Erosion Troughs Research Articles

Reconstructing parameters of the Holocene paleofloods in alluvial lowland river valleys – An example from the Bug valley (East Poland)

One of the ways to improve the accuracy of hydrological forecasts is to extend the data strings with the parameters of the maximum flows in the river from the period preceding their instrumental recording. The reconstruction of such parameters is difficult in the case of alluvial river valleys, mainly due to the difficulties in determining the shape of the channel cross-section. The article proposes a method for reconstructing extreme Holocene paleo-flow in the case of large alluvial rivers in the European Plain. It is based on identifying specific features of the geological structure of the valley, as well as elements of its bottom morphology, which can act as high water marks (HWM). The research was carried out in the section of the Bug valley, a large lowland river flowing through Ukraine, Belarus, and Poland.In the valley reach under analysis, the cross-section of the high water channel is determined by: the surface of the resistant to erosion sub-alluvial bedrock protrusion built of glacial till, and traces of flood erosion on the Pleistocene terraces, including traces of dune washouts. The age of the paleo-flow was determined by means of the C14 dating of sediments filling the flood erosion troughs. Due to the limited number of tests, the reconstructed maximum flow values are subject to uncertainty. Yet, even quite uncertain the reconstructed paleofloods may result in a significant improvement in the estimates of high quantiles using the flood frequency analysis, or at least allow to prepare for the floods not recorded by the monitoring system. In consequence, increasing the number of measurement points, and thus improving the correctness of the determination of paleo channels cross-sections, may contribute to a significant reduction in the uncertainty of the obtained paleo-flow values.

Model of pattern formation in marsh ecosystems with nonlocal interactions.

Smooth cordgrass Spartina alterniflora is a grass species commonly found in tidal marshes. It is an ecosystem engineer, capable of modifying the structure of its surrounding environment through various feedbacks. The scale-dependent feedback between marsh grass and sediment volume is particularly of interest. Locally, the marsh vegetation attenuates hydrodynamic energy, enhancing sediment accretion and promoting further vegetation growth. In turn, the diverted water flow promotes the formation of erosion troughs over longer distances. This scale-dependent feedback may explain the characteristic spatially varying marsh shoreline, commonly observed in nature. We propose a mathematical framework to model grass-sediment dynamics as a system of reaction-diffusion equations with an additional nonlocal term quantifying the short-range positive and long-range negative grass-sediment interactions. We use a Mexican-hat kernel function to model this scale-dependent feedback. We perform a steady state biharmonic approximation of our system and derive conditions for the emergence of spatial patterns, corresponding to a spatially varying marsh shoreline. We find that the emergence of such patterns depends on the spatial scale and strength of the scale-dependent feedback, specified by the width and amplitude of the Mexican-hat kernel function.

Biological Degradation of Chinese Fir with Trametes Versicolor (L.) Lloyd.

Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) has been an important afforestation species in northeast China. It has obvious defects of buckling and cracking easily, which are caused by its chemical components. Trametes versicolor (L.) Lloyd, a white-rot fungus, can decompose the cellulose, hemicellulose, and lignin in the wood. White-rot fungus was used to biologically degrade Chinese fir wood. The effects of different degradation time on the Chinese fir wood’s mechanical properties, micromorphology, chemical components, and crystallinity were studied. The results showed that the heartwood of Chinese fir was more durable than the sapwood and the durability class of Chinese fir was III. Trametes versicolor (L.) Lloyd had a greater influence on the mechanical properties (especially with respect to the modulus of elasticity (MOE)) for the sapwood. Trametes versicolor (L.) Lloyd degraded Chinese fir and colonized the lumen of various wood cell types in Chinese fir, penetrated cell walls via pits, caused erosion troughs and bore holes, and removed all cell layers. The ability of white-rot fungus to change the chemical composition mass fraction for Chinese fir was: hemicellulose > lignin > cellulose. The durability of the chemical compositions was: lignin > cellulose > hemicellulose. The crystallinity of the cellulose decreased and the mean size of the ordered (crystalline) domains increased after being treated by white-rot fungus.

Histological changes in the cell wall structure during wood decay by Trametes hirsuta and Trametes versicolor in neem (Azadirachta Indica A. Juss)

ABSTRACTStructural alterations in the wood cell walls of neem inoculated with by Trametes hirsuta and T. versicolor were studied by microscopic methods. In vitro decayed wood showed extensive weight loss of test blocks (26.7 and 41.38% by T. versicolor and T. hirsuta, respectively) at the end of 3 months. Selective delignification in the initial phase followed by simultaneous removal of lignin was evident in test blocks inoculated with both the species. The separation of middle lamellae and patches of cellulosic polysaccharides stained blue with Astra blue in the delignified region of the fiber wall during early stages indicates selective mode of decay. In contrast, the occurrence of erosion troughs with characteristic U-notch in tangential sections is a characteristic feature of simultaneous rot that was apparent after 3 months of incubation. The decay pattern occurred concomitantly in all the xylem elements irrespective of general resistance pattern shown by vessel and axial parenchyma cells. At an advance stage, both species of Trametes showed formation of erosion channels along the microfibrils angle of cellulose which is considered as characteristics of soft rot decay type. The sharing of white rot and soft rot decay pattern by both the fungi suggest a phylogenetic link between both groups of fungi.

Wood decay by Chlorociboria aeruginascens (Nyl.) Kanouse (Helotiales, Leotiaceae) and associated basidiomycete fungi

Two isolates of Chlorociboria aeruginascens (Nyl.) Kanouse incubated axenically on aspen wood blocks resulted in 18% and 32% mass loss after 134 wks (2 yrs 8 mo). Aspen wood decayed by C. aeruginascens contained cavities in the S2 layer of the secondary cell wall, similar to Type I soft rot attack, as well as erosion troughs and overall thinning and erosion of wood cell walls, resembling decay by Type II soft rot fungi. Using a selective medium, basidiomycete fungi were isolated from 9 of 17 samples of wood from a variety of tree species colonized and stained by Chlorociboria sp. (putatively C. aeruginascens) in a mixed hardwood forest from northern North America. Basidiomycete fungi were identified by ITS sequencing and cultural tests and were shown to be predominantly species of common white rot fungi. In axenic decay tests with aspen blocks, basidiomycete isolates caused mass losses in the range of 10%–50% after 26 wks incubation. Decay tests in which a basidiomycete isolate was co-inoculated with an isolate of C. aeruginascens did not differ significantly (p < 0.05) in mass loss from those caused by the respective basidiomycete alone. Results suggest that decay of wood colonized by C. aeruginascens is principally caused by white rot fungi and is neither enhanced nor inhibited by the presence of C. aeruginascens.

Anatomical changes in the cell-wall structure of Leucaena leucocephala (Lam.) de Wit as caused by the decay fungi Trametes versicolor and Trametes hirsuta

The structural changes in the cell wall and delignification pattern caused by Trametes versicolor and Trametes hirsuta in the sap wood of Leucaena leucocephala were examined by light and confocal laser scanning microscopy. The in vitro decay test was conducted for 12 weeks. Both species of Trametes used in this study caused anatomical characteristics specific to simultaneous white rot. Formation of boreholes, erosion troughs, erosion channels with U-shaped notches in tangential sections and thinning of cell walls were evident in the wood inoculated with each of the fungal species. Cell separation due to removal of middle lamellae occurred at the early stages of infection (30 d) with T. versicolor. In contrast, middle lamellae remained intact in wood inoculated with T. hirsuta and showed cell separation due to degradation of the outer layer of the secondary wall and degradation of the middle lamellae observed only in severely decayed wood at late stages. Confocal microscopy revealed the delignification pattern particularly from cell corners and vessel walls at an advanced stage of decay, indicating strong ligninolytic activity of both species in the sapwood of L. leucocephala.

Characteristics of tidal-bore deposits and facies associations in the Qiantang Estuary, China

Abstract The characteristics of tidal-bore deposition in the Qiantang Estuary are studied on the basis of core strata and grain-size data, and lateral and longitudinal associations with other sedimentary facies are synthesized. A typical depositional package by tidal bores and associated flows is generally initiated with (1) an undular/planar erosion base, overlain by (2) a massive sandy bed, and (3) a sandy bed with parallel laminations or some thinly heterolithic beds. The depositional units, especially the parallel laminations, are prone to deformation into convolute bedding, flames, and boiled sand patches with water-escape structures. In the middle estuary, tidal-bore deposits (TBDs) at the main channel and the lower tidal flat transit laterally into alternative beds of TBDs andz heterolithic beds at the middle tidal flat, and then toward incomplete tidal rhythmites on the higher tidal flat. TBDs are generally coarser and less sorted than tidal sandy deposits (TSDs), and tidal muddy deposits (TMDs) have finer grains, less sorting and lower positive skewness than either TSDs or TBDs. Therefore, bivariate plotting of size parameters is a useful tool to differentiate between these three genetic sedimentary bed types. Along the axis, three facies divisions are obvious and consist of: (1) linear depositional ridges and erosion troughs at the outer estuary, (2) TBDs at the middle estuary, and (3) coarse fluvial deposits at the upper estuary. The tripartite facies model of the Qiantang Estuary is similar to other well-known tide-dominated estuarine facies models, but it is the first to stress tidal-bore deposition in the sedimentary facies using detailed discriminative textural and structural characteristics. The approaches offer the potential to better understand tidal-bore processes and their important role in sediment dispersion and facies formation within modern and ancient macrotidal to hypertidal estuaries.

Anatomical studies on decaying wood of Mangifera indica by two white rot fungi Schizophyllum commune and Flavadon flavus

Basidiomycetes fungi Schizophyllum commune and Flavadon flavus very commonly cause white rot decay in felled trees. The pattern of wood decay caused by two fungi viz. S. commune and F. flavus in Mangifera indica wood is investigated using light and scanning electron microscopy. Samples inoculated with S. commune and F. flavus exhibited a combination of simultaneous decay and selective delignification. Separation or loosening of cells was the characteristic feature for selective decay, while presence of erosion troughs, reduction in cell wall thickening, bore holes, erosion channels were diagnostic features for simultaneous type of decay. Infected samples of S. commune showed separation among cells followed by cell wall thinning and presence of erosion troughs. In contrast F. flavus infected wood initially showed presence of bore holes and erosion channels followed by simultaneous loosening of cells.

Comparative study on the delignification of Azadirachta indica (L) Del., wood by Chrysosporium asperatum and Trichoderma harzianum

Structural alterations induced in response to degradation by two white rot Basidiomycetes on the secondary xylem of Azadirachta indica (L) Del., was compared. In vitro decay test was employed to investigate the pattern of delignification of Azadirachta wood by Trichoderma harzianum and Chrysosporium asperatum. Wood samples inoculated with both the strains were analyzed for different periods viz. 30, 60, 90 and 120 days after fungal inoculation. Initially there was no appreciable percent weight loss of the wood blocks but later on (after 60 days) it increased rapidly and was found similar for both the strains (43–46% of wood mass). Samples inoculated with both the strains showed dual pattern of degradation i.e. selective delignification in the initial stage followed by simultaneous rot during advance stage of decay. Separation of the cells due to dissolution of middle lamella was the characteristic feature of both strains but in the advanced stage of decay, formation of erosion troughs were conspicuous in all the cell types. Other features such as cell wall thinning, rounded pit erosion, formation of erosion channels and bore holes were also observed frequently. Initially, fungal invasion started through the vessel lumen, followed by all the cell types of the xylem. From the vessels, mycelia entered into the adjacent rays and parenchyma cells through the pits. In advanced stage, degradation was so pronounced that rays were partially or even completely destroyed while many cells including vessels were either deformed or destroyed due to loss of rigidity of their walls. Structural alterations induced in response to C. asperatum and T. harzianum attack is described in details.

Density‐dependent linkage of scale‐dependent feedbacks: a flume study on the intertidal macrophyte Spartina anglica

Spartina anglica is an autogenic ecosystem engineer. At a local (within‐vegetation) scale, it improves plant growth by enhancing sediment accretion through attenuation of hydrodynamic energy with its shoots. This constitutes a short‐range positive feedback. The vegetation also shows a long‐distance negative feedback through formation of erosion troughs around the tussock, which are restricting lateral expansion. There is a growing recognition of the important role of such scale‐dependent feedbacks for landscape structuring and ecosystem stability. By a series of flume studies, we provide direct experimental evidence that 1) both the local positive and the long‐distance negative feedback are strongly density‐dependent with clear thresholds, and 2) that both feedbacks are inherently linked via their density dependence, partly as the result of conservation laws. The observed thresholds occurred at vegetation densities commonly found in the field. We demonstrate that threshold densities are affected by external hydrodynamic forcing for the long‐distance negative feedback. We expect the same to be true for the local positive feedback (sediment accretion), so that under mild hydrodynamic forcing, this local positive feedback may occur in the absence of a long‐distance negative feedback (formation of erosion troughs). The density dependence of nearby positive and the long‐distance negative feedback and how external conditions affect the linkage of both feedbacks are important factors shaping the vegetated salt‐marsh landscape.

PATTERNS OF DECAY CAUSED BY PYCNOPORUS SANGUINEUS AND GANODERMA LUCIDUM (APHYLLOPHORALES) IN POPLAR WOOD

Populus deltoides clones are widely planted in Argentina, in a region called “Paraná River Delta”. In this site, Pycnoporus sanguineus and Ganoderma lucidum (Aphyllophorales) cause white-rot decay in both living and felled poplar trees. The purpose of this work was to estimate, through laboratory decay tests, the ability of both fungi to degrade poplar wood and to describe the patterns of decay using light and scanning electron microscopy. Two exposure times were analyzed: 75 and 150 days. The percent weight loss produced by both fungal strains was similar for both exposure periods (c. 50–60% of wood mass) but microscopic observations showed there were different patterns of decay. Samples inoculated with P. sanguineus showed a selective delignification, whereas those inoculated with G. lucidum exhibited a combination of simultaneous decay and selective delignification. Separation among cells was the main diagnostic feature for selective decay. By contrast, the presence of erosion troughs, cell wall thinning, bore holes, rounded pit erosion and erosion channels were diagnostic for the simultaneous type of decay.

Persistence of the gelatinous layer within altered tension‐wood fibres of beech degraded by Ustulina deusta

The gelatinous layer (G‐layer) of tension‐wood fibres in reaction wood of beech showed alterations as a result of the physiological processes involved in the conversion of sapwood into false heartwood or reaction‐zone tissue. Using transmitted‐light, fluorescence and UV microscopy, polyphenolic compounds were found to infiltrate and encrust the cellulose microfibrils within the G‐layer. Experiments with naturally infected and artificially inoculated wood showed that these processes affect the rate and mode of degradation by wood‐decaying fungi. Thus, although the ascomycete Ustulina deusta was able to degrade the G‐layer from within the lumina of tension‐wood fibres in unaltered sapwood, it failed to do so for a prolonged period within false heartwood and reaction zones. In both situations, however, there was some degradation of the underlying secondary wall in the form of erosion troughs which can be attributed to soft rot ‘type II’, and internal cavity formation typical for ‘type I’ attack. The present study indicates that not only cell type, but also alterations in the cell wall structure, affect the activity and degradation mode of decay fungi in beech.

Ultrastructural changes during wood decay by Antrodiella sp. RK1

Southern yellow pine (softwood) and maple (hardwood) wood decayed for 12 weeks by Antrodiella sp. RK1 had average weight losses of 20 and 19%, respectively, and approximately 34 to 35% lignin loss. The ratio of percentage lignin loss to glucose loss was 3.6 and 2.7 for softwood and hardwood, respectively. There was negligible loss of other wood sugars such as xylose, arabinose, galactose and mannose. Scanning electron microscopy revealed the presence of erosion troughs and bore holes in decayed samples of both softwood and hardwood. Secondary walls were void of lignin, middle lamella and cell corners were extensively decayed. Ca(2+) crystals were abundantly present in the areas of decay. Transmission electron micrographs revealed the presence of hyphal sheath and growth of hyphae directly through the cell corners.

Colloidal Gold Cytochemistry of Endo-1,4-β-Glucanase, 1,4-β- D -Glucan Cellobiohydrolase, and Endo-1,4-β-Xylanase: Ultrastructure of Sound and Decayed Birch Wood

Colloidal gold coupled to endo-1,4-beta-glucanase II (EG II) and 1,4-beta-D-glucan cellobiohydrolase I (CBH I), isolated from Trichoderma reesei (QM9414), and endo-1,4-beta-xylanase from Aureobasium pullulans (NRRLY-2311-1) was used successfully to determine the ultrastructural localization of cellulose and xylan in sound birch wood. In addition, these enzyme-gold complexes demonstrated the distribution of cellulose and xylan after decay by three white rot fungi, Phanerochaete chrysosporium, Phellinus pini, and Trametes versicolor, and one brown rot fungus, Fomitopis pinicola. Transverse sections of sound wood showed that EG II was localized primarily on the S(1) layer of the secondary wall, whereas CBH I labeled all layers of the secondary wall. Oblique sections showed a high concentration of gold labeling, using EG II or CBH I. Preference for the sides of the microfibrillar structure was observed for both EG II and CBH I, whereas only CBH I had a specificity for the cut ends of microfibrils. Labeling with the xylanase-gold complex occurred primarily in the inner regions of the S(2) layer, S(1), and the middle lamella. In contrast, little labeling occurred in the middle lamella with EG II or CBH I. Intercellular regions within the cell corners of the middle lamella were less electron dense and labeled positively when EG II- and xylanase-gold were used. Wood decayed by P. chrysosporium or P. pini was delignified, and extensive degradation of the middle lamella was evident. The remaining secondary walls labeled with EG II and CBH I, but little labeling was found with the xylanase-gold complex. Wood decayed by T. versicolor was nonselective, and erosion of all cell wall layers was apparent. Remaining wall layers near sites of erosion labeled with both EG II and CBH I. Erosion troughs that reached the S(1) layer or the middle lamella had less xylanase-gold labeling in the adjacent cell wall that remained. Brown-rotted wood had very low levels of gold particles present in sections treated with EG II or xylanase. Labeling with CBH I had the lowest concentrations in the S(2) layer near cell lumina and corresponded to sites with the most extensive degradation.

Studies of Paleozoic Fungi. IV. Wood-Decaying Fungi in Callixylon newberryi from the Upper Devonian

An extensive fungal infection is present in silicified specimens of Callixylon newberryi (Dawson) Elkins and Wieland from the Upper Devonian of Indiana. Fungi are represented by branched, septate filaments with both terminal and intercalary chlamydospores. Clamp connections were not observed. Tracheids of the secondary xylem, decayed in varying degrees, show erosion troughs, cavities, and extensive lysis of tracheid walls. The pattern of decay is most similar to modern-day white rots, which are typically caused by basidiomycetes, while hyphal features are characteristic of either ascomycetes or basidiomycetes. The presence of wood decay coupled with a septate mycelium suggests the presence of higher fungi in the Devonian and indicates a more diverse Devonian mycoflora than has previously been recognized.

STUDIES OF PALEOZOIC FUNGI. IV. WOOD‐DECAYING FUNGI IN CALLIXYLON NEWBERRYI FROM THE UPPER DEVONIAN

An extensive fungal infection is present in silicified specimens of Callixylon newberryi (Dawson) Elkins and Wieland from the Upper Devonian of Indiana. Fungi are represented by branched, septate filaments with both terminal and intercalary chlamydospores. Clamp connections were not observed. Tracheids of the secondary xylem, decayed in varying degrees, show erosion troughs, cavities, and extensive lysis of tracheid walls. The pattern of decay is most similar to modern‐day white rots, which are typically caused by basidiomycetes, while hyphal features are characteristic of either ascomycetes or basidiomycetes. The presence of wood decay coupled with a septate mycelium suggests the presence of higher fungi in the Devonian and indicates a more diverse Devonian mycoflora than has previously been recognized.

Changes in structural and chemical components of wood delignified by fungi

Cerrena unicolor, Ganoderma applanatum, Ischnoderma resinosum and Poria medulla-panis were associated with birch wood that had been selectively delignified in the forest. Preferential lignin degradation was not uniformly distributed throughout the decayed wood. A typical white rot causing a simultaneous removal of all cell wall components was also present. In the delignified wood, 95 to 98% of the lignin was removed as well as substantial amounts of hemicelluloses. Scanning and transmission electron microscopy were used to identify the micromorphological and ultrastructural changes that occurred in the cells during degradation. In delignified areas the compound middle lamella was extensively degraded causing a defibration of cells. The secondary wall, especially the S2 layer, remained relatively unaltered. In simultaneously white-rotted wood all cell wall layers were progressively removed from the lumen toward the middle lamella causing erosion troughs or holes to form. Large voids filled with fungal mycelia resulted from a coalition of degraded areas. Birch wood decayed in laboratory soil-block tests was also intermittently delignified. Selective delignification, sparsely distributed throughout the wood, and a simultaneous rot resulting in the removal of all cell wall components were evident. Scanning electron microscopy appears to be an efficient technique for examining decayed wood for fungi with the capacity to selectively delignify wood.

Characteristics of black zones associated with delignified wood

Several white-rot fungi cause two micromorphologically distinct types of decay. White-rot fungi typically cause a simultaneous removal of all cell wall components in close proximity to fungal hyphae. This type of degradation results in erosion troughs and holes in the cell walls. In addition, a selective removal of lignin and hemicellulose can occur intermittently throughout the decayed wood. Selectively delignified wood can be characterized by the complete removal of middle lamellae, resulting in a defibration of cells and exposure of cellulosic macrofibrils within cell walls.

Electron Microscopy of Cellulose Decomposition by Brown-Rot Fungi

The degradation of isolated cellulose by 11 brown-rot fungi was observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). SEM showed random growth of all the fungi over the fiber surface and that none of the fungi penetrated into the fibers by means of bore holes. Erosion troughs or depressions in the fiber surface at points of hyphal contact were not visible. When viewed by TEM, hyphae of some fungi were present in fiber walls and lumen. However, cellulose within fibers was extensively degraded whether or not they had been invaded by hyphae, indicating that the initial dissolution of cellulose is accomplished by a small diffusable depolymerizing agent. An extracellular matrix or sheath encased hyphae of all the fungi. Sheaths often spread away from hyphae and sometimes encircled the fibers. Cytoplasmic material from autolyzed cells was commonly observed in sheaths, and often the material totally permeated the fiber. This suggests that some cytoplasmic organelles, such as microbodies, may be involved in the production of the agent employed by brown-rot fungi to degrade cellulose.

Short Communication: Microscopic decay pattern of yellow meranti caused by white-rot fungus Phlebia brevispora

Erwin. 2016. Microscopic decay pattern of yellow meranti (Shorea gibbosa) wood caused by white-rot fungus Plebia brevispora. Biodiversitas 17: 417-421. The anatomical changes of wood decaying by white-rot fungus Phlebia brevispora could provide the basis for evaluating and analysis of decay on yellow meranti (Shorea gibbosa) heartwood. By using soil-block test procedure of JIS K-1571 and microscopic analysis, a progressive decay in vitro of S. gibbosa wood caused by P. brevispora was well characterized.The percentage of wood weight loss was ranged from 0.91% to 12.34%in 2-12 weeks' incubation. On the first 6 weeks of incubation of S. gibbosa infected with P. brevispora, the early stages decay, in which pit erosion and slight erosion of cell walls facilitated by hyphal spreading among cells. The intermediate decay features of numerous and conspicuous holes as well as erosion troughs in cell walls were found after 8 weeks' incubation. Furthermore, complete degradation of wood cell components, defined as the advanced stage of decay, was found in some areas of wood after 12 weeks' incubation. The pattern of wood decay was similar to those of the decayed xylem of S. gibbosa stem canker in field conditions.