on using the effective contact angle and the water drop penetration time for classification of water repellency in dune soils sandy soils are often water repellent when dry in sloping areas this may result in surface runoff and erosion water repellency in soils can be classified with the solid liquid contact angle which is difficult to determine another method is the water drop penetration time this method is not only easier to apply but provides a more useful scale for classifying water repellent soils moreover it is directly related to erosion hazard because runoff depends on the time required for the infiltration of rain drops a close relationship was found between the contact angle and the water drop penetration time in dune soils along the coast of the netherlands

enhanced riverine carbon flux from carbonate catchment to the ocean a comparative hydrogeochemical study on ishigaki and iriomote islands southwestern japan 1 riverine carbon transportation is an important carbon flux connecting reservoirs of the atmosphere continents and oceans the flux is strongly related to the important roles of rivers such as regulation of climate change and buffering of ocean acidification here to evaluate the linkage of such functions of rivers and geological characteristics of the watersheds we present the results of a comparative hydrogeochemical study conducted on small subtropical watersheds of aluminosilicate dominated iriomote island and carbonate based ishigaki island southwestern japan rivers on ishigaki island exhibited much higher alkalinity than rivers on iriomote island which was even higher than the mean value of major rivers in the world such as the saint lawrence and the mississippi this high alkalinity was the result of carbonate dissolution enhanced by soil originated co2 as a result of this high inorganic carbon input the ratio of inorganic carbon and nutrients of the river water was higher than that of marine organic matter such as the redfield ratio making the coastal seas a potential source of co2 for the atmosphere

ancient runoff farming and soil aggradation in terraced wadi fields negev israel obliteration of sedimentary strata by ants scorpions and humans abstract ancient terraced fields in ephemeral stream valleys in the negev desert enabled farming based on runoff water from local rainfall the runoff was captured by stone terrace walls which were built across suitable wadis in various archaeological periods runoff floods added not only water to the fields but also fine sediment however alluvial stratification is usually absent in such terraced wadi fields why we addressed this question at the rural archaeological site of horvat haluqim in the central negev highlands our geoarchaeological excavations in area 3 of terraced field 12 revealed the existence of laminar alluvial stratification but only in the upper 5 cm micromorphology showed a gradual decline in the preservation of laminae with depth radiocarbon dating showed that the upper 50 cm of the terrace soil accumulated during the past 1300 years therefore the average aggradation rate seems about 0 4 mm year similar to modern sedimentation measurements we found evidence for bioturbation particularly by ants and scorpions in the terraced wadi fields at horvat haluqim scorpions evict the soil crumbs excavated from the subsoil on one side of the crescent shaped entrance to their burrows ants on the other hand place the excavated soil crumbs all around the entrance to their underground nest besides bioturbation human soil disturbance by farming is far more destructive to alluvial stratification hoeing and ploughing tillage can erase alluvial laminae from the surface to a depth of about 10 cm in one farming season clear evidence of ancient farming activities in area 3 was found in darker soil layers from a depth of 45 cm 92 cm laminar alluvial strata have not survived in these layers micromorphology revealed fine charcoal bone and pottery fragments interpreted as kitchen household refuse added as fertilizer to the aggrading soil surface in addition non burned dung fragments and non charred spherulites were found indicating also the use of animal dung as manure darker soil layers have a lower bulk density and a high porosity with an extremely large amount of fine pores probably ancient root channels of barley or wheat though runoff flows kept adding laminated alluvial layers to the aggrading terraced wadi fields the fine laminae initial facies did not endure the tooth of time they were gradually obliterated by bioturbation and or rapidly erased by human farming activities tillage and manuring so that laminae are non existent in the ultimate facies of the aggrading sediment soil in agricultural terraced wadi fields

development of partial rock veneers by root throw in a subalpine setting rock veneers stabilize hillslope surfaces occur especially in areas of immature soil and form through a variety of process sets that includes root throw near westcliffe colorado usa data were collected from a 20 500 m transect on the east slope of the sangre de cristo mountains ages of pit mound complexes with rock fragments exposed at the surface by root throw ranged from recent freshly toppled tree to unknown complete tree decay calculations based on dimensions of the pit mound complexes estimated time of tree toppling sizes of exposed rock fragments and percentage rock covers at pit mound complexes as well as within the transect area indicate that recent rates of root throw have resulted in only partial rock veneering since late pleistocene deglaciation weathering of rock fragments prevents development of an extensive rock veneer and causes a balance achieved within an estimated 700 years between the rates of rock fragment exposure by root throw and clast disintegration by chemical reduction the estimated rate of rock fragment reduction accounts for part of the fluvial sediment yields observed for forested subalpine areas of western north america copyright 2005 john wiley sons ltd

relationships between climate and soil hydrological and erosional characteristics along climatic gradients in mediterranean limestone areas an investigation was undertaken to determine the relationships between climate and soil hydrological and erosional characteristics rainfall simulation experiments were carried out along three climatological gradients on similar limestone lithologies in the mediterranean region standard experiments were used to characterize each site so that an objective comparison could be made at each of the eleven south facing slopes three experiments were carried out a total of 33 plots were selected for the experiments located in the galilee and carmel mountains israel crete greece and alicante spain simulated rainfall was used in order to measure time to ponding and runoff steady state infiltration rate runoff coefficient runoff sediment concentration and the erosion rate at each of the 33 selected plots the mean annual rainfall is not directly correlated with soil erodibility infiltration and runoff the effect of climate on geomorphological processes does not have a great impact on runoff and infiltration at pedon scale during the wet seasons studied the local thunderstorms discourage any kind of soil moisture trends along the climatic gradients and thus on hydrological processes human impacts mainly grazing and fires seem to be the most relevant factors for soil hydrological and erosional response in the mediterranean region

distribution of marine organisms and its geological significance in the modern reef complex of the ryukyu islands abstract extensive investigations of biota in the reef complex around the ryukyu islands have revealed ecologic specificity of many benthic organisms and have shown that characteristic assemblages are found in each of the topographic zones and sub areas the moat is divisible into a nearshore seagrass bed and an offshore sand bottom both inner reef flat and outer reef flat are characterized by abundant occurrences of hermatypic corals and nonarticulated coralline algae however the former is dominated by branching and foliaceous forms of corals and various large fleshy erect forms of algae whereas the latter is dominated by encrusting and tabular forms of corals lacking these algae corals and coralline algae are not present on the reef crest which is covered by rubble and gravel where algal turf and sargassum are spreading encrusting and tabular forms of corals flourish on the shallower part of the reef slope with high coverage while with increasing depth the coverage decreases and the dominating coral forms change with hemispherical and encrusting forms on the middle part of reef slope and foliaceous and encrusting forms on the deeper part of reef slope nonarticulated coralline algae are distributed throughout the reef slope the composition of coral and coralline algal assemblages changes dramatically with increasing depth foraminiferal algal nodules rhodoliths are the most abundant constituent on the island shelf commonly with cycloclypeus carpenteri there are likely to be two types of shelves in tropical to subtropical regions nutrient rich halimeda dominant and nutrient poor rhodolith dominant sediments abundant in bryozoan skeletons occur occasionally on the shelf

modeling the tor dotted crests bedrock edges and parabolic profiles of high alpine surfaces of the wind river range wyoming abstract broad low curvature surfaces common to many alpine landscapes and particularly well expressed in the laramide ranges of the western usa appear to be roughly in steady state with respect to the current surface processes uniform thin order 1 m regolith covers the crystalline bedrock with the exception of occasional tors at ridgecrests the surfaces are commonly edged by bedrock lips at the tops of cliffs that bound the intervening glacial troughs regolith production is low order 10 m year on bare bedrock and reaches a maximum under tens of centimeters of regolith all of these characteristics may be accounted for with a numerical model that is faithful to the periglacial surface processes presently operating on these surfaces hillslope transport is modeled assuming the dominant process is frost creep transport efficiency depends linearly upon local slope and appropriately vanishes in the absence of regolith frost frequency scales the rate of motion while the ratio of frost penetration depth to regolith thickness dictates the degree to which the process is curtailed by available regolith initial conditions include initial mean slope and bedrock roughness and a uniform regolith cover boundary conditions are imposed by dictating that the edges of the calculation space be lowered at a rate appropriate for glacial incision broad convex surfaces emerge over time scales of order 1 million years all surfaces rapidly decouple from the bounding glacial troughs as the high negative curvature at the edges disallows accumulation of regolith these bedrock edges lower at a few microns per year while the troughs lower at many times this rate as the bedrock edges therefore serve as the effective boundary condition for the remaining surface the surfaces operate independently of both lowering and widening of the glacial troughs for a reasonable set of transport and weathering rates the final steady state landscape is sensitive to the initial condition in particular the steeper the initial landscape the more likely tors are to develop as the high curvature disallows accumulation of regolith these tors in turn limit the lowering rate of the crest and the landscape retains significant local relief low relief initial conditions more likely lead to parabolic surfaces that lack tors that tors are more likely on the crests reflects the high initial curvature at the crest tors on the side slopes are eliminated the present high surfaces in the laramide ranges of the western usa imply operation of periglacial surface processes over millions of years the occasional tors imply a steeper rather than flatter initial landscape the strong decoupling of surfaces from glacial troughs justifies their use as local geomorphic markers that allow calculation of relief production since glacial incision was initiated on the other hand their present low curvature does not require a landscape history in which these surfaces were once joined as an initially widespread erosion surface

a weathering intensity index for the australian continent using airborne gamma ray spectrometry and digital terrain analysis abstract weathering intensity largely controls the degree to which primary minerals are altered to secondary components including clay minerals and oxides as weathering intensity increases there are changes in the hydrological geochemical and geophysical characteristics of the regolith thus once calibrated weathering intensity can be used to predict a range of regolith properties a weathering intensity index wii over the australian continent has been developed at a 100 m resolution using regression models based on airborne gamma ray spectrometry imagery and the shuttle radar topography mission srtm elevation data airborne gamma ray spectrometry measures the concentration of three radioelements potassium k thorium th and uranium u at the earth s surface the total gamma ray flux dose is also calculated based on the weighted additions of the three radioelements regolith accounts for over 85 of the australian land area and has a major influence in determining the composition of surface materials and in controlling hydrological and geomorphological processes the weathering intensity prediction is based on the integration of two regression models the first uses relief over landscapes with low gamma ray emissions and the second incorporates radioelement distributions and relief the application of a stepwise forward multiple regression for the second model generated a weathering intensity index equation of wii 6 751 0 851 k 1 319 relief 2 682 th k 2 590 dose the wii has been developed for erosional landscapes but also has the potential to inform on deposition processes and materials the wii correlates well with site based geochemical indices and existing regolith mapping interpretation of the wii from regional to local scales and its application in providing more reliable and spatially explicit information on regolith properties are described

biogeochemical and physical factors influencing seawater ƒco2 and air sea co2 exchange on the bermuda coral reef it is uncertain whether coral reef ecosystems are oceanic sources or sinks of carbon dioxide co2 understanding the complex interactions between biogeochemical and physical processes within reef ecosystems is important for determining the contribution of coral reefs to the global carbon cycle and the air sea flux of co2 the influence of biogeochemical and physical processes on co2 cycling was examined for 1 month at hog reef flat part of the rim reef of bermuda the fugacity of seawater co2 co2 was measured hourly by use of a carbon interface ocean atmosphere buoy providing the longest time series of seawater co2 data on a coral reef ecosystem seawater co2 ranged from 340 to 470 atm with a diurnal variability ranging from 20 60 atm air sea co2 was directed from ocean to atmosphere with a mean flux of 3 3 4 6 mmoles co2 m 2 d 1 the reef data are compared with a seawater co2 time series collected at the u s joint global ocean flux study bermuda atlantic time series study bats site 31 50 n 64 10 w in the sargasso sea surrounding bermuda sargasso sea waters are the original source for bermuda platform water providing a context for understanding the biogeochemical modification of reef water at hog reef flat seawater fco2 at hog reef flat was elevated relative to the sargasso sea by 0 to 120 atm primarily as a result of calcium carbonate production however the ability of the reef to act either as a source or sink of co2 to from the atmosphere largely depended on the air sea co2 disequilibrium of offshore sargasso sea waters impinging on the reef site this study also revealed that an assessment of the fate of co2 on coral reefs is dependent on understanding the reef s physical regime and forcing the dynamics of wind tide platform circulation and fluxes of offshore or onshore waters are necessary context for all coral reef sites

dynamics of carbonate chemistry production and calcification of the florida reef tract 2009 2010 evidence for seasonal dissolution ocean acidification is projected to lower the ar of reefal waters by 0 3 0 4 units by the end of century making it more difficult for calcifying organisms to secrete calcium carbonate while at the same time making the environment more favorable for abiotic and biotic dissolution of the reefal framework there is great interest in being able to project the point in time when coral reefs will cross the tipping point between being net depositional to net erosional in terms of their carbonate budgets periodic in situ assessments of the balance between carbonate production and dissolution that spans seasonal time scales may prove useful in monitoring and formulating projections of the impact of ocean acidification on reefal carbonate production this study represents the first broad scale geochemical survey of the rates of net community production ncp and net community calcification ncc across the florida reef tract frt surveys were performed at approximately quarterly intervals in 2009 2010 across seven onshore offshore transects spanning the upper middle and lower florida keys averaged across the frt the rates of ncp and ncc were positive during the spring summer at 62 7 and 17 2 mmol m 2 d 1 respectively and negative during the fall winter at 33 6 and 7 2 mmol m 2 d 1 the most significant finding of the study was that the northernmost reef is already net erosional 1 1 0 4 kg caco3 m 2 yr 1 and midreefs to the south were net depositional on an annual basis 0 4 0 1 kg caco3 m 2 yr 1 but erosional during the fall and winter only the two southernmost reefs were net depositional year round these results indicate that parts of the frt have already crossed the tipping point for carbonate production and other parts are getting close

fire and the evolution of steep soil mantled landscapes recent burns in the western united states attest to the signif icant geomorphic impact of fire in mountainous landscapes yet we lack the ability to predict and interpret fire related erosion over millennial time scales a diverse set of geomorphic processes is often invoked following fire the magnitude of postfire erosional processes coupled with temporal variations in fire frequency dic tate the extent to which fires affect sediment production and land scape evolution in the oregon coast range several models for long term rates of soil production and transport have been tested and calibrated although treatment of fire related processes has been limited following recent fires in the oregon coast range we observed extensive colluvial transport via dry ravel localized bed rock emergence due to excess transport and talus like accumula tion in adjacent low order valleys soils exhibited extreme but dis continuous hydrophobicity and no evidence for rilling or gullying was observed using a field based data set for fire induced dry rav el transport we calibrated a physically based transport model that indicates that soil flux varies nonlinearly with gradient the post fire critical gradient 1 03 which governs the slope at which flux increases rapidly is lower than the previously estimated long term value 1 27 reflecting the reduction of slope roughness from in cineration of vegetation by using a high resolution topographic data set generated via airborne laser swath mapping we modeled the spatial pattern of postfire and long term erosion rates postfire erosion rates exceed long term rates which average 0 1 mm yr 21 by a factor of six and subtle topographic variations generated local patches of rapid postfire erosion commonly 1 mm yr 21 our sim ulations indicate that fire related processes may account for 50 of temporally averaged sediment production on steep hillslopes our analysis provides a mechanistic explanation for the coincident early holocene timing of increased fire frequency and regional ag gradation in oregon coast range drainage basins given the sen sitivity of steep hillslopes to fire driven transport changes in cli mate and fire frequency may affect soil resources by perturbing the balance between soil transport and production

estimation of earthquake hazard parameters from incomplete data files part iii incorporation of uncertainty of earthquake occurrence model most probabilistic seismic hazard analysis procedures require that at least three seismic source parameters be known namely the mean seismic activity rate the gutenberg richter b value and the area characteristic seismogenic source maximum possible earthquake magnitude m max in almost all currently used seismic hazard assessment procedures that utilize these three parameters it is explicitly assumed that all three remain constant over time and space however closer examination of most earthquake catalogs has indicated that significant spatial and temporal variations existed in the seismic activity rate as well as in the gutenberg richter b value in this study the maximum likelihood estimation of these earthquake hazard parameters considers the incompleteness of the catalogs the uncertainty in the earthquake magnitude determination as well as the uncertainty associated with the applied earthquake occurrence models the uncertainty in the earthquake occurrence models is introduced by assuming that both the mean seismic activity rate and the gutenberg richter b value are random variables each described by the gamma distribution this approach results in the extension of the classic frequency magnitude gutenberg richter relation and the poisson distribution of the number of earthquakes with their compounded counterparts benjamin 1968 campbell 1982 1983 the proposed procedure was applied in the estimation of the seismicity parameters in an area that had experienced the strongest and most devastating earthquake in contemporary south african history namely the 29 september 1969 m w 6 3 ceres tulbagh event in this example it was shown that the introduction of uncertainty in the earthquake occurrence model reduced the mean return periods leading to an increase of the estimated seismic hazard additionally this study confirmed that accounting for magnitude uncertainties had the opposite effect that is it brought about increases in the return periods or equivalently a reduction of the estimated seismic hazard

extreme value distribution of earthquake magnitude commentaire sur l article de gan zi jun et tung c c paru dans phys earth planet int 1983 32 325 330

sediment transport by dry ravel 1 dry ravel is a general term that describes the rolling bouncing and sliding of individual particles down a slope and is a dominant hillslope sediment transport process in steep arid and semiarid landscapes during fires particles can be mobilized by the collapse of sediment wedges that have accumulated behind vegetation on a daily basis particles may be mobilized by bioturbation and by small landslides experiments on a dry ravel flume indicate that a basic expression of the momentum equation predicts the distance traveled by particles propelled down a rough surface this equation is further elaborated to produce a nonlinear slope dependent transport equation for dry ravel that represents the rate at which sediment crosses a contour width of slope sediment traps installed on two hillslope transects near santa barbara california measured the flux from dry ravel initiated by bioturbation and the data support the form of the equation additionally a physical model based on the infinite slope stability analysis is proposed for the initiation of dry ravel by landsliding the analytical result from this model is supported by experiments and field data reported by others

tree root mounds and their role in transporting soil on forested landscapes the growth and decay of tree roots can stir and transport soil this is one process that contributes to the mass movement of soil on hillslope to explore the efficiency of this process we document the mounding of soil beside ponderosa and lodgepole pine trees in the forests that dominate the mid elevations of colorado s boulder creek watershed mounds are best expressed around ponderosa pines reaching vertical displacements above the far field slopes of order 10 20 cm fading into the slope by roughly 100 cm distance from the trunks with common diameters of 30 cm positive mounding occurs on all sides of trees on slopes indicating that the mounding is not attributable to deflection of a creeping flow of soil around the tree but rather to the insertion of root volume on all sides in the subsurface mounding is commonly asymmetric even on cross slope profiles significant variation in the mound sizes results in no clear relationship between tree diameter and root volume displaced these observations motivated the development of a discrete element model of tree root growth using the liggghts model in which grains we specified to be root cells were allowed to enlarge within the simulated granular matrix mounding could be reproduced with the majority of the vertical displacement of the surface being attributable to reduction of the bulk density due to dilation of the granular matrix during root enlargement finally we develop a previous analysis of the role of roots in transporting soil during growth and decay cycles we find that even in shallow soils the root cycle can drive significant soil transport down forested montane slopes copyright 2013 john wiley sons ltd

sediment transport by burrowing mammals marin county california abstract field observations suggest that burrowing activity is the primary mode of sediment transport currently active in a small grassland drainage basin in marin county california spatial concentrations of the 1 150 gopher mounds surveyed vary from 0 16 mounds m on interfluves to 0 32 mounds m on sideslopes and in the topographic hollow with localized concentrations of up to 2 88 mounds m on the margins of the colluvial deposit simple models of sediment transport by burrowing activity yield estimates of between 0 91 and 2 33 cm3 cm yr for the basin as a whole with absolute minimum and maximum rates of 048 and 6 31 cm3 cm yr i these values are similar to those previously estimated for this area lehre 1982 and are nearly an order of magnitude less than average long term sediment transport rates at the same site reneau 1988 key words sediment transport erosion rates bioturbation introduction burrowing animals disturb and transport soil in environments ranging from alpine tundra to humid grasslands hansen and morris

the role of symbiotic algae in the formation of the coral polyp skeleton 3 d morphological study based on x ray microcomputed tomography symbiotic algae of primary polyps play an important role in calcification of coral skeletons however the function of the symbiotic algae including the way they influence the physical features of their host skeleton under various conditions is not well understood we used x ray micro computed tomography to observe skeletal shape characteristics in symbiotic and aposymbiotic primary polyps of acropora digitifera that were cultured at various temperature and pco2 levels temperature 27 29 33 c pco2 400 800 1000 atm symbiotic polyps had a basal plate with a well developed folding margin supporting the branched skeleton whereas aposymbiotic ones did not the features of the folding margin suggest that it might be the initial growth stage of the epitheca in addition three dimensional 3 d morphological measurements made by x ray micro computed tomography show that the branched skeletons of symbiotic primary polyps were taller than those of aposymbiotic ones suggesting that zooxanthellae in coral primary polyps play a critical role in the height growth of skeletal branches furthermore results of the temperature and pco2 controlled experiments suggest that global warming might greatly affect the activity of zooxanthellae whereas ocean acidification might reduce calcification by damaging the coral host itself our findings provide new knowledge about the role of zooxanthellae in coral calcification this article is protected by copyright all rights reserved

estimates of the rate of regolith production using and from an alpine hillslope abstract the production of regolith is a fundamental geomorphic process because most surface processes transport only unconsolidated material we use concentrations of the cosmogenic radionuclides crns 10 be and 26 al in regolith and bedrock to deduce the rate of production of regolith on an alpine hillslope in the wind river range wy these calculations are based on a theoretical model which we develop here this model shows that it is important to consider dissolution of regolith in regolith production and in basin averaged erosion rate studies rates of production of regolith are uniform along the hillslope and the mean rates for the entire hillslope deduced from 10 be and 26 al are 14 3 4 0 and 13 0 4 0 m ma 1 respectively rates of production of regolith deduced from 10 be concentrations in regolith mantled bedrock support the rates deduced from regolith concentrations in the alpine environment examined here the rate of production of regolith beneath 90 cm of regolith is nearly twice as fast as the average rate of production of regolith on bare rock surfaces which small et al small e e anderson r s repka j l finkel r 1997 erosion rates of alpine bedrock summit surfaces deduced from in situ 10 be and 26 al earth and planetary science letters 150 413 425 previously documented rock mantled with regolith probably weathers more rapidly than bare rock because the water required for frost weathering is limited on bare rock surfaces because the hillslope examined here is convex with constant curvature and regolith production and thickness are uniform down the slope the regolith volume flux must be proportional to the local slope of the hillside therefore our results are consistent with gilbert s gilbert g k 1909 the convexity of hilltops journal of geology 17 344 350 steady state hillslope hypothesis if tor height and the difference between rates of weathering on bare and regolith mantled rock provide a fair estimate of the age of summit flats steady state hillslope conditions have been attained in less than several million years

quantification of soil production and downslope creep rates from cosmogenic 10be accumulations on a hillslope profile average soil transport rates over a period of 3500 yr on a convex soil mantled hillslope have been quantified using a mass balance model that incorporates the soil concentration of the cosmogenic isotope 10 be the 10 be model results support the assumption used in most geomorphic models that the soil creep rate is proportional to surface gradient the predicted diffusion coefficient is 360 55 cm 3 yr 1 cm 1 contour length and the average rate of soil production is 0 026 0 007 cm yr within the uncertainty of this technique the data do not reject g k gilbert9s hypothesis that some hillslopes may exist in a condition of dynamic equilibrium with a uniform soil production rate however the model does not require an assumption of dynamic equilibrium and may be an approach that uniquely allows the quantification of a local soil production rate law

the soil production function a brief history and its rediscovery abstract in 1877 g k gilbert reasoned that the rate at which bedrock is converted to soil reaches a maximum under an optimal soil depth that facilitates contact between bedrock and water such that freeze thaw and chemical weathering are maximised in doing so he outlined the functional dependence of soil production bedrock weathering on local soil depth however the concept of a soil production function does not appear to have been utilised until well into the following century when carson and kirkby carson m a kirkby m j 1972 hillslope form and process cambridge university press cambridge 475 pp expressed it as a notional relationship they also noted that at depths less than optimum instability exists that will either drive soil depth to the optimal weathering depth or to zero depth more recent work has also described a declining exponential soil production function in which the highest rate is at zero soil depth despite dealing with a fundamental issue in soil science viz soil formation the soil production concept has been applied mostly to landscape evolution studies the situation is ripe for its use in soil science and developments in techniques such as cosmogenic nuclides will assist this

short term soil mixing quantified with fallout radionuclides soil mixing plays a significant role in contaminant transport carbon sequestration and landscape evolution yet the rates and driving mechanisms are poorly constrained here we use depth profiles and advection diffusion modeling of fallout nuclides to quantify differences in short term 7 be and weapons derived isotopes and quantify mixing with a steady state model of vertical 210 pb transport on a forested landscape in the bega valley in southeastern australia and on grasslands in marin county california where bioturbation is documented as the dominant sediment transport mechanism we calculate diffusion like mixing coefficients of 1 2 cm 2 yr 1 in montane forest soils of northern new england we observe little field evidence of short term mixing and find that the traditional advection diffusion model fails to describe 210 pb profiles because nuclide profiles here can be described with a simple model of litterfall organic matter decay and radioactive decay we argue that diffusion like processes are barely active on short time scales and that the advection diffusion model overestimates diffusion like transport while animal bioturbation and soil freezing cycles have little effect on the fate of elements in new england physical soil mixing drives transport at bega valley and marin county we suggest that the absence of soil stirring that we quantify in new england forests may explain the slow physical erosion here 0 2 cm k y relative to the actively bioturbated soils of bega valley and marin county 5 10 cm k y

immediate effects of wildfires on water repellency and aggregate stability in mediterranean calcareous soils alkaline soils are considered much less prone to developing water repellency induced by fire than acidic soils here we report on the persistence of water repellency present in calcareous soils immediately after wildfires in 10 burned areas in se spain its distribution in different aggregate size fractions 2 2 1 1 0 5 0 5 0 25 and 0 25 mm and on results from aggregate stability tests we also distinguished between soil samples taken beneath pine pinus halepensis and beneath understory vegetation burning appears to have increased the frequency of water repellency occurrence with 74 of burned samples being classified as water repellent compared to 33 from unburned terrain in the composite fraction 2 mm the persistence of water repellency after fire was highly variable but nevertheless showed statistical differences at p 0 001 comparing burned vs unburned moreover statistical differences in the persistence of water repellency were found in soil samples taken from beneath pine between burned and unburned and also beneath understory vegetation results showed that soil beneath understory tend to have lower values of water repellency persistence than soil beneath pine burned soils showed higher aggregate stability a positive tendency was observed between aggregate stability and water repellency the observed changes in wr and as could have implications for soil hydrological behaviour

geogenesis pedogenesis and multiple causality in the formation of texture contrast soils abstract coarse over fine vertical texture contrasts vtc are common in soils and weathering profiles in a variety of environmental settings including many where inheritance or surficial processes alone cannot account for them a multiple causality model is presented here which shows that texture contrasts can form in response to a combination of ubiquitous phenomena there are six key elements downward translocation by water erosional winnowing soil mixing by bioturbation the tendency for surface clay additions to be mobilized while subsurface clays are more likely to remain in place and biological facilitation of moisture flux no element alone is sufficient to create a vtc but not all are necessary in any given regolith the model is illustrated by application to case studies in the ouachita mountains arkansas ridgetops in eastern kentucky the lower coastal plain of north carolina and the upper coastal plain of east texas the implications for interpretation of soils paleosols and weathering profiles is that the presence of a textural contrast by itself does not connote any particular set of geogenic or pedogenic processs or controls texture contrasts may be geogenic pedogenic or both given the widespread occurrence of the mechanisms of the multiple causality model vertical texture contrasts are inevitable

diurnal and seasonal variations of carbonate system parameters on luhuitou fringing reef sanya bay hainan island south china sea the 3 day diurnal dynamics of carbonate system and related parameters on luhuitou fringing reef of sanya bay adjacent to the south china sea scs were observed in december of 2009 early winter april spring july summer and november late autumn of 2010 the luhuitou fringing reef ecosystem was generally dominated by macro and planktonic algae throughout the year except by coralline algae in winter the system parameters showed distinct diurnal trends in the four seasons averaged ranges of diurnal variation for dissolved oxygen and partial pressure of co2 pco 2 were higher in the autumn 4 67 mg l 1 and 218 2 mu atm respectively than other seasons averaged ranges of diurnal variation for normalized total alkalinity nta was higher in the winter 61 3 mu mol kg 1 and lower in the spring 16 0 mu nol kg 1 the diurnal variations are mainly controlled by biological activities especially by the processes of photosynthesis and respiration in the reef ecosystem in winter however calcification and dissolution contributed more to the diurnal variations compared with the other three seasons total alkalinity was largely related to seasonal changes in river inflow rates dissolved oxygen ph total co2 and aragonite saturation also showed seasonal variations these variations were mainly controlled by the seasonal changes of photosynthesis and respiration which were mainly affected by changes in benthic community structure temperature and river inflow rates the oversaturated pco 2 in the reef ecosystem with respect to the atmosphere in the winter and summer resulted in co2 discharge from the reef ecosystem to the scs the whole system served as net source of co2 to the atmosphere and the adjacent south china sea on an annual time scale c 2013 elsevier ltd all rights reserved

breakdown of mineral grains by earthworms and beetle larvae feeding experiments were conducted quantitatively to examine the breakdown of mineral grains by earthworm eisenia feida and larva of beetle protaetia lugubris insperata crushed and sieved test minerals of k feldspar and or quartz were mixed with artificial humus that contained no mineral grains the mixture was fed to the soil animals in the plastic containers after 1 4 and 7 day experimental durations the ingested mineral grains were collected from the casts excreted by the soil animals in each container even 1 day after feeding of mineral grains the casts of soil animals contained finer rounded mineral grains that were not included in the initial prepared mineral samples

magnitudes of large shallow earthquakes from 1904 to 1980 abstract in order to obtain a uniform magnitude catalogue surface wave magnitudes ms and broad band body wave magnitudes mb have been determined for large shallow earthquakes from 1904 to 1980 in making the catalogue homogeneous the author consistently adheres to the original definitions of ms and mb given by gutenberg 1945 and gutenberg and richter 1956 the determinations of ms and mb are all based on the amplitude and period data listed in gutenberg and richter s unpublished notes bulletins from stations worldwide and other basic information mb is measured on broad band instruments in periods of 8 s consistency of the magnitude determinations from these different sources is carefully checked in detail more than 900 shallow shocks of magnitude 7 and over are catalogued the meaning of the magnitude scales in various catalogues is examined in terms of ms and mb most of the magnitudes listed by gutenberg and richter 1954 in their seismicity of the earth are basically ms for large shocks shallower than 40 km but are basically mb for large shocks at depths of 40 60 km the surface wave magnitudes given by earthquake data reports are higher than ms by 0 2 unit whether the combined horizontal amplitude or the vertical amplitude is used mb and the currently used 1 s body wave magnitude are measured at different periods and should not be directly compared

bioerosion of a modern bedrock stream bed by insect larvae conecuh river alabama implications for ichnotaxonomy continental ichnofacies and biogeomorphology abstract observations along the conecuh river southern alabama demonstrate the impact that insect larvae can have on bioerosion of freshwater aquatic bedrock substrates eocene siliceous claystones and sandstones exposed along the river are locally densely riddled by modern burrows produced by chironomid midge and trichopteran caddisfly larvae chironomid larvae produce diminutive u shaped burrows u width 2 7 mm u length 1 4 cm burrow diameter 0 5 2 0 mm generally oriented normal to bedrock surfaces trichopteran larvae generally produce somewhat larger burrow depth 2 4 cm burrow diameter 4 6 mm vertical crudely y shaped burrows consisting of an upper u tube which is extended above the substrate by agglutinated chimneys and one or two basal subvertical shafts both burrow types exhibit faint scratch traces on exposed burrow margins and silk and sediment linings that include a thicker constructed wall or septum in interlimb areas of their u tubes distribution of the two structure types is controlled by bedrock texture and induration tracemaker propensity to occupy transiently available substrates and other as yet unidentified factors chironomid and trichopteran larvae burrows in these firmgrounds resemble the ichnotaxa arenicolites and polykladichnus respectively however differences in burrow production in soft versus firm substrates combined with uncertainties with regard to potential modes of preservation of the modern burrows make it difficult to establish ichnotaxonomic equivalence and raise broader questions regarding inferred behavior and ichnotaxonomy of u form burrows in firmgrounds e g rhizocorallium regardless of ichnotaxonomic assignment ichnofabrics produced by modern insect larvae in fluvial firmgrounds closely match those diagnostic of the glossifungites ichnofacies in marine and marginal strata and thus the scope of this ichnofacies arguably should be expanded to include comparable ichnofossil assemblages preserved in ancient continental deposits beyond their implications for palichnology observations made herein underscore the need to include bedrock stream channels and their biota in integrative biogeomorphologic investigations

soil degradation factors along a mediterranean pluviometric gradient in southern spain article i nfo the modifications to soil properties that resulted from changes in water availability along a pluviometric gradient from 240 to 1100 mm mean annual rainfall were investigated the study was carried out at eight experimental sites in southern spain and assessed the influence of a reduction in annual average rainfall along the pluviometric gradient on various physical chemical and hydrological properties of the topsoil and on the biotic characteristics of the environment the aims were to assess the soil degradation status and to determine if any of the soil variables studied could be used as soil degradation indicators for each experimental site the relationships among a series of edaphic hydrological and biological properties were investigated and the principal factors affecting soil degradation were determined using principal component analysis the properties included the clay silt and sand content organic matter retained organic carbon salinity cation exchange capacity structural stability usle k factor bulk density saturated hydraulic conductivity soil moisture the number of vegetal species and vegetation cover the results show that relationships among biotic and abiotic factors control soil degradation processes from wet to semiarid arid conditions along the mediterranean pluviometric gradient a precipitation based soil degradation threshold of approximately 500 mm year 1 was established as below this level the vegetation is no longer associated with the presence of greater soil moisture content but adapts to degradation as evidenced by the appearance of xerophytic species

are mima like mounds the consequence of long term stability of vegetation spatial patterning abstract the origins of large 5 m diameter 1 m height and regularly spaced i e over dispersed non anthropogenic earth mounds e g mima mounds heuweltjies nabhkas that occur across all biomes remain unresolved an extensive literature documenting diverse explanations for mound genesis has accumulated that primarily ascribes mound formation to faunal agents recent modeling efforts suggest that both abiotic and biotic processes commonly interact to produce striking vegetation patterning e g spots labyrinths the hypothesis that many earth mounds apart from those with a clear faunal genesis e g termitaria may result from vegetation trapping of sediment or aeolian dust and or protection of soil from erosion is reviewed here the literature on the occurrence and properties of some of these mima like mounds is reviewed and the evidence for their origins evaluated some mounds such as coppice dunes otherwise known as nabkhas clearly form as a consequence of aeolian deposition of sediment around vegetation patches however the clay stone and rock content of some mima like mounds is not consistent with purely aeolian origins instead it is suggested that non aeolian mound over dispersion elongation volumes soil properties and stratigraphy are consistent with vegetation patches protecting soil from erosion resulting in preferential erosional deflation of the inter mound area leaving regularly spaced mounds although mima like mounds around the world are formed in diverse vegetation types climates and edaphic conditions many may be long term products of vegetation spatial patterning in which plant canopies and root systems increase sediment capture and reduce erosional losses

the contrasted response of ash to wetting abstract after a wildfire the soil is covered by ash ash properties depend on vegetation type amount of fuel and fire intensity the ash layer controls the post fire soil hydrologic response but little is known about the effect of ash thickness and ash type on infiltration which is relevant for post fire runoff and soil losses and for ecosystems rehabilitation and restoration this paper analyses the role of i ash type black or white ii thickness 5 15 and 30 mm thick and iii temporal variation 0 15 and 40 days under three simulated rain events 55 mm for 1 h on soil surface hydrology the rainfall was simulated on 0 25 m2 plots and time to ponding runoff and runoff discharge were measured the infiltration rates the initial infiltration rate f0 the steady state infiltration rate fc and the infiltration decay factor k were calculated and the horton infiltration equation applied the results show that soils covered with white ash doubled the runoff rates of soils covered with black ash in general runoff decreases as the ash thickness increases and the runoff decreases with the number of rainfall events after the fire in plots covered with white ash ponding time and k are positively correlated by the ash thickness and f0 and fc are correlated by the rainfall events in three runs ash type and ash depth are key factors on the soil hydrology after a wildfire

the effects of bioturbation on soil processes and sediment transport abstract plants and animals exploit the soil for food and shelter and in the process affect it in many different ways for example uprooted trees may break up bedrock transport soil downslope increase the heterogeneity of soil respiration rates and inhibit soil horizonation in this contribution we review previously published papers that provide insights into the process of bioturbation we focus particularly on studies that allow us to place bioturbation within a quantitative framework that links the form of hillslopes with the processes of sediment transport and soil production using geometrical relationships and data from others work we derive simple sediment flux equations for tree throw and root growth and decay

effects of slope angle on mass movement by tree uprooting abstract an examination of 189 well delineated mounds and pits in sandy soils of northern lower michigan all presumably formed by tree uprooting was used to determine the effects of slope angle on morphology and volume and to assess the potential importance of uprooting to mass movement slopes ranged from zero to 54 data indicate that mound and pit volumes increase with increasing slope angle suggesting that on gentle slopes more of the disturbed soil wastes off the mound back into the new pit mounds are often elongated in the downslope direction on steep slopes based on regression analyses slopes of 47 are generally sufficient for all mound soil to slump or wash off in a downslope direction rather than into the upslope pit thus on steep slopes pit volumes provide a better representation of root plate volume pit depth can also be used as a surrogate for rooting depth on steep slopes where infilling from the mound is minimal

the effect of ash and needle cover on surface runoff and erosion in the immediate post fire period abstract hillslopes are thought to be most susceptible to enhanced surface runoff and erosion immediately following wildfire due to removal of protective vegetation and litter cover and in many cases a fire induced reduction in soil wettability this enhanced susceptibility declines as vegetation and litter layer recover for logistical reasons however few studies have been able to examine the responses of burnt terrain immediately following burning and little is therefore known about the effect of the wettable ash layer that often covers the ground until it is redistributed or removed by wind or water erosion here we quantify the effects of ash and needle cast ground cover on surface runoff generation and soil erodibility in the immediate post fire period 2 10 days following a severe wildfire in an aleppo pine forest over calcareous soils in mediterranean eastern spain a homogenous vegetation cover and lack of wind during the fire resulted in 100 ash cover 36 mm mean depth across the study area the ground fire did not consume the tree crowns but its high intensity caused complete tree mortality leading to subsequent needle fall hydrological and erosional responses were measured for fifteen 1 hour rainfall simulations 55 mm h 1 on 0 25 m2 circular plots for each of three terrain types i ash and needle covered ii ash only covered and iii bare furthermore ash and needle cast cover were monitored over an eleven week period on otherwise undisturbed terrain to examine its evolution during the first critical months following burning the soils exhibited no or slight post fire water repellency the overlying wettable ash layer had a porosity of 83 providing a water storage capacity of 30 mm a third of the plots with ground cover did not generate any surface runoff ash needle and ash only plots showed 25 and 18 fold reductions in surface runoff respectively compared to bare terrain mean sediment yield from covered plots was more than two orders of magnitudes lower than from bare plots the ash cover remained unchanged during the first two weeks while overlying needle cast more than doubled heavy rainfall 153 mm over a subsequent six day period removed the ash almost entirely where no needle cast was present whereas on ash and needle covered ground only a limited redistribution and accumulation into litter dams occurred the results quantify the potential importance of ash deposits on the susceptibility of hillslopes to surface runoff and erosion immediately following fire the combination of ash and needle cast appears particularly effective in reducing hillslope responses the outcomes demonstrate clearly that the widely held notion of landscapes being most susceptible to surface runoff and erosion directly after burning is not correct where a fire has resulted in substantial ash deposition instead the susceptibility will be greatest following a storm event of sufficient severity to remove this protective layer and before the onset of vegetation recovery

water repellency and pore clogging at early successional stages of microbiotic crusts on inland dunes brandenburg ne germany abstract biological soil crusts play a key role for hydrological processes in many open landscapes they seal the topsoil and generate surface run off utilization of the mineral substrate at early stages of microbiotic crusts was investigated using scanning electron microscopy sem water repellency indices were measured using the ethanol water microinfiltrometer method and steady state water flow was determined on the dry crusts and after 300 600 1200 and 1800 s of wetting thus allowing to follow pore clogging through swelling of extracellular polymeric substances eps it was found that water repellency increases with initial crust development where filamentous cyanobacteria and filamentous green algae were dominating but decreases as coccal algae bryophytes and fungi associated with bryophytes emerged swelling of eps took place immediately after wetting and its influence on steady state water flow was most pronounced when filamentous cyanobacteria and algae partially filled in the matrix pores and enmeshed sand grains still leaving micropore channels available for free water infiltration but prior to appearance of coccal algae bryophytes and associated fungi which formed a dense cover on the surface it was concluded that a new phase of crust succession was accompanied by easier wettability but slower infiltration transition from hydrophobicity to pore clogging as ruling mechanisms causing water run off may occur during wetting of individual biological crusts but also during crust succession over time

longevity of treethrow microtopography implications for mass wasting abstract this study examines and compares methods of dating pit mound microtopography formed by tree uprooting and provides 14 c evidence for the longevity of these landforms microtopography can often by dated by reference to known meteorological phenomena or within certain age constraints by dendrochronologic means we used 14 c analysis of buried wood and charcoal in treethrow mounds in michigan and wisconsin u s a to arrive at estimates of the geochronometric ages of treethrow mounds results indicate that mounds in these areas often persist for more than 1000 years which are two to five times longer than published estimates by less reliable methods the longevity of treethrow mounds in these regions is ascribed to l sandy porous soils which minimize runoff 2 a continuous mat of forest litter and vegetation cover 3 surface concentrations of gravel which may act as an armor 4 large initial size of the features and 5 soil freezing implications are that rates of mass movement due to uprooting may be substantially less than studies from other regions suggest

erosion rates in the southern oregon coast range evidence for an equilibrium between hillslope erosion and sediment yield the relationship of hillslope erosion rates and sediment yield is often poorly defined because of short periods of measurement and inherent spatial and temporal variability in erosion processes in landscapes containing hillslopes crenulated by alternating topographic noses and hollows estimates of local hillslope erosion rates averaged over long time periods can be obtained by analysing colluvial deposits in the hollows hollows act as local traps for a portion of the colluvium transported down hillslopes and erosion rates can be calculated using the age and size of the deposits and the size of the contributing source area analysis of colluvial deposits in nine oregon coast range hollows has yielded average colluvial transport rates into the hollows of about 35 cm3cm 1yr 1 and average bedrock lowering rates of about 007 mm yr for the last 4000 to 15000 yr these rates are consistent with maximum bedrock exfoliation rates of about 0 09 mm yr calculated from six of the hollows supporting the interpretation that exfoliation rates limit erosion rates on these slopes sediment yield measurements from nine coast range streams provide similar basin wide denudation rates of between 0 05 and 0 08 mm yr 1 suggesting an approximate steady state between sediment production on hillslopes and sediment yield in addition modern sediment yields are similar in basins varying in size from 1 to 1500 km2 suggesting that erosion rates are spatially uniform and providing additional evidence for an approximate equilibrium in the landscape

ant mounds as a source of sediment in a tropical rainforest in lutzito catchment on barro colorado island panama extraordinarily high suspended sediment yields of 1 2mgha 1 year 1 were generated despite the dense forest cover coinciding with erosion resistant soils we hypothesized that ant mounding activity is an important zoogeomorphological mechanism in this area providing relevant quantities of easily transportable material at the soil surface to test this hypothesis all ant mound material was collected collected for dry mass determination from thirty 4m 2 plots installed in the study area every 1 3days during the 39 day sampling period additionally three ground nesting ant species responsible for mounds in the study area ectatomma ruidum trachymyrmex cornetzi and strumigenys marginiventris were identified on the basis of the total of 1 38kg of material collected in the wet season of 2011 the estimate for the whole 8months wet season amounts to 725kgha 1 as this value is in the same order of magnitude as sediment output it shows that ants may act as important ecosystem engineers and contribute to sediment production here by providing large quantities of fine grained readily erodible material at the soil surface for subsequent transport to the streambed copyright 2014 john wiley sons ltd

soil production on a retreating escarpment in southeastern australia the functional dependence of bedrock conversion to soil on the overlying soil depth the soil production function has been widely recognized as essential to understanding landscape evolution but was quantified only recently here we report soil production rates for the first time at the base of a retreating escarpment on the soil mantled hilly slopes in the upper bega valley southeastern australia concentrations of 10 be and 26 al in bedrock from the base of the soil column show that soil production rates decline exponentially with increasing soil depth these data define a soil production function with a maximum soil production rate of 53 m m y under no soil mantle and a minimum of 7 m m y under 100 cm of soil thus constraining landscape evolution rates subsequent to escarpment retreat the form of this function is supported by an inverse linear relationship between topographic curvature and soil depth that also suggests that simple creep does not adequately characterize the hillslope processes spatial variation of soil production shows a landscape out of dynamic equilibrium possibly in response to the propagation of the escarpment through the field area within the past few million years in addition we present a method that tests the assumption of locally constant soil depth and lowering rates using concentrations of 10 be and 26 al on the surfaces of emergent tors

ant mounds as a source of sediment on citrus orchard plantations in eastern spain a three scale rainfall simulation approach abstract ants are widely found in mediterranean soils where they increase water infiltration rates by forming soil macropores during nest construction while higher water infiltration usually results in lower soil erosion rates new soil brought to the surface by ant activity could increase sediments available for erosion this could be especially important in intensively managed citrus orchards where surface mineral soil is exposed due to the lack of vegetation cover as a consequence of herbicide treatments in the summer of 2009 rainfall simulations of low frequency high intensity rainstorms were conducted in an orange orchard in eastern spain on plots that contained ant nests and adjacent paired plots without ant nests since soil erosion is a scale dependent process we used three plot sizes 0 25 m 2 1 m 2 and 12 m 2 to determine the effect of ant burrowing and nesting on soil and water losses ant nests decreased water losses from 22 5 at 0 25 m 2 to 10 6 at 12 m 2 but soil erosion rates were nearly double in areas with ant activity 0 56 to 0 59 mg ha 1 h 1 as compared to soil with no ants 0 31 to 0 36 mg ha 1 h 1 our results indicate that the presence of ants can increase soil erosion when rainfall intensity is greater than the infiltration capacity of the ant macropores

roots rock and regolith biomechanical and biochemical weathering by trees and its impact on hillslopes a critical literature review the role of trees and forests as a critical component of the biosphere and critical zone and of the earth system more generally is widely appreciated less known and acknowledged are the geomorphological functions of tree roots although their importance has been widely referred to in soil studies paleopedology and paleobotany tree roots and their impact on weathering processes and soil production were incorporated in the devonian plant hypothesis and tree root casts served as a key evidence of recognition of past soils in geology sedimentology and paleopedology however knowledge of biomechanical and biochemical weathering induced by vascular plant roots mainly trees has been rarely utilized in geomorphic studies biogeomorphic and pedologic studies in recent decades have highlighted the importance of tree uprooting in which roots play a primary role in soil development regolith disturbance and bedrock mining other important functions of roots were also recognized e g soil displacement by growing roots infilling of stump holes and root cavities root groove development direct and indirect effects taking place in the rhizosphere and mycorrhizosphere mainly biochemical weathering of minerals support by microbial communities and symbiotic fungi and changes in porosity permeability and hydrology of soils in the root zone however further studies are urgently needed because many aspects of biochemical and biomechanical weathering are not well understood this is especially true with respect to taxa specific impacts variations in root architectures edaphic settings ecological relationships and geographic ranges result in substantially different biogeomorphic impacts of different tree species additionally the same species in different environmental settings may have different effects

breaking ground pedological geological and ecological implications of soil bioturbation abstract soil and its biota are fundamental components of the critical zone earth s living skin that most directly sustains life within that zone geologically rapid soil and saprolite displacement by biota particularly invertebrate meso and macrofauna affects a large proportion of earth s soils this was first recognised by late 19th century observers on both sides of the atlantic ocean who regarded bioturbation as fundamental to soil formation throughout much of the 20th century however the agronomical focus of soil scientists and the dominant paradigm of landscape evolution relegated bioturbation as a result many aspects of bioturbation are still not widely appreciated only in the last few decades has a re evaluation commenced in a range of disciplines primary effects of bioturbation which we quantify herein include soil production from saprolite the formation of surface mounds soil burial and downslope transport rates of bioturbation can be as rapid as sustained maximum rates of tectonic uplift in concert with surface geomorphic processes bioturbation alters fundamental properties of soil including particle size distribution porosity the content of carbon and other nutrients and creep flux rate the precise influence of biotic mixing is regulated by its depth function earth s incredibly diverse soil biota also perform a number of functions at a range of spatial and temporal scales that extend beyond soil to landscape evolution ecosystem engineering niche construction and carbon cycling understanding these linkages which have operated since the evolution of trees in the devonian period is of growing importance as we seek a fuller picture of earth s history to predict and manage its future

some aspects of the regional variation in the amount of available sediment produced by isopods and porcupines northern negev israel a recent study conducted in the sde boqer experimental site drew the attention to the possible influence of the burrowing and digging activity of some desert animals on the spatial variation of erosion rates over arid limestone slopes such activity provides loose soil aggregates which are easier to remove by shallow overland flows than is the compacted and crusted loessial soil in order to study the regional extent of available sediment amounts produced by the biological activity six plots were selected in the northern negev in the range of 65 mm to 310 mm average annual rainfall amount all plots had the same north facing aspect and the same lithologic composition their size varied from 1110 m2 to 5470 m2 available sediment produced was found to vary from 3 g to 70 g m2 increasing with rainfall amount the distribution of available sediment within each plot was not spatially uniform depending greatly on the spatial distribution of bedrock surfaces and soil cover the overall possible influence of the biotic activity on short term cycles of soil erosion over limestone arid slopes in the negev is discussed

impact of fault parameter uncertainties on earthquake recurrence probability examined by monte carlo simulation an example in central taiwan abstract the region around taiwan is well known for its unique geological setting which has resulted in a high seismicity the central geological survey taiwan cgst has launched a series of investigation on characterizing the active faults on the island the cgst revealed that there are 33 active faults and their fault parameters are suggested in the latest publication in 2010 however the uncertainties of return period and earthquake magnitude are not provided the main objective of the paper is to study the impact of unspecified parameter uncertainties on recurrence earthquake probabilities in addition a numerical approach involving the use of monte carlo simulation was proposed to estimate the exceedance probabilities in which the parameter uncertainties were taken into account the meishan fault in central taiwan with the best estimate return period of 162 years and earthquake magnitude of 7 1 was used as an example the analyses verified the impact of parameter uncertainties on the exceedance probability in fault induced earthquake recurrence when uncertainty is high the exceedance probability associated with large magnitudes is high it was also observed that the probabilistic analysis in this study can generate a realistic continuous distribution of exceedance probabilities that cannot be obtained by a deterministic approach the best estimate distribution of exceedance probability was established by enveloping the curves estimated by both deterministic and probabilistic approaches accordingly the best estimate exceedance probability for a 7 5 magnitude earthquake recurring in 2011 2060 induced by the meishan fault in central taiwan was estimated as 11

cosmogenic nuclides topography and the spatial variation of soil depth abstract if the rate of bedrock conversion to a mobile layer of soil depends on the local thickness of soil then hillslopes on uniform bedrock in a landscape approaching dynamic equilibrium should be mantled by a uniform thickness of soil conversely if the depth of soil varies across an actively eroding landscape then rates of soil production will also vary and consequently the landscape will not be in morphologic equilibrium the slow evolution of hillslopes relative to the tempo of climatic variations and tectonic adjustments would suggest that local morphologic disequilibrium may be expected in many landscapes here we explore this issue of equilibrium landscapes through a previously developed model that predicts the spatial variation in thickness of soil as a consequence of the local balance between soil production and erosion first we confirm the assumption in the model that soil production varies inversely with the thickness of soil using two independent methods one method uses the theoretical prediction that at local steady state soil production equals removal the depth of soil should vary inversely with hillslope curvature the second method relies on direct measurements of in situ produced concentrations of cosmogenic 10 be and 26 al in bedrock at the base of the soil column for our study site in northern california the two methods agree and yield the expression that the rate of soil production declines exponentially with the thickness of soil from 0 077 mm year with no soil mantle to 0 0077 mm year under 1 m of soil we then use this function of soil production in a coupled production and diffusive model of sediment transport to explore the controls on the spatial variation of the depth of soil on four separate spur ridges noses where we measured the data for the function of soil production model predictions are sensitive to boundary conditions grid scale and run time nonetheless we found good agreement between predicted and observed depths of soil as long as we used the observed function of soil production the four noses each have spatially varying curvature and consequently have varying depths of soil implying morphologic disequilibrium we suggest that our study site has been subjected to a wave of incision and varying intensities of erosion because of tectonic and climatic oscillations that have a frequency shorter than the morphologic response time of the landscape

origins and implications of soil layering abstract layering is common in soils due to a variety of pedologic and geologic processes and has important consequences for the interpretation of soils and landscapes layering can derive from original sedimentary layering depositional upbuilding episodic surface erosion deposition and stability soil production by weathering vertical or lateral translocation bioturbation and various combinations of these complex and polygenetic models incorporate both geogenic and pedogenic processes and allow for physical and biological processes as well as both vertical and horizontal movements we review these conceptual frameworks and synthesize them into a vertical contrast model vcm for interpreting layered surficial materials the vcm incorporates a variety of geologic and pedologic processes which may create destroy enhance or obscure vertical contrasts the model is illustrated via application to sites in the ouachita mountains usa and northwest saxonian lowlands germany the examples illustrate the importance of a comprehensive pedogeomorphic interpretation of layering since neither standard stratigraphic or top down pedogenetic principles necessarily apply the examples also show that the same process can sometimes contemporaneously both create and destroy vertical contrasts

vegetation arcs and litter dams similarities and differences abstract vegetation arcs are near parallel bands of denser vegetation aligned perpendicular to slope and separated by barer inter arc zones these patterns occur in arid and semi arid areas of gentle to very gentle gradient similar but much smaller scale patterns here referred to as litter dams and microterraces occur in a variety of climatic regions from tropical to temperate to arid on steeper slopes as well as on very gentle slopes we describe similarities between arcs and dams in attributes such as shape orientation cross sectional profile spatial organisation and surface features arrangement of plants surface crusts differences are in spatial and temporal scale range of wavelengths or spacing between bands is 25 300 m for arcs and 0 1 2 m for dams with regard to time arcs may be stable for tens to a hundred or more years while dams may be ephemeral or remain stable for more than a decade overland flow involving the transport of organic material leaves charcoal faecal pellets as floating load over comparatively bare surfaces is an important factor in the maintenance of vegetation arcs and formation of and maintenance of litter dams recognising the importance of gradient to transport by overland flow a preliminary investigation of the relationship between wavelength and gradient was conducted a combined analysis of a limited set of arc and dam data describes parallel lines which may indicate that similar processes are operating at the two scales this would allow the convenience of process studies on dams as an aid in understanding the origin of arcs however the difference in the intercept of the two lines with the ln wavelength axis may indicate changes in process that preclude extrapolations from one spatio temporal scale to the other

chemical weathering and long term co2 consumption in the ayeyarwady and mekong river basins in the himalayas the role of terrestrial river systems in the global carbon cycle on a long timescale has been a subject of interest especially in the context of past climate changes such as the global cooling in the cenozoic the discharges of water and carbon into the ocean from the himalayan watersheds are among the highest in the world however there are few reliable geochemical data from the ayeyarwady river this study focused on reevaluating chemical weathering in the himalayan watersheds based on samples taken from the ayeyarwady mekong and chao phraya rivers and on chemical analysis of the composition of dissolved substances in these rivers comparisons of water quality showed that unlike in previous studies the total alkalinity budgets of the ayeyarwady are dominated by carbonate rather than silicate weathering long term co2 consumption by silicate weathering in the ayeyarwady is estimated to be only 63 145 109 mol yr 1 which is only 10 of the previous estimate our results also suggest that the total himalayan watersheds account for only about 10 of the total global co2 consumption by silicate weathering although we need further studies chemical weathering and associated co2 uptake in the himalayas likely played a lesser role in long term global cooling in the past than previously appreciated

soil hydrophobicity effects on rainsplash simulated rainfall and photographic evidence laboratory rainfall simulation experiments indicate greater splash losses for hydrophobic water repellent than for wettable sandy loam soils at different rainfall intensities durations and soil surface inclinations using synchronized video cameras with different shutter speeds and stroboscopically illuminated 35 mm still photography differences in splash droplets and ejection trajectory characteristics are examined for hydrophobic soil raindrop impact gives rise to fewer larger slower moving daughter ejection droplets which carry more sediment and hence follow shorter range trajectories compared with wettable soil implications for erosion of hydrophobic soils are discussed

soil and water losses from new citrus orchards growing on sloped soils in the western mediterranean basin ten representative research sites were selected in eastern spain to assess soil erosion rates and processes in new citrus orchards on sloping soils the experimental plots were located at representatives sites on limestone in areas with 498 to 715 mm year 1 mean annual rainfall north facing slopes herbicide treated and new less than 3 years old plantations ten rainfall simulation experiments 1 h at 55 mm h 1 on 0 25 m2 plots were carried out at each of the 10 selected study sites to determine the interill soil erosion and runoff rates the 100 rainfall simulation tests 10 10 m showed that ponding and runoff occurred in all the plots and quickly 121 and 195 s respectively following rainfall initiation runoff discharge was one third of the rainfall and sediment concentration reached 10 4 g l 1 the soil erosion rates were 2 4 mg ha 1 h 1 under 5 year return period rainfall thunderstorms these are among the highest soil erosion rates measured in the western mediterranean basin similar to badland mine spoil and road embankment land surfaces the positive relationship between runoff discharge and sediment concentration r2 0 83 shows that the sediment availability is very high soil erosion rates on new citrus orchards growing on sloped soils are neither tolerable nor sustainable copyright 2009 john wiley sons ltd

bioturbation and erosion rates along the soil hillslope conveyor belt part 1 insights from single grain feldspar luminescence the interplay of bioturbation soil production and long term erosion deposition in soil and landscape co evolution is poorly understood single grain post infrared infrared stimulated luminescence post ir irsl measurements on sand sized grains of feldspar from the soil matrix can provide direct information on all three processes to explore the potential of this novel method we propose a conceptual model of how post ir irsl derived burial age and fraction of surface visiting grains change with soil depth and along a hillslope catena we then tested this conceptual model by comparison with post ir irsl results for 15 samples taken at different depths within four soil profiles along a hillslope catena in the santa clotilde critical zone observatory southern spain in our work we observed clear differences in apparent post ir irsl burial age distributions with depth along the catena with younger ages and more linear age depth structure for the hill base profile indicating the influence of lateral deposition processes we noted shallower soils and truncated burial age depth functions for the two erosional mid slope profiles and an exponential decline of burial age with depth for the hill top profile we suggest that the downslope increase in the fraction of surface visiting grains at intermediate depths 20 cm indicates creep to be the dominant erosion process our study demonstrates that single grain feldspar luminescence signature depth profiles provide a new way of tracing vertical and lateral soil mixing and transport processes in addition we propose a new objective luminescence based criterion for mapping the soil bedrock boundary thus producing soil depths in better agreement with geomorphological process considerations our work highlights the possibilities of feldspar single grain techniques to provide quantitative insights into soil production bioturbation and erosion deposition

the extent and significance of bioturbation on 137cs distributions in upland soils abstract differences between measured 137cs activity depth profiles and idealised undisturbed profiles generated from an exponential model suggest that faunal turbation has redistributed 137cs in mineral and organic upland soils in southern scotland bioturbation is also demonstrated by the vertical displacement of other inputs to the soils of known age non native tree pollen and spheroidal carbonaceous particles scps the causes and mechanisms of bioturbation were further investigated by soil micromorphology well drained mineral soils with active populations of earthworms are the most bioturbated showing near complete homogenisation to depths of about 20 cm enchytraeids also seem to remobilise 137cs by the digestion of organic matter and may be the main cause of 137cs redistribution in organic rich upland soils relative rates of mixing are evaluated by comparing 137cs depth profiles

soil transport driven by biological processes over millennial time scales downslope soil transport in the absence of overland flow has been attributed to numerous mechanisms including particle by particle creep and disturbances associated with biological activity process stochasticity and difficulties associated with field measurement have obscured the characterization of relevant long term soil transport rates and mechanisms in a series of incised fluvial terraces along the charwell river south island new zealand we documented vertical profiles of tephra concentration and topographic derivatives along a hillslope transect to quantify soil transport processes along the undissected hilltop we observed a thin primary tephra layer ca 22 6 ka within loess deposits 80 cm below the landscape surface in the downslope direction the depth to the highly concentrated tephra layer decreases coincident with an increase in hillslope convexity which is proportional to landscape lowering rate if soil flux varies linearly with hillslope gradient exhumation of the tephra layer results from landscape lowering due to disturbance driven soil transport approximately 20 m downslope of the interfluve the depth to the tephra layer declines to 40 50 cm peak tephra concentrations decrease by a factor of 4 and tephra is distributed uniformly within the upper 40 cm of soil the transition from a thin highly concentrated tephra layer at depth to less concentrated widely distributed tephra in the upper soil may result from soil mixing and transport by biological disturbances along our transect the depth to this transition is 50 cm coincident with the rooting depth of podocarp and nothofagus trees that populated the region during much of the holocene our observations can be used to calibrate the linear transport model but more important they suggest that over geomorphic time scales stochastic bioturbation may generate a well mixed and mobile soil layer the depth of which is primarily determined by flora characteristics

erosion and sediment transport on steep marly hillslopes draix haute provence france an experimental field study abstract despite a thin regolith layer measured sediment yields indicate denudation rates of more than 10 to 20 mm yr 1 on strongly denuded slopes in black marl terres noires near draix alpes de haute provence overland flow and rainfall simulation experiments were conducted on three slopes in the draix erosional research basin to determine the nature and intensity of hillslope erosion processes the experiments showed that during a single storm sediment transport includes water solid mixtures with a wide range of concentrations from highly charged rill flow up to 400 g l 1 to hyperconcentrated flow up to 800 g l 1 to debris flows up to 1400 g l 1 miniature debris flows mdfs strongly controlled sediment transport as long as the sediment store was not depleted slope surfaces were completely reworked in the winter and the regolith layer was rebuilt temperature records from nine recent winter periods indicate that conditions are favourable for soil frost processes

rock fragment distributions and regolith evolution in the ouachita mountains arkansas usa rock fragments in the regolith are a persistent property that reflects the combined influences of geologic controls erosion deposition bioturbation and weathering the distribution of rock fragments in regoliths of the ouachita mountains arkansas shows that sandstone fragments are common in all layers even if sandstone is absent in parent material shale and sandstone fragments are produced at the bedrock weathering front but the shale weathers rapidly and intact fragments are rare in the solum sandstone is weathered from ridgetop outcrops and transported downslope some of these fragments are moved downward by faunalturbation and by transport into pits associated with rotting tree stumps upward movement by treethrow is common resulting in a net concentration of rocks near the surface however the highest fragment concentrations are in the lower regolith indicating active production at the weathering front the regolith is a dynamic feature reflecting the influences of vertical and horizontal processes of active weathering at the bedrock interface and of surficial sediment movements the role of trees in redistributing rock fragments suggests that significant regolith mixing occurs over time scales associated with forest vegetation communities and that forest soils have likely been extensively mixed within holocene and historic time copyright 2005 john wiley sons ltd

coral reefs may start dissolving when atmospheric co2 doubles 1 calcification rates in stony corals are expected to decline significantly in the near future due to ocean acidification in this study we provide a global estimate of the decline in calcification of coral reefs as a result of increase in sea surface temperature and partial pressure of co2 this estimate unlike previously reported estimates is based on an empirical rate law developed from field observations for gross community calcification as a function of aragonite degree of saturation arag sea surface temperature and live coral cover calcification rates were calculated for more than 9 000 reef locations using model values of arag and sea surface temperature at different levels of atmospheric co2 the maps we produced show that by the time atmospheric partial pressure of co2 will reach 560 ppm all coral reefs will cease to grow and start to dissolve

soil creep and convex upward velocity profiles theoretical and experimental investigation of disturbance driven sediment transport on hillslopes the movement of unconsolidated materials near the earth s surface is often driven by disturbances that occur at a range of spatial and temporal scales the nature of these disturbances ranges from highly variable such as tree turnover to periodic and predictable such as frost heave or creep to explore the effect of probabilistic disturbances on surface processes we formulated a granular creep model with analogy to rate process theory rpt used for chemical reactions according to the theory individual particles must be energized to a height greater than adjacent particles in order for grain dilation and transport to occur the height of neighbouring particles which is akin to activation energy in chemical reactions varies with slope angle such that energy barriers get smaller in the downslope direction as slopes steepen when slopes approach the friction limited angle of repose the height of energy barriers approaches zero and grains ow in the absence of disturbance an exponential function is used to describe the probability distribution of particle excitation height although alternative distributions are possible we tested model predictions of granular dynamics in an experimental sandpile in the sandpile acoustic energy serves as the disturbance agent such that grains dilate and shear in response particle velocities are controlled by the frequency of energy pulses that result in grain displacement using tracer particles we observed a convex upward velocity pro le near the surface of the sandpile consistent with predictions of our rpt based velocity model in addition we depth integrated the velocity model to predict how ux rates vary with inclination of the sandpile and observed non linear ux gradient curves consistent with model predictions by varying the acoustic energy level in the experimental sandpile we documented changes in the rate of grain movement similar changes in modelled velocities were achieved by varying the exponent of the particle excitation probability distribution the general agreement between observed and modelled granular behaviour in our simple laboratory sandpile supports the utility of rpt based methods for modelling transport processes e g soil creep frost heave and till deformation thus enabling us to account for the probabilistic nature of disturbances that liberate sediment in natural landscapes copyright 2004 john wiley sons ltd

the mechanism of production enhancement in coral reef carbonate systems model and empirical results coral reefs are characterized by enormous carbonate production of the organisms it is known that rapid calcification is linked to photosynthesis under control of the carbonate equilibrium in seawater we have established a model simulating the coexisting states of photosynthesis and calcification in order to examine the effects of photosynthesis and calcification on the carbonate system in seawater supposing that the rates of photosynthesis and calcification are proportional to concentrations of their inorganic carbon source the model calculations indicate that three kinds of unique interactions of the organic and inorganic carbon productions are expected these are photosynthetic enhancement of calcification calcification which benefits photosynthesis and carbonate dissolution induced by respiration the first effect appears when the photosynthetic rate is more than approximately 1 2 larger than that of calcification this effect is caused by the increase of co32 content and carbonate saturation degree in seawater if photosynthesis use molecular carbon dioxide the second effect occurs when the calcification rate is more than approximately 1 6 times larger than that of photosynthesis time series model experiments indicate that photosynthesis and calcification potentially enhance each other and that organic and inorganic carbon is produced more efficiently in the coexisting system than in the isolated reactions these coexisting effects on production enhancement of photosynthesis and calcification are expected to appear not only in the internal pool of organisms but also in a reef environment which is isolated from the outer ocean during low tide according to the measurements on the fringing type shiraho reef in the ryukyu islands the diurnal change of water properties ph total alkalinity total carbon dioxide and carbonate saturation degree were conspicuous this environment offers an appropriate condition for the appearance of these coexisting effects the photosynthetic enhancement of calcification and the respiratory inducement of decalcification were observed during day time and night time slack water periods respectively these coexisting effects especially the photosynthetic enhancement of calcification appear to play important roles for fluorishing coral reef communities

stochastic processes of soil production and transport erosion rates topographic variation and cosmogenic nuclides in the oregon coast range landscapes in areas of active uplift and erosion can only remain soil mantled if the local production of soil equals or exceeds the local erosion rate the soil production rate varies with soil depth hence local variation in soil depth may provide clues about spatial variation in erosion rates if uplift and the consequent erosion rates are sufficiently uniform in space and time then there will be tendency toward equilibrium landforms shaped by the erosional processes soil mantle thickness would adjust such that soil production matched the erosion previous work in the oregon coast range suggested that there may be a tendency locally toward equilibrium between hillslope erosion and sediment yield here results from a new methodology based on cosmogenic radionuclide accumulation in bedrock minerals at the base of the soil column are reported we quantify how soil production varies with soil thickness in the southern oregon coast range and explore further the issue of landscape equilibrium apparent soil production is determined to be an inverse exponential function of soil depth with a maximum inferred production rate of 268 m ma 1 occurring under zero soil depth this rate depends however on the degree of weathering of the underlying bedrock the stochastic and large scale nature of soil production by biogenic processes leads to large temporal and spatial variations in soil depth the spatial variation of soil depth neither supports nor rejects equilibrium morphology our observed catchment averaged erosion rate of 117 m ma 1 is however similar to that estimated for the region by others and to soil production rates under thin and intermediate soils typical for the steep ridges we suggest that portions of the oregon coast range may be eroding at roughly the same rate but that local competition between drainage networks and episodic erosional events leads to landforms that are out of equilibrium locally and have a spatially varying soil mantle copyright 2001 john wiley sons ltd

quantifying the rate and depth dependence of bioturbation based on optically stimulated luminescence osl dates and meteoric 10be both the rate and the vertical distribution of soil disturbance modify soil properties such as porosity particle size chemical composition and age structure all of which play an important role in a soil s biogeochemical functioning whereas rates of mixing have been previously quantified the nature of bioturbation s depth dependence remains poorly constrained here we constrain for the first time the relationship between mixing rate and depth in a bioturbated soil in northeast queensland australia using a novel method combining osl optically stimulated luminescence ages and meteoric beryllium 10 10be inventories we find that the best fit mixing rate decreases non linearly with increasing soil depth in this soil and the characteristic length scale of 0 28 m over which the mixing coefficient decays is comparable to reported rooting depth coefficients in addition we show that estimates of surface mixing rates from osl data are highly dependent on erosion rate and that erosion rate must be constrained if accurate mixing rates are to be quantified we calculate surface diffusion like mixing coefficients of 1 8 10 4 and 2 1 10 4 m2 yr 1 for the studied soil for two different estimates of soil erosion 2014 the authors earth surface processes and landforms published by john wiley sons ltd

soil production in heath and forest blue mountains australia influence of lithology and palaeoclimate an erratum has been published for this article in earth surfaces processes and landforms 25 13 2005 1683 1686 recent determinations of soil production from in situ cosmogenic nuclides indicate that production decreases exponentially with soil depth this contrasts with a long held assumption that maximum soil production occurs under a soil cover of finite depth sites in the blue mountains australia show a sharp decrease of soil depth where vegetation changes from forested plateau surfaces to heath covered spurs and bands of bare rock in the heath suggest that soil production depends on presence of a finite depth of soil the substrate varies from hard ferruginized sandstone to soft saprolite in situ 10be determinations indicate that apparent rates of erosion and soil production are greater under the relatively thin heath soil than under the thicker forest soil but in contrast to other studies these sites do not show significant depth dependence of apparent soil production the pattern reflects both hardness variation in the rock substrate and the effect of late quaternary climatic change optically stimulated luminescence osl dating indicates that soil 30 cm depth is of holocene age whereas the deeper soil is substantially older the age break coincides with a stone line interpreted as a former surface lag deposit assuming that pre holocene soil depths were 30 cm less than today recalculated soil production tends to decrease with increasing depth soil production at this site requires soil cover but bare rock patches and vegetation comprise a shifting mosaic in the long term average rates of erosion and soil production decrease with increasing soil depth copyright 2005 john wiley sons ltd

extreme value distribution of earthquake magnitude abstract probability distribution of maximum earthquake magnitude is first derived for an unspecified probability distribution of earthquake magnitude a model for energy release of large earthquakes similar to that of adler lomnitz and lomnitz is introduced from which the probability distribution of earthquake magnitude is obtained an extensive set of world data for shallow earthquakes covering the period from 1904 to 1980 is used to determine the parameters of the probability distribution of maximum earthquake magnitude because of the special form of probability distribution of earthquake magnitude a simple iterative scheme is devised to facilitate the estimation of these parameters by the method of least squares the agreement between the empirical and derived probability distributions of maximum earthquake magnitude is excellent

estimate of earthquake hazard in the vrancea romania region a maximum likelihood method is used to estimate the earthquake hazard parameters maximum magnitudemmax annual activity rate and theb value of the gutenberg richter equation in the vrancea romania region the applied procedure permits the use of mixed catalogs with incomplete historical as well as complete instrumental parts the consideration of variable detection thresholds and the incorporation of earthquake magnitude uncertainty

a paleopedologic and ichnologic perspective of the terrestrial pennsylvanian landscape in the distal appalachian basin u s a abstract the conemaugh group of southeastern ohio contains numerous ichnofossil bearing paleosols in both the lower glenshaw and upper casselman formations which were deposited during the kasimovian and gzhelian 305 301 ma along the distal edge of the appalachian basin this study examined the small scale twenty four stratigraphic sections were measured from ten sites in athens county ohio from which thirty paleosols were identified and described detailed field descriptions allowed differentiation of four distinct pedotypes one in the glenshaw formation and three in the casselman formation the glenshaw pedotype gpt is a vertisol that formed on a proximal to distal floodplain the three casselman pedotypes represent entisols inceptisols cpti alfisols cptii and vertisols cptiii all four types contain evidence of alteration by post pedogenic processes such as drowning by migrating river channels or rising sea level or a gradual transition from one alluvial subenvironment to another as a result of channel migration eight morphologically distinct ichnofossils were observed in the conemaugh group paleosols including three types of rhizoliths lined and unlined vertical to subhorizontal shafts chambers sinuous burrows with and without bioglyphs and general burrow mottling these ichnofossils occur in distinct assemblages that form unique ichnocoenoses within each of the four pedotypes they were produced by various plants arthropod detritivores carnivores and herbivores as well as amphibians and early reptiles as temporary to permanent members of complex soil ecosystems pedogenic properties combined with ichnofossil diversity abundance and distribution increase the understanding of the complexity of late pennsylvanian soil ecosystems and provide details on the small scale variations in paleosols due to short term autogenic changes in alluvial environments although broad regional studies across 10 2 10 3 of kilometers are important small scale variations over less than 1 km are needed to understand the effects of localized changes in hydrology topography organisms and sedimentary processes on soil formation and soil biodiversity consideration of these types of localized studies is also vital when attempting to interpret regional to global scale aspects of environment such as climate from paleosols

animating the biodynamics of soil thickness using process vector analysis a dynamic denudation approach to soil formation this paper expands the dynamic denudation framework of landscape evolution by providing new process insights and details on how soil and its signature morphological feature the biomantle form and function in the environment we examine soils and their biomantles from disparate parts of the world from the tropics through midlatitudes and hyperarid through perhumid a range that exhibits varying environments for and of life we then explicate the process pathways that cause soils to thicken and thin and to even disappear then reform we do this by examining thickness relationships where soil thickness st and biomantle thickness bt are functions of upbuilding u and deepening d minus removal r processes hence st bt f u d r upbuilding has two subsets u1 which includes all exogenous allochthonous outside mineral and or organic inputs to the soil system and u2 which includes all endogenous autochthonous in situ processes and productions including weathering exogenous u1 inputs include eolian and slopewash inputs sedimentations of mineral and organic materials mass wasting accumulations and the like endogenous u2 processes and productions include the sum of in situ bioturbations biosynthetic productions organic accumulations biovoid productions weathering and volume increases caused by their sum endogenous upbuildings which dominantly occur in the biomantle are basically biodynamic bd processes and productions hence u2 bd therefore if exogenous upbuildings u1 are minimal or zero then biomantle thickness bt is expressed by bt f u2 r or bt f bd r drawing on these relationships we employ a graphic conceptual device called process vector analysis in a digital animation see supplementary materials or cf https netfiles uiuc edu jdomier www temp biomantle html that illustrates the main pathways that form both earth s soil and its unique epidermis the biomantle we then discuss the main elements of the animation using still frames that represent thickness turning points we end by encouraging researchers instructors and students to view earth s landforms and soils as integrated dynamic entities that are constantly coevolving elements of a global subaerial subaqueous continuum

can terra rossa become water repellent by burning a laboratory approach abstract fire usually induces water repellency wr in soils reduction in infiltration rates increase of runoff and erosion are some of the consequences of wr in fire affected soils most forest soils can develop wr by burning however some previous observations in burned terra rossa soils have shown little changes in wr laboratory controlled experiments have been done with samples of terra rossa from 14 different sites the objectives are to confirm whether the observed is a common behaviour of terra rossa and to explore the factors controlling the wettability of this soil type after burning samples from the upper 2 5 cm of terra rossa were collected from 12 forest sites of the alicante province spain and from 2 sites in the mt carmel haifa israel with similar environmental conditions laboratory burning of samples at 250 c 300 c and 350 c was performed with and without the addition of litter of pinus halepensis the results confirm that all soils have a very low susceptibility to become water repellent by burning without the addition of litter wr was not detected in any soil sample at any temperature of burning with the addition of litter wr was present only in six of the soils after some of the heating treatments although all soils had enough soil organic matter som to develop wr by heating the ratio between som and clay content was considerably lower compared to other types of forest soils of the region in which wr has been found after forest fires this could explain in part the lower susceptibility of terra rossa to become water repellent by burning since as some authors have indicated fine textured soils are less prone to develop soil wr due to their high specific surface area from mineralogical analysis of the clay fraction we found that the dominant clay types in the studied terra rossa were kaolinite and illite with the exception of one soil where ca montmorillonite content is higher than kaolinite and illite ca montmorillonite was present in only three of the soils comparing the soil properties between the group of terra rossa that in no case become water repellent wettables with the group that in some cases developed wr potentially water repellents some differences were found the kaolinite content is higher in the wettables group p vs kaolinite contents the kaolinite content being the main factor contributing to this separation these results are in agreement with those obtained in experiments with clay additions to water repellent soils in order to reduce the wr and also with some studies which found that kaolinite is one of the most effective clay minerals for this purpose

gopher bioturbation field evidence for non linear hillslope diffusion it has generally been assumed that diffusive sediment transport on soil mantled hillslopes is linearly dependent on hillslope gradient fieldwork was done near santa barbara california to develop a sediment transport equation for bioturbation by the pocket gopher thomomys bottae and to determine whether it supports linear diffusion the route taken by the sediment is divided into two parts a subsurface path followed by a surface path the first is the transport of soil through the burrow to the burrow opening the second is the discharge of sediment from the burrow opening onto the hillslope surface the total volumetric sediment flux as a function of hillslope gradient is found to be qs cm3 cm 1 a 1 176 dz dx 3 189 dz dx 2 68 dz dx 34 dz dx 0 4 this result does not support the use of linear diffusion for hillslopes where gopher bioturbation is the dominant mode of sediment transport a one dimensional hillslope evolution program was used to evolve hillslope profiles according to non linear and linear diffusion and to compare them to a typical hillslope the non linear case more closely resembles the actual profile with a convex cap at the divide leading into a straight midslope section copyright 2000 john wiley sons ltd

domination of hillslope denudation by tree uprooting in an old growth forest abstract razula forest preserve in the carpathian mountains of the czech republic is an unmanaged forest that has not been logged or otherwise anthropically disturbed for at least 83 years preceded by only infrequent selective logging we examined this 25 ha area to determine the dominant geomorphological processes on the hillslope tree uprooting displaces about 2 9 m 3 of soil and regolith per year representing about 1 5 uprooted trees ha 1 yr 1 based on forest inventory records dating back to 1972 and contemporary measurements of displaced soil and pit mound topography resulting from uprooting pits and mounds occupy 14 of the ground surface despite typical slope gradients of 0 05 mm 1 and up to 0 41 little evidence of mass wasting e g slump or flow scars or deposits colluvial deposits was noted in the field except in association with pit mound pairs small avalanche and ravel features are common on the upslope side of uproot pits surface runoff features were rare and poorly connected but do include stemwash erosion associated with stemflow no rills or channels were found above the valley bottom area and only small localized areas of erosion and forest litter debris indicating overland flow where these features occurred they either disappeared a short distance downslope indicating infiltration or indicate flow into tree throw pits surface erosion is also inhibited by surface armoring of coarse rock fragments associated with uprooting as well as by the nearly complete vegetation and litter cover these results show that the combination of direct and indirect impacts of tree uprooting can dominate slope processes in old growth unmanaged forests the greater observed expression of different hillslope processes in adjacent managed forests where tree uprooting dynamics are blocked by management activities suggests that human interventions can change the slope process regime in forest ecosystems

burial and turbulent transport by bioturbation a 27 year experiment in southeast australia in order to assess the net effect and relative importance of geomorphic processes at two natural woodland sites in southeast australia 100 small tiles were placed on the soil surface in 1979 and their movement was monitored over the course of nearly three decades rates of tile burial and other tile displacement were considerable but also markedly random being largely inconsistent with expected patterns of displacement by orthodox creep and rainwash processes this included substantial upslope displacement and burial depths that ranged from zero to 5 cm we suggest that such turbulent transport in the topsoil has mostly been caused by the direct and indirect transfer of soil and clasts by animals and plants i e bioturbation in addition to direct evidence of biota interacting with tiles the effectiveness of bioturbation at our sites has been well established and the overall tile burial rate of 0 25 to 0 4 mm yr 1 is comparable to rates of surface mounding patterns of tile movement are generally consistent with soils geomorphic theory regarding the biomantle and bioturbation driven stonelayer formation and provide further evidence that soil transfer and slope movement in many situations are markedly random and complex processes copyright 2010 john wiley sons ltd

process based model linking pocket gopher thomomys bottae activity to sediment transport and soil thickness burrowing organisms assist in shaping earth surfaces and are simultaneously affected by the environment they inhabit however a conceptual framework is not yet available to describe this feedback we introduce a model that connects the population density of soil burrowing animals to sediment transport via energy the model combined with avail able data from california hillslopes where soil erosion is driven by pocket gophers thom omys bottae suggests that a gopher annually expends 9 kj of energy or 1 of re ported burrowing energy expenditure in generating sediment transport the model is used to evaluate the case that gophers prefer to populate thicker soils the results suggest that this behavior may drastically dampen the spatial and temporal variations of soil thickness and gopher populations implying that burrowing organisms may create landscapes dis tinct from those affected by abiotic processes

a process based model for colluvial soil depth and shallow landsliding using digital elevation data a model is proposed for predicting the spatial variation in colluvial soil depth the results of which are used in a separate model to examine the effects of root strength and vertically varying saturated conductivity on slope stability the soil depth model solves for the mass balance between soil production from underlying bedrock and the divergence of diffusive soil transport this model is applied using high resolution digital elevation data of a well studied site in northern california and the evolving soil depth is solved using a finite difference model under varying initial conditions the field data support an exponential decline of soil production with increasing soil depth and a diffusivity of about 50 cm 2 yr the predicted pattern of thick and thin colluvium corresponds well with field observations soil thickness on ridges rapidly obtain an equilibrium depth which suggests that detailed field observations relating soil depth to local topographic curvature could further test this model bedrock emerges where the curvature causes divergent transport to exceed the soil production rate hence the spatial pattern of bedrock outcrops places constraints on the production law the infinite slope stability model uses the predicted soil depth to estimate the effects of root cohesion and vertically varying saturated conductivity low cohesion soils overlying low conductivity bedrock are shown to be least stable the model may be most useful in analyses of slope instability associated with vegetation changes from either land use or climate change although practical applications may be limited by the need to assign values to several spatially varying parameters although both the soil depth and slope stability models offer local mechanistic predictions that can be applied to large areas representation of the finest scale valleys in the digital terrain model significantly influences local model predictions this argues for preserving fine scale topographic detail and using relatively fine grid sizes even in analyses of large catchments

evidence for nonlinear diffusive sediment transport on hillslopes and implications for landscape morphology steep soil mantled hillslopes evolve through the downslope movement of soil driven largely by slope dependent transport processes most landscape evolution models represent hillslope transport by linear diffusion in which rates of sediment transport are proportional to slope such that equilibrium hillslopes should have constant curvature between divides and channels on many soil mantled hillslopes however curvature appears to vary systematically such that slopes are typically convex near the divide and become increasingly planar downslope this suggests that linear diffusion is not an adequate model to describe the entire morphology of soil mantled hillslopes here we show that the interaction between local disturbances such as rainsplash and biogenic activity and frictional and gravitational forces results in a diffusive transport law that depends nonlinearly on hillslope gradient our proposed transport law 1 approximates linear diffusion at low gradients and 2 indicates that sediment flux increases rapidly as gradient approaches a critical value we calibrated and tested this transport law using high resolution topographic data from the oregon coast range these data obtained by airborne laser altimetry allow us to characterize hillslope morphology at 2 m scale at five small basins in our study area hillslope curvature approaches zero with increasing gradient consistent with our proposed nonlinear diffusive transport law hillslope gradients tend to cluster near values for which sediment flux increases rapidly with slope such that large changes in erosion rate will correspond to small changes in gradient therefore average hillslope gradient is unlikely to be a reliable indicator of rates of tectonic forcing or baselevel lowering where hillslope erosion is dominated by nonlinear diffusion rates of tectonic forcing will be more reliably reflected in hillslope curvature near the divide rather than average hillslope gradient

litter dams and microterraces formed on hillslopes subject to rainwash in the sydney basin australia abstract observations of the results of erosion on hillslopes destabilized by fire were made over various periods up to 4 5 years in the sydney basin australia on many sites a microrelief form of litter dams and microterraces were noted and the conditions favouring their formation identified litter dams formed during the first runoff event after the fire in normal conditions they stabilized rapidly then slowly deteriorated over 3 or 4 years a general model of litter dam and microterrace morphology and sedimentology is presented and their significance in the genesis of hillslope soils is discussed