Showing papers in "Catena in 1985"

Selectivity and transport capacity of thin flows in relation to rill erosion

Abstract: Summary Laboratory experiments were conducted to evaluate the transport capacity and the selective transport of thin flows. The aggregate size as well as the grain size of the eroded and transported loamy materials could best be related to the shear velocity of the flow, whereby it was observed that, when the shear velocity was greater than 3.0–3.5 cm/s, transport and erosion of loamy materials becomes aselective. Sediment concentration however could best be related to the product of mean and shear velocity. The transport capacity of thin flows for a well sorted Tongrian sand (D 50 ≅ 100 μ m) starts rising rapidly at a shear velocity of 3.15 cm/s. It could thus be expected that the erosive power of a thin flow would increase rapidly once a shear velocity of 3.0–3.5 cm/s is exceeded and that this value might be a valuable threshold for the onset of rill erosion. This is confirmed by field observations.

Effect of antecedent soil moisture content on rainwash erosion

Abstract: The effect of antecedent soil moisture on rainwash erosion was evaluated in a series of field experiments by using 0.84 m 2 erosion plots and the modified Toronto simulator which delivered artificial rain at an intensity of 50 mm hr −1 (0.38 J m −2 s −1 kinetic energy). It was observed that antecedent moisture content is a significant factor contributing to variations in measured rainwash eroson. Extrapolation from the collected data suggests that rainwash differs by 4 to 5 times if the full range of antecedent moisture content is considered. For the soils tested which are cohesive in nature, the effect of antecedent moisture is not confined to enhanced runoff capacity, but also shear strength reduction.

Modification of heavy mineral assemblages in English coversands by acid pedochemical weathering

Abstract: Summary Weathering of non-opaque heavy minerals in five English soil profiles developed in texturally homogeneous Late Devensian coversands has been investigated by spline interpolation of detailed mineral counts. Values for D90 (90% mineral depletion) derived from the splines suggest a depletion sequence that is generally applicable to moderately acid weathering of sediments: apatite (+ olivines) > amphiboles + pyroxenes > epidotes > garnets > more resistant minerals. Weathered minerals form three groups, each of which is eliminated in an almost discrete stage. Weathering is accompanied by a characteristic developmental sequence of surface textures. Weathering rates of most of the silicate minerals are probably determined mainly by their Fe2+ contents, effective surface areas and soil pH. Considerable variations in the depth and severity of weathering between profiles may reflect differences in vegetation histories. Heavy mineral weathering is related to soil chemistry to examine its implications for podzol genesis.

A preliminary investigation-of solifluction macrofabrics

Abstract: Summary Statistical analysis of clast orientation in various parts of solifluction lobes demonstrates large departures from uniformity. Although concentration is not homogeneous, the clasts of all samples are strongly oriented parallel to the direction faced by the slope, and dip upslope. This pattern probably reflects operation of both flow and creep processes. Samples are coplanar after rotation of data into the plane of their respective local slopes, and this transformation is suggested as a precursor to statistical analysis in future studies. Three-dimensional fabric analysis is a useful tool for establishing the direction in which movement occurred within fossil solifluction deposits, but should be accompanied by other lines of evidence for establishing the origin of such deposits.

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.

A portable rainfall simulator for studying factors affecting runoff, infiltration and soil loss

Abstract: Summary A new, yet simple and easy to operate rainfall simulator was developed in view of infiltration research to be done on Oxisols in the State of Parana, Brazil. A drop-forming unit is mounted 3 m above the ground in a frame containing 4 water reservoirs which provide polyethylene tubes with water. Drop size is governed by different tube diameters (inner diameter 0,1–1 mm) and lies in the order of 2,82–3,72 mm, whereas rainfall intensity is controlled by water head in the reservoirs and reservoir height adjustment and can be adjusted to intensities between 0–185 mm/h. Rainfall produced by the simulator attains about 60–80% of the kinetic energy of natural rainfall. The diameter of the produced drops also lies in the range of naturally encountered raindrops. The infiltration rate as determined by the difference between run-off and rainfall intensity is presented for an Oxisol.

Field calibration of a recording turbidity meter

Abstract: The methods in common use for collecting data on suspended solids concentrations in streamflow and for calculating total load are either inaccurate or unnecessarily expensive. Recording turbidity meters offer a potential solution to these problems when used in association with a calibration between suspended solids concentrations and turbidity. In this paper a method is described for the field calibration of a recording turbidity meter. Optical neutral density filters are used instead of Formazin standards to check instrumental consistency in the field. Calibration with suspended solids concentrations is carried out using an automatic sampler whose operation is recorded together with turbidity on a two track recorder. The calibration curve is a second order polynomial in which turbidity explains 97% of the variance in suspended solids concentration.

Geomorphologic relationships and ages of soils on alluvial fans in the Rio General Valley, Costa Rica

Abstract: Soil-geomorphic relationships on alluvial fans in the Rio General Valley, Costa Rica, show that the sequence of alluvial fan surfaces and soil development on them is related chiefly to uplift of the bordering mountain ranges and not significantly to climatic change. The oldest and most strongly developed soils are found only on the highest surfaces; successively younger and less-developed soils have lower positions. Oxisols characterize the oldest surfaces, Alfisols the intermediate ones, and Entisols the youngest surfaces. Minimum ages of these surfaces are estimated, from the extrapolation of sedimentation rates, solum development rates, and the rate of channel incision based on two radiocarbon dates, to range from about 45,000 to 65,000 years for the oldest, to approximately 100 years for the most recent surface. Pedons representative of the soils on the principal alluvial surfaces are described in terms of the physical, chemical, and mineralogic characteristic. We propose that the soils studied are a chrono-catena that represents soils development through time for this region, and can be used to establish a minimum time scale by which to guage stage and rate of soil development in a humid tropical environment.

Early and middle holocene soils at the lubbock lake archeological site, Texas

Abstract: Summary Two buried soils have been identified in early and middle Holocene sediments at the Lubbock Lake site, a well-stratified archeological locality in Yellowhouse Draw, Lubbock County, Texas. The Firstview Soil formed in organic-rich lacustrine and sandy eolian sediments deposited from 11,000 to 8,500 yr B.P. The soil developed from 8,500 to about 6,300 yr B.P. and exhibits O-A-C and A-C profiles. The lacustrine facies (found along the valley axis) has a relatively high organic matter content, contains abundant silicified root remains, and commonly exhibits a gley horizon immediately below the A horizon, indicating that the soil formed in a marsh with the water table at or just below the surface. The soil becomes coarser-grained, better-drained, and weakly calcareous toward the valley margin, reflecting the facies change in parent material. The overlying Yellowhouse Soil formed in highly calcareous lacustrine sediments (along the valley axis) and sandy eolian material (along the valley margin), with deposition and pedogenesis occurring between 6,300 and 5,000 yr B.P. The soil exhibits A-C and sometimes A-B-C profiles. The relatively high organic matter content of the A horizon and minimal leaching of carbonate in the C horizon of the valley-axis facies suggest that the water table was high during pedogenesis. The valley-margin facies of the soil exhibits some evidence of clay illuviation. The contrasting field and chemical characteristics of the valley-axis facies of the two soils and the sedimentological data indicate a sudden change in the water geochemistry and local environmental change. Soils with morphologies, parent material, and age similar to that of the Firstview Soil are not common in valley fills on the Southern High Plains, whereas soils similar to the Yellowhouse Soil are widespread. These data indicate a regional climatic change toward conditions of increased eolian activity, reduced effective moisture, and possibly warmer temperatures.

Granular disintegration of gneiss and migmatites

Abstract: Summary Weathering of Precambrian gneiss and granitoid migmatites in the Kora area of Central Kenya is essentially a two-stage process. In the first stage the rocks experience granular disintegration due to the widening of grain boundary microcracks and loosening of the rock structure. SEM and microprobe data indicate that during this stage chemical alteration of biotite and feldspars is limited and occurs mainly on grain margins and along microcracks. No evidence has been found to suggest that stresses created by extensive alteration and expansion of biotite are primarily responsible for granular disintegration. The second stage of weathering involves development of intragranular microcracks and progressive chemical decomposition with leaching of Ca, Mg, Na and K from biotite and feldspars.

The erodibility of highly calcareous soil material from southern Spain

Abstract: The erodibility of highly calcareous and gypsiferous soils from three locations in southern Spain is examined The reasons for the poor structural condition of the soils are reviewed and attention given to the problem of obtaining good analytical data for highly calcareous materials The most erodible soils are from areas of badlands where sodium salts are present in the parent material These and all of the soils except those containing pedogenic oxides (for example free iron) or high amounts of organic material are subject to slaking and have low rates of water acceptance The aggregate stability, as measured by an ultrasonic dispersion procedure and by the water-drop test, is relatively low for all materials except those containing high amounts of organic matter The size-distibution of the breakdown products of the aggregates obtained by different procedures is considered

Weathering of quartz grains in the liquefied horizon of permafrost solonchaks in the arid steppe zone, Central Mongolia

Abstract: Morphoscopic investigations of quartz grains (0,6–0,8 mm) were carried out with the use of scanning electron microscope. The grains originated from the liquefied horizon of the strongly alkaline permafrost solonchaks of the arid steppe zone of Central Mongolia. The grain surface in this horizon is smoothed due to various processes of chemical corrosion and by deposition of silicate crusts of variable thickness. The record of the preceding abrasion resulting from transportation of weathered material to their deposition site was blurred by the above mentioned processes. The permanently hydrated cool environment favoured moreover the cryohydrothermal block- and granular disintegration as well as the cryothermal and cryomechanical fracture and chipping.

A method for identification and mapping potentially acid sulfate soils in Jutland, Denmark

Abstract: A method for mapping potentially acid sulfate soils in Jutland, Denmark is described. First the wetlands were outlined, using already existing topographic maps. Then 7900 profiles, evenly distributed over the wetland areas, were examined to point out areas with potentially acid sulfate soils. The method used to identify potentially acid sulfate material was, for carbonate-free samples, a pH-measuring at the sampling time and after the samples were inoculated with soil water extract from an acid sulfate soil and 2, 8 or 16 weeks of incubation. For carbonate-containing samples the pyrite content was compared to the acid-neutralizing capacity. A map was constructed showing the ratio of profiles containing potentially acid sulfate soil samples to total number of profiles examined within natural geographical wetland regions. The investigation showed that 35% of the wetlands in Jutland have a high frequency of potentially acid sulfate soils.

Wind erosion of arable soils in east Shropshire (England) during spring 1983

Abstract: Severe blowing of light sandy soils in east Shropshire during spring 1983 was caused by a particular combination of hydrological, pedological, meteorological and agricultural factors. The characteristics of eroded topsoil demonstrated selective removal of finer-textured material. Deposition took two forms. Fine sand was deposited at field boundaries as small dune features, whereas very fine sand and silt were deposited further downwind as a veneer of dust. Analysis of the dust indicates that it is of high value for crop nutrition. Selective export of such high quality soil from sites of active plant growth is considered as detrimental for the soil's ability to act as a medium for sustained crop yield.

Field parameterization of an empirical sheetwash transport equation

Abstract: Specially designed instruments were used to sample surface water and sediment discharge on a set of small hillslopes. The data set produced is unique as it includes simultaneous observations of surface water and sediment discharge, local surface declivity and drainage area at several points over the slope surface, and the precipitation intensity taken a number of times through natural storm events. The data are used to parameterize an empirical sediment transport law, expressing sediment transport as a power function of the local declivity and surface water discharge. A good fit to the observed data is achieved, suggesting that these field techniques may be used to parameterize the equation for different soils. A dynamic catena effect involving surface grain size, local declivity and the form of the sediment transport equation is recognized that may have significant implications for the form of sediment transport and long-term hillslope development.

Promoted erosion and controlled colluviation: A proposal concerning land management and landscape evolution

Abstract: The upper limit of colluvial sections constitutes a marked dynamic discontinuity on slopes as is made clear by the discussion of a colluviation model. But in general little is known about the nature of processes and interactions which govern the transition between the eroded slope section and colluvial land systems. The principle of controlled colluviation, an eventual strategy for land and water management in some areas with heavily eroded soils, is explained. It is illustrated by an example from the northern Negev desert. It is argued that soil erosion can have positive effects, at least in some arid areas, and that trapping water and sediment might be an alternative for inefficient erosion control on upper slope sections.

Patterned ground by rainstorm erosion on the Colorado plateau, Utah

Abstract: This short notice deals with the effect of highly intensive rainstorms (more than 25 mm/h or 8 mm/10 min.) on bare surfaces, producing cones and needles of earth up to 12 cm in cryptogamic surface layers of Canyonlands National Park by splash erosion, and widespread stone stripes resembling periglacial features on the steeper slopes (up to more than 40°) by rainwash in the areas of Red Canyon and Bryce Canyon National Park. A large amount of coarse material can be moved within a very short time, and the surface patterns survive at least for several months.

Spatial scale and drainage basin morphometric interaction

Abstract: Summary The effect of spatial scale changes on the interaction amongst morphometric properties of drainage basins is examined through order-by-order principal components analysis of eight morphometric parameters. The results reveal striking similarities in the intercorrelation structures of basin morphology irrespective of the spatial scale of investigation. The strength of the interaction amongst the variables in each correlation set, however, varies with basin order; the intensity of interaction among the planimetric elements increases while that of slope attributes decreases with increase in basin size. The former is attributed to the inherent capability of a stream system to regulate itself by size adjustments in stream segment number and lengths while the latter arises from the less sensitive link between valley-side and stream channel slopes in higher-order stream segments because of flood plain deposition. These size-related variations sign-post the need to confine applied morphometric intercorrelation studies to samples of higher-order basins, the morphological properties of which are spatial averages of those of the lower-order basins nested within them.

Dynamics of water, temperature, and salts in typical aridic soils after artificial rainstorms

Abstract: Summary In order to learn more about soil genesis, and ecology in the extremely dry desert of southwestern Egypt, we carried out irrigation experiments at four sites representing four typical (Solonchak and Yermosol) types of soil occurrence in this region. The irrigations simulated the rare episodic rainstorms. We measured water content, temperature, and salt content at various depths in the soil profiles for several weeks, at first hourly, then daily; we also observed changes in soil morphology. Thus, we obtained the rates of evaporation, water penetration, and salt migration at these sites. We speculate on the meaning of these data regarding soil genesis, and ecology in hyperarid deserts.

Anthropogenic increase of winter surface albedo

Abstract: Summary The range of surface albedo in winter increased fourfold after densely forested swamps in Orange County, New York were turned into farmland, making the local microclimate considerably more sensitive to the presence and duration of snow cover. Today, the peaty onion fields when dry have an albedo of 0.08 when snowfree and 0.79 when covered with fresh snow. Before clearance in the late 18th century, the albedo of the swamps ranged from approximately 0.10 when snowfree to 0.28 when snow covered. Prior to the arrival of white settlers, the regional surface albedo, as modeled over a large portion of southeastern New York, ranged from 0.12 when snowfree to 0.31 when snow covered. It ranged from 0.15 (snow-free) to 0.59 (snow covered) when deforestation peaked in the late 19th century. Present values are 0.14 and 0.47, respectively. As a result of these changes in albedo, we estimate that approximately the same amount of solar radiation was absorbed in the naturally vegetated New York region in a snowy winter (with the ground snow covered 75% of the time) as in a snow-dry winter in the late 19th century (with a 10% duration of snow). Deforestation elsewhere in the middle latitudes has had qualitatively similar effects.

Hydraulic conductivity of a swelling clay in relation to irrigation water quality

Abstract: The effect of soil water quality on the unsaturated hydraulic conductivity of a clay soil in the 0.18–0.30 g/g moisture content range was evaluated. The cation concentration and SAR of the soil varied from 0.5 me/l to 500 me/l and 5 to 35 (me/l)−1/2, respectively. The relative hydraulic conductivity changes ascribed to solution salinity level were independent of soil moisture content but highly dependent of SAR and cation concentration. The decrease in hydraulic conductivity associated with increase in SAR and decrease in salinity level of the soil solution were attributed mainly to Ex-Na+-induced swelling. Based on the threshold concentration curves, an empirical relationship relating reduction in hydraulic conductivity and soil solution properties has been established for Vertisols having smectite clay mineralogy. The pore structural stability model proposed by Cass and Sumner, 1982 , Cass and Sumner, 1982 for saturated systems was applied successfully to an unsaturated system.

A diffusion model for a settling non-consolidated dust mass

Abstract: A physical model, describing and predicting the lateral diffusion of a non-consolidated dust mass that settles down freely in air, is presented It appears that in the total diffusion process a distinction has to be made between two (in origin totally different) types of diffusion In the case of the first diffusion type, the settling dust mass acts as a closed system and all the particles fall with the same velocity In the second diffusion type, the dust mass no longer acts as a closed system and each particle settles with its own fall velocity Both of these diffusion types are investigated The result is a set of four equations: the first and the second describe the starting point of the lateral diffusion, the third describes the lateral diffusion of the first type and the fourth describes the lateral diffusion of the second type The equations are tested in six diffusion experiments and their validity seems to be very high The physical and mathematical construction of the model allows extension of the formulae so that the frame of the model can be used in several other sedimentological, fluid dynamical or geomorphological research domains The model shows clearly that the classical sedimentation techniques, which are very frequently used in grain size distribution measurements, can lead to completely wrong results if no extreme care is observed in connection with the concentration of the settling sediment

Estimating dry-season crop water requirements from climatological and soil available water capacity data in the sedimentary and basement complex areas of Southern Nigeria

Abstract: Summary Data on available water capacities of three agriculturally important soils at Onne, Ikenne and Ilora in Southern Nigeria were used with climatological data to estimate crops' water requirements during the dry season. About 70% of the total available water within one-meter depth were released between 0.1 and 0.5 bar tension and this corresponded to the range of readily available water. These values were 96mm M −1 , 85mm M −1 and 78mm M −1 for Onne, Ikenne and Ilora soils respectively and were influenced by the texture of the soils rather than their landscape positions or geologic origin. The water budget showed that during the dry-season months there is soil moisture utilization and also net deficits of 147 mm at Onne, 340 mm at Ikenne and 347 mm at Ilora indicating that only supplemental irrigation may be needed. Crop evapotranspiration varied from 5.0 to 6.0 mm day −1 , rooting depths from 30 to 100 cm, irrigation depths from 4.8 to 16.0 cm and irrigation intervals from 4 to 15 days. These irrigation depths and intervals should be expected to be the same for similar crops grown on similar soils within any part of the Southern Nigeria.

Geomorphology, water table and soil relationships in holocene beach ridges in southern sierra leone

Abstract: The coast of southern Sierra Leone is fringed by a wave-built beach ridge barrier characterized by young, weakly developed soils composed of medium to coarse quartz sand. These littoral deposits have been more or less extensively modified by geomorphic processes resulting from sea level oscillations and possibly climatic fluctuations. Soil heterogeneity in these young beach deposits results from spatial and temporal variations in water table level. Such variations occur in response to geomorphic variables such as topography, beach ridge dissection or progradation and swale incision.

Surface textures of intrafault quartz grains as an indicator of fault movement

Abstract: Summary Quartz grains obtained from gouges which accompany faults are observed by means of a scanning electron microscope. It is assumed that quartz grains in the gouge are formed from the breakage of quartz in the parent rock due to fault movement, with corrosion by groundwater occurring on grain surfaces after the movement. Therefore, surface textures or morphology of the grains can become a good indicator in examining the mode of fracture at the time of faulting, or the length of time elapsed since the fault moved.

Phosphate retention: Relative dating of holocene soil development

Abstract: Measurements of percentage phosphate retention are presented for two soil chronosequences on till deposits in the Mount Cook region, New Zealand. Changes in the capacity of phosphate retention as a function of time and depth in the soil profile is a useful relative dating tool for examining post-depositional surface modifications. As an index of soil development it has the advantage that it is applicable to all stages of Holocene soil development unlike other more temporally restricted techniques. Estimates of surface age are taken from earlier work using rock weathering rind thickness analysis. The corresponding pattern of soil development for corresponding members of both sequences demonstrates the consistency between different relative age dating techniques.

Development of sustained land use by understanding soil and landscape formation in the desert fringe area of NW-Egypt

Abstract: A soil survey was carried out in a small area on the mediterranean coast in north-west Egypt, 20 km east of Marsa Matrouh. The objective was to give a scientific contribution to land use planning in the coastal zone. Between plateaus and depressions the following soil units have been found (description according to the FAO-classification): a Calcic Yermosol (petrocalcic, saline and sodic phase), a Calcic Yermosol with exposed calcrete, a Haplic Yermosol and a Luvic Yermosol (sodic phase). In wadi beds Calcaric Fluvisols and on wadi banks Calcaric Regosols were determined. Analysed as characteristic soils were a Calcic, a Haplic and a Luvic Yermosol. From analysis and field observations site qualities were derived. In all profiles and depths the soils have high pH values, a moderate salt content and a high calcium carbonate content. The nutrient supply is neither a limiting nor a differing factor. Rooting depth, water capacity and position are important site qualities. They were compared with the demands of potential crops for the area (olives, figs, date palms, barley, water melons, alfalfa). So suitable areas for the crops were found. The deep Luvic Yermosol fit for all crops, the extremely shallow Calcic Yermosol (petrocalcic phase) is unsuitable for all crops. Measures for the improvement of rainfed agriculture are recommended.

To the problem of joint soil moisture and groundwater analysis in basin response studies

Abstract: The integrated response of a river basin on precipitation event is highly dependent on the spatial distribution of soil moisture content and groundwater levels in the basin. A statistical approach for the description of these distributions and their interrelationships is presented. In Swedish moraines groundwaters are very near to the land surface. Soil moisture content is therefore highly controlled by the position of the groundwater level. This dependence is described by means of conditional distributions. The spatial distribution of soil moisture content and groundwater levels have been related to geomorphological units in the basin. The statistical moisture conditions characteristics of these units proved to be different within a basin but were the same for the same units of different basins with similar physiographic conditions. The suggested approach can be used to describe the integrated runoff response in a river basin.

Les apports de la connaissance des sols intertropicaux au developpement de la pedologie: La contribution des pedologues francais

Abstract: Depuis maintenant pres de 40 ans, des equipes de recherches francaises, principalement de l'ORSTOM mais aussi d'autres institutions tel l'IRAT, etudient les sols, et leur mise en valeur, des regions intertropicales. Plusieurs groupes, du CNRS, de l'INRA, de diverses Universites, ont apporte leur appui a ces equipes qui ont principalement travaille en Afrique et en Amerique Latine, mais aussi dans quelques pays d'Asie et du Pacifique. Ces etudes concernent maintenant plus de 10 millions de km2. Mais plus encore que les surfaces couvertes, ce qu'il faut surtout souligner c'est que ces etudes ont ete menees, sur le terrain, a des echelles tres variees, depuis le 1/500 000eme jusqu'a des echelles tres fines (1/1000eme par exemple) et qu'elles ont ete, progressivement, de plus en plus souvent accompagnees d'observations et de mesures detaillees concernant: les constituants, les organisations microscopiques, les proprietes physico-chimiques, les regimes hydriques etc. … De plus, beaucoup de ces etudes ont ete menees en relations etroites avec des geologues, des geochimistes, des geomorphologues, des hydrologues, des ecologistes, des agronomes …, mais aussi avec des economistes, des sociologues, des ethnologues, … toutes ces collaborations ayant permis de mieux cerner les relations qui existent entre les couvertures pedologiques et leur environnement physique, biologique, humain. Tout au cours de ces 40 annees de travail a travers le monde, les quelques centaines de pedologues francais intertropicaux ont eu bien sur a s'interroger en permanence sur les demarches et sur les methodes: - pour l'etude des sols, - pour l'application de ces etudes, - pour le transfert, d'une region a l'autre, des connaissances acquises. Ils ont ainsi participe a tous les grands debats internationaux concernant: - les methodes d'observations, de mesure, de representation cartographique, des sols et de leurs caracteres; - les classifications pedologiques; - les demarches pour les cartes thematiques; - etc. … Aujourd'hui, il est important de faire le point: 40 annees de pedologie intertropicale nous ont beaucoup appris, ont beaucoup fait evoluer nos concepts, notre vision du sol, nos methodes d'approche et de raisonnement. En quoi tout ceci a-t-il irrigue la pedologie? En quoi les specificites du monde tropical, les voies methodologiques que ces specificites nous ont amenes a decouvrir et a suivre, modifient-elles la comprehension que l'on peut avoir aujourd'hui du sol, de son evolution, des voies a privilegier pour son etude et pour son utilisation? Sans vouloir etre exhaustif, c'est cette evaluation que je propose de faire ici, a grands traits. Mais d'abord, que sont les specificites du monde intertropical, en tous les cas celui ou les pedologues francais ont principalement travaille.