe fire damage, suggesting irregular burning; one of the forest areas sampled was in the process of regeneration after clearing. The area is not subject to animal grazing, but termites are universally abunlPresent address: International Institute of Tropical Agriculture, PMB 5320, Ibadan, Nigeria. 224 BIOTROPICA 11 (3): 224-234 1979 This content downloaded from 157.55.39.149 on Sat, 09 Jul 2016 05:56:45 UTC All use subject to http://about.jstor.org/terms dant and are probably an important factor in the ecology of the area.

SOIL DRAINAGE CLASSES AND SOIL WATER TABLE RELATIONS IN MEDIUM AND COARSE TEXTURED SOILS IN SOUTHERN ONTARIO

Water table levels were recorded for up to 5 yr on five soil catenas, each containing a well, imperfectly, poorly and very poorly drained member. Water table measurements in combination with soil morphology were used to establish the zone of free water saturation and from this, periods of saturation were recorded at pre-determined depths or, alternatively, mean high water table and mean low water table levels were calculated for the periods 1 Jan.–31 Dec. and 1 May–31 Oct. Periods of saturation for well/imperfectly and imperfectly/very poorly drained soils were significantly different at the.2 level of probability, but there was no significant difference between the imperfectly/poorly or poorly/very poorly drained members. At the.05 level of probability, only two drainage classes were significantly different. The large within -class variability raises some conern over relying on soil morphology to determine water table characteristics and as well, questions the usefulness of soil drainage classes as currently defined. The significance of the data is discussed in relation to soil mapping, tile drainage and septic tank disposal of wastes.

Organic Phosphorus Changes Over a Growing Season in Some Borolls and Associated Aquoll of South Dakota

AbstractThe objective of this research was to study changes in soil organic phosphorus for five members of a soil catena over a growing season. Three horizons of each of five pedons were sampled on the South Dakota University Research Farm at 2‐week intervals 10 April–23 October. Samples were taken at noon each sampling date when temperatures were recorded using a dial thermometer. Precipitation was that recorded by the Research Farm gauge between sampling periods. Soil samples were analyzed for total and organic‐P, available‐P and pH. The pedons also were analyzed for CEC, exchangeable cations, total nitrogen and organic carbon. Catena members appeared to have seasonal changes in organic phosphorus but the change was significant only for the north‐facing member. When examined for each sampling date the organic phosphorus changes were significantly related to precipitation for the sloping Borolls but not in the Borolls occupying level positions nor the associated Aquoll.

Weathering of Karroo argillite under equatorial conditions

The mineralogical composition of a soil catena from Karroo argillite (shale) from Bengamisa, in oriental Zaire is reported in relation to the particle size distribution and to the extent of quartz enrichment as a measure of weathering. Chemical properties such as exchangeable Al 3+ and base saturation were strongly influenced by the relief. Of the free citrate-bicarbonate-dithionite (CBD) iron oxides, less than 5 to 10% were mobile in pH 3 ammonium oxalate. The proportion of aluminum mobilized in the latter was 17 to 44%, whereas only 0.1 to 1% of the SiO 2 was. Feldspars were almost entirely altered by the weathering process and the weathering of mica resulted in increased mica contents in the clay and fine silt fractions and in labile expanded mixed-layer complexes containing mica, vermiculite and montmorillonite. The kaolinite content increased with depth of solum, presumed to reflect degree of soil development.

Clay Mineral Stability as Related to Activities of Aluminium, Silicon, and Magnesium in Matrix Solution of Montmorillonite-Containing Soils

AbstractThe influence of geomorphological site characteristics on soil clay mineral stability of montmorillonite-containing horizons of a southern Wisconsin soil catena was interpreted in terms of the solute activity function values of pSi(OH)4, pH-1/2pMg2+ and pH-1/3pAl3+ in suspensions of the separated clay fractions. Montmorillonite stability and/or formation vs that of kaolinite for the soil clays was evaluated by a plot of the solute activity functions on a three dimensional diagram derived for montmorillonite, kaolinite, and gibbsite at constant temperature (25°C) and constant pressure (one atm.). Although all the soil clays contained both montmorillonite and kaolinite, the position of the soil clay solute activity functions in the stability diagram clearly reflected the influence of the geomorphological—geochemical site conditions in which each soil horizon was developed, with corresponding differences in the SiO2/Al2O3 molar ratio of the reactive fraction. Montmorillonite stability positions of the solute activity functions were induced by soils (clays with reactive fractions with SiO2/Al2O3 molar ratios = 3–4) from calcareous or poorly drained horizons, while kaolinite stability positions of the functions were induced by soils (clays with reactive fractions of SiO2/Al2O3 molar ratios = 2) from acid, freely drained horizons.

Soil landscape systems: A model of soil Genesis

The paper describes a model of the soil system. There are two different, partly complementary means of building such a model. One approach is to construct, using empirical physical science methods, an isomorphic model, in which each and every component (variable) of the system is an element in the model. The other approach is to build, using a systems synthesis methodology, a homomorphic model, in which several components of the system are grouped to form a single element in the model. The latter method is adopted in this paper because of its suitability for modelling at the level of the whole soil system. As regards forming the basis of a homorphic model of the whole soil system, existing concepts of soil genesis have limitations: either they are very complex isomorphic models, the implementation of which presents virtually insurmountable problems; or they are homomorphs but too general to be used in their present form. And the concepts make no reference to the functional boundaries of soil system units. Indeed, such a unit has not yet been satisfactorily defined; the nearest to it is the soil catena, which is considered at length in the paper. Some of these problems are resolved by the concept of soil landscape systems which, synoptically, is as follows. A basic functional of the soil system, it is proposed, is a three-dimensional body of soil known as a soil landscape system or a “valley basin”, that (1) is bounded by the soil surface, valley watershed and weathering front at the base of the soil; (2) forms part of a more extensive valley basin network; and (3) functions as an open system. The flux of solids, colloids and solutes within and across the landscape is shown to be organized within the framework of these soil system units, and is discussed in terms of inputs, outputs and storages of the soil skeleton (clastic sediment) subsystem, the soil plasma subsystem and the soil solution subsystem. The value if the soil landscape system concept as a homomorphic model is stated. Five main advantages are outlined which relate to the five main features of the model: it has clearly and comprehensively defined basic system elements; it has functionally defined, three-dimensional system boundaries; the relationships between elements can be established from empirical hypotheses; there is transport and conservation of matter and energy as in the very successful models of hydrological systems and ecosystems; change of the system through time can be directly studied by computer simulation and not indirectly by statistical extrapolation from empirically derived behaviour patterns. The model, it is hoped, should provide a rational physical basis for simulating soil systems.

A tentative re-examination of the soil catena in the type area of Kware, North-West Tanzania

Assessment of individual soil characteristics along soil-slope transects on a volcanic hill, Ndoro, in the Kware area, first studied by MILNE, shows that these could not be predicted using assumptions about catenary relationships, neither is it possible to assume that comparable soil characteristics will exist at similar heights on adjacent traverses. It is possible to suggest a structural catena, probably most readily explained in terms of cultural influences. A simple model of soil variation shows that factor groups of coarse and medium sand along with silt and fine sand combine with other soil physical characteristics to explain most — 80 per cent — of the variability of the studied soil properties though, individually, such textural parameters are not readily interpreted in terms of catenary relationships, apart from percent silt and structure grade, which are relatively highly correlated with altitude. The factor groups show a marked lack of inter-correlation. Assumptions relating to soil physical characteristics derived from catenary relationships are therefore unsound and not recommended. L'estimation des propriétés pédologiques individuelles le long des coupes pentes-sol sur une colline volcanique, Ndoro, aux environs de Kware, premièrement étudiées par MILNE, montre que celles ne prédit pas si on utilise les suppositions basées sur les relations caténaires. A même temps ce n'est pas possible de supposer que les propriétés des sols sont identiques aux élévations comparables sur des traverses voisines. C'est possible de proposer un catena structural, plus probablement expliqué par les influences culturelles. Un modèle très simple de la variation des sols montre que deux groupes des facteurs, le sable gros plus sable moyen, et le vase plus le sable fin, et avec autre caractéristiques physiques du sol moins importantes, faîtes une combinaison qui s'explique la plupart (80 %) de la variation des propriétés étudiées, ainsi que les paramètres texturels, individuellement, ne sont pas expliqués par l'hypothèse des relations caténaires, en dehors de la pourcentage du vase et les classes du structure, qui montrent une corrélation assez elévée avec l'altitude. Autrement tous les groupes des facteurs manquent presque totalement l'intercorrélation. Ainsi les conclusions basées sur un supposition des relations entre les propriétés physiques du sol et les conditions caténaires sont inexactes.

A soil catena on weathered basalt in Queensland

Deep weathering in the upper layers of basalt flows in central Queensland led to the deveIopment of lateritic profiles with a surface cover of leached red clay soils overlying ferruginous and mottled zones. Subsequent erosion and bevelling of the weathered mantle left small residuals of the old surface and exposed the underlying weathered zones. In places the mantle was completely removed to uncover fresh rock. A soil catena comprising six zones with associated discrete plant communities developed in these landscapes. Soil differences are related to variations in the intensity of weathering of parent materials and the leaching, translocation, and precipitation of differentially soluble and mobile constituents of the parent rock. The sequence of clay minerals is kaolinite -->kaolinite + randomly interstratified material + montmorillonite --> montmorillonite. The distribution of the plant communities is closeIy associated with variations in soil properties, particularly those which affect water relationships.

EFFECTS OF TOPOGRAPHICAL POSITIONS, SOIL TEST VALUES, AND FERTILIZER USE ON YIELDS OF WHEAT IN A COMPLEX OF BLACK CHERNOZEMIC AND GLEYSOLIC SOILS

In southeastern Saskatchewan, from 1965 to 1968, wheat was grown in 15 experiments testing N, P, and NP fertilizers on 8–12% topographical slopes on an association of Black Chernozemic and Gleysolic soils developed on moderately rolling calcareous glacial till. All tests were on summer fallow. Without fertilizer, the yield of wheat ranged from 1150 kg/ha on the crown of the knolls to 1930 kg/ha in the depressions. Phosphate fertilizer increased the yield of grain by 20–30% on the crowns, upper slopes, and midslopes (70% of the area) and by less than 10% on the lower slopes and in the depressions. Excluding the depressional areas (10% of the area), the average phosphorus content was 10 ppm in the surface soil. The average NO3-N content of the top 60 cm of soil was 34 ppm. The basic pedological and microclimatological factors of the soil catena affected the yields of wheat more than soil fertility (and fertilizers).

A runoff potential rating table for soils

A runoff potential rating table based on the soil catena concept is proposed to group soils of similar runoff potential. Seven runoff potential ratings are given according to internal drainage, depth and texture of the soil, as well as subsurface soil conditions. The proposed rating table is to be applied to a detailed soil survey. In the absence of adequate soil reports an air photo analysis approach is also tentatively suggested in conjunction with the use of the proposed system. The rating system enables engineers to classify soils hydrologically.

A Catena in Tropical Moist Semi-Deciduous Forest Near Kade, Ghana

Numerous accounts have been written about the West African forests, and forest soil catenas have been described separately by a number of workers (e.g. Greenwood 1938; Vine 1941; Charter 1949; Nye 1954). But there has usually been little or no attempt to relate the soil to the natural vegetation except in the most general way. The present study has been carried out to help to fill this gap in our knowledge. The vegetation, both above and below ground on a catena in Ghanaian forest near Kade, has been examined to see to what extent it can be related to soil differences. Observations have also been made on some of the relevant microclimatic factors. The Agricultural Research Station of the University of Ghana near Kade (0?55' W, 6?09' N) lies in Taylor's (1952, 1960) Celtis-Triplochiton association of the moist semideciduous forest. This association covers the greatest area of the moist semi-deciduous forest of Ghana and is separated from the savanna by a drier type of forest (Taylor's Antiaris-Chlorophora association) to the north and east. In the south-west it is separated from the evergreen forest by a belt of forest intermediate in character between the moist semi-deciduous type and the evergreen type (Taylor's Lophira-Triplochiton association). The distribution of these forest types is shown in Fig. 1. Much of the 2700 ac (1093 ha) of the Research Station has been developed for agricultural purposes but some parts of the forest have probably not been much disturbed for at least 50 years. It is in one such area that the observations described in this paper were made. Teams of staff and students of the Botany Department of the University of Ghana have visited and worked there at intervals since 1964. The bulk of the work described, however, was accomplished during the Easter vacation of 1968. Because of the facilities available at the Agricultural Research Station the forest at Kade has been the subject of several studies by other workers. The area we examined, for instance, stands only a few hundred metres from the area in which Greenland & Kowal (1960) obtained their figures on the mineral content of the soils and the vegetation; as the forest they studied was essentially similar to our sample areas these figures can probably be taken equally to apply also to our area. The main macroclimatic features of the Kade area are summarized in Fig. 2. It will be noted that the rainfall is of the characteristic two-peak type with maxima in July and October, and that January is the only month with less than 5 cm (2 in.) of rain on average. Mean monthly maximum and minimum temperatures, especially the latter, are very steady throughout the year. Relative humidity measured at 09.00 GMT varies only from 86 to 90% but taken at 15.00 GMT it falls to as low as 53Y% during the 'dry' season when the dry Harmattan wind blows from the north-east during January-February.

Types of Geochemical Soil Catenas

AbstractBy analogy with soil catenas, which are groups of related soils differing from one another as a result of variation in relief and drainage, the author suggests the existence of geochemical soil catenas, in which the lateral migration of chemical elements links the related soils of uplands, slopes, and depressions into a geochemical entity. On the basis of the conditions of migration, soils are divided into geochemically autonomous, eluvial soils on uplands and geochemically subordinate soils on slopes (transaccumulative situations) and in depressions (superaqueous situations). In humid regions, geochemical soil catenas are distinguished mainly on the basis of the mobility of iron and aluminum compounds; in arid regions, mostly in terms of the mobility of the sulfates and chlorides of sodium and calcium. Geochemical soil catenas in the periglacial situations of the Antarctic and the Tien Shan and in the humid subarctic situation of northern Scandinavia were investigated in the field. The field data...