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At least 37 records · Page 2Linked to original sources
USGS2001

Erosion and sediment delivery following removal of forest roads

Erosion control treatments were applied to abandoned logging roads in California, with the goal of reducing road-related sediment input to streams and restoring natural hydrologic patterns on the landscape. Treatment of stream crossings involved excavating culverts and associated road fill and reshaping streambanks. A variety of techniques were applied to road benches, which included decompacting the road surface, placing unstable road fill in more stable locations, and re-establishing natural surface drainage patterns. Following treatment and a 12-year recurrence-interval storm, some road reaches and excavated stream crossings showed evidence of mass movement failures, gullying, bank erosion and channel incision. Post-treatment erosion from excavated stream crossings was related to two variables: a surrogate for stream power (drainage area × channel gradient) and the volume of fill excavated from the channel. Post-treatment erosion on road reaches was related to four explanatory variables: method of treatment, hillslope position (upper, mid-slope or lower), date of treatment, and an interaction term (hillslope position × method of treatment). Sediment delivery from treated roads in upper, middle and lower hillslope positions was 10, 135 and 550 m 3 of sediment per kilometre of treated roads, respectively. In contrast, inventories of almost 500 km of forest roads in adjacent catchments indicate that untreated roads produced 1500 to 4700 m 3 of sediment per kilometre of road length. Erosion from 300 km of treated roads contributed less than 2 per cent of the total sediment load of Redwood Creek during the period 1978 to 1998. Although road removal treatments do not completely eliminate erosion associated with forest roads, they do substantially reduce sediment yields from abandoned logging roads.

Earth Surface Processes and Landforms↗
USGS2004

Modern sediment yield compared to geologic rates of sediment production in a semi-arid basin, New Mexico: Assessing the human impact

In the semi-arid Arroyo Chavez basin of New Mexico, a 2.28 km2 sub-basin of the Rio Puerco, we contrasted short-term rates (3 years) of sediment yield measured with sediment traps and dams with long-term, geologic rates (???10 000 years) of sediment production measured using 10Be. Examination of erosion rates at different time-scales provides the opportunity to contrast the human impact on erosion with background or geologic rates of sediment production. Arroyo Chavez is grazed and we were interested in whether differences in erosion rates observed at the two time-scales are due to grazing. The geologic rate of sediment production, 0-27 kg m-2 a -1 is similar to the modern sediment yields measured for geomorphic surfaces including colluvial slopes, gently sloping hillslopes, and the mesa top which ranged from 0.12 to 1.03 kg m -2 a-1. The differences between modern sediment yield and geologic rates of sediment production were most noticeable for the alluvial valley floor, which had modern sediment yields as high as 3.35 kg m-2 a-1. The hydraulic state of the arroyo determines whether the alluvial valley floor is aggrading or degrading. Arroyo Chavez is incised and the alluvial valley floor is gullied and piped and is a source of sediment. The alluvial valley floor is also the portion of the basin most modified by human disturbance including grazing and gas pipeline activity, both of which serve to increase erosion rates. ?? 2004 John Wiley and Sons, Ltd.

Earth Surface Processes and Landforms↗
USGS2005

Estimation of regional material yield from coastal landslides based on historical digital terrain modelling

High-resolution historical (1942) and recent (1994) digital terrain models were derived from aerial photographs along the Big Sur coastline in central California to measure the long-term volume of material that enters the nearshore environment. During the 52-year measurement time period, an average of 21 000 ?? 3100 m3 km-1 a-1 of material was eroded from nine study sections distributed along the coast, with a low yield of 1000 ?? 240 m3 km-1 a-1 and a high of 46 700 ?? 7300 m3 km-1 a-1. The results compare well with known volumes from several deep-seated landslides in the area and suggest that the processes by which material is delivered to the coast are episodic in nature. In addition, a number of parameters are investigated to determine what influences the substantial variation in yield along the coast. It is found that the magnitude of regional coastal landslide sediment yield is primarily related to the physical strength of the slope-forming material. Coastal Highway 1 runs along the lower portion of the slope along this stretch of coastline, and winter storms frequently damage the highway. The California Department of Transportation is responsible for maintaining this scenic highway while minimizing the impacts to the coastal ecosystems that are part of the Monterey Bay National Marine Sanctuary. This study provides environmental managers with critical background data on the volumes of material that historically enter the nearshore from landslides, as well as demonstrating the application of deriving historical digital terrain data to model landscape evolution. Published in 2005 by John Wiley & Sons, Ltd.

Earth Surface Processes and Landforms↗
USGS2005

Development of partial rock veneers by root throw in a subalpine setting

Rock veneers stabilize hillslope surfaces, occur especially in areas of immature soil, and form through a variety of process sets that includes root throw. Near Westcliffe, Colorado, USA, data were collected from a 20 ?? 500 m transect on the east slope of the Sangre de Cristo Mountains. Ages of pit/mound complexes with rock fragments exposed at the surface by root throw ranged from recent (freshly toppled tree) to unknown (complete tree decay). Calculations based on dimensions of the pit/mound complexes, estimated time of free topppling, sizes of exposed rock fragments, and percentage rock covers at pit/mound complexes, as well as within the transect area, indicate that recent rates of root throw have resulted in only partial rock veneering since late Pleistocene deglaciation. Weathering of rock fragments prevent development of an extensive rock veneer and causes a balance, achieved within an estimated 700 years, between the rates of rock-fragment exposure by root throw and clast disintegration by chemical reduction. The estimated rate of rock-fragment reduction accounts for part of the fluvial sediment yields observed for forested subalpine areas of western North America. Copyright ?? 2005 John Wiley & Sons, Ltd.

Earth Surface Processes and Landforms↗
USGS2005

Rainfall characteristics for shallow landsliding in Seattle, Washington, USA

Shallow landsliding in the Seattle, Washington, area, has caused the occasional loss of human life and millions of dollars in damage to property. The effective management of the hazzard requires an understanding of the rainfall conditions that result in landslides. We present an empirical approach to quantify the antecedent moisture conditions and rainstorm intensity and duration that have triggered shallow landsliding using 25 years of hourly rainfull data and a complementary record of landslide occurrence. Our approach combines a simple water balance to estimate the antecedent moisture conditions of hillslope materials and a rainfall intensity-duration threshold to identify periods when shallow landsliding can be expected. The water balance is calibrated with field-monitoring data and combined with the rainfall intensity-duration threshold using a decision tree. Results are cast in terms of a hypothetical landslide warning system. Two widespread landslide events are correctly identified by the warning scheme; however, it is less accurate for more isolated landsliding. Copyright ?? 2005 John Wiley & Sons, Ltd.

Earth Surface Processes and Landforms↗
USGS2005

Spatial structures of stream and hillslope drainage networks following gully erosion after wildfire

The drainage networks of catchment areas burned by wildfire were analysed at several scales. The smallest scale (1-1000 m2) representative of hillslopes, and the small scale (1000 m2 to 1 km2), representative of small catchments, were characterized by the analysis of field measurements. The large scale (1-1000 km2), representative of perennial stream networks, was derived from a 30-m digital elevation model and analysed by computer analysis. Scaling laws used to describe large-scale drainage networks could be extrapolated to the small scale but could not describe the smallest scale of drainage structures observed in the hillslope region. The hillslope drainage network appears to have a second-order effect that reduces the number of order 1 and order 2 streams predicted by the large-scale channel structure. This network comprises two spatial patterns of rills with width-to-depth ratios typically less than 10. One pattern is parallel rills draining nearly planar hillslope surfaces, and the other pattern is three to six converging rills draining the critical source area uphill from an order 1 channel head. The magnitude of this critical area depends on infiltration, hillslope roughness and critical shear stress for erosion of sediment, all of which can be substantially altered by wildfire. Order 1 and 2 streams were found to constitute the interface region, which is altered by a disturbance, like wildfire, from subtle unchannelized drainages in unburned catchments to incised drainages. These drainages are characterized by gullies also with width-to-depth ratios typically less than 10 in burned catchments. The regions (hillslope, interface and chanel) had different drainage network structures to collect and transfer water and sediment. Copyright ?? 2005 John Wiley & Sons, Ltd.

Earth Surface Processes and Landforms↗
USGS2005

Using cosmogenic nuclides to contrast rates of erosion and sediment yield in a semi-arid, arroyo-dominated landscape, Rio Puerco Basin, New Mexico

Analysis of in-situ-produced 10Be and 26Al in 52 fluvial sediment samples shows that millennial-scale rates of erosion vary widely (7 to 366 m Ma-1) through the lithologically and topographically complex Rio Puerco Basin of northern New Mexico. Using isotopic analysis of both headwater and downstream samples, we determined that the semi-arid, Rio Puerco Basin is eroding, on average, about 100 m Ma-1. This rapid rate of erosion is consistent with estimates made using other techniques and is likely to result from a combination of easily eroded lithologies, sparse vegetation, and monsoon-dominated rainfall. Data from 331 stream water samples collected by the US Geological Survey between 1960 and 1995 are consistent with basin-wide, average chemical denudation rates of only about 1??4 m Ma-1; thus, the erosion rates we calculate may be considered rates of sediment generation because physical weathering accounts for almost 99 per cent of mass loss. The isotopic data reveal that sediment is generally well mixed downstream with the area-weighted average sediment generation rate for 16 headwater samples (234 ton km-2 a-1 for basin area 170 to 1169 km2) matching well that estimated from a single sample collected far downstream (238 ton km-2 a-1, basin area = 14 225 km2). A series of 15 samples, collected from an arroyo wall and representing deposition through the late Holocene, indicates that 10Be concentration in sediment delivered by the fluvial system has not changed appreciably over the last 1200 years despite at least two cycles of arroyo cutting and filling. Other samples (n = 21) were collected along the drainage network. Rio Puerco erosion rates scale directly with a variety of metrics describing vegetation, precipitation, and rock erodibility. Using the headwater basins for calibration, the erosion rates for both the downstream samples and also the data set as a whole, are best modelled by considering a combination of relief and vegetation metrics, both of which co-vary with precipitation and erodibility as inferred from lithology. On average, contemporary sediment yields, determined by monitoring suspended-sediment discharge, exceed cosmogenically determined millennial-scale erosion rates by nearly a factor of two. This discrepancy, between short-term rates of sediment yield and long-term rates of erosion, suggests that more sediment is currently being exported from the basin than is being produced. Because the failure of incised channel walls and the head cutting of arroyo complexes appear to be the main sources of channel sediment today, this incongruence between rates of sediment supply and sediment yield is likely to be transitory, reflecting the current states of the arroyo cycle and perhaps the influence of current or past land-use patterns. Copyright ?? 2005 John Wiley & Sons, Ltd.

Earth Surface Processes and Landforms↗
USGS2005

Episodic incision of the Colorado River in Glen Canyon, Utah

Incision rates of the Colorado River are integral to understanding the development of the Colorado Plateau. Here we calculate episodic incision rates of the Colorado River based on absolute ages of two levels of Quaternary deposits adjacent to Glen Canyon, Utah, along the north flank of Navajo Mountain. Minimum surface ages are determined by a combination of cosmogenic radionuclide surface exposure ages, uranium series and soil-development formation times. Bedrock incision rates of the Colorado River between c. 500 ka and c. 250 ka, and c. 250 ka to present are c. 0??4 m ka-1 and c. 0??7 m ka-1, respectively. These rates are more than double the rates reported in the Grand Canyon, suggesting that the Colorado River above Lees Ferry is out of equilibrium with the lower section of the river. We also determine incision rates of two tributaries to the Colorado River. Oak Creek and Bridge Creek flow off Navajo Mountain into Glen Canyon from the southeast. Oak Creek and Bridge Creek both have incision rates of c. 0??6 m ka-1 over the past c. 100 ka at points about 9 km away from the main stem of the Colorado River. Copyright ?? 2005 John Wiley & Sons, Ltd.

Earth Surface Processes and Landforms↗
USGS2005

Dating floodplain sediments using tree-ring response to burial

Floodplain sediments can be dated precisely based on the change in anatomy of tree rings upon burial. When a stem of tamarisk (Tamarix ramosissima) or sandbar willow (Salix exigua) is buried, subsequent annual rings in the buried section resemble the rings of roots: rings become narrower, vessels within the rings become larger, and transitions between rings become less distinct. We combined observations of these changes with tree-ring counts to determine the year of deposition of sedimentary beds exposed in a 150-m-long trench across the floodplain of the Rio Puerco, a rapidly filling arroyo in New Mexico. This method reliably dated most beds thicker than about 30 cm to within a year of deposition. Floodplain aggradation rates varied dramatically through time and space. Sediment deposition was mostly limited to brief overbank flows occurring every few years. The most rapid deposition occurred on channel-margin levees, which migrated laterally during channel narrowing. At the decadal timescale, the cross-section-average sediment deposition rate was steady, but there was a shift in the spatial pattern of deposition in the 1980s. From 1936 to 1986, sediment deposition occurred by channel narrowing, with little change in elevation of the thalweg. After 1986 sediment deposition occurred by vertical aggradation. From 1936 to 2000 about 27 per cent of the arroyo cross-section filled with sediment. The rate of filling from 1962 to 2000 was 0-8 vertical m/decade or 85 m2/decade. Published in 2005 by John Wiley & Sons, Ltd.

Earth Surface Processes and Landforms↗
USGS2006

Wind erodibility of soils at Fort Irwin, California (Mojave Desert), USA, before and after trampling disturbance: Implications for land management

Recently disturbed and 'control' (i.e. less recently disturbed) soils in the Mojave Desert were compared for their vulnerability to wind erosion, using a wind tunnel, before and after being experimentally trampled. Before trampling, control sites had greater cyanobacterial biomass, soil surface stability, threshold friction velocities (TFV, i.e. the wind speed required to move soil particles), and sediment yield than sites that had been more recently disturbed by military manoeuvres. After trampling, all sites showed a large drop in TFVs and a concomitant increase in sediment yield. Simple correlation analyses showed that the decline in TFVs and the rise in sediment yield were significantly related to cyanobacterial biomass (as indicated by soil chlorophyll a). However, chlorophyll a amounts were very low compared to chlorophyll a amounts found at cooler desert sites, where chlorophyll a is often the most important factor in determining TFV and sediment yield. Multiple regression analyses showed that other factors at Fort Irwin were more important than cyanobacterial biomass in determining the overall site susceptibility to wind erosion. These factors included soil texture (especially the fine, medium and coarse sand fractions), rock cover, and the inherent stability of the soil (as indicated by subsurface soil stability tests). Thus, our results indicate that there is a threshold of biomass below which cyanobacterial crusts are not the dominant factor in soil vulnerability to wind erosion. Most undisturbed soil surfaces in the Mojave Desert region produce very little sediment, but even moderate disturbance increases soil loss from these sites. Because current weathering rates and dust inputs are very low, soil formation rates are low as well. Therefore, soil loss in this region is likely to have long-term effects.

Earth Surface Processes and Landforms↗
USGS2006

Coupling chemical weathering with soil production across soil-mantled landscapes

Soil-covered upland landscapes constitute a critical part of the habitable world. Our understanding of how they evolve as a function of different climatic, tectonic and geological regimes is important across a wide range of disciplines and depends, in part, on understanding the links between chemical and physical weathering processes. Extensive previous work has shown that soil production rates decrease with increasing soil column thickness, but chemical weathering rates were not measured. Here we examine a granitic, soil-mantled hillslope at Point Reyes, California, where soil production rates were determined using in situ produced cosmogenic nuclides ( 10 Be and 26 Al), and we quantify the extent as well as the rates of chemical weathering of the saprolite from beneath soil from across the landscape. We collected saprolite samples from the base of soil pits and analysed them for abrasion pH as well as for major and trace elements by X-ray fluorescence spectroscopy, and for clay mineralogy by X-ray diffraction spectroscopy. Our results show for the first time that chemical weathering rates decrease with increasing soil thickness and account for 13 to 51 per cent of total denudation. We also show that spatial variation in chemical weathering appears to be topographically controlled: weathering rate decreases with slope across the divergent ridge and increases with upslope contributing area in the convergent swale. Furthermore, to determine the best measure for the extent of saprolite weathering, we compared four different chemical weathering indices – the Vogt ratio, the chemical index of alteration (CIA), Parker's index, and the silicon–aluminium ratio – with saprolite pH. Measurements of the CIA were the most closely correlated with saprolite pH, showing that weathering intensity decreases linearly with an increase in saprolite pH from 4·7 to almost 7. Data presented here are among the first to couple directly rates of soil production and chemical weathering with how topography is likely to control weathering at a hillslope scale.

Earth Surface Processes and Landforms↗
USGS2007

Dust emission from wet and dry playas in the Mojave Desert, USA

The interactions between playa hydrology and playa-surface sediments are important factors that control the type and amount of dust emitted from playas as a result of wind erosion. The production of evaporite minerals during evaporative loss of near-surface ground water results in both the creation and maintenance of several centimeters or more of loose sediment on and near the surfaces of wet playas. Observations that characterize the texture, mineralogic composition and hardness of playa surfaces at Franklin Lake, Soda Lake and West Cronese Lake playas in the Mojave Desert (California), along with imaging of dust emission using automated digital photography, indicate that these kinds of surface sediment are highly susceptible to dust emission. The surfaces of wet playas are dynamic - surface texture and sediment availability to wind erosion change rapidly, primarily in response to fluctuations in water-table depth, rainfall and rates of evaporation. In contrast, dry playas are characterized by ground water at depth. Consequently, dry playas commonly have hard surfaces that produce little or no dust if undisturbed except for transient silt and clay deposited on surfaces by wind and water. Although not the dominant type of global dust, salt-rich dusts from wet playas may be important with respect to radiative properties of dust plumes, atmospheric chemistry, windborne nutrients and human health.

California↗
USGS2008

The experimental basis for interpreting particle and magnetic fabrics of sheared till

Particle fabrics of basal tills may allow testing of the bed-deformation model of glacier flow, which requires high bed shear strains (>100). Field studies, however, have not yielded a systematic relationship between shear-strain magnitude and fabric development. To isolate this relationship four basal tills and viscous putty were sheared in a ring-shear device to strains as high as 714. Fabric was characterized within a zone of shear deformation using the long-axis orientations of fine-gravel and sand particles and the anisotropy of magnetic susceptibility (AMS) of small (???5-8 cm3) intact samples. Results indicate that till particles rotate toward the plane of shearing with long-axis orientations that become tightly clustered in the direction of shear (0??78 < S1 < 0??94 for three-dimensional data). These strong, steady-state fabrics are attained at shear strains of 7-30, with no evidence of fabric weakening with further strain, regardless of the specific till or particle-size fraction under consideration. These results do not support the Jeffery model of particle rotation, which correctly describes particle rotation in the viscous putty but not in the tills, owing to fluid-mechanical assumptions of the model that are violated in till. The sensitivity of fabric development to shear-strain magnitude indicates that, for most till units where shear-strain magnitude is poorly known, attributing fabric variations to spatial differences in other variables, such as till thickness or water content, will be inherently speculative. Attributing fabric characteristics to particular basal till facies is uncertain because shear-strain magnitude is unlikely to be closely correlated to till facies. Weak or spatially variable fabrics, in the absence of post-depositional disturbance or major deviations from unidirectional simple shear, indicate that till has not been pervasively sheared to the high strains required by the bed-deformation model. Strong flow-parallel fabrics are a necessary but insufficient criterion for confirming the model. Copyright ?? 2008 John Wiley & Sons, Ltd.

Earth Surface Processes and Landforms↗
USGS2009

Rapid incision of the Colorado River in Glen Canyon - insights from channel profiles, local incision rates, and modeling of lithologic controls

The Colorado River system in southern Utah and northern Arizona is continuing to adjust to the baselevel fall responsible for the carving of the Grand Canyon. Estimates of bedrock incision rates in this area vary widely, hinting at the transient state of the Colorado and its tributaries. In conjunction with these data, we use longitudinal profiles of the Colorado and tributaries between Marble Canyon and Cataract Canyon to investigate the incision history of the Colorado in this region. We find that almost all of the tributaries in this region steepen as they enter the Colorado River. The consistent presence of oversteepened reaches with similar elevation drops in the lower section of these channels, and their coincidence within a corridor of high local relief along the Colorado, suggest that the tributaries are steepening in response to an episode of increased incision rate on the mainstem. This analysis makes testable predictions about spatial variations in incision rates; these predictions are consistent with existing rate estimates and can be used to guide further studies. We also present cosmogenic nuclide data from the Henry Mountains of southern Utah. We measured in situ 10 Be concentrations on four gravel-covered strath surfaces elevated from 1 m to 110 m above Trachyte Creek. The surfaces yield exposure ages that range from approximately 2??5 ka to 267 ka and suggest incision rates that vary between 350 and 600 m/my. These incision rates are similar to other rates determined within the high-relief corridor. Available data thus support the interpretation that tributaries of the Colorado River upstream of the Grand Canyon are responding to a recent pulse of rapid incision on the Colorado. Numerical modeling of detachment-limited bedrock incision suggests that this incision pulse is likely related to the upstream-dipping lithologic boundary at the northern edge of the Kaibab upwarp. ?? 2009 John Wiley & Sons, Ltd.

Earth Surface Processes and Landforms↗
USGS2009

Quantifying periglacial erosion: Insights on a glacial sediment budget, Matanuska Glacier, Alaska

Glacial erosion rates are estimated to be among the highest in the world. Few studies have attempted, however, to quantify the flux of sediment from the periglacial landscape to a glacier. Here, erosion rates from the nonglacial landscape above the Matanuska Glacier, Alaska are presented and compare with an 8-yr record of proglacial suspended sediment yield. Non-glacial lowering rates range from 1??8 ?? 0??5 mm yr -1 to 8??5 ?? 3??4 mm yr -1 from estimates of rock fall and debris-flow fan volumes. An average erosion rate of 0??08 ?? 0??04 mm yr -1 from eight convex-up ridge crests was determined using in situ produced cosmogenic 10 Be. Extrapolating these rates, based on landscape morphometry, to the Matanuska basin (58% ice-cover), it was found that nonglacial processes account for an annual sediment flux of 2??3 ?? 1??0 ?? 10 6 t. Suspended sediment data for 8 years and an assumed bedload to estimate the annual sediment yield at the Matanuska terminus to be 2??9 ?? 1??0 ?? 10 6 t, corresponding to an erosion rate of 1??8 ?? 0??6 mm yr -1 : nonglacial sources therefore account for 80 ?? 45% of the proglacial yield. A similar set of analyses were used for a small tributary sub-basin (32% ice-cover) to determine an erosion rate of 12??1 ?? 6??9 mm yr -1 , based on proglacial sediment yield, with the nonglacial sediment flux equal to 10 ?? 7% of the proglacial yield. It is suggested that erosion rates by nonglacial processes are similar to inferred subglacial rates, such that the ice-free regions of a glaciated landscape contribute significantly to the glacial sediment budget. The similar magnitude of nonglacial and glacial rates implies that partially glaciated landscapes will respond rapidly to changes in climate and base level through a rapid nonglacial response to glacially driven incision. ?? 2009 John Wiley & Sons, Ltd.

Earth Surface Processes and Landforms↗
USGS2010

Shear-rate-dependent strength control on the dynamics of rainfall-triggered landslides, Tokushima Prefecture, Japan

A typhoon (Typhoon No. 10) attacked Shikoku Island and the Tyugoku area of Japan in 2004. This typhoon produced a new daily precipitation record of 1317 mm on Shikoku Island and triggered hundreds of landslides in Tokushima Prefecture. One catastrophic landslide was triggered in the Shiraishi area of Kisawa village, and destroyed more than 10 houses while also leaving an unstable block high on the slope. The unstable block kept moving after the event, showing accelerating and decelerating movement during and after rainfall and reaching a displacement of several meters before countermeasures were put into place. To examine the mechanism for this landsliding characteristic, samples (weathered serpentinite) were taken from the field, and their shear behaviours examined using ring shear tests. The test results revealed that the residual shear strength of the samples is positively dependent on the shear rate, which may provide an explanation for the continuous acceleratingdecelerating process of the landsliding. The roughness of the shear surface and the microstructure of the shear zone were measured and observed by laser microscope and SEM techniques in an attempt to clarify the mechanism of shear rate effect on the residual shear strength. Copyright ?? 2010 John Wiley & Sons, Ltd.

Earth Surface Processes and Landforms↗
USGS2011

Response of surface processes to climatic change in the dunefields and Loess Plateau of North China during the late Quaternary

This paper draws on recent optically stimulated luminescence (OSL) dating to evaluate the long‐held assumption that dust accumulation rates in the Loess Plateau and the extent of active aeolian sand in the dunefields to the north have varied together over time, because both are controlled by the strength of the Asian monsoons and also possibly because the dunefields are proximal loess sources. The results show there is little evidence that high rates of loess accumulation coincided with well‐dated episodes of extensive dune activity in the Mu Us, Otindag, and Horqin dunefields, at 11–8 ka and 1–0 ka. Explanations for the apparent lack of coupling include local variation in the trapping of dust and post‐depositional preservation of the loess and dune sediments, in response to varying local environmental conditions. In addition, a substantial portion of the loess may be transported directly from source areas where dust emission has somewhat different climatic and geomorphic controls than aeolian sand activity within the dunefields. The results of this study cast doubt on the use of loess accumulation rate as a palaeoclimatic proxy at millennial timescale. The dunefield and loess stratigraphic records are interpreted as primarily recording changes in effective moisture at a local scale, but the timing of late Quaternary dune activity, along with a variety of other evidence, indicates that moisture changes in many of the drylands of northern China may not be in phase with precipitation in core regions of the Asian monsoons.

Earth Surface Processes and Landforms↗
USGS2011

The interactions between vegetation and erosion: new directions for research at the interface of ecology and geomorphology

Vegetation and processes of erosion and deposition are interactive. An objective of this paper is to review selected studies that emphasize the interdependencies. The reviews suggest new directions for research uniting ecology and geomorphology – the sub‐discipline of biogeomorphology. The research, which recently has become vigorous, includes the sources, movement, and fates of fluvial loads of sediment, organic carbon, nutrients, contaminants, and woody debris to low‐energy storage sites; the function of biota in causing soil evolution, stability, and sequestration of carbon; the development of new methods to characterize watersheds based on edaphic conditions; and the refinement of current empirical and conceptual models and dendrochronological techniques to measure landscape change. These well acknowledged topics and others less well anticipated ensure that biogeomorphology will remain vibrant.

Earth Surface Processes and Landforms↗