assessment of radiometric correction techniques in analyzing vegetation variability and change using time series of landsat images abstract the homogeneity of time series of satellite images is crucial when studying abrupt or gradual changes in vegetation cover via remote sensing data various sources of noise affect the information received by satellites making it difficult to differentiate the surface signal from noise and complicates attempts to obtain homogeneous time series we compare different procedures developed to create homogeneous time series of landsat images including sensor calibration atmospheric and topographic correction and radiometric normalization two seasonal time series of landsat images were created for the middle ebro valley ne spain covering the period 1984 2007 different processing steps were tested and the best option selected according to quantitative statistics obtained from invariant areas simultaneous medium resolution images and field measurements the optimum procedure includes cross calibration between landsat sensors atmospheric correction using complex radiative transfer models a non lambertian topographic correction and a relative radiometric normalization using an automatic procedure finally three case studies are presented to illustrate the role of the different radiometric correction procedures when analyzing and explaining gradual and abrupt temporal changes in vegetation cover as well as temporal variability we have shown that to analyze different vegetation processes with landsat data it is necessary to accurately ensure the homogeneity of the multitemporal datasets by means of complex radiometric correction procedures failure to follow such a procedure may mean that the analyzed processes are non recognizable and that the obtained results are invalid

effects of vegetation change on interrill runoff and erosion walnut gulch southern arizona during the past 100 years grassland has been replaced by shrubland in many parts of the american southwest the effects of this vegetation change on interrill runoff and erosion are investigated by performing field experiments on small and large runoff plots located on contemporary grassland and shrubland hillslopes in walnut gulch experimental watershed the experiments indicate that the vegetation change causes runoff and erosion to increase in interrill areas by decreasing resistance to overland flow decreasing runon infiltration increasing the spatial heterogeneity of the plant canopy and possibly increasing the susceptibility of the soil to frost action increased runoff and erosion result in stripping of the soil a horizon the formation of desert pavement in intershrub areas and the development of rills fines remain and accumulate only under shrubs where they form islands of fertility shrubs are able to regenerate in these islands but it is difficult for any plants to become established in intershrub areas consequently there is an increase in the spatial heterogeneity of soil resources and this spatial heterogeneity is self perpetuating increasing spatial heterogeneity of soil resources is considered to be characteristic of the process of desertification

geomorphology within the interdisciplinary science of environmental flows article i nfo the field tradition in geomorphology informs beyond studying landforms by also providing a stage for understand ing how geomorphic elements influence the ecology of biota the intersection between fluvial geomorphology and riverine ecology represents an ideal confluence to examine the contribution of the geomorphic field tradition to en vironmental flows and show this area of riverine management as a research frontier for applied geomorphology environmental flows have consisted of a set of ecological based stream flow guidelines designed to inform sustain able water resource management that supports healthy riverine habitats and provides sufficient water supply for society geomorphological understanding is central to environmental flows because it is the interaction between flow form and substrate that influences habitat type condition availability and biotic use across space and time this relationship varies longitudinally laterally vertically overtime and across macro to mesoscale morphologies withintheriverine environment thegeomorphictemplateis therefore asintegralasthe flow wereviewedstudies where field evidence indicated that geomorphology impacts the effectiveness of environmental flow strategies and wemakethecasefortheneedtoincreasegeomorphic considerationsinenvironmental flows although flow iscom monly referred toas themaster variablein environmental flows geomorphologymediatestheeffectsof flow regime on ecological processes concepts and applications from this perspective on the role of geomorphology in riverine ecosystem research will inform the practice policy and implementation of environmental flows

geomorphology and ecosystems challenges and keys for success in bridging disciplines geomorphology plays a fundamental role in controlling many ecosystem processes and in turn ecosystems can have a profound influence on many geomorphic forms and processes over the past few decades a proliferation of research has developed at the interface of geomorphology and ecosystems ecology the 2005 binghamton symposium brought together some of the leading researchers from both communities to address these critical interfaces between the disciplines this paper reviews some of the aspects of the disciplines of geomorphology and ecosystems ecology and the papers presented at the symposium the papers in this volume illustrate the current status of the disciplines the difficulties in bridging the disciplines and the issues that are emerging as research priorities

the use of caesium 137 to estimate agricultural erosion on steep slopes in a tropical watershed the estimation of erosion and sediment delivery rates in tropical mountain watersheds is difficult and most of the methods widely used for estimating soil erosion over large areas have serious limitations the 137 cs approach has potential for quantifying soil erosion because it can provide retrospective estimates of long term since 1963 net sediment redistribution relatively quickly despite its great potential 137 cs has not yet been used in an extensive reconnaissance level survey of erosion in complex tropical mountain environments the objective of this study was to examine the applicability of the 137 cs method to estimate erosion on steep tropical agricultural lands 23 to 80 slopes in the nizao watershed a humid tropical mountain area of the dominican republic in this study we i examine the variation of 137 cs in ten reference sites eight coffee groves and two forested sites and ii estimate erosion from 14 cultivated fields the soil pool of 137 cs ranged from to 150 to 192 mbq cm 2 on reference sites with minimal erosion variability among reference sites was less than expected for such complex mountain terrain the variability within coffee and forested reference average cv 28 sites was similar to the variability found on grassland and forested reference sites in the temperate zone the estimated annual soil loss from 14 sampled fields ranged from 6 to 61 t ha 1 year 1 with an overall mean of 26 t ha 1 year 1 overall the soil erosion estimates found using the 137 cs method were much lower than those often assumed for such steep tropical hillsides these erosion estimates account for soil loss since 1963 only and it seems likely that soil losses may have been much higher in earlier decades immediately after initial forest clearing earlier in the 20th century

the 137cs technique applied to steep mediterranean slopes part ii landscape evolution and model calibration over the past years the caesium 137 cs 137 technique has been successfully applied in numerous environments all over the world this technique is using the worldwide distribution of the anthropogenic cs 137 radionuclide and its redistribution associated with soil particles as an effective estimation of net soil loss rates in contrast to numerous studies on deep often cultivated clay soils with gentle to intermediate slopes typical mediterranean shallow stony soils on steep slopes have received less attention in this paper the landscape evolution over the past 37 years has been evaluated using the cs 137 technique for two lithological different areas under contrasting land use in the alora case study area malaga spain in soils on gneiss and serpentinite bedrock several transects have been selected on steep slopes up to 35 with mean soil depths from 37 cm for gneiss to 24 em for serpentinite estimating net soil redistribution rates from radionuclide distributions depends on the calculation of the local area reference inventory and the used calibration technique several methods have been tested and final results were found to differ considerably after careful parameter selection the resulting net soil redistribution estimates for the different transects have been compared with simulations of a simple landscape evolution model resulting in different possible scenarios of erosional response total net soil loss for the study area range from 2 3 0 25 to 69 1 7 8 t ha 1 year 1 for serpentinite and gneiss slopes respectively differences in total slope sediment budgets as well as differences along the transeets reveal influences of landscape representation and land use in this case the impact of soil translocation by tillage and resulting erosion rates are far more important than possible parent material induced differences however comparing the two sampled areas not only net rates but spatial patterns as well reveal important differences in distribution over the landscape of net erosion and net sedimentation zones c 2003 elsevier b v all rights reserved

variations in sediment sources and yields in the finger lakes and catskills regions of new york the proportional contributions of stream bank and surface sources to fine sediment loads in watersheds in new york state were quantified with uncertainty analysis eroding streamside glacial drift including glaciolacustrine deposits were examined to help explain variations in the proportional contributions made by bank erosion sediment sources were quantified by comparing concentrations of the bomb derived radionuclide 137 cs in fluvial sediment with sediment from potential source areas such as agricultural soils forest soils and stream banks to compare sediment sources in streams containing abundant deposits of fine grained glacial drift with watersheds that lacked moderate or extensive streamside deposits samples were taken from 15 watersheds in the region the mean contribution of bank erosion to sediment loads in the six streams with glaciolacustrine deposits was 60 range 46 76 the proportional contribution of bank erosion was also important in one stream lacking glaciolacustrine deposits 57 but was less important in the remainder with contributions ranging from 0 to 46 data from this study on the varying contributions of bank erosion and data from past studies of sediment yield in 15 watersheds of new york state suggest that eroding streamside glacial deposits dominate sediment yield in many watersheds in other watersheds past impacts to streams such as channelization have also resulted in high levels of bank erosion copyright 2007 john wiley sons ltd

topographic normalization of landsat tm images of forest based on subpixel sun canopy sensor geometry abstract because trees are geotropic perpendicular to the geoid topography has no control over the sun crown geometry what topography does influence is the relative positioning of trees and thus the amount of shadowing cast by them within the canopy as satellite sensors in general measure the collective radiance of many trees inside their instantaneous field of view the overall canopy brightness at the pixel scale is strongly controlled by canopy shadowing and hence by the topography the removal of or compensation for topographic effects on forest images should be based on the normalization of mutual shadowing at the subpixel scale rather than on the normalization of sun terrain sensor geometry at the pixel scale the sun canopy sensor scs topographic correction model was developed to characterize and hence correct the topographic effects on forest images testing with simulated image data showed the scs model to be accurate root mean squared residual error

functional ecomorphology feedbacks between form and function in fluvial landscape ecosystems abstract the relationship between form and function has been a central organizing principle in biology throughout its history as a formal science this concept has been relevant from molecules to organisms but loses meaning at population and community levels where study targets are abstract collectives and assemblages ecosystems include organisms and abiotic factors but ecosystem ecology too has developed until recently without a strong spatially explicit reference landscape ecology provides an opportunity to once again anneal form and function and to consider reciprocal causation between them this ecomorphologic view can be applied at a variety of ecologically relevant scales and consists of an investigation of how geomorphology provides a structural template that shapes and is shaped by ecological processes running water ecosystems illustrate several principles governing the interaction of landscape form and ecological function subsumed by the concept of functional ecomorphology particularly lucrative are ecosystem level interactions between geologic form and biogeochemical processes integrated by hydrologic flowpaths while the utility of a flowpath based approach is most apparent in streams spatially explicit biogeochemical processing pervades all landscapes and may be of general ecological application

palaeozoic landscapes shaped by plant evolution fluvial landscapes diversified markedly over the 250 million years between the cambrian and pennsylvanian periods the diversification occurred in tandem with the evolution of vascular plants and expanding vegetation cover in the absence of widespread vegetation landscapes during the cambrian and ordovican periods were dominated by rivers with wide sand beds and aeolian tracts during the late silurian and devonian periods the appearance of vascular plants with root systems was associated with the development of channelled sand bed rivers meandering rivers and muddy floodplains the widespread expansion of trees by the early pennsylvanian marks the appearance of narrow fixed channels some representing anabranching systems and braided rivers with vegetated islands we conclude that the development of roots stabilized the banks of rivers and streams the subsequent appearance of woody debris led to log jams that promoted the rapid formation of new river channels our contention is supported by studies of modern fluvial systems and laboratory experiments in turn fluvial styles influenced plant evolution as new ecological settings developed along the fluvial systems we suggest that terrestrial plant and landscape evolution allowed colonization by an increasingly diverse array of organisms

relation between infiltration and stone cover on a semiarid hillslope southern arizona abstract a knowledge of the spatial distribution of infiltration rates is essential to the application of realistic distributed rainfall runoff models in semiarid areas one method of determining this distribution is to develop a predictive equation based on a readily observable surface property such as stone cover previous studies of the relation between infiltration and stone cover on shrub covered semiarid hillslopes have yielded both positive and negative correlations it is suggested that positive correlations result where infiltration measurements are confined to areas between large shrubs negative correlations on the other hand reflect pronounced shrub intershrub differences in infiltration and stone cover and are found where both shrub and intershrub areas are sampled in this study of a semiarid hillslope in southern arizona both shrub and intershrub areas are sampled and a negative correlation is obtained between infiltration and stone cover this correlation arises from the fact that under shrubs fine sediments have accumulated primarily as a result of differential splash whereas between shrubs such sediments have been selectively removed by a combination of rainsplash and overland flow leaving behind a gravel lag consequently infiltration rates are higher under shrubs than between them owing to the higher percentage of sand in the surface soil the larger quantity of organic matter both within the soil and on its surface and the greater digging and burrowing by animals in addition simulated rainfall experiments imply that shrubs with moderately dense canopies are more effective than adjacent surface gravels in dissipating the kinetic energy of raindrops and thereby reducing surface sealing and promoting infiltration inasmuch as the field site is typical of gentle shrub covered piedmont hillslopes over much of the sonoran desert inverse relations between infiltration rate and stone cover are probably characteristic of such hillslopes and may be used to predict the spatial distribution of infiltration rates for inclusion in rainfall runoff models

hydrogeomorphic edge detection and delineation of landscape functional units from lidar digital elevation models 1 a new method is introduced to delineate hydrogeomorphic elements from light detection and ranging lidar digital elevation models landscape segmentation is achieved using an edge detection procedure to identify boundaries defining rapid changes in the tan d index of landscape drainage potential these boundaries define homogenous functional landscape units that can be classified according to different topographically derived indices such as mean of the expected hydraulic gradient approximated by tan d mean topographic wetness index and mean ratio of flow path lengths to flow path gradients l g two case studies are presented in which the new method was applied 1 to map forested wetlands and nonwetland saturation prone depressional areas and improve regression models of dissolved organic carbon source areas in the muskoka haliburton region of south central ontario and 2 to spatially characterize near surface soil moisture patterns along a complex upland hillslope catena in a small experimental watershed in northwestern ontario both case studies point to the critical role of local drainage conditions and slope geometry in dictating spatial patterns of terrain wetness in complex boreal shield landscapes the results cast uncertainty on the role of upslope contributing area as a first order control on terrain wetness in this environment nevertheless the results highlight the strong potential of digital terrain analysis to improve conceptualization of hydrological processes in the boreal shield and they are conceptually consistent with the emerging paradigm of runoff generation in this region we propose hydrogeomorphic edge detection and classification as a way to improve the characterization of landscape functional units in boreal shield watersheds for process oriented and model based ecohydrological research

channel initiation and the problem of landscape scale since the 1940s it has been proposed that landscape dissection into distinct valleys is limited by a threshold of channelization that sets a finite scale to the landscape this threshold is equal to the hillslope length that is just shorter than that necessary to support a channel head a field study supports this hypothesis by showing that an empirically defined topographic threshold associated with channel head locations also defines the border between essentially smooth undissected hillslopes and the valley bottoms to which they drain this finding contradicts assertions that landscapes are scale independent and suggests that landscape response to changes in climate or land use depends on the corresponding changes in the threshold of channelization

evaluation of topographic effects in remotely sensed data abstract remotely sensed data are generally analyzed assuming flat terrain as the spectral signature of the ground depends upon the orientation of the surface slope the topography has to be considered for efficient radiometric corrections in mountainous regions in this paper we present a modelization of the atmospheric downward radiance at the ground level which gives us the relative contributions of the direct solar beam and of the diffused radiation for different atmospheric turbidities and different solar incidence angles lastly we estimate the influence of the topography on these contributions to show up which effects can be neglected

considering river structure and stability in the light of evolution feedbacks between riparian vegetation and hydrogeomorphology river ecological functioning can be conceptualized according to a four dimensional framework based on the responses of aquatic and riparian communities to hydrogeomorphic constraints along the longitudinal transverse vertical and temporal dimensions of rivers contemporary riparian vegetation responds to river dynamics at ecological timescales but riparian vegetation in one form or another has existed on earth since at least the middle ordovician c 450 ma and has been a significant controlling factor on river geomorphology since the late silurian c 420 ma on such evolutionary timescales plant adaptations to the fluvial environment and the subsequent effects of these adaptations on fluvial sediment and landform dynamics resulted in the emergence from the silurian to the carboniferous of a variety of contrasted fluvial biogeomorphic types where water flow morphodynamics and vegetation interacted to different degrees here we identify several of these types and describe the consequences for biogeomorphic structure and stability i e resistance and resilience along the four river dimensions of feedbacks between riparian plants and hydrogeomorphic processes on contrasting ecological and evolutionary timescales

dart radiative transfer modelling for sloping landscapes abstract topography is one of the key factors that impact remotely sensed data and their interpretation indeed combined with the viewing geometry and neighbour effects it strongly affects the direct diffuse and multi scattered scene irradiance which in turn impacts the radiative budget and remote sensing signals of the landscapes the increased availability of digital elevation models dem and the advancement of 3d radiative transfer rt models allow us to better address these topographic effects dart discrete anisotropic radiative transfer is one of the most accurate and comprehensive 3d rt models that simulate remote sensing observations of natural and urban landscapes with topography and atmosphere it simulates environmental effects i e impact of adjacent landscape on the observed landscape using a so called infinite slope mode that infinitely duplicates the observed landscape while ensuring the continuity of slope and altitude at the dem edges up to dart version 5 7 4 this mode was slightly inaccurate and computer intensive depending on the topography this paper presents an innovative modelling strategy that greatly improves it in terms of accuracy image quality and computer efficiency for that a fictive auxiliary oblique plane adapted to the landscape topography is introduced for managing the scene illumination the earth atmosphere coupling and the storage of the radiation that exits the scene before being projected onto the sensor plane improvements and validations are illustrated both visually and quantitatively by dart images radiometric products and radiative budget for example the observed reflectance of a lambertian slope is equal to the expected analytical value in addition the solar plane reflectance of a forest on a mountain slope experimental scene has an average error of about 0 01 relative to the reflectance of the same forest stand in the reference scene i e nine duplications of the experimental scene this new modelling is already integrated in the official dart version https dart omp eu

feasible optimality of vegetation patterns in river basins 1 we examine mechanisms leading to organization of vegetation patterns within the channel network structure of a semi arid new mexico river basin under the controlling influence of water stress we compare the actual pattern of water stress within the basin to patterns resulting from two algorithms of local stress optimization which proceed from an initial fully random vegetation distribution here we show that the distribution of vegetation and basin water stress derived from an algorithm that maintains local optimization within the network flow path exhibits considerably better agreement with the actual distribution than one that ignores the network structure of the basin these results suggest the pattern of actual vegetation observed within the basin corresponds to a condition of feasible optimality in which organization is constrained by the stochastic nature of local interactions mediated by the network configuration the principles of such organization have important consequences regarding the interaction between land cover change and hydrological dynamics in river basins as well as the biogeographical evolution of landscapes

recent advances in the use of public domain satellite imagery for mineral exploration a review of landsat 8 and sentinel 2 applications abstract thanks to their wide coverage and the valuable spectral information remote sensing data constitute a popular instrument in the mineral exploration toolbox in recent times the remote sensing community has witnessed the launch of the new and improved landsat 8 and sentinel 2 multispectral sensors the former constitutes the eighth sensor of the landsat series launched by the national aeronautics and space administration nasa while the latter is linked to the sentinel mission launched by the european space agency esa the main objective of our contribution is to provide a comprehensive review of the use of the landsat 8 and sentinel 2 multispectral sensors in mineral exploration the free and open access to these data and their enhanced spectral and spatial characteristics compared to the existing multispectral sensors has clearly promoted the use of remotely sensed in mineral exploration in addition as illustrated by the case studies presented in this paper landsat 8 and sentinel 2 data present effective and accurate mapping tools for mineral exploration both sensors identified iron oxides and al oh absorption features in addition to silicate and carbonate minerals our review indicated that landsat 8 is by far the more popular sensor in mineral exploration applications greater uptake of sentinel 2 and further case studies will be necessary to better demonstrate its capabilities and potential

spatial variability in the timing nature and extent of channel response to typical human disturbance along the upper hunter river new south wales australia prior to european settlement the upper hunter river near muswellbrook new south wales was a passively meandering gravel bed river of moderate sinuosity and relatively uniform channel width analyses of floodplain sedimentology archival records parish maps and aerial photographs document marked spatial variability in the pattern of channel change since european settlement in the 1820s different types rates and extents of change are reported for seven zones of adjustment along an 8 km study reach this variable adjustment reflects imposed antecedent controls buried terrace material and bedrock which have significantly influenced local variability in river sensitivity to change as well as contemporary morphodynamics and geomorphic complexity local variability in system responses to disturbance has important implications for future river management and rehabilitation

crayfish and fish as bioturbators of streambed sediments assessing joint effects of species with different mechanistic abilities abstract many studies illustrate that bioturbating animal species individually affect aquatic sediments through diverse mechanistic abilities whereas assessments of joint effects of such species on sediments are relatively rare such joint effects have implications for real systems in which different bioturbators coexist but are difficult to predict for two reasons first they can be additive being the sum of the individual effects of each species or they can be positive or negative interactive being greater or smaller than the sum of the individual effects second if interactive they can depend on biotic interactions that affect the bioturbating activities of the species and or they can depend on physical interactions among bioturbator induced sediment modifications using experimental streams we assessed such joint effects on gravel sand sediments for flow and sediment conditions preferred by barbel barbus barbus but also used by gudgeon gobio gobio and in a second experiment for flow and sediment conditions preferred by both male crayfish orconectes limosus and gudgeon these species have different mechanistic abilities to affect gravel and or sand in stream beds in each experiment we measured i the transport of gravel and sand at baseflow during 12 experimental days ii four sediment surface characteristics after 12 d and iii the critical shear stress c causing incipient gravel and sand motion during experimental floods after 12 d gudgeon contributed differently to the joint effects in the two experiments which related to its individual weight prevailing baseflow shear stress sediment particle weight and sediment mixture availability of surface sand overall the species pairs had predominantly negative interactive joint effects on the sediment variables assessed by us both a literature survey and observations during the experiments provided no evidence for direct biotic interactions between barbel and gudgeon or crayfish and gudgeon so one would reasonably associate their negative interactive effects on the sediments with physical interactions among bioturbator induced sediment surface modifications individually each species reduced the percentage of sand in the surface layer and the surface algal cover to relatively low values so that the species pairs could not accomplish much greater joint effects on these variables explaining their negative interactive effects on them as algal cover particularly affected the c for gravel and sand the negative interactive effects of the animals on this surface variable chained toward the c for the sediments on which the species pairs also had negative interactive effects such chained negative interactive effects on sediment variables are seemingly a general pattern of joint bioturbator effects on aquatic sediments i e the many so far described single species effects should be smaller than their sum if the species coexists in nature

atmospheric corrections to satellite radiometric data over rugged terrain radlometnc measurements from satelhtes m the solar portmn of the electromagnetic spectrum can be converted to measurements of surface eratance over rugged terrain the satelhte image must be precisely registered to a terrain data set for small areas a first order polynomial mterpolatmn scheme is generally satisfactory for the geometric rectlficatmn if there are saturated plxels a nearest neighbor procedure is used for the mterpolated satellite radiance nmnbers otherwise a cublc convolutmn algorithm is used path radiance and path transmittance are calculated wlth a simple spectral model whmh reqmres an estimate of the water vapor and aerosol content of the atmosphere

seasonal variation in surface subsurface water exchange and lateral hyporheic area of two stream aquifer systems abstract we used two dimensional unconfined transient groundwater flow models to investigate the interface between stream and groundwater flow systems or hyporheic zone of two first order streams that drain catchments with distinctly different alluvial sediments and bedrock lithology particle tracking showed that lateral hyporheic area planimetric area of flow paths lateral to the stream that are recharged by and return to the stream with travel times of 10 days or less differed between the two study streams and varied with discharge within each system at the rio calaveras welded tuff lateral hyporheic area ranged from 1 7 to 4 m 2 over the annual cycle in the aspen creek system sandstone lateral hyporheic area 1 1 5 m 2 was restricted to roughly half of that observed at rio calaveras the size of the hyporheic zone lateral to the streams at both sites decreased by approximately 50 during high flows sensitivity analyses indicated that changes in the hydraulic conductivity of alluvial and streambed sediments and variation in recharge rates have greatest impact on the magnitude direction and spatial distribution of stream groundwater exchange

incorporating ecogeomorphic feedbacks to better understand resiliency in streams a review and directions forward decades of interdisciplinary research show river form and function depends on interactions between the living and nonliving world but a dominant paradigm underlying ecogeomorphic work consists of a top down unidirectional approach with abiotic forces driving biotic systems stream form and location within the stream network does dictate the habitat and resources available for organisms and overall community structure yet this traditional hierarchal framework on its own is inadequate in communicating information regarding the influence of biological systems on fluvial geomorphology that lead to changes in channel morphology sediment cycling and system scale functions e g sediment yield biogeochemical nutrient cycling substantial evidence that organisms influence fluvial geomorphology exists specifically the ability of aquatic vegetation and lotic animals to modify flow velocities and sediment deposition and transport thus challenging the traditional hierarchal framework researchers recognize the need for ecogeomorphic frameworks that conceptualize feedbacks between organisms sediment transport and geomorphic structure furthermore vital ecosystem processes such as biogeochemical nutrient cycling represent the conversations that are occurring between geomorphological and biological systems here we review and synthesize selected case studies highlighting the role organisms play in moderating geomorphic processes and likely interact with these processes to have an impact on an essential ecosystem process biogeochemical nutrient recycling we explore whether biophysical interactions can provide information essential to improving predictions of system scale river functions specifically sediment transport and biogeochemical cycling and discuss tools used to study these interactions we suggest that current conceptual frameworks should acknowledge that hydrologic geomorphologic and ecologic processes operate on different temporal scales generating bidirectional feedback loops over space and time hydro and geomorphologic processes operating episodically during bankfull conditions influence ecological processes e g biogeochemical cycling occurring over longer time periods during base flow conditions this ecological activity generates the antecedent conditions that influence the hydro and geomorphologic processes occurring during the next high flow event creating a bidirectional feedback this feedback should enhance the resiliency of fluvial landforms and ecosystem processes allowing physical and biological processes to pull and push against each other over time

large woody debris physical process and riparian forest development in montane river networks of the pacific northwest abstract we present a conceptual biogeomorphic model of riparian forest development in montane river networks the role of physical process in driving the structure composition and spatial distribution of riparian forests is examined we classify the drainage network into disturbance process based segments including 1 debris flow and avalanche channels 2 fluvial and debris flow channels and 3 fluvial channels riparian forests are shown to be significant in the development of channel morphology through the stabilization of active floodplains and as sources of large woody debris olwd lwd is operationally defined as wood 0 1 m diameter and 1 m length lwd plays a key role in the development of montane riparian forests lwd deposited in the active channel and floodplain provides sites for vegetation colonization forest island growth and coalescence and forest floodplain development riparian forest patterns parallel the distribution of hillslope and fluvial processes through the network riparian forest structure composition and spatial distribution through the network are driven by the major disturbance processes including 1 avalanches 2 debris flows and 3 flooding riparian forest patterns also reflect the action of lwd in the organization and development of forested floodplains in gravel bedded montane river networks the focus of our examples are montane river networks of the pacific northwest usa

modeling surface longwave radiation over high relief terrain abstract thermal anisotropy is an important phenomenon in thermal infrared remote sensing as it restricts the retrieval accuracy of surface longwave radiation slr topography is an essential controlling factor for the directionality of slr for high relief regions e g mountain regions where there is land surface heterogeneity and non isothermal properties at pixel scales however satellite sensors can only receive radiance from a specific surface object at a small number of simultaneous viewing angles which makes the quantitative modeling of thermal anisotropy challenging therefore we developed the topographic longwave radiation model tlrm to describe the directionality of slr components taking into account the variability of both subpixel topography and thermal anisotropy in high relief regions the reliability of tlrm was validated using the discrete anisotropic radiative transfer dart model over two typical geomorphic areas a valley scene and a peak scene the preliminary validation shows good agreement in terms of surface upward longwave radiance which confirms the potential of tlrm for capturing the anisotropic patterns of land surfaces the radiance values simulated by the dart model were first revised for the spectral mismatch then they are used to correct residual deviation for tlrm using linear regressions the root mean square error rmse and coefficient of determination r2 were 0 830 w m2 sr and 0 746 for the valley scene respectively and 0 239 w m2 sr and 0 711 for the peak scene respectively compared with tlrm models that do not consider terrain effects generate significant discrepancies in high relief slr components the differences in downward longwave radiation can reach 60 w m2 in valleys without considering terrain effects based on the reference of hemispherical upward longwave radiation surface upward longwave radiation estimated by the direct estimation method had a bias of 11 41 w m2 and standard deviation std of 7 30 w m2 while the directional upward longwave radiation had a bias of 5 99 w m2 and std of 4 08 w m2 showing lower estimation variation the discrepancy between surface net longwave radiation nlr and terrain corrected nlr ranged between 50 and 130 w m2 with clear negative biases mainly occurring in valleys with higher spatial resolutions of remotely sensed imagery the influence of complex terrain on land surface radiative flux has become more significant this parameterization scheme is expected to better represent the topographic effects on slr enhance understanding of thermal anisotropy in non isothermal mixed pixel areas of high relief and improve the inversion accuracy of slr

meander dynamics in a changing river corridor abstract in the first decades of the twentieth century the ebro river was the iberian channel with the most active fluvial dynamics and the most remarkable spatial temporal evolution its meandering typology the dimensions of its floodplain with an average width 3 0 km and the singularities of its flow regime produced a especially interesting set of river functions from the perspective of the fluvial geomorphology of the largest mediterranean channels the largest dynamics of the ebro river are concentrated along the meandering profile of the central sector during the twentieth century this sector experienced a large alteration of its geomorphological structure we present here an analysis of this evolution through the cartographic study of a long segment of the river 250 km in 1927 1956 and 2003 the study is focused on a wide set of geomorphic parameters and indicators that represent the forms of the meander belt its lateral dynamics and the overall mobility of the river corridor the results of the analysis show a large transformation of the meander dynamics as well as a massive loss of the river lateral activity most of which occurred in the second half of the twentieth century this intense geomorphological transformation becomes visible in i the large reduction of the bankfull width and the active channel area ii the decrease in the rate of lateral channel migration iii the loss of channel activity and iv the large reduction of coincidence of the active channel areas however the most traditional form parameters i e wavelength amplitude radius of curvature and meander length do not show significant differences throughout the time interval analysed the study reinforces the necessity of integrating a wide range of dynamic indicators which may complement the classical form parameters and represent the real functioning of the river corridor in the geomorphological analyses of meander dynamics this work also shows the most important procedures for the recuperation of the ecomorphological processes of the meander belt it highlights the most urgent measurement for ecological recovery and illustrates the management scenarios that have led to the present day situation of the river system this work further highlights the management scenarios that could be most important for the continued good status of the meander dynamics in this changing river corridor

formation and dynamics of vegetated fluvial landforms follow the biogeomorphological succession model in a channelized river feedback between hydrogeomorphological processes and riparian plants drives landscape dynamics and vegetation succession in river corridors we describe the consequences of biogeomorphological feedback on the formation and dynamics of vegetated fluvial landforms based on observations from the channelized isere river in france the channel was laterally confined with embankments and mostly straightened from the beginning of the 1970s to the end of the 1990s alternate bars were progressively but heavily colonized by vegetation this context presented an exceptional opportunity to analyse temporal adjustments between fluvial landforms and vegetation succession from bare gravel bars to mature upland forest as the consequence of biogeomorphological interactions based on a gis analysis of aerial photographs between 1948 and 1996 we show that the spatiotemporal organization of vegetated bars within the river channel observed in 1996 resulted from a bioconstruction and biostabilization effect of vegetation and interactions between bars of varying age size and mobility field measurements in 1996 reflected how a strong positive feedback between sedimentary dynamics and riparian vegetation succession resulted in the construction of the vegetated bars a highly significant statistical association of geomorphological and vegetation variables rv of co inertia analysis 0 41 p 0 001 explained 95 of the variability in just one axis supporting the existence of very strong feedback between geomorphological changes i e the transformation of small bare alternate bars to fluvial landforms covered by mature upland forest and vegetation succession such dynamics reflect the fluvial biogeomorphological successions model as described by the authors earlier 2020 john wiley sons ltd

the definition of remotely sensed reflectance quantities suitable for rugged terrain abstract the anisotropic scattering behavior of land surface is characterized by its bidirectional reflectance distribution function brdf however a physically consistent brdf definition is still lacking for heterogeneous and rugged terrain that accounts for approximately 24 of earth s land surface in this study we revisited current brdf definitions and updated them for rugged terrain with few dependent parameters illumination and viewing geometries terrain shadows effective areas of illumination and observation and anisotropic reflectance properties of subpixel scale slopes furthermore the bidirectional reflectance factor brf hemispherical directional reflectance factor hdrf directional hemispheric reflectance dhr and bi hemispherical reflectance bhr were proposed within the current physical framework of reflectance quantities these reflectance quantities have been adopted by the 3 d discrete anisotropic radiative transfer dart model to provide the simulations of remote sensing images to highlight the importance of a proper usage of such reflectance terms we used dart simulations to present the topographic effects on these reflectance quantities finally the other issues with respect to surface brdf brf such as spatial scale of rugged terrain characterization of anisotropic reflectance of micro scale surfaces derivative reflectance quantities topographic parameters wavelength dependence and reciprocity and future perspective were discussed

the sedimentary record of carboniferous rivers continuing influence of land plant evolution on alluvial processes and palaeozoic ecosystems abstract evidence from modern rivers and the deep time geological record attests to the fundamental importance of plant life for the construction of physical habitats within fluvial environments data from an extensive literature review and original fieldwork demonstrates that many landforms and geomorphic features of modern river systems appear in the palaeozoic stratigraphic record once terrestrial vegetation had adopted certain evolutionary advances for example stable point bars are associated with the onset of rooted plants in the siluro devonian and avulsive and anabranching fluvial systems become common at the same time as extensive arborescent vegetation in the carboniferous in this paper we demonstrate a correlation between the diversification of physical fluvial environments and the expansion of terrestrial fauna and flora with an emphasis on the culmination of these trends within carboniferous alluvial systems many extrinsic factors have been considered as possible controls on the evolutionary timelines of terrestrialization for organisms however a fundamental prerequisite for achieving terrestrial biodiversity was the variety of physical habitats especially riparian systems available for newly evolved organisms in association with abundant lowland meandering systems the widespread appearance across carboniferous alluvial plains of fixed channel and anabranching reaches created further physical landforms for colonization and would have promoted increasingly complex hyporheic flow regimes furthermore the associated increase in arborescent vegetation and supply of large woody debris to inland and coastal rivers would have created a wealth of microhabitats for continental organisms we argue that the expanding extent and diversity of physical alluvial niches during the palaeozoic is an underappreciated driver of the terrestrialization of early continental life the study of the deep time fossil and stratigraphic record also illustrates that vegetation is a fundamental prerequisite for the creation of biogeomorphic alluvial landforms and physical habitats and microhabitats

reciprocal interactions and adjustments between fluvial landforms and vegetation dynamics in river corridors a review of complementary approaches abstract until recently one way relationships between flow dynamics geomorphology and plant ecology were considered dominantly when studying the functioning of river systems whereby fluvial landforms and hydrogeomorphic processes drive the evolution of riparian plant communities however biological communities may significantly control geomorphic processes and have strong impacts on landform dynamics in order to fully identify the processes linked to river dynamics changes in time and space of fluvial landforms and associated plant communities conceptual multidisciplinary progress is clearly needed to understand the mutual interactions and feedbacks between fluvial landforms and vegetation community dynamics this paper presents a detailed literature review of fluvial geomorphology riparian plant ecology and hydraulic engineering knowledge the historical and recent development of ecological plant succession theory toward the integration of hydrogeomorphic disturbances is discussed as well as the integration of vegetation within geomorphology as a significant landform control factor incorporating both hydrogeomorphic controls on riparian vegetation dynamics and mechanical impacts of vegetation structures on flow properties and sediment dynamics recent progress in ecology hydraulic engineering and fluvial geomorphology emphasises interdependence between biological and physical forms and processes based on this literature review a fluvial biogeomorphic succession concept is proposed to link fluvial landform and riparian vegetation community evolution within a bi directional model the succession of fluvial landforms and associated vegetation communities is composed of four main critical phases that represent a shift in the relative dominance of hydrogeomorphic and ecological processes as a response to biostabilisation and passive bioconstruction processes the positive feedbacks associated with this shift lead to the development of characteristic biogeomorphic structures such as vegetated banks islands or floodplains which are moderated by the biogeomorphic functional roles of ecosystem engineers that induce or reinforce the positive feedbacks this fluvial biogeomorphic succession concept relates the natural darwinian selection and ecological succession theories to fluvial geomorphology

populus nigra l establishment and fluvial landform construction biogeomorphic dynamics within a channelized river populations of the riparian pioneer species populus nigra l which establish on alluvial bars within river channels modulate sediment dynamics and fluvial landforms dense cohorts of p nigra have colonized gravel point bars along the channelized river garonne france during the last 20 years and have enhanced the vertical lateral and longitudinal development of the bars for this period the geomorphic characteristics of two wooded point bars on this laterally stable river are closely linked to the spatial distribution and intensity of establishment and resistance of different cohorts of p nigra furthermore p nigra colonization dynamics were controlled by engineer effects of this same species this relationship is illustrated by a significant correlation between key geomorphic and biological variables measured in situ and characterized with a set of four aerial photographs taken between 2000 and 2010 the development of wooded point bars which are discrete biogeomorphic units over the studied period appear to result from a specific biogeomorphic positive feedback of matter aggregation and vegetation establishment related to sediment trapping and stabilization by pioneer engineer plants we propose a conceptual model of biogeomorphic unit construction for channelized lateral stable rivers we consider the resultant biogeomorphic units as functional from an ecological point of view because p nigra enhances at the cohort scale i its own inherent capacity to resist hydrogeomorphic disturbances and ii its resilience capacity as a result of successful colonization especially downstream of mature poplar stands

topographic effects in avhrr ndvi data an investigation is made of the errors induced in the normalized difference vegetation index ndvi by topographic variation the advanced radiometric ray tracer ararat is used to simulate avhrr imagery for various viewing and illumination conditions at 1 1 km and 50 m resolution topographic error is calculated as the difference between the variable terrain simulation and a flat plane simulation correlation between this error and various topographic factors such as shadowing and adjacement hill illumination are examined the importance of sky occlusion as a topographic factor is highlighted while topographic errors of 13 5 are found in the 50 m resolution simulations these errors are reduced markedly in the 1 1 km dataset to approximately 3

buttresses of tropical rainforest trees influence hillslope processes during heavy rainfall events the buttresses of tropical rainforest trees limit the occurrence of stemflow generated overland flow and soil erosion on hillslopes buttresses promote infiltration by causing stemflow to diverge into separate flow paths on the trunk and by increasing the stemflow contact area at the ground surface buttresses oriented normal to hillslopes function as barriers that further promote infiltration and limit the downslope transport of sediments and chemically enriched stemflow water these relationships between buttressing stemflow and hillslope processes have not been previously noted in the literature buttresses are generally regarded as mechanically efficient support structures that increase the resistance of trees to windthrow and uprooting however this also has an inhibiting effect on hillslope processes because the mounds of bare soil uprooted by tree falls are particularly vulnerable to rainsplash erosion

a fast canopy reflectance model to simulate realistic remote sensing scenarios a model for light interaction has been developed to compute spectral and bidirectional reflectance from discontinuous canopies approximated by an arbitrary configuration of plants the model assumes certain principles of geometric models e g that sensor integrates the radiance reflected from tree plants shaded soil and illuminated soil however the model attempts to compensate for errors due to multiple scattering in vegetation canopies that lead to nonlinear mixing in contrast to geometric models tree crowns are treated as porous partially transmitting geometric bodies reflectance of canopy and shadowed ground are nonlinear mixtures of leaves and background signatures which are moreover influenced by parameters of canopy such as leaf area index lai coefficient of attenuation and leaves transmittance optical parameters are not constant but stochastic variables are controlled by a certain texture in canopy envelopes and roughness and relief in surface background the model may also be run using backgrounds presenting variable topography and comprising different landscape features on imported real images the model predicts the basic features of the bidirectional reflectance factor brf i e bowl shape and the hotspot but unlike common models it is well suited to address the spectral and spatial domains for example the model provides a fast and efficient strategy to derive hyperspectral images at appropriate spatial resolutions e g regional scale over a wide range of ecosystems

linking environmental regimes space and time interpretations of structural and functional connectivity connectivity as a concept has been increasingly part of discussions or explanations in hydrology geomorphology and ecology we address recent critiques of this approach by demonstrating how a refinement which distinguishes structural connectivity from functional connectivity can be used to explain patterns observed in very different environmental systems these systems are found in linkages between surface and subsurface flowpaths and the hyporheos in the river don a temperate river channel in yorkshire uk in surface and subsurface fluxes in agricultural land in the uk and in vegetation and surface conditions in a degrading environment at the sevilleta lter site in the semi arid southwest usa first we demonstrate long term geological and structural controls mediated by in channel processes second human organization of landscape elements is a significant control on runoff and erosion so that similar events can produce very different responses and vice versa third linkages between the removal of grass vegetation and runoff and erosion produce non linear and path dependent feedbacks which control the subsequent degradation of the landscape making the process difficult to reverse as a result of these studies we argue that even in cases where connectivity cannot be directly quantified at least at present this limitation does not prevent the concept from being a useful heuristic device for exploring responses of complex systems furthermore this result implies that an increasing need exists for disciplinary connectivity to investigate such systems

conceptual assessment of dis connectivity and its application to the ganga river dispersal system abstract connectivity in river dispersal systems is an important evolving concept and helps in understanding their dynamics in this study the types of connectivity have been defined on the basis of two components namely physical contact and transfer of material based on this four types of connectivity are recognized these are a active connected system b inactive connected system c partially active connected system and d disconnected system connectivity indices have been proposed based on the process understanding of different types of connectivity this conceptual understanding of connectivity has been applied to the ganga dispersal system a large river system results of the connectivity analysis on the ganga dispersal system reveal that different sets of data such as sediment budgets geochemical isotopic data and radiogenic 238 u 234 u 230 th data are noncoherent therefore developing rigorous and well constrained quantitative multidisciplinary data sets is needed to have a better understanding of connectivity at multiple spatio temporal scales in large river dispersal systems this would ultimately help model the dynamics of such systems

extending a turbid medium brdf model to allow sloping terrain with a vertical plant stand this paper extends the turbid medium approach used for modeling bidirectional reflectance from horizontal plant canopies to sloping terrain with a vertically oriented plant stand previous treatments have accounted for terrain slope by simple adaptation to an inclined plane of models for horizontal surfaces however such treatments implicitly assume that plants grow perpendicularly to the surface despite the fact that plant stems continue to grow vertically on slopes the authors investigate the differences between their new vertical growth model and the more usual perpendicular to the surface growth model in terms of the effect on canopy albedo and bidirectional reflectance factors although the effect of leaf angle distribution on the albedo is different for both the vertical growth and perpendicular growth models it appears to be a much smaller effect than that due to terrain slope for the bidirectional reflectance factors brfs the magnitude and sign of the differences between the two models varies with the direction of observation the slope and the leaf angle distribution and can exceed 10 for a planophile canopy a comparison between modeled and measured data shows that model predictions under the vertical growth assumption are consistent with measurements whereas the assumption of perpendicular growth can lead to large errors