Physiographic Context Research Articles

The Reliability of W-flow Run-off-Rainfall Model in Predicting Rainfall to the Discharge

This research intends to predict the discharge (run-off) from rainfall for which the model is built using W-flow. The research location is in the Gajah Mungkur reservoir (Wonogiri) in Indonesia. The estimation of reservoir inflow has an important role, mainly in the scheme of reservoir operation and management. However, the heterogeneity of complex spatial and temporal patterns of rainfall and also the physiographic context of a watershed cause the development of a model of real-time run-off and rainfall that can accurately predict the reservoir inflow to become a challenge in the development of water resources. In relation to the analysis and prediction of rainfall, the constraint and problem that is still often faced is the minimal availability of observed rainfall data spatially as well as temporally; the time series of rainfall data is not long and complete enough; and the number of rainfall stations is less evenly distributed. The methodology consists of carrying out the literature study, collecting as much rainfall data as possible to build a W flow model, then carrying out the model calibration and analyzing the prediction of real-time reservoir inflow for operation. The result shows that the dependable discharge of the Wonogiri watershed shows that there are two peak discharges, which happened on February II (the second half of February) and December II (the second half of December). However, the discharge is decreasing in July and reaching its lowest level in October II (the second half of October). Doi: 10.28991/CEJ-2023-09-07-015 Full Text: PDF

Soil carbon in the South Atlantic United States: Land use change, forest management, and physiographic context

Evidence-based forest carbon (C) management requires identifying baseline patterns and drivers of soil organic carbon (SOC) stocks, and their responses to land use change and management, at scales relevant to landowners and resource professionals. The growth of datasets related to SOC, which is the largest terrestrial C pool, facilitates use of synthesis techniques to assess SOC stocks and changes at management-relevant scales. We report results from a synthesis using meta-analysis of published studies, as well as two large databases, in which we identify baseline patterns and drivers, quantify influences of land use change and forest management, and provide ecological context for distinct management regimes and their SOC impacts. We conducted this, the fourth in a series of ecoregional SOC assessments, for the South Atlantic States, which are disproportionately important to the national-scale forest C sink and forest products industry in the U.S. At the ecoregional level, baseline SOC stocks vary with climatic, topographic, and soil physical factors such as temperature and precipitation, slope gradient and aspect, and soil texture. Land use change and forest management modestly influence SOC stocks. Reforestation on previously cultivated lands increases SOC stocks, while deforestation for cultivation has the opposite effect; for continuously forested lands, harvesting is associated with SOC increases and prescribed fire with SOC declines. Effects of reforestation are large and positive for upper mineral soils (+30%) but not detectable in lower mineral soils. Negative effects of prescribed fire are due to significant C losses from organic horizons (-46%); fire and harvest have no impacts on upper mineral soils but both increase SOC in lower mineral soils (+8.2 and +46%, respectively, with high uncertainty in the latter). Inceptisols are generally more negatively impacted by prescribed fire or harvest than Ultisols, and covariance between inherent factors (including soil taxonomy) and management impacts indicates how interior vs. coastal physiographic sections differ in their management regimes and SOC trends. In the cooler, wetter, topographically rugged interior hardwood forests, which have larger baseline SOC stocks, prescribed fire and even light harvesting generally decrease SOC; in contrast, intensively managed coastal plain pine plantations begin with small initial SOC stocks, but exhibit rapid gains over even a single rotation. This covariance between place (physiography) and practice (management regime) suggests that distinct approaches to forest C management may be complementary to other ecological or production goals, when implemented as part of wider (e.g., state-level) forest C or climate policy.

Plio-Quaternary sequences and tectonic events in the northern Adriatic Sea (northern Italy)

The analysis of multichannel seismic profiles and their correlation with well data in the northern Adriatic Sea (Northern Italy) has allowed to document Plio-Quaternary episodes of tectonic subsidence and uplift. They affected the sedimentation above the Mesozoic to lower Eocene Friuli-Dinaric Carbonate Platform (FDCP) and the unit composed of the Eocene Trieste Flysch and the Miocene Molassa (TFM), as well as the sedimentary succession lying SW of the FDCP. In particular, the early Zanclean reflooding that postdated the Messinian Salinity Crisis, was followed by the SW-ward progradation of a highstand to forced regressive shelf-slope system (Sequence 1). Forced regression was controlled by a main episode of tectonic uplift that occurred at the end of the Zanclean. This tectonic event also led to the formation of the sequence boundary separating the two main sequences that compose the Plio-Quaternary succession. The lower part of Sequence 2 (Piacenzian to late Pleistocene) recorded a two-step subsidence phase, which led to drowning episodes during Piacenzian and in particular late Gelasian (transgressive systems tract of Sequence 2). They were associated with the partial flooding of the TFM and the Miocene deposits overlying the FDPC, and with a downward bending of the pre-Calabrian succession toward the Apennine chain. The accommodation created during the late Gelasian drowning event was filled in part by an Alpine-sourced, SW-ward prograding system, and in part by the NE-ward paleo-Po prograding system (highstand systems tract of Sequence 2). The most recent part of Sequence 2 documents the last glacio-eustatic cycles in a physiographic context characterized by a very low gradient.

Climatic niche comparisons of eastern North American and eastern Asian disjunct plant genera

AbstractAimWhile the floras of eastern Asia (EA) and eastern North America (ENA) share numerous genera, they have drastically different species richness. Despite an overall similarity in the quality of their temperate climates, the climate of EA is more spatially heterogeneous than that of ENA. Spatial environmental heterogeneity has been found to play a key role in influencing species richness in some regions. Here, we tested the following hypotheses: (a) EA species will occupy larger climatic niches than their ENA congeners, (b) congeners of EA‐ENA disjunct genera will occupy statistically equivalent climatic niches, and (c) congeners of EA‐ENA disjunct genera will occupy more similar climatic niches than expected by their respective physiographic context.LocationNorth America and Asia.Time periodPresent.Major taxa studiedSeed plants.MethodsPredictions generated by ecological niche models (ENMs) were compared for 88 species across 31 EA‐ENA disjunct genera. ENM predictions were assessed for geographic and ecological breadth. Tests for niche equivalency and similarity were performed for congeneric species pairs to determine if species of disjunct genera have experienced niche conservatism or divergence.ResultsEA species tend to occupy greater amounts of climatic niche space than their close relatives in ENA. Over two‐thirds of the conducted niche comparisons show that EA‐ENA congeners either occupy equivalent climatic niche space within these broader climatic regimes or occupy non‐equivalent niches that are as similar as expected given their physiographic contexts.Main conclusionsEA species tend to occupy larger climatic niches, and congeners of EA‐ENA disjunct genera tend to occupy equivalent/similar niche space within their respective distributions, with differences in occupied niches possibly due to their respective physiographic contexts, highlighting how niche‐neutral processes and niche conservatism may affect the distributions of disjunct species.

Soil Carbon in the South Atlantic United States: Land Use Change, Forest Management, and Physiographic Context

Soil Carbon in the South Atlantic United States: Land Use Change, Forest Management, and Physiographic Context

Mapping parent material as part of a nested approach to soil mapping in the Arkansas River Valley

Soil mappers have traditionally relied on tacit knowledge and qualitative assessment of soil-landscape relationships to obtain the physiographic context necessary to predict soil distribution and spatial patterns. This assessment implicitly utilizes a nested hierarchical approach based on differences in the phenomenon scale of soil forming factors where climate, landscape, parent material, and topography are examined in sequence to create a model of soil-landscape relationships. Our objective was to predict parent material distribution using expert knowledge paired with quantitative digital terrain attributes as part of a nested approach to digital soil mapping. The study took place at an 890-hectare research farm in Logan County, Arkansas, which is part of the Arkansas River Valley. Two major groups of parent material are identifiable in the Arkansas River Valley: residual sandstone and shale on erosional uplands, and silty/clayey pedisediment in depositional areas. A 5-m digital elevation model was used to derive thirteen terrain attributes for the study site. Three of the terrain attributes, namely topographic position index, multi-resolution valley bottom flatness, and vertical distance to channel network, were utilized as part of a rule-based approach to model parent material distribution based on preliminary reconnaissance and expert knowledge of the area. The model was validated by sampling 20 locations using a conditioned Latin hypercube sampling (cLHS) design to evaluate the prediction accuracy. Seventy-five percent of cLHS samples were accurately predicted to be residuum or pedisediment. The resulting map also had 90% agreement with the National Cooperative Soil Survey map; however, the digital map was able to provide more spatially explicit information especially on inclusions. Incorporating parent material distribution as part of a nested hierarchical approach to digital soil mapping aids in constraining and predicting soil properties, enables a more straightforward examination of physiographic context and can ultimately lead to more accurate digital soil maps for land management.

Propuesta para una Delimitación Geográfica Integral del Manglar de Nosara, Guanacaste, Costa Rica

Studying the characteristics of the physiographic context of a region, supported with geographic information systems, remote sensing inputs, and digital elevation models, allows to analyze the horizontal distribution of plant species of a mangrove, and this contributes its geographical delimitation. This paper shows that there are potential physiographic conditions for the expansion of the mangrove in Nosara. Thus, its current delimitation, by means of landmarks, could be overcome due to plant adaptability resulting from the future increase in sea level. Therefore, an additional geographical area is recommended to play a role within the coastal master plans as a buffer zone that not only facilitates the adaptive migration (resilience) of the vegetal species of the mangrove but also allows the creation of management plans for the future.

Introducing nested spatial scales in multi-stress models: towards better assessment of human impacts on river ecosystems

We investigated the relationships between the ecological status of wadeable rivers and the intensity of various stressors related with hydromorphological alterations, nutrient, and organic matter contaminations. The French invertebrate-based multimetric index (I2M2), which efficiently responds to the effects of both physical and chemical and hydromorphological stressors, was used as descriptor of river reach ecological status. We developed a model focusing on the effects of hydromorphological and physical and chemical stressor gradients on the I2M2 in different physiographic contexts. The potential confounding effects of natural geographic conditions and watershed scale pressure gradients were taken into account and neutralized by gathering watersheds into homogeneous clusters integrated as an interaction factor in the model. Whatever effects were considered (general or within-spatial clusters), the I2M2 was impaired similarly by the same stressor types, being negatively influenced by an increase in BOD5, ammonium, nitrite, nitrate, and total phosphorus concentrations. The I2M2 was also negatively influenced by variables describing hydromorphology at the reach scale, especially by the ‘loss of sinuosity,’ ‘increasing rates of bank erosion,’ ‘flow reductions,’ and ‘alteration of pool/riffle succession.’ The I2M2 was generally more strongly impaired by physical and chemical pressures than by hydromorphological alterations.

Hydrogeomorphic exploration of a local headwater stream in low mountainous environment following detailed field survey protocol (Mecsek Mountains, Hungary)

Comprehensive field survey of the physiographic context and channel morphology is a key to distinguish characteristic hydrogeomorphic reaches of a watercourse. In this analysis field data were collected during seasonal campaigns following a field survey protocol developed in the Polish Carpathian Mountains. Complementary information was conducted from cartographic materials and digital elevation model to map diverse sections of the semi-natural Váralja Stream in the Eastern Mecsek Mountains. Geological, geomorphological and anthropogenic effects had to be considered as decisive factors in recent fluvial development, with emphasis on the sediment transport influenced by woody debris. A total of 12 hydrogeomorphic reaches were identified along the stream by interpreting the spatial arrangement of channel forms and analysing the characteristics of the watershed environment. The mapped reaches are connected with transitional zones of different length. Step systems are typical on the upper reach of the stream, but they were found to be the result of the geological composition and structure of the region. It was also proven that woody debris accumulations, made up of tree trunks, branches and roots have significant influence on the channel evolution of the Váralja stream. Even though the presented field survey instructions were field-tested in alpine catchments the conducted research confirmed the applicability of such workflow in low mountainous environment. Furthermore, the results on the hydrogeomorphic conditions of this small watershed with intense relief provide useful information for understanding the flash floods occurring in the region.

Examination of aerial diatom flushing across watersheds in Luxembourg, Oregon and Slovakia for tracing episodic hydrological connectivity

Abstract Hydrological processes research remains a field that is severely measurement limited. While conventional tracers (geochemicals, isotopes) have brought extremely valuable insights into water source and flowpaths, they nonetheless have limitations that clearly constrain their range of application. Integrating hydrology and ecology in catchment science has been repeatedly advocated as offering potential for interdisciplinary studies that are eventually to provide a holistic view of catchment functioning. In this context, aerial diatoms have been shown to have the potential for detecting of the onset/cessation of rapid water flowpaths within the hillslope-riparian zone-stream continuum. However, many open questions prevail as to aerial diatom reservoir size, depletion and recovery, as well as to their mobilisation and transport processes. Moreover, aerial diatoms remain poorly known compared to freshwater species and new species are still being discovered. Here, we ask whether aerial diatom flushing can be observed in three catchments with contrasting physiographic characteristics in Luxembourg, Oregon (USA) and Slovakia. This is a prerequisite for qualifying aerial diatoms as a robust indicator of the onset/cessation of rapid water flowpaths across a wider range of physiographical contexts. One species in particular, (Hantzschia amphioxys (Ehr.) Grunow), was found to be common to the three investigated catchments. Aerial diatom species were flushed, in different relative proportions, to the river network during rainfall-runoff events in all three catchments. Our take-away message from this preliminary examination is that aerial diatoms appear to have a potential for tracing episodic hydrological connectivity through a wider range of physiographic contexts and therefore serve as a complementary tool to conventional hydrological tracers.

A channel evolution model to guide sustainable urban stream restoration

Channel evolution models (CEMs) are used to structure the interpretation of observed channel morphology to support long‐term restoration of these systems. However, channels reflect the variety of their watersheds' climatological, ecological and physiographic contexts, and so no single CEM can be truly ‘global’. Unrecognised differences between the assumptions and the reality of evolutionary trajectories of particular streams can subsequently lead to restoration actions that neither fully achieve their intended objectives nor successfully self‐maintain even limited improvements. Despite the daunting variety of biophysical settings, however, urbanisation imposes distinctive, homogenising influences on virtually all watercourses, suggesting that even a relatively small set of evolutionary pathways can embrace much of the diversity of critical watershed drivers on urban channels. CEMs describing single‐thread channel response to incision are most common in the published literature, but not every urban disturbance yields this classic sequence, initiated by excess transport capacity followed by incision, bank erosion, widening and ultimately a lowered re‐equilibrated channel. A comprehensive urban CEM must also include responses under less common (but locally ubiquitous) conditions, such as excess sediment relative to transport capacity (the ‘inverse’ of the classic CEM), imposed constraints on vertical and/or lateral adjustment, and multi‐thread channels or those influenced by instream or riparian vegetation. An urban CEM also requires a hierarchical framework that acknowledges fundamental differences in the process drivers within any given watershed, because a single observation of channel form can rarely pinpoint the context or evolutionary trajectory of every stream. We present a geomorphic framework for diagnosing and predicting the evolution of urban streams, potentially guiding the selection of restoration targets that are achievable within an urban context and sustainable without ongoing maintenance.

A staged geogenetic approach to underwater archaeological prospection in the Port of Rotterdam (Yangtzehaven, Maasvlakte, The Netherlands): A geological and palaeoenvironmental case study for local mapping of Mesolithic lowland landscapes

This study presents the geogenetic approach to detect presently drowned archaeological sites in the transgressive palaeoenvironment of the Holocene Rhine-Meuse delta. A staged and practical approach is advocated in which subsurface archaeological predictions are based on geological mapping and palaeoenvironmental reconstruction of the underwater location. The study area is located in the Maasvlakte harbour extension of the Port of Rotterdam, formerly a part of the southern North Sea. Prior to construction works, it was suggested that dredging of the new harbour (Yangtzehaven) would disturb the subsurface stratigraphy to around −21 m below present mean sea level, a zone which is known to contain archaeological remains. The staged approach makes use of geological data starting from a conceptual model that indicates the depths of layers that could be rich in Upper Palaeolithic/early Mesolithic artefacts. This initial model is used to determine the strategy of the subsequent phases of investigation, such as whether to proceed with dredging as part of the engineering work, down to 17 m water depth, to remove the upper (younger) sands and thereby improve the opportunities for underwater survey of fluvio-deltaic layers of Mesolithic age. Following the development of the initial site model, a full-area investigation was carried out using geophysics and coring, the latter providing material for palaeoenvironmental analysis. This allowed the reconstruction of the long-drowned former landscape, which included inland dune areas and local drainage systems and provided the physiographic context for the geoprospection of Mesolithic archeology. This predictive modeling identified two areas in the harbour for detailed investigation, again employing geophysics and coring at higher resolutions, allowing fine tuning of the palaeolandscape models at the localities of presumed highest archeological potential. Cores from one of the selected areas, an inland dune area within the Early Holocene wetland region, yielded in-situ evidence of Mesolithic occupation of this site in what is now the southern North Sea. These finds and the palaeolandscape context created with the data from the prospection phases were critical in the decision to undertake an underwater archaeological excavation using a large, boat-mounted grab sampling system. This paper provides an account of the geological and palaeoenvironmental work undertaken in the prospective phases leading up to the discovery of the site, highlighting the importance of the staged geogenetic approach for informing sampling strategies and securing high-quality information on landscape contexts, which in turn, informed archaeological decision-making and geoprospection strategies. Such an approach has wider generic application for palaeolandscape reconstruction and mapping at regional scales.

Análisis e interpretación de los perfiles longitudinales en la red fluvial del sur y sureste de Mallorca

The analysis of river longitudinal profiles through the channel topography, derived from digital elevation model, is particularly useful for the extraction of geomorphological indicators. Surface topography reflects the competition and interaction between climatic and tectonic forces and. the shape of the longitudinal river profile contains this information. The modern landscape, defined by its climatic, geological history and current tectonic forces, has a state, transient or steady, that can be described through these indicators. In this work we have analysed 74 longitudinal profiles of 60 drainage basins located in the south and southeast of Mallorca, an area with semi-arid climatic conditions, low rates on tectonic activity and limited Quaternary dating. Through geomorphological indicators such as concavity and convexity, the results show that there are areas in clear state of immaturity and imbalance with a convex river profile and others with a concave profile on a dynamic equilibrium. There are 6 zones with particular characteristics affected by the local topography caused by crustal tilting and Neogene tectonic structures that disrupt that balance. The different carbonate lithologies, with its contrasting response to erosion and dissolution processes, display breakpoints on the concave-upward stream profiles, called knickpoints. In 31 of the 37 streams, lithological knickpoints have been found where the river flows through the contact between materials of the Pliocene and the Quaternary, and the Tortonian and the Messinian calcarenites. Moreover, for the physiographic context of the study area, a threshold has been found in the minimum drainage area, between 2.3 × 105 and 7.2 × 105 m2, from which a knickpoint is generated due to flow concentration. A knickpoint in the longitudinal profiles is a factor that generates a transient state in the evolution of the drainage network. In addition, reconstruction of paleoprofiles from knickpoints is useful for determining eustatic level changes or fault displacement under certain conditions. A 30 m displacement has been identified on a stream of the southern area which may indicate an uncharted dip slip fault block displacement.

Watershed rainfall forecasting using neuro-fuzzy networks with the assimilation of multi-sensor information

Summary The complex temporal heterogeneity of rainfall coupled with mountainous physiographic context makes a great challenge in the development of accurate short-term rainfall forecasts. This study aims to explore the effectiveness of multiple rainfall sources (gauge measurement, and radar and satellite products) for assimilation-based multi-sensor precipitation estimates and make multi-step-ahead rainfall forecasts based on the assimilated precipitation. Bias correction procedures for both radar and satellite precipitation products were first built, and the radar and satellite precipitation products were generated through the Quantitative Precipitation Estimation and Segregation Using Multiple Sensors (QPESUMS) and the Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks-Cloud Classification System (PERSIANN-CCS), respectively. Next, the synthesized assimilated precipitation was obtained by merging three precipitation sources (gauges, radars and satellites) according to their individual weighting factors optimized by nonlinear search methods. Finally, the multi-step-ahead rainfall forecasting was carried out by using the adaptive network-based fuzzy inference system (ANFIS). The Shihmen Reservoir watershed in northern Taiwan was the study area, where 641 hourly data sets of thirteen historical typhoon events were collected. Results revealed that the bias adjustments in QPESUMS and PERSIANN-CCS products did improve the accuracy of these precipitation products (in particular, 30–60% improvement rates for the QPESUMS, in terms of RMSE), and the adjusted PERSIANN-CCS and QPESUMS individually provided about 10% and 24% contribution accordingly to the assimilated precipitation. As far as rainfall forecasting is concerned, the results demonstrated that the ANFIS fed with the assimilated precipitation provided reliable and stable forecasts with the correlation coefficients higher than 0.85 and 0.72 for one- and two-hour-ahead rainfall forecasting, respectively. The obtained forecasting results are very valuable information for the flood warning in the study watershed during typhoon periods.

Predicting community–environment relationships of stream fishes across multiple drainage basins: Insights into model generality and the effect of spatial extent

Resource managers increasingly rely on predictive models to understand species–environment relationships. Stream fish communities are influenced by longitudinal position within the stream network as well as local environmental characteristics that are constrained by catchment characteristics. Despite an abundance of studies quantifying species–environment relationships, few studies have evaluated the generality of these relationships among basins and spatial extents. We modeled community composition of stream fishes in thirteen sub-basins, nested within three basins in Kansas, USA using constrained ordination and environmental predictor variables representing (1) longitudinal network position, (2) local habitat, and (3) catchment characteristics. We tested the generality of species–environment relationships by quantifying the variation in model performance and the importance of environmental variables among the thirteen sub-basins and among three spatial extents (sub-basin, basin, state). Model performance was variable across the thirteen sub-basins, with adjusted constrained inertia ranging from 0.13 to 0.36. The importance of environmental variables was also variable among sub-basins, but longitudinal network position consistently predicted more variation in community composition than local or catchment variables. Model performance did not differ among spatial extents, but the importance of longitudinal network position decreased at broader spatial extents whereas local and catchment variables increased in importance. Results of this study support the longstanding frameworks of the river continuum and hierarchically-structured habitat. We show that (1) the relative importance of longitudinal network position, local characteristics, and catchment characteristics can vary from one region to another and (2) the spatial extent at which predictive habitat models are developed can influence the perceived importance of different environmental predictor variables. Resource managers should consider physiographic context and spatial extent when developing predictive habitat models for management and conservation purposes.

Including spatial distribution in a data-driven rainfall-runoff model to improve reservoir inflow forecasting in Taiwan

Multi-step ahead inflow forecasting has a critical role to play in reservoir operation and management in Taiwan during typhoons as statutory legislation requires a minimum of 3-hours warning to be issued before any reservoir releases are made. However, the complex spatial and temporal heterogeneity of typhoon rainfall, coupled with a remote and mountainous physiographic context makes the development of real-time rainfall-runoff models that can accurately predict reservoir inflow several hours ahead of time challenging. Consequently, there is an urgent, operational requirement for models that can enhance reservoir inflow prediction at forecast horizons of more than 3-hours. In this paper we develop a novel semi-distributed, data-driven, rainfall-runoff model for the Shihmen catchment, north Taiwan. A suite of Adaptive Network-based Fuzzy Inference System solutions is created using various combinations of auto-regressive, spatially-lumped radar and point-based rain gauge predictors. Different levels of spatially-aggregated radar-derived rainfall data are used to generate 4, 8 and 12 sub-catchment input drivers. In general, the semi-distributed radar rainfall models outperform their less complex counterparts in predictions of reservoir inflow at lead-times greater than 3-hours. Performance is found to be optimal when spatial aggregation is restricted to 4 sub-catchments, with up to 30% improvements in the performance over lumped and point-based models being evident at 5-hour lead times. The potential benefits of applying semi-distributed, data-driven models in reservoir inflow modelling specifically, and hydrological modelling more generally, is thus demonstrated.

The foundation species influence of eastern hemlock (Tsuga canadensis) on biodiversity and ecosystem function on the Unglaciated Allegheny Plateau

Foundation species are defined as abundant species that regulate ecosystem processes of a community through a small number of strong interactions, and eastern hemlock (Tsuga canadensis) is often cited as an example foundation species. Much of the understanding of its influence on ecosystem dynamics comes from investigations into the impact of hemlock mortality following invasion by an invasive pest, hemlock woolly adelgid (Adelges tsugae). While this information is invaluable, uncertainty remains about how much of these changes are due to disturbance, and are thus temporary, and how much is attributed to the role of hemlock, which are more permanent. To clarify the role of hemlock in intact forests, we investigated community composition and resource availability in eight hemlock dominated riparian forests on the Unglaciated Allegheny Plateau of Ohio, USA. In transects at 10, 30 and 50m from headwater streams, we measured all vegetation strata and physiographic context. Light availability was quantified using hemispherical photography during the growing season and the deciduous leaf-off period. We also measured soil chemistry and leaf litter biomass and chemistry as metrics of nutrient cycling and productivity, and determined the relative decomposition rate using cellulose paper.Comparisons across transects indicated a high degree of similarity in community composition and function due to the direct and indirect effects of hemlock dominance. Species richness was low, with slight increases moving upslope from the streams. Productivity (leaf litter biomass), light availability (canopy openness) in the growing season and deciduous leaf-off period, and nutrient cycling (decomposition and leaf litter chemistry) was also similar across transects. Non-metric multidimensional scaling analyses indicated differences in species composition 10m from streams compared to 30 and 50m away from the streams. Structural equation modeling (SEM) indicated hemlock dominance has a strong negative influence on vegetation species richness, as well as light availability and productivity. This indicates that as a foundation species, hemlock exerts a stronger biotic control than dampens the abiotic influence of environmental differences, overwhelming subtle but predictable patterns in species composition. Whether other foundation species, particularly conifers, structure ecosystems through similar mechanisms merits further investigation.

Test of three methods to detect the overbank flow from water level time‐series analysis

AbstractIn this study, we propose to identify morphological and hydraulic characteristics related to overbank flows in the water level time‐series available at many gauged stations. The results obtained at 13 river stations (the catchment sizes vary from 10 to 1700 km2 with contrasted geology, land use and rainfalls regime) show that overflow mechanisms at the river‐reach scale can be systematically identified in the water level frequency distribution estimated with the peaks‐over‐threshold (POT) method. A first level (Lts1) was in the range of the incipient flooding onto the floodplain. Even if the definition of this level is variable in terms of flooded area at the reach scale, this method can be useful in providing a first estimation of the bankfull level for many gauged stations, without complex and costly field surveys. A second level (Lts2) was systematically detected on average 38 cm above the topographic flat floodplain elevation. The Lts2 inflection in the water‐level frequency distribution is assumed to reflect a composite effect of catchment hydrology and local hydraulics and channel geometry, without possibility to make a clear distinction between both processes at the moment. The local or reach scale effect would probably play an essential role in the frequency distribution as flood attenuation at catchment scale may explain the inflection Lts2 at only three sites. In light of the knowledge acquired in laboratory flumes with compound channels, most of the time Lts2 level would correspond to the level of resumption of flow both in the main channel and the floodplain. Once this method is validated in various physiographic contexts, it should apply to many hydrometric stations for both synchronic (e.g. regional analysis) and diachronic analysis (e.g. evolution over time of the bankfull discharge) to evaluate anthropic impacts on river morphology. Copyright © 2010 John Wiley & Sons, Ltd.

Morphological patterns of Aptian Lithocodium-Bacinella geobodies: relation to environment and scale

Lithocodium aggregatum and Bacinella irregularis are now extinct, shallow marine life forms of unknown taxonomic origin. Forming part of the tropical platform biota during much of the Mesozoic, these organisms experienced bloom periods and temporarily replaced rudist–coral assemblages during parts of the Early Aptian. Within the limitations of time resolution, this ‘out-of-balance’ facies is coeval with the Oceanic Anoxic Event 1a-related black shale deposition in oceanic basins but the triggering factors remain poorly understood. Here, a platform-wide comparison of Lithocodium–Bacinella geobodies and morphotypes from the Sultanate of Oman is presented and placed in its environmental, bathymetric and physiographic context. Lithocodium–Bacinella geobodies reach from kilometre-scale ‘superstructures’ to delicate centimetre-sized growth forms. Clearly, scale matters and care must be taken when drawing conclusions based on spatially limited observational data. Whilst the factors that cause Lithocodium–Bacinella expansion should probably be considered in a global context, regional to local factors affected growth patterns in a more predictable manner. Here, the unresolved taxonomic relationship remains the main obstacle in any attempt to unravel the response of Lithocodium–Bacinella to specific or interlinked environmental parameters as different organisms respond differently to changing environment. Acknowledging these limitations, the following tentative patterns are observed: (i) Lithocodium–Bacinella tolerated a wide range of hydrodynamic levels and responded to differences in energy level or physiographic settings (margin, intrashelf basin, inner platform) by obtaining characteristic growth forms. (ii) Lithocodium–Bacinella favoured low-sediment input but had the ability to react to higher sedimentation rates by enhanced upward growth; a feature perhaps pointing to a phototrophic metabolism. Circumstantial evidence for continuous growth within the upper-sediment column is debated. (iii) The availability of accommodation space had a direct influence on the maximum size of geobodies formed. (iv) Fluctuating nutrient levels and sea water alkalinity may have affected the growth potential of Lithocodium–Bacinella. Understanding the relationship between Lithocodium–Bacinella morphogenesis on a wide range of scales and local environmental parameters allows for better prediction of the spatial distribution of reservoir properties and also results in an improved interpretation of palaeoenvironments. This study might represent a useful first step in this direction.

Late survival of Neanderthals at the southernmost extreme of Europe

The late survival of archaic hominin populations and their long contemporaneity with modern humans is now clear for southeast Asia. In Europe the extinction of the Neanderthals, firmly associated with Mousterian technology, has received much attention, and evidence of their survival after 35 kyr bp has recently been put in doubt. Here we present data, based on a high-resolution record of human occupation from Gorham's Cave, Gibraltar, that establish the survival of a population of Neanderthals to 28 kyr bp. These Neanderthals survived in the southernmost point of Europe, within a particular physiographic context, and are the last currently recorded anywhere. Our results show that the Neanderthals survived in isolated refuges well after the arrival of modern humans in Europe.