inductively mapping expert derived soil landscape units within dambo wetland catenae using multispectral and topographic data abstract constructing a cost effective and detailed digital soil map of africa will require the extensive utilization of both legacy soil data and legacy soil landscape knowledge which in africa is primarily available from reconnaissance scale catena or association maps and related studies we evaluated a hybrid approach for disaggregating reconnaissance scale soil maps rapid and inexpensive delineation of representative soil landscape units in the field using expert knowledge followed by the use of inductive empirical and correlative modeling techniques to map these landscape units our 2214 km 2 study area located in central uganda consisted predominantly of catenae that terminate in seasonal valley floor wetlands called dambos a type of landscape that can be found throughout the african continent for model training and validation we identified four landscape classes in the field using published expert knowledge well drained uplands red soils sloping dambo wetland margins gradient 2 frequently inundated dambo bottoms hummocky microtopography and flat dambo floors default using binary decision trees bdt with multispectral and topographic remote sensing covariates we created a 20 m resolution map of these four classes multispectral inputs included reflectance values vegetation indices and spectral mixture modeling fractions from systeme pour l observacion de la terre spot 4 satellite images acquired in december 2006 and february 2007 topographic inputs consisted of a digital elevation model dem from shuttle radar topography mission srtm data slope and 20 relative elevation layers calculated using moving windows of various sizes decision rules were based upon the following input variables the normalized difference vegetation index ndvi the normalized difference infrared index ndii the shortwave infrared swir reflectance northing slope and two relative elevation layers the overall classification accuracy of 75 5 and kappa coefficient of 0 67 suggest that a combination of multispectral topographic and spatial data may be used to reliably classify landscape classes for dambo terminated catenae at 59 of the 2214 km 2 study area the upland class was by far the most abundant with margins at 21 floors at 12 and bottoms at 8 a statistical analysis of soil property data from a small catchment located within the study area showed significant class differences in soil texture color organic carbon soc base saturation ph effective cation exchange capacity ecec and clay mineralogy though detailed soil maps are rare in africa reconnaissance soil maps can be inexpensively disaggregated to provide a valuable starting point for digital soil mapping

a rudimentary mechanistic model for soil production and landscape development a rudimentary mechanistic model for soil production and landscape development is proposed the continuity equation of the model assumes that the change in soil thickness over time depends on the production of soil from the weathering of bedrock and the transport of soil through natural surface erosion the parameters for the model include the weathering rate and erosive diffusivity weathering rate is expressed as an exponential decay function of soil thickness which represents mechanical weathering erosive diffusivity can be estimated from soil erosion models the model is solved numerically using the finite difference approach and is applied to a numerical example simulation is performed for a hypothetical landscape with a series of hills and valleys results show the development rate of soil initially is very large and slows down until it reaches a steady state defined by a constant change in soil thickness the model also exhibits the characteristics of a nonlinear dynamic system nonlinearity of soil thickness and curvature and initial randomness appears to cause chaos instability in the system the results show promising progress in quantitative modelling of pedogenesis the limitations and suggested improvements of the model are also presented

soils slopes and source rocks application of a soil chemistry model to nutrient delivery to rift lakes abstract the topographic evolution of rift basins may be critical to the deposition of lacustrine source rocks such as the organic rich lower cretaceous shales of the south atlantic margin soils have been proposed as a key link between topography and source rock deposition by providing nutrients for the algae growth in rift lakes decreasing topographic relief from active rift to late rift has several effects on soils soils become thicker and finer erosion of dead surface and soil organic matter decreases and the fractionation of precipitation between runoff and infiltration may favor increased infiltration this hypothesis is tested by application of century a complex box model that simulates transfer of nutrients within soil pools the model is first applied to a rainforest soil with several parameters individually varied infiltration experiments show that the concentrations of c n and p in groundwater decrease rapidly as infiltration decreases whether due to increased slope or to decreased precipitation increased erosion of surface plant litter and topsoil results in substantially decreased nutrient concentrations in groundwater increased sand content in soil causes an increase in nutrient concentration we integrate these variables in analyzing topographic swathes from the rio grande rift comparing the southern part of the rift where topography is relatively old and reduced to the northern rift c and p concentrations in groundwater increase as slope gradient decreases resulting in substantially larger c and p concentrations in groundwater in the southern rift than the northern rift nitrogen concentrations in groundwater depends on whether infiltration varies as a function of slope gradient in experiments where the fraction of infiltrated precipitation decreased with increasing slope n concentrations was also substantially higher in the southern rift but in experiments where that fraction was held constant n concentrations was lower in the southern rift these simulations demonstrate that evolving topography during rift development can significantly influence nutrient concentrations in groundwater and if these nutrients flow into rift lakes and stimulate organic productivity account for the deposition of rich oil prone source rocks in late rift stages

robust geochemical indices for redox and weathering on a granitic laterite landscape in central uganda abstract most geochemical studies of laterite formation have been based on detailed examinations of a small number of hopefully representative profiles due to spatial variability in bedrock composition and geomorphic processes that sort materials by size density and other properties experimental designs developed for the geochemical analysis of single soil profiles are of limited use in landscape investigations in this study of a laterite landscape on a granitic rock in uganda we used element concentrations from neutron activation analysis naa to develop a suite of robust geochemical indices for landscape scale analysis of weathering and oxidation reduction redox processes in laterite formation to capture k feldspar weathering the k hf ratio served as a good proxy for feldspar zircon mineral ratios while k na ratios indexed feldspar concentration to quartz using principal components analysis we derived an index of rare earth elements ree leaching relative to th and an index of heavy to light ree hree lree fractionation we used the fe sc ratio to ascertain the absolute redox vs relative weathering fe accumulation in laterite formation with absolute fe accumulation also associated with lower fe as ratios mn ce ba nodules and concretions were identified by characteristically high ce values with individual ce values as high as 5000 g g 1 the relatively large amounts of k feldspar k avg is 4000 g g 1 and low degree of hree lree fractionation suggest that this landscape is weathered less than generally assumed the fe and mn derived indices highlight the important role of oxidation reduction processes in iron accumulation overall our findings suggest that the current ferricrete mantled hilltops were formerly located on a lower poorly drained part of the landscape

terrain attributes and spatial distribution of soil mineralogical attributes abstract in soil studies there is an increasing tendency to quantify heterogeneous soil attributes by georeferencing leading to the pedometry in this context terrain attributes play important role for the characterization of distinct surfaces under different pedogenetic processes the soil mineralogical assembly expresses factors and pedogenetic processes involved in soil formation that affect their physical and chemical characteristics this work objective was to investigate the spatial distribution of soil mineralogical attributes using topographic terrain attributes as tools for the characterization of high or low mineral content environments and their relationships with soil chemical characteristics this study was carried out in the canguiri experiment station of the federal university of parana at curitiba state of parana brazil soil sampling in the studied area was collected in a regular grid of 135 points the clay fraction after dithionite citrate bicarbonate dcb extraction was analyzed to determine kaolinite ka and gibbsite gb concentrations by thermogravimetry tg and their respective dehydroxylation temperature peaks such mineral crystallographic attributes were determined by x ray diffraction xrd high amorphous al contents tended to be related to higher organic carbon oc values in which areas the terrain attributes indicated smooth relief and predominance of pedimentation processes the terrain attributes differentiated areas with higher ka ka gb ratios that is with higher ka values located near drainage channels and with silica accumulation meanwhile areas with higher proportion of gb were found on flat summit the mineralogical attributes studied in this work influenced some soil chemical characteristics satisfactory results were obtained with the use of topographic terrain attributes to characterize distinct surfaces since they were related to some of the mineralogical attributes formation

a rudimentary mechanistic model for soil formation and landscape development ii a two dimensional model incorporating chemical weathering the necessity for a quantitative analysis of pedogenesis has become more compelling in the last few decades in part one of this paper we proposed a rudimentary mechanistic model that considers soil formation spatially at the catena scale this paper extends the model for soil formation in a landscape conditioned by a digital elevation model and further illustrates the application of the model in quantifying pedogenesis the current model states that the change in soil thickness over time depends on the physical weathering rate of rock the loss due to chemical weathering and the transport of soil through erosion the rate of physical weathering or lowering of the bedrock surface is represented as an exponential decline with soil thickness the chemical weathering rate is modelled as a negative exponential function of both soil thickness and time assuming uni dimensional weathering the rate of chemical weathering can be expressed as a reduction in soil thickness the movement of materials in the landscape is characterized by diffusive transport the model is solved numerically using the finite difference approach and applied to a digital elevation model the results for simulation of soil formation in a landscape after 10 000 years shows that the soil accumulates thickens in the gullies and erodes thins in the ridges the soil from the upper slope is transported down slope by the erosion processes and fills the gullies soil thickness is highly correlated with the profile curvature the effect of climate rock type and land management is illustrated by different combinations of weathering rate and erosive diffusivity to illustrate the effect of irregularity and randomness on the stability of the solution and the soil development spatially correlated normally distributed random numbers were added to the initial soil elevation the small randomness appears to cause instability chaos in the system dimensionality analysis of the soil thickness as a function of time confirms the non linear chaotic behaviour of the model rather than merely random noise a difference plot of the soil thickness time series unveiled the presence of a strange attractor alternatively these results may be a result of numerical instability

slope gradient and aspect effects on soils developed from sandstone in pennsylvania abstract this study was initiated to determine the basic characteristics and genesis of soils on gentle to very steep slopes on two contrasting slope aspects two transects a southwest sw and a northwest nw transect were laid out on a sandstone ridge across the summit and steepest convex shoulder positions the thickness of the o a and e horizons was not related to slope gradient across soils on all slope gradients and aspects this indicates that the present rate of soil formation is greater than erosion the influence of erosion on steep slopes could be off set by lateral movement of through flow water above the b horizon or the process of tree throw masks slope gradient effects solum depth b horizon thickness clay fe and al indexes decreased with increasing slope for both the nw and sw aspects organic carbon index decreased with increasing slope for the sw aspect decreases in effective precipitation over relatively larger surface areas at steep versus lower slope gradients a longer influence of periglacial erosion following the wisconsinan glacial advance and present slow but significant soil creep could cause these differences in soil development across the slope solum depth b horizon thickness clay fe and al indexes showed a smaller decrease across the nw compared to the sw slope organic carbon did not decrease across the nw slope the e horizon was also slightly thicker on the nw compared to the sw slope these aspect differences were probably caused by less evaporation on shaded nw compared to sunny sw slopes which produce generally higher moisture levels and more effective eluviation and illuviation on the nw slope

digital terrain modelling a review of hydrological geomorphological and biological applications the topography of a catchment has a major impact on the hydrological geomorphological and biological processes active in the landscape the spatial distribution of topographic attributes can often be used as an indirect measure of the spatial variability of these processes and allows them to be mapped using relatively simple techniques many geographic information systems are being developed that store topographic information as the primary data for analysing water resource and biological problems furthermore topography can be used to develop more physically realistic structures for hydrologic and water quality models that directly account for the impact of topography on the hydrology digital elevation models are the primary data used in the analysis of catchment topography we describe elevation data sources digital elevation model structures and the analysis of digital elevation data for hydrological geomorphological and biological applications some hydrologic models that make use of digital representations of topography are also considered

a sediment transport model for incision of gullies on steep topography 1 we have conducted surveys of gullies that developed in a small steep watershed in the idaho batholith after a severe wildfire followed by intense precipitation we measured gully length and cross sections to estimate the volumes of sediment loss due to gully formation these volume estimates are assumed to provide an estimate of sediment transport capacity at each survey cross section from the single gully forming thunderstorm sediment transport models commonly relate transport capacity to overland flow shear stress which is related to runoff rate slope and drainage area we have estimated the runoff rate and duration associated with the gully forming event and used the sediment volume measurements to calibrate a general physically based sediment transport equation in this steep high shear stress environment we find that a shear stress exponent of 3 corresponding to drainage area and slope exponents of m 2 1 and n 2 25 match our data this shear stress exponent of 3 is approximately 2 times higher than those for bed load transport in alluvial rivers but is in the range of shear stress exponents derived from flume experiments on steep slopes and with total load equations the concavity index of the gully profiles obtained theoretically from the area and slope exponents of the sediment transport equation c m 1 n agrees well with the observed profile concavity of the gullies our results although preliminary because of the uncertainty associated with the sediment volume estimates suggest that for steep hillslopes such as those in our study area a greater nonlinearity in the sediment transport function exists than that assumed in some existing hillslope erosion models which calculate sediment transport capacity using the bed load equations developed for rivers

geochemical differences in an oxisol spodosol toposequence of amazonia brazil the morphology and geochemical characteristics of the soils of a toposequence near manaus brazil have been determined such toposequences occur on slopes leading down into valleys cut in a nearly level plateau oxisols form the upper and spodosols the lower members of toposequences the transition from the oxisols down the slope through a band of ultisols to the spodosols is very gradual lowest members of the toposequences spodosols do not occupy the valley floors great contrasts as well as shared characteristics occur among members of the toposequence chosen for study proportions of clay in the oxisols are 80 90 as contrasted to 2 5 in the spodosols changes in amounts of clay are gradual continuing down the slope the clay fraction is kaolinitic all soils are strongly acid and have very low base saturation the characteristics of the soils imply that several processes of weathering and pedogenesis have been operative the small amount of sio2 in the oxisols is attributed to dissolution of quartz without corresponding hydrolysis of kaolinite the decreases in clay contents and increases in quartz in the soils from the upper to the lower end of the toposequence are attributed to a combination of hydrolytic weathering and either or both of clay eluviation and selective erosion of that fraction the sequence of soils within the toposequences further suggests that a podzolization process begins when a critical stage in impoverishment is reached destruction of clay minerals continues but the migration of organo mineral complexes within profiles becomes important a part of those complexes moves out of the spodosols to form black waters in the streams

statistical geochemical and morphological analyses of stone line formation in uganda abstract the resolution of conflicting fluvial allochthonic erosion and deposition and bioturbation autochthonic faunal turbation theories of stone line formation has important implications for tropical geomorphology with the former indicating dynamic punctuated landscape development and the latter implying relative landscape stability with ongoing moderate erosion on a gentle hill in central uganda we quantitatively characterized and statistically modeled gravel distributions for 93 profiles elemental analysis of k selected rare earth elements ree and appropriate index elements were employed to test for compositional differences between soils above and saprolite below hilltop stone lines we also excavated and carefully described four indicative profiles the results of this study were difficult to reconcile with the bioturbation theory of stone line formation important findings included i the lack of a consistent gravel free biomantle with a weak connection between biomantle thickness and stone line depth ii highly variable stone line depth with a strong inverse relationship between stone line depth and maximum gravel content iii unweathered and rounded cobbles in a stone line over saprolite with angular highly weathered quartz and iv a statistically significant geochemical difference between soils and saprolites with evidence of a less weathered surface mantle over more weathered saprolite these findings indicated a sedimentary origin for soils at this site even for what is presently a flat geomorphically isolated hilltop evidence from this study and previous work on the geochemistry of this site geochim cosmochim acta 67 2003 2711 suggests that the contemporary hilltop once occupied a lower landscape position

the initiation and growth of gullies in madagascar are humans to blame abstract lavaka madagascar s unusual gullies require thick lateritic regolith on smoothly convex hills and they are initiated locally by a variety of cultural and natural proximate causes such as paths roads defensive trenches around hillforts steep fields unchanneled to slightly concentrated storm run off springs mass movements etc growth continues by rain attack incision by run off earthfalls caused by wetting and drying cycles and especially basal sapping by diffuse groundwater flow above bedrock somewhat in that order lavaka are less directly permitted and promoted by 1 hardening of exposed laterite surfaces which creates a hard soft hard profile from bedrock to laterite which favors incision relative to lateral erosion 2 the superimposition of concave run off profiles onto convex hills and locally 3 re equilibration of watersheds after stream piracy and faulting run off and hardening are interrelated with devegetation because hardening results from exposure following devegetation because both hardening and devegetation increase run off relative to infiltration and because hardening rain attack and run off impede vegetation devegetation is certainly worsened by harmful human activities such as range burning forest cutting and or overgrazing but tectonism and natural climatic aridification are probably ultimately more important given that many lavaka are simply a natural part of the landscape s evolution and that some lavaka clearly predate primary uncut rain forest

loess accumulation during the last glacial maximum evidence from urluia southeastern romania abstract the eastern european loess steppe represents one of the most substantial landform types on the continent yet the impact on this region of the last glacial maximum lgm the coldest climatic episode during the last full glacial cycle is relatively poorly understood this is in part due to the comparatively small number of sites which have been reliably dated and in part due to the need to better elucidate depositional models for loess environments at both local and regional scales here we present a high frequency age depth profile for the last 40 ky from a loess deposit at urluia in southeastern romania using fine grained quartz optically stimulated luminescence osl dating and environmental magnetism analyses loess accumulation at the site for this period is well constrained by a clearly identifiable tephra deposit corresponding to the ca 39 ka campanian ignimbrite we show that the tephra is directly overlain by a relatively thin layer of loess corresponding to marine isotope stage mis 3 which is partially overprinted by a weakly developed paleosol the sequence is dominated by a 6 8 m package of primary loess of lgm age the eight osl samples from this package group together around a mean age of 21 6 1 5 ka and suggest rapid and substantial deposition during this phase the uppermost part of the section indicates significantly reduced loess accumulation during the deglacial period into the holocene less than 2 m in total thickness the rapid accumulation of loess during the lgm at urluia is consistent with increased sedimentation at other loess profiles in the lower danube basin although the variable thickness of these deposits across the catchment highlights the need to more explicitly investigate depositional models for loess the urluia record complements emerging data which suggests that the lower danube loess steppe was cold dry and windy during the lgm yet experienced milder climates than comparable latitudes further west and north and did not undergo periglacial activity

initiation and evolution of gullies along the shoreline of lake huron over one hundred gullies are deeply incised into algonquin bluff along the eastern shoreline of lake huron aerial photographs between 1930 and 1992 were used to measure temporal changes in area and length of a sample of forty four gullies regression analysis shows that gully area and length have increased in a linear fashion and that gully initiation occurred in the nineteenth century gully initiation coincides with deforestation and settlement of the area surface drainage was redirected into drainage ditches concentrating the flow and enhancing gully erosion natural processes associated with climatic fluctuations are probably insufficient to cause gully initiation but may contribute to ongoing gully expansion

spatial delineation of organic carbon rich colluvial soils in chernozem regions by terrain analysis and fuzzy classification abstract colluvial soils are considered to be the direct result of accelerated soil erosion resulting in accumulation of humus rich soil material in terrain depressions and base parts of slopes the organic carbon concentration in these soils and their depth make them an important organic carbon storage mapping the colluvial soils therefore represents an important contribution in total carbon stock estimation a method of delineating colluvial soils is proposed by applying a combination of high resolution digital elevation model analysis and detailed field survey two models based on fuzzy classification of soil units were created using different topographic derivatives as the only input parameters to predict the colluvial soil area on a morphologically diverse study site in the southern moravia czech republic the model that considers only the derivatives with a strong relationship to colluvial soil occurrence reached 71 accuracy in colluvial area delineation while the model combining six commonly used derivatives showed less favorable results the main advantage of the method lies in a low demand of input soil data and its relatively high accuracy

response of alluvial rivers to slow active tectonic movement alluvial rivers respond to valley slope deformation caused by active tectonics in various ways depending on the rate and amount of surficial deformation and on the type of river on the basis of experimental results and field examples hypothetical models of river response to anticlinal uplift and synclinal subsidence were developed for different types of alluvial rivers an experimental braided channel responded to anticlinal uplift across the channel with degradation and terrace formation in the central part of the uplift with subsidence aggradation in the central reach was the main response transverse bars developed downstream of the subsidence axis an experimental meandering channel responded to slope steepening with a sinuosity increase bank erosion and point bar growth occurred downstream of the anticlinal axis and upstream of the synclinal axis upstream of the uplift axis and downstream of the subsidence axis where the slope was flattened water flooded over bars local convexity in longitudinal profiles of the middle rio grande new mexico is considered to be formed by a domal uplift local aggradation and degradation could be explained by the effect of uplift the san joaquin river california which is now highly controlled does not show clear adjustment to the rapid subsidence due to ground water withdrawal it shows however a channel pattern adjustment to active tectonic subsidence that has been occurring for a long time the san antonio and guadalupe rivers in texas both increase their sinuosity significantly where monoclinal movements steepen valley slopes

elucidation of soil landform interrelationships by canonical ordination analysis abstract this paper examines the robustness of various multivariate ordination methods applied to elucidate the relationship between soil developed on hillslope and the environment in a south australian subcatchment canonical correspondence analyses were found to be less attractive than the linear methods i e principal component analysis and redundancy analysis because interrelations among soil variables and or between soil and the landform attributes are more linear than unimodal among the linear methods standard redundancy analysis following transformation of soil data gave a clearer insight into pedogenetic implications of soil landform interactions gradient angle plan convexity profile convexity and to a lesser extent upslope distance and area account for much of the soil variation in the study area gradient influences the distribution of surficial soil particles which is suggestive of selective removal and deposition of fine materials on the mid to lower slopes higher subsoil clay percentage associated with concave slopes may be ascribed to either increased weathering rate and or flux of fine material due to convergence of water flows solum depth and depth to bedrock also appeared to have controlled some of the contemporary pedo geomorphological processes eluvio illuvial processes are more pronounced in the relatively deep lower slope pedons evidenced by cutans in their subsoil layers soil colours are related to the soil depth attributes slope and upslope distance and area probably through the influence of these attributes on soil drainage condition the extent to which landform and parent material related attributes e g depth to bedrock affect soil development and distribution patterns in the study area is shown quantitatively these findings have considerably improved our understanding of soil genesis in the study area and also point to the importance of land unit delineation to design sampling patterns the enhanced sampling design would be beneficial in terms of reduced extrapolation error and thus misclassification of soil

development of longitudinal profiles of alluvial channels in response to base level lowering degradation of alluvial channels in cohesive sediments was studied in 15 m and 20 m long flumes with a slope of 0 01 cm cm degradation was initiated by lowering base level to a fixed position and the development of the longitudinal profile of the channel is analysed through a model formulated as a heat diffusion equation it is based on the equation of sediment continuity combined with an assumption regarding sediment transport namely that sediment discharge is linearly proportional to the channel slope in accordance with the boundary and initial conditions imposed by the experimental setup and procedure the basic equation is amenable to an analytical solution which defines bed elevation at any distance and time as a function of the amount of base level lowering and a diffusion coefficient additional problems arising from bank erosion and channel armouring are also treated successfully within the framework of the same model the results show that in homogeneous alluvial sediments not subject to armouring the ultimate result of base level lowering by a certain amount is degradation all along the channel by the same amount the main impact of erosion is felt in the early stages after initiation of the process and mainly near the mouth the rate of degradation at any station along the channel reaches a peak and then slowly decreases with time and the peak rate is attenuated with distance from the outlet the model permits the prediction of intermediate stages of profile development at any distance from the outlet and at different times

medium term gully headcut retreat rates in southeast spain determined from aerial photographs and ground measurements this paper deals with gully retreat rates at different time scales whereby the short term time scale may span a time interval of 1 5 years the medium term time scale a time interval of 5 50 years and the long term time scale a time interval of more than 50 years an analysis of high altitude aerial photographs in combination with ground measurements allowed us to quantify volumetric gully head retreat rates for 12 permanent gullies in southeast spain guadalentin and guadix study areas over a 40 43 year time interval medium term time scale this resulted in an average retreat rate ve of 17 4 m3 year 1 a power relationship between drainage basin area a and medium term volumetric gully head retreat rate ve 0 069a0 380 r2 0 51 n 21 was found by combining the gully head retreat rates obtained in this study with those obtained by a dendrochronological method the exponent b and the coefficient of determination r2 of the power relationships ve aab increases from the short term to the long term time scale expressing the increasing importance of drainage basin area in gully development with time considerable differences between gully head retreat rates measured at the short and medium term time scales at individual gullies showed the importance of land use changes and unsuccessful management practices on gully head retreat and the episodic nature of gully head retreat when piping and tension cracking are involved higher gully head retreat rates are obtained at the medium term time scale compared to the short term time scale but the differences are not significantly different at 10 the medium term methods tend to measure proportionally more high gully retreat rates but less extreme values compared to the short term method this is explained by a more equal distribution of extreme rainfall events both in space and time at a longer term time scale and hence a higher probability of measuring the average effect of both small and extreme rainfall events at each gully

potential terrain controls on soil color texture contrast and grain size deposition for the original catena landscape in uganda abstract inspired by the catena concept we returned to the landscape of origin for this idea in central uganda and applied quantitative soil landscape modeling techniques to the study of soil formation in particular we employed generalized least squares gls regression to identify potential terrain and other controls on surface texture with the goal of explaining texture contrast formation for well drained red soils and fluvial deposition for yellow gray lowland soils well drained red soils and poorly drained yellow gray soils were identified using a high resolution spectroradiometer and soil redness was highly correlated with a measure of elevation above the valley floor for the yellow gray soils sand content and sand grain size increased with greater slope gradient and in converging areas evidence supporting fluvial control of surface soil composition for red soils texture contrast increased on lower backslopes decreased over ferricrete rich parent material and had no significant association with either infiltration or runoff influenced locations surprisingly texture contrast was also reduced or even inverted on fine scale convexities

ground temperature histories in eastern and central canada from geothermal measurements evidence of climatic change abstract inverse and direct methods have been used to analyze a large number of borehole temperature logs in order to infer past climatic changes results indicate a warming of 1 2 c in eastern and central canada during the past 150 years a period of cooling between 500 and 200 years before present corresponding to the time of the little ice age has also been identified in the same areas a regional ground temperature history is estimated for eastern and central canada from the simultaneous inversion of several temperature logs the inferred temperature changes appear correlated with the concentration of atmospheric carbon dioxide as reported from a greenland ice core and agree with existing meteorological and dendrochronological records for the area