ecology and forest management
Volume 188, numbers 1 to 3,
February 5, 2004
, pages 363-380
Author links open the overlay panel,
https://doi.org/10.1016/j.foreco.2003.08.007Get rights and content
Individual trees can have a significant impactsoil morphology. If these impacts are not random, such that some microsites are repeatedly preferentially affected by trees, complex local spatial variability of soils would result. A self-reinforcing model of tree pedological influences (SRPIT) is proposed to explain patterns of soil variability in the Ouachita Mountains, Arkansas. SRPIT assumes that trees prefer to settle in sites that are rich in nutrients and poor in rock fragments compared to adjacent sites. The biomechanical effects of trees on soil and root decay preserve and amplify differences between rock fragments and nutrients compared to surrounding soils, thus increasing the likelihood that trees will become successfully established in the future. The connections assumed in the SRPIT model are dynamically unstable, which would be necessary for the functioning of self-reinforcing mechanisms. Soil variability in 16 study plots is dominated by local within-plot variability, indicating highly localized biological effects and consistent with the SRPIT model. Within 0.127 eachha 4 to 11 different series and 4 to 9 different classes of rock fragments were found. Of the 10 paired pits in each plot, 3 to 7 pairs had different series in pits typically less than 1 m apart. On average, each of the 16 plots had 6.3 different soil types and 6 different rock fragment classes, and 60% of the sample pairs differed in soil series. Analysis of the areal richness of soil series and rock fragment classes shows that pedodiversity is dominated by within-plot variability rather than between-plot variability. Vertical variations in the concentration of rock fragments in 40 out of 58 pits are consistent with the redistribution of soil material by tree felling, and there is also evidence of displacement of rock fragments by tree growth and deposition on tree stumps. Overall, the results suggest that morphological effects of individual tree soils are an important source of spatial soil variability in forests and that such effects are not random over time. Thus, even relatively homogeneous areas can be characterized by tree-rich areas that host repeated generations of trees and sparsely tree-poor areas that rarely host trees.
Individual trees can have a significant impact on the nature and properties of the soils on which they grow. Beyond transient and rapid-response changes in soil chemical and microbiological processes, trees can have an important impact on persistent and long-lasting soil morphological properties. Soil scientists and geomorphologists have generally assumed that an area with reasonably consistent environmental constraints and edaphic controls is equally likely to grow a tree at any given point in the forest ecosystem over time. In addition, it is generally assumed that over the course of several generations of forest communities, eventually the entire forest floor is exposed to the effects of trees. The purpose of this article is to examine the possibility that ecological and pedological memory play a key role in relationships between tree location and soil morphology. "Memory" in this sense occurs when the location of trees is influenced by previous tree locations, namely through the effects of trees on soil properties.
Few would argue that the assumption of a random probability of seed formation and tree growth is strictly true at the microscale, acknowledging the patchy nature of Edaphic controls and resources. However, many soil and geomorphologists are comfortable with this assumption as a generalization over soil timescales, as long as sites consistent with topography, drainage, orientation, microclimate, principal geology, and disturbance and management regimes are considered.
This article proposes an alternative conceptual model in which self-reinforcing processes result in the same microsites being preferentially occupied by trees. Instead of the random probability that trees will become established and overall land cover will eventually be affected by tree effects, the proposed model suggests that there will be tree-rich areas where soils have repeatedly supported trees, and tree-poor areas where trees have grown infrequently trees. grew up.
Because of the nature of the field study that inspired it, this framework is primarily proposed and explored in a pedo-geomorphic context rather than an ecological context. In the course of researching the relationships between soil morphology, vegetation, and forest management in the Ouachita National Forest, Arkansas, we found unexpected spatial differences in soils over short distances and small areas, and within plots, where plant community, management, and history resided uniformly. The conceptual model of self-reinforcing soil influence of trees (SRPIT) was developed to interpret or explain the observed local variability.
The basic argument of the article is based on the extreme variability of soil properties in small areas where (by study design) source material, topography and drainage, orientation, climate and time are relatively constant. While biotic factors are readily invoked to explain many chemical and biological properties of soils, the variations observed at Ouachita sites are based on variations in fundamental morphological properties such as soil thickness, abundance and distribution of soil fragments. Rock and the presence of specific horizons. While these latter variations may be related to the effects of trees, the general pattern of soil variability is difficult to explain if all areas of the forest floor are ultimately equally likely to be impacted or impacted by trees. The SRPIT model, based on published literature as well as our field observations, was developed to explain the observed soil landscape. The proposed model cannot be tested directly against observations. Simulation modeling would also be ineffective, since any simulation model that takes into account the basic postulates of the SRPIT model would inevitably deliver model-consistent results. Therefore, the proposed model is evaluated against three general criteria:
Are the relationships between trees and soils in the model unstable? Instability would mean that small variations persist and increase, which is a necessity for the creation of the tree-rich and tree-sparse zones postulated in the model.
Is there pedological evidence that supports the mechanisms postulated in the model?
Is the spatial pattern or signature of soil variability consistent with highly localized and self-reinforcing pedological effects of trees?
Vegetation affects soil through its effects on erosion and deposition, soil structure, organic matter dynamics, soil chemistry, hydrology and bioturbation. Therefore, significant changes in vegetation type and land cover often have significant, and often significant, impacts on soils. These effects can occur in the context of disturbances such as fires or storms, human activities such as harvesting, or slower changes associated with processes such as succession. cause is often
When a tree becomes established, there are three impacts related to rock fragments. First, the presence of the tree prevents the introduction of rock fragments by processes such as massive weathering and the disturbance of fauna at that particular site. Second, soil displacement from tree growth can cause soil fragments to be moved away from the tree. Third, there is the possibility of tree tossing and subsequent redistribution of thick clasts. All three phenomena deplete the rock growth site
field of study
The Ouachita Mountains cover an area approximately 100 km wide north-south and 320 km east-west in central Arkansas and eastern Oklahoma (Fig. 3). They consist of a complex of east-west trending ridges and intermontane basins. The ridges are narrow and parallel with moderately steep slopes and sharp, even ridges. The ridges range from 230 to 850 m above sea level, while the intermontane valleys range from 150 to 380 m. The local relief varies between 75 and 530 m and increases from east to west.
The Ouachita Mountains are
The SRPIT model shown in Fig. 1 can be translated into the interaction matrix shown in Table 2.
The matrix has the following characteristic equation:The λ are the complex eigenvalues of the matrix whose real parts are the Lyapunov exponents of the system. The second coefficient is positive and violates the stability criterion, indicating that the system is unstable.
Instability means that small deviations in the initial conditions or
Pedological memory and the SRPIT model
There is increasing recognition that small variations in initial soil formation conditions or the effects of small and short-term perturbations (e.g. biotic effects) can become unstable over time (Ibáñez, 1994, Ibáñez et al., 1990, McBratney). , 1998, Minasny and McBratney, 1999, Phillips, 1998, Phillips, 1999, Phillips, 2000). This creates a soil variability which, compared to the measurable and observable variation of factors such as parent material,
Individual trees can have a significant impact on soil morphology. If these impacts are not random, such that some microsites are preferentially and repeatedly influenced by trees, complex local spatial variability of soils would result through ecological and pedological memory. Self-reinforcing tree pedological influences (SRPIT) are proposed to explain soil variability patterns in the Ouachita Mountains, Arkansas.
The hypothetical connections in the SRPIT model are dynamically unstable
This project was supported by USDA Forest Services Cooperative Grant SRS 01-CA-11330124-516. We thank Ken Luckow, Jan Emerson, J. Swafford, Eric Swafford, Greg Swafford, J. Grant Barber, Raymond McGrath, Freddie Woodral, and Thomas Dozier of the Forest Service for their help. Kristin Adams, Linda Martin, Zach Musselman, Alice Turkington, and Taro Futamura from the University of Kentucky helped with the fieldwork.
Podzolicization among forests and dull grassland vegetation in northern Michigan
Podzolicization of soils under individual tree canopies in southwestern British Columbia, Canada
- NOT A WORD.ibañezet al.
Pedodiversity and scaling laws: sharing Martin and Rey's views on the role of the Shannon index as a measure of diversity
- NOT A WORD.ibañezet al.
Landscapes of soils and hydrographic basins in Mediterranean mountain areas
- NOT A WORD.ibañezet al.
Pedodiversity: concepts and measures
- NOT A WORD.ibañezet al.
Pedodiversity and global soil patterns at coarse scales (with discussion)
- B.Minasniet al.
A rudimentary mechanistic model for soil production and landscape development
Divergent evolution and the spatial structure of soil-landscape variability
- J.D.Phillipset al.
Deterministic uncertainty and complex pedogenesis in some Pleistocene dune soils
- R. J.estimated
Effects of tree felling microtopography on spodosol properties and formation, Michigan, USA.
Longevity of tree felling microtopography: Implications for mass wastage
Loblolly pine productivity is affected by decaying root systems
For. Eco. Administer.
Influence of a single tree on soil properties in the mountains of eastern Kentucky.
Windthrow and tree replacement in a beech and maple forest with a climax
Early stages of podsolization under Corsican pine (Pinus nigra Arn. ssp. laricio)
Changes in infiltration and interrow erosion due to long-term mandatory burns in Louisiana
water supply. Bull.
Aggregate stability under oak and pine after four decades of soil development
Soil Science Soc. At the. J
Soil carbon turnover in a recovering temperate forest
Globe Biogeochemistry. Cycles
Evolution of river dissection landscapes in Mediterranean settings: quantitative estimates and geomorphic, pedological, and phytocenotic impacts
Effects of deforestation on vegetative regeneration and soil quality in degraded and protected tropical semi-evergreen forests of Bangladesh
soil degradation. Development
Evolution of the biomantle and redistribution of terrestrial materials and artifacts.
Changes in soil profile development and nutrient status due to afforestation of agricultural land
Forest ecosystems generate pedogenetic mosaics from debris, trees, and disturbances
Forest ecosystems are extremely diverse and heterogeneous in terms of organisms, soils, waste such as wood waste, and disturbance regimes. However, little attention has been paid to the causes, intensity, self-organization and functioning of forest floor heterogeneity within individual stands. The concept of “pedogenic patches” is introduced to integrate ecology and soil formation into a holistic view of forest soil heterogeneity. We define “pedogenic patches” as spatially limited and temporally defined locations that contain at least one soil-forming factor that differs enough from its surroundings to give rise to differing intensities of soil processes and hence divergent pedogenic processes. According to this definition, individual components of soil-forming factors such as wood debris, trees, tree canopy gaps, boulders, and riverbanks can generate pedogenic patches if the rate of the pedogenic process results in a different soil morphology compared to the surrounding environment. The quantitative intensity of a pedogenic area depends on the size, age, number and characteristics of soil-forming factors and processes. Furthermore, pedogenic surfaces are the quanta of soil formation: punctiform pedogenic surfaces with some degree of intense, persistent, and resilient pedogenesis can move in forest ecosystems, thus creating patchwork soil landscapes of varying heterogeneity. Forest ecosystem studies could identify pedogenetic areas to measure soil formation and assess forest soil heterogeneity using different diversity indices. This would provide new insights into forest soil function, soil-regulated biodiversity, how forests evolve through disturbance, and the ecological trade-offs of self-organizing ecosystems.
Large short-term fluctuations in soil properties in a natural grassland are indicative of non-arborescent catena disturbance
The location of the landscape also determines soil formation and therefore the properties of the soil are related to the location of the landscape. In many landscapes, the importance of landscape position is high and there are therefore strong relationships between soil properties and landscape position. This applies in particular to agricultural landscapes in which local soil differences have been compensated for by tillage. This is less true for some forest landscapes, where the local effects of trees on soil formation have resulted in increased local variation. This raises the question of whether soil-landscape relationships are strong in natural grasslands without trees or plowing. We answer this question for natural prairie slopes in the Great Plains of the United States by quantifying soil-landscape relationships and soil spatial autocorrelation based on a data set of 100 soil observations. We find that soil-landscape relationships are weak, even taking into account the specific topographical features of the study area, and that short-term variations in soil properties are almost as large as long-term variations. We conclude that natural processes unrelated to trees disrupt the formation of clear catenas and hypothesize that this may involve small burrowing mammals and the filling of fractures in the parent material with finer material.
Pedogenesis in terms of geomorphology
2022, Treatise on Geomorphology
The integration of geomorphological and pedological investigations forms the field of soil geomorphology. The geomorphological studies of soils consist of six main elements, including the evolution of chronosequences, soils as indicators of landscape stability, soils as indicators of climate change, soil evolution and catchment area development, soils as indicators of erosion processes and deposits, and soils as indicators of Quaternary parent materials and Stratigraphy. Land surface morphology fundamentally controls the patterns of water movement through landscapes. These patterns, in turn, affect the way solid and dissolved materials move, leading to the formation of soils with special properties. This article examines the role of each of these principles in soil landscape evolution and concludes with a list of challenges faced by soil geomorphology in terms of modeling soil landscape evolution.
The microtopography determines the pH of the soil in Swiss flysch areas
Because topography is a key factor in soil formation and strongly affects soil physical and chemical properties, terrain attributes are routinely used in digital soil mapping to spatially predict soil properties. Forests on flysch sediments along the northern slopes of the Swiss Alps often show strong microrelief. The dominant soil types are trough gleysols and ridge cambisols with large pH variations within short distances. Based on soil evolution theory, we expected that soil formation processes driven by microscale topographical variations would shape microscale spatial patterns of soil properties at different sites within the flysch region. Therefore, the main aim of the study was to investigate model extrapolation within flysch regions, which has proven difficult in many other geological substrates. At three sites, each with an area of about 2 ha, we first created three local models to investigate whether a correlation between microtopography and topsoil pH can be derived from high-resolution terrain attributes and pH measurements. Using data from all three sites, we then calibrated a common model and examined model extrapolation by calibrating models with data from two sites and predicting the pH at the third site. All models were based on multiple linear regressions using 0.5 m resolution terrain attributes derived from a multiscale approach as explanatory variables. The R with cross validation2For local pH models, it varied between 0.56 and 0.77 and the corresponding RMSE between 0.57 and 0.64 pH units. The R2and RMSE for the joint model were 0.60 and 0.76, respectively. Results of local modeling suggest that microtopography is a dominant soil formation factor in flysch sediments, triggering soil genesis on a submeter to meter spatial scale. Although the extrapolated models showed reduced predictive power with R2With values of 0.25, 0.46 and 0.53, the selected terrain attributes were relatively similar across models, which can indicate common driving processes. The results of the joint model suggest that using high-resolution terrain attributes provides a fairly accurate spatial prediction of the highly variable pH of topsoil in forests on top of flysch sediments across Switzerland.
Influence of trees and forests on the Devonian landscape and weathering processes affecting global Earth system properties: a critical review
2020, Earth Science Reviews
The evolution of land plants, the first vascular plants, the first trees, and then entire forest ecosystems had far-reaching implications for Earth system dynamics. These innovations are considered important moments in the evolution of the atmosphere, biosphere, and oceans, even though the impacts may have been delayed by hundreds of thousands or millions of years. These fundamental changes in the Earth's history took place in the Paleozoic: from the Ordovician, the time of the first land plants, to the Carboniferous, which was dominated by forest ecosystems. The Devonian Plant Hypothesis (DPH) was the first concept to offer a comprehensive and logical explanation of the many environmental changes that accompanied tree/forest evolution over this period. The DPH highlighted the influence of deep-rooted vascular plants, especially trees, on the processes of weathering, pedogenesis, nutrient transport and CO2Cycle, deposition of organic and inorganic carbon and points to other possible consequences in the marine environment (oceanic anoxia and late Devonian extinctions). Here we try to combine DPH and the related biodiversity extension, the Devonian plant explosion (DePE), with the concept of biogeomorphic ecosystem engineering (BEE). This idea connects the growth and activity of trees with the initiation and/or modification of geomorphological processes and thus with the emergence or deterioration of geomorphological forms. We focus on trees and forest ecosystems as the likely dominant driver of plant-related change. We note that while there is ample evidence that trees are important biogeomorphic ecosystem engineers, treating DPH is difficult due to limited, difficult to interpret, or controversial data. However, we argue that the BEE concept sheds new light on DPH and suggests new data sources that should be able to answer our main question: Were Devonian trees engineers of the biogeomorphic ecosystem?
Fallen logs improve soil properties in old-growth temperate forests in northern Iran
Dead trees, especially fallen logs, play an important role in forest ecosystem dynamics. The contribution of decaying wood to the C and nutrient stores in the forest soil depends on the tree species and the degree of wood decay. However, the extent to which fallen logs affect soil properties in temperate forests has been poorly studied. In this study, a mixed beech forest in the Liresar region of Mazandaran Province in northern Iran was selected to investigate whether and how the presence of fallen logs affects soil quality and soil function. The soils under the degraded trunks were compared to the soils in the vicinity of two dominant tree species. (beech and hornbeam). We then examined how these effects occurred in the decay of the fallen logs by comparing the timbers of both tree species at four degrees of decay. The degree of decomposition of the fallen logs was divided into four classes (DC1-DC4). Eight dead trees of each tree species were selected in the center of each sample area. Three composite soil samples were collected under each rotting log and 100 cm from a rotting log at two soil depths (0-15 and 15-30 cm) to analyze the main soil physicochemical properties and microbial activity. The results showed that the fallen logs affected the physical soil (5% wetter than the control soils), chemical soil (2% lower pH, 100% increase in organic C and total N in the case of hornbeam and a 2% increase in in the soil) impaired P) and biologically. Properties (microbial respiration of the soil improved by 10% and microbial biomass C 620 and 351.5 mg kg−1and microbial biomass N 66.47 and 32.18 mg kg−1, or in the case of beech and hornbeam), resulting in soil microsites that differ markedly from those without fallen trunks. The presence of fallen logs increased soil microbial activity and soil fertility as the wood decayed. Therefore, the presence of fallen logs is an important factor affecting forest soils and must be taken into account in forest management.
Possible impact of the use of biodiesel in road traffic on air quality in the urban area of Porto, Portugal
Atmospheric Environment, Band 125, Teil A, 2016, S. 78-91
The aim of this work is to evaluate the impact of the use of biodiesel blends in road traffic on air quality. In this framework, the WRF-EURAD numerical modeling system was applied to air quality in Portugal and the urban area of Porto, enforced by two emission scenarios (including CO, NOx, PM10, PM2.5, VOCDM, formaldehyde, acetaldehyde, acrolein and benzene). ): a reference scenario with no biofuels and a scenario where a B20 fuel (20% biodiesel/80% diesel, v/v) is used by the diesel vehicle fleet. With regard to carbonyl compounds, the emission scenarios indicate that B20 fuel can lead to a 20% increase in formaldehyde, acetaldehyde and acrolein emissions, leading to an increase in ozone equivalent production. On the other hand, air quality modeling confirmed that the use of B20 helps control air pollution and improves CO and NO2Concentrations in urban air catchment areas are around 20% and 10%, respectively, taking into account a regional simulation grid. However, according to the city-level simulation, NO2In the metropolitan area of Porto, values may increase by around 1% due to the use of B20. For the other pollutants studied, namely PM10 and PM2.5, the average concentrations across the area are reduced, but by an insignificant amount of <1%.
Studying fire-related succession in the dry mixed grass subregion of Alberta using MODIS and Landsat
Rangeland Ecology & Management, Band 67, Nummer 3, 2014, S. 307-317
Fire is a major disturbance process that has historically occurred on the northern Great Plains. Previous research from the northern dry mixed-grass prairie suggests that C4 (warm season) grasses are replacing peak C3 (cool season) species with increased fire, particularly in spring. This hypothesis was tested at the landscape scale at Canadian Forces Base Suffield, Alberta by examining the relationship between ecosystem states (C3 dominant, C3/C4 codominant, C4 dominant) derived from a functional type classification of the multitemporal MODIS plant ( Pseudo R2: 0.598, overall accuracy: 0.74) and digitized annual fire history from the Landsat archive (1972-2007). Probit regression showed that succession processes were different between distribution sites, with C4-dominant pixels being positively associated with fire (P < 0.001, pseudo-R2= 1) and completely replaced the dominant C3 pixels in clay distribution areas after 14 fires in 36 years. In contrast, codominant C3 and C3/C4 pixels were associated with fires at blowout distribution sites (P < 0.001, pseudo-R2= 1), with codominant C3/C4 pixels replacing dominant C3 pixels with increasing fire. Finally, there were no statistically significant relationships between ecosystem states and fires for Sands dispersal sites. Recovery analysis revealed that after clay containing pixels suffered three to six burns in 18 years, followed by 18 years of dormancy, the dominant C3 pixels were reduced by more than 30% compared to unburned pixels. Finally, the timing of the subannual fires (2001–2009) was examined using Wilcoxon signed rank tests between the spatial extent of spring and summer fires using MODIS burned area data. The results indicate that fires are not limited to the spring season (P < 0.05) but occur throughout the growing season. Although fire timing does not appear to play a role in succession evolution, this ecosystem is generally sensitive to repeated fires, and C3-climax species take decades to recover.
Investigation of temporal trends of DDT in fish communities in Lake Erie using dynamic linear models
Journal of Great Lakes Research, Band 39, Nummer 3, 2013, S. 437-448
The industrial pesticide dichlorodiphenyltrichloroethane (DDT) was initially touted for its effectiveness against malaria and agricultural pests, but was eventually banned in North America in the 1970s due to growing concerns about its harmful effects on wildlife. Despite the successful termination of its commercial use, the persistent and bioaccumulating nature of DDT has resulted in sustained concentrations in aquatic food chains, particularly in fish species of higher trophic levels. In this study, we used dynamic linear models to compare the temporal trends of four DDT compounds (p,p′-DDT, o,p′-DDT, p,p′-DDE, and p,p′-DDD) in nine examine fish. Species in Lake Erie from 1976 to 2007, considering both fish length and lipid content as covariates. Our results indicate that levels of p,p′-DDT and o,p′-DDT decreased, often to the limit of detection, with rates of decrease being slower in the second half of the study period. The p,p′-DDE levels were much more variable, showing large fluctuations over time (though generally with a net downward trend), with annual rates of change in the corresponding concentrations being negative or (more recently) close to zero. Similarly, p,p′-DDD levels fluctuated over time (albeit to a lesser extent), with a gradual slower decline in many fish species, such as smallmouth bass and sea bass. The results are consistent with our understanding that DDE and DDD are degradation products of p,p′-DDT and therefore continue to be produced when DDT is degraded. The declining trends seen in nearly all conspecifics and fish species indicate a reduced risk of DDT to Lake Erie fish communities.
Paleoecology of the ancient city of Tanais (3rd century BC – 5th century AD) on the northeast coast of the Sea of Azov (Russia)
International Quaternary, Band 516, 2019, S. 98-110
Key events in the history of the ancient city of Tanais were recorded against the backdrop of climate change from the 3rd century BC. considered. C. and ended in the V century AD. C. To reconstruct the climatic changes during the city's existence, we used palynological, microbiomorphic, and palaeopedological analyzes of palaeosoils and culture strata from the Tanais and neighboring settlements. Located on the right bank of the Tanais (Don) river near its confluence with the Sea of Azov, the ancient city maintained trade and economic relations with the barbarian (nomadic) population living in the steppes near the Don and Sea of Azov First Iron Age. It has been shown that the foundation of Tanais in the 3rd century BC occurred. C. and its growth up to the 2nd century BC. C. took place under climatic conditions that were comparable to those of modern times. The city's most devastating conquest by the Bosphorus king Polemon came in the late 1st century BC. C., when the aridity of the climate was at its peak and the city of Tanais probably suffered an economic crisis. Examination of the chronosequence of the soils buried under the stone walls of the city and other nearby settlements at different times revealed a decrease in organic carbon and an increase in carbonate and gypsum content in the paleosoils since the 3rd century BC. to the beginning of the 2nd century AD. These data confirm a strong climatic drought in the change of eras. As can be seen from pollen analysis, throughout the period of existence the city was surrounded by steppe communities, but coniferous (pine) pollen was also found in the spectra of all chronointervals. The highest proportion of pollen from cultivated plants and weeds (4-6%) is found in accumulations that can be assigned to the first period of city life (2ndNorth Dakota-1. century B.C. BC). The microbiomorphic analysis was consistent with the pollen data and provided additional data on woody plants and rushes, which were extensively used for the population's economic activities in the first period of the city's existence. From the mid-2nd century to the end of the 4th century AD climatic conditions can be considered humid and favorable for bioproductivity. Another wave of droughts occurred on the border of the fourth and fifth centuries AD. At the end of the 5th century AD the city ceased to exist.
Hydraulic geometry of contiguous channels subjected to bottom level lowering
Geomorphologie, Band 197, 2013, S. 76-8
This study extends previous contributions on dynamic stream channel adjustments to base-level changes. We have studied an in situ response of self-formed cohesive channels to a basal level drop, conditions resembling a gradual change in elevation and/or climate. Empirical hydraulic geometry equations for natural cohesive clay streams are presented using data from eight canals draining perennial brackish water sources and emptying into the Dead Sea. Examination of downstream variations in flow head and power ratios suggests the existence of three distinct regions where channel adaptation to bottom level drop is unequally distributed among hydraulic geometry variables. The values of the flow velocity exponent m are low (0.11 ≤ m ≤ 0.24) and the middle section of the channel has the lowest exponent. The depth exponent f has the lowest value (f≈0.3) for the highest areas of the channel, the rest have higher values (f≈0.4). The smallest width exponent (b=0.35) characterizes the upper reaches. These values and their spatial distribution show a regular pattern. We show that the range of the lowest channel is adjusted by profile steepness and channel taper (f>b); the mechanism that prevails in the central sections of the canal is lateral adjustment (width), the sections are transiently transformed towards equilibrium; The higher areas exhibit wide and shallow channel cross-sections resulting from a series of bank collapses and the resulting accumulation of sediments, leading to a local reduction in head and forcing further channel widening. The results of this study not only provide insight into how cohesive channels regulate their geometry, but also show how hydraulic forces overcome the resistance of the substrate, adjusting the slope and dimensions of the channel and thus affecting the range of channel morphology and models in the Scale. the power of the current.
The influence of the relative depth of the liquid on the initial dynamics of the bed shape in the flow of a closed horizontal tube
International Journal of Multiphase Flow, Band 93, 2017, S. 1-16
Measurements of time-dependent bed shapes generated by the deposition of solid plastic particles in two-phase liquid-solid flows were performed using a novel ultrasonic echo method and video image analysis in a 100 liter closed-loop mud flow circuit. The results are presented for sediment bed thicknesses over a range of nominal flow rates and initial bed depths and combined in different phase diagrams based on different parameter combinations, categorizing bed shapes into five types. In doing so, the novel observation was made that the type of bed shape formed depends on both the flow rate and the initial relative bed or liquid depth, with waves and dunes being observed in the same system and in a single experiment. In addition, the number of critical shields at the onset of particle motion is measured as θSouth Carolina= 0.094 ± 0.043, hysteretic behavior is observed and the evolution and extent of each type of time-dependent bed shape are analyzed in detail and compared with various expressions for initial and equilibrium dimensions from the literature. A set of universal scales for bedforms in all types of conduit is proposed, ultimately to unify observations of bedforms in pipes with those of channels and natural flows.
Copyright © 2003 Elsevier B.V. All rights reserved.