共查询到20条相似文献，搜索用时 0 毫秒
1.
Soils in a lower Hunter valley vineyard, New South Wales, Australia, were sampled and analysed for caesium‐137, an indicator of soil erosion status, in 1984–1985 and 2004. From the time of the vineyard's first establishment in 1971 to 1985, estimated soil losses were 250 tonnes (equivalent to 64.2 t ha?1 yr?1). Re‐sampling in 2004 showed that soil losses were 48 tonnes in the 19 years since 1985, equivalent to 9.7 t ha?1 yr?1. The decline in erosion rates may be explained by a change in land and soil management from intensive cultivation to one of no cultivation (sod culture) in 1998, and a lower annual rainfall and fewer rain‐days per year in the period from 1986 to 2004. 相似文献
2.
A survey of soil erosion was conducted in Australia using the fallout radioisotope caesium‐137 as an indicator of topsoil redistribution. Two hundred and six sites were sampled, 100 within rotational cropping and horticultural use, 52 within uncultivated permanent pasture and forest, and 54 in rangelands. Average net soil losses were approximately equal for cultivated cropping lands and rangelands (ca. 5.5 t ha?1 yr?1), and just over 1 t ha?1 yr?1 for pasture and forest. The Mann Whitney U Test revealed that losses under cropping and rangeland conditions were significantly higher (p < 0.05) than under uncultivated pasture and forest. Soil loss was negatively correlated with mean annual rainfall and slope gradient, and positively correlated with slope length (Spearman's rank correlation). There was no correlation between rates of soil loss and a rainfall erosi‐vity index. An assessment of erosional events was provided by landholders for 104 sites, with their ranking being weakly but significantly correlated with soil loss estimates (r =+0.35). Sixty percent of sites had net soil losses greater than 1 t ha?1 yr?1, and 74% of sites had losses of more than 0.5 t ha?1 yr?1. This latter rate may be regarded as a limit for a tolerable level of soil loss. These high rates of soil loss have occurred since the mid‐1950s despite there being significant landholder awareness of the soil erosion hazard. 相似文献
3.
以兰州市为例,使用ASTER 30米分辨率的数字高程模型DEM并提取了兰州市周边所有地名信息;通过收集、整理地名,主要地名类型有:滩、坪、台、山、沟、湾、屲(洼)、岭、岘、梁、岗、咀等;通过地名与地貌分析,发现兰州地名命名及分布在很大程度上能够反映兰州市的地形地貌,且兰州地名类型的分布随高程呈现出一定规律;每一高程面上的地名数量与该高程面上兰州市的面积变化并没形成对应关系,在1800-1900 m、2100-2800 m高程,地名数量与面积对应较好;通过分析进一步证明了我国地名命名系统和地貌之间的关系,说明在我国文化地理及自然地理等学科的发展中具有融合现象。 相似文献
4.
Medium to large natural catchments are often more spatially heterogeneous than small catchments or single landforms. Attempting to model landform evolution of large areas is consequently more complex. This paper demonstrates that modelling landform evolution in medium to large catchments can be improved by calibrating the model to smaller, more geomorphologically homogenous sub‐catchments. The paper investigates landform evolution in the Ngarradj catchment in the Northern Territory of Australia (a medium scale catchment of approximately 67 km2). The catchment is complex and contains two distinct landform regions; an upland plateau region with highly dissected sandstone and shallow, sandy soils, and a lowlands region with gentle, wooded slopes and floodplains with deep, sandy soils. The SIBERIA landform evolution model is calibrated and applied to the Ngarradj catchment. The complexity of the Ngarradj catchment is incorporated into the modelling by dividing the catchment into three sub‐catchments (Swift Creek (SC), Upper Main (UM) and East Tributary (ET)) which are relatively homogeneous and for which hydrology and sediment transport data are available. A discharge‐area relationship and long‐term, sediment loss rates for the catchment are derived based on an annual series flood frequency analysis of a 20 year runoff record predicted in a previous study. Sediment transport modelling incorporates both suspended and bedload sediment loss. The denudation rates derived using these data are 37, 63 and 77 mm kyr?1 for the SC, UM and ET sub‐catchments, respectively. Model predictions indicate that the UM sub‐catchment will have the greatest mean erosion. This is balanced by the large amount of deposition that will occur in the upper Ngarradj valley of the UM sub‐catchment. Further deposition occurs on the floodplain of Ngarradj, with the area between the SC and ET/UM (up‐stream) sub‐catchments experiencing a small net accretion of sediment (15 mm kyr?1). 相似文献
5.
Pamela E. Tetford Joseph R. Desloges Dimitri Nakassis 《Journal of Field Archaeology》2013,38(7):538-550
Complex interactions between topography, near-surface geology, active tectonics, climate, and human activity shape a landscape, conditioning archaeological deposits and making sediment deposits from surface erosion important archives. There is a potential relationship between the intensity of geomorphic processes and surface artifact distribution. This study assesses the potential relationship between soil erosion by water and the spatial distribution of archaeological surface artifacts in the Inachos River watershed, Greece. The mountainous, semi-arid Mediterranean region is particularly vulnerable to soil loss. Soil erosion is quantified by applying the Revised Universal Soil Loss Equation in a GIS framework. Estimates of soil loss vary spatially compared to surface artifact finds of the pedestrian survey of the Western Argolid Regional Project. A statistically significant relationship is identified between surface erosion rates and artifact density. Preferential topography for occupation suggests this is an associative rather than causative relationship. Knowledgeable interpretation of artifact distribution enables accurate reconstruction of human settlement history. 相似文献
6.
Bryan K. Miller Martin Furholt Jamsranjav Bayarsaikhan Tömörbaatar Tüvshinjargal Lennart Brandtstätter Joshua Wright 《Journal of Field Archaeology》2019,44(4):267-286
Walled sites attributed to the Xiongnu steppe empire (2nd century b.c.–1st century a.d.) constitute the earliest investments in explicitly non-mortuary built environments among pastoralists of the Mongolian Steppe. These permanent constructions are important precedents to the medieval towns of subsequent steppe empires, yet very little of the complete layouts and surrounding remains of the large enclosures are understood. Our investigations of the walled site at Kherlen-Bars in eastern Mongolia are among the first surveys to fully document all aspects above and below ground across an entire Iron Age walled site area. In addition to detailed documentation of the large structures, our geomagnetic prospections and digital elevation modeling brought to light numerous small sub-surface and subtle-surface features that show such early walled sites, often deemed virtually empty, to be far more complex and diachronic in their formation processes and possible functions. 相似文献
7.
The 137Cs (caesium‐137) method was used to investigate medium‐term rates of sediment deposition on the floodplain of the Labasa River, on Vanua Levu island in northern Fiji. The Labasa basin is commercially important for sugarcane farming, which provides much revenue and sustains the economy in the greater Labasa area. Alluvium was sampled at three riverbank sites in vertical increments of 30 mm. Measured net vertical accretion rates, based on analysis of depth‐profiles of 137Cs activity, ranged from 10 mm yr?1 at a low‐lying site near a tributary confluence with the main river, to 60 mm yr?1 on a levée that was elevated slightly above the adjacent floodplain. These rates of accretion are high, but in general agreement with rates recorded using similar methods in other tropical Pacific island river systems. Soil erosion under sugarcane on hilly parts of the lower Labasa basin is an important factor in rapid floodplain development. Observations made during Cyclone Ami, which traversed Vanua Levu island in early 2003, illustrate the major contribution of severe storm events to floodplain sediment supply, by triggering numerous landslides on catchment slopes and in‐channel debris floods, and by generating large‐magnitude overbank floods. 相似文献
8.
NGUYEN VAN DE IAN DOUGLAS JULIA MCMORROW SARAH LINDLEY DAO KIM NGUYEN THUY BINH TRAN THI VAN LE HUU THANH NGUYEN THO 《Geographical Research》2008,46(1):4-16
To help improve the well‐being of the local people, a joint Vietnamese‐UK team set out to establish a way of estimating soil and nutrient losses under different land management scenarios, using field data extrapolated through remote sensing and GIS, to obtain catchment‐wide estimates of the impact of land cover change. Immigration from remote provinces to the Dong Phu District of Binh Phuóc Province, about 120 km north of Ho Chi Minh City, has led to disruption of soil surface stability on easily eroded clayey sandstones, creating rapid nutrient depletion that affects crop yields and siltation in the channel of the Rach Rat river downstream. The poor farmers of the areas see crop yields drop dramatically after two or three years of cultivation due to the fertility decline. Soil loss varies dramatically between wet season and dry season and with ground cover. Erosion bridge measurements showed a mean loss of 85.2 t ha?1 y?1 under cassava saplings with cashew nuts, 43.3 t ha?1 y?1 on uncultivated land and 41.7 t ha?1 y?1 under mature cassava. The rates of erosion were higher than those reported in many other parts of Vietnam, reflecting the high erodibility of the friable sandy soils on the steep side‐slopes of the Rach Rat catchment. However, although the actual measurements provide better soil loss data than estimates based on the parameters of soil loss equations, a large number of measurement sites is needed to provide adequate coverage of the crop and slope combinations in this dissected terrain for good prediction using GIS and remote sensing. 相似文献
9.
Siân Jones Stuart Jeffrey Mhairi Maxwell Alex Hale Cara Jones 《International Journal of Heritage Studies》2018,24(4):333-353
This article examines the question of authenticity in relation to 3D visualisation of historic objects and monuments. Much of the literature locates their authenticity in the accuracy of the data and/or the realism of the resulting models. Yet critics argue that 3D visualisations undermine the experience of authenticity, disrupting people’s access to the materiality, biography and aura of their historic counterparts. The ACCORD project takes questions of authenticity and 3D visualisation into a new arena – that of community heritage practice – and uses rapid ethnographic methods to examine whether and how such visualisations acquire authenticity. The results demonstrate that subtle forms of migration and borrowing occur between the original and the digital, creating new forms of authenticity associated with the digital object. Likewise, the creation of digital models mediates the authenticity and status of their original counterparts through the networks of relations in which they are embedded. The current pre-occupation with the binary question of whether 3D digital models are authentic or not obscures the wider work that such objects do in respect to the cultural politics of ownership, attachment, place-making and regeneration. The article both advances theoretical debates and has important implications for heritage visualisation practice. 相似文献
10.
David Manley Ron Johnston Kelvyn Jones 《Tijdschrift voor economische en sociale geografie = Journal of economic and social geography = Revue de géographie économique et humaine = Zeitschrift für ?konomische und soziale Geographie = Revista de geografía económica y social》2019,110(3):319-338
There has been a growing appreciation that the processes generating urban residential segregation operate at multiple scales, stimulating innovations into the measurement of their outcomes. This paper applies a multi‐level modelling approach to that issue to the situation in Auckland, where multiple migration streams from both Pacific Island and Asian origins have created a complex multi‐ethnic city. We identify two distinct trends. For the larger ethnic groups segregation remained static despite rapid growth over a recent twelve‐year period. For the smaller groups growth has been combined with considerable change; they initially clustered in a few localities and areas within them but then experienced considerable reduction in the intensity of that segregation. By spatially decomposing the segregation levels, this paper extends our appreciation of its underpinning processes when they apply to migration streams that differ in their nature from those on which traditional residential location‐decision theory has been based. 相似文献
11.
MIN HUA JEN RON JOHNSTON KELVYN JONES RICHARD HARRIS AXEL GANDY 《Tijdschrift voor economische en sociale geografie = Journal of economic and social geography = Revue de géographie économique et humaine = Zeitschrift für ?konomische und soziale Geographie = Revista de geografía económica y social》2010,101(1):73-90
Life expectancy at birth has increased substantially at the global scale over recent decades, but the improvements have not been experienced equally across all countries – in large part reflecting changes in economic and social situations. To identify the spatial variations in life expectancy at birth across a large number of countries over a 33‐year period, this paper provides an expository account of a developing modelling methodology for the analysis of spatio‐temporal trajectories. It identifies broad patterns of change and simultaneously examines between‐ and within‐country variation to assess the degree to which patterns of life expectancy are becoming more or less similar at national and sub‐national scales. 相似文献
12.
Soil (SL) and organic carbon losses (SOCL) have increased with human population and climate change linked extreme events. While SL and SOCL are clearly associated with surface run‐off, the impact of land use is still not well understood. This article elucidates the effects of land use, surface cover, and other environmental factors on SL and SOCL using data from 55 published studies. The overall SL (12.34 ± 2.25 Mg ha?1 year?1) and SOCL (21.80 ± 0.91 g C m?2 year?1) suggests substantial losses of the fertile topsoil globally. Grasslands (4.19 ± 1.22 Mg ha?1 year?1) had 77%, 66%, and 41% lower SL than orchards, croplands, and forests, respectively, which is attributable to higher soil organic matter and surface cover. Croplands had the highest SOCL at 22.78 ± 2.22 g C m?2 year?1. Natural vegetation had 98% and 70% lower run‐off and SL than did plant residue mulched plots, indicating its great potential for surface run‐off and soil erosion control. Rainfall and slope were key drivers of soil erosion, while soil surface cover, SOC, and clay content decreased. These findings improve our knowledge on soil and organic carbon losses, which is useful for fostering sustainable management of soils and natural vegetation to enhance ecosystems functionality. 相似文献
13.
Hans Huisman Glenn Heeres Bertil van Os Willem Derickx Jeroen Schoorl 《Conservation and Management of Archaeological Sites》2013,15(1-3):205-216
Slope soil erosion is one of the main threats to archaeological sites. Several methods were applied to establish the erosion rates at archaeological sites. Digital elevation models (DEMs) from three different dates were used. We compared the elevations from these three models to estimate erosion. We also applied the landscape evolution model LAPSUS with the available DEMs as basis. Spatial processing errors and effects of tillage and harvesting practices explain most of the DEM elevation differences between the recordings. Increased DEM resolution does not result in more precise or reliable erosion. The present technological level of landscape evolution modelling makes it possible to indicate areas most vulnerable to soil displacement by surface runoff erosion and tillage. Future research, using sediment and surface dating techniques such as deposit of radionuclides, heavy metals and OSL dating will provide a more accurate estimation of erosion rates and the subsequent impact on archaeological sites. 相似文献
14.
The Mediterranean ecosystem of Mt. Carmel, Israel, is subjected to an increasing number of forest fires of various extents and severities. The impacts of forest fires on runoff and erosion are widely documented and include increased peak flows and soil loss until the return of a vegetation cover. Most studies, however, treat fire as a single event, whereas the present study is aimed at exploring the long‐term effects of repeated forest fires on eco‐geomorphic processes. The study integrates the results of plot‐based, detailed analysis of post‐fire runoff and erosion with vegetation recovery analysis, at a temporal‐spatial scale which includes the effect of reburning. Our results indicate that forest fires lead to a significant increase in runoff and sediment yields, particularly during the first two years following the disturbance, up to five orders of magnitude higher than from the adjacent unburnt control plots. 相似文献
15.
DAO KIM NGUYEN THUY BINH LE T. V. PHUONG IAN DOUGLAS NGUYEN VAN DE JULIA MCMORROW SARAH LINDLEY TRAN THI VAN LE HUU THANH NGUYEN THO 《Geographical Research》2008,46(1):17-26
Several parts of Binh Phuóc Province, southern Vietnam, suffer from degraded soils and vegetation as a result of both natural erosion of weak mud rocks and sandstones and intensive human activity, especially through land clearing for agriculture on unstable slopes, deforestation, and abandonment of poor farmland. The underlying cause of this land degradation has been the farming habits of migrants of varying ethnic groups who have settled in the area since 1980. The indigenous farming knowledge of these people and the role of that knowledge in soil erosion were examined by a series of household surveys. They enabled farming practices to be related to ground cover established from a 2002 Landsat 7 ETM (Enhanced Thematic Mapper), and erosion data from a series of erosion bridge measurements. A GIS (Geographical Information System) approach was piloted as a means of identifying areas vulnerable to erosion. This could then be combined with the understanding of farming practices to reveal the relative roles of farmer behaviour, crop cover, and slope and soil characteristics in the erosion process. Land use, local people's knowledge and economic realities are the main factors, as well as natural conditions, that drive this land degradation. 相似文献
16.
Grant W.G. Cochrane Trudy Doelman Simon Greenwood Jamie Reeves 《Archaeology in Oceania》2013,48(2):92-100
We use a non‐site survey methodology and statistical significance testing to evaluate Hall's (1992a) predictive model of stone artefact distributions in the south‐east Australian highlands. The study area is a 19.5 km2 rectangular corridor in the Limestone Creek valley, north‐east Victoria. The study confirms a number of Hall's predictions about the relationship between stone artefact density and environmental factors. The strongest relationship is between artefact density and slope. This relationship is probably a reflection of both cultural and non‐cultural processes, which have promoted higher artefact density on the more subdued terrain. We also found that less common artefact types such as retouched tools and cores had the least predictable spatial distributions, although this may be a reflection of the small sample size. 相似文献
17.
Abstract Semi-arid landscapes are vulnerable to cultivation, overgrazing and climate variability, although it is difficult to identify the relative significance of these three factors. In the South African Karoo, the ‘desertification debate' seeks to explain a change to more shrubby vegetation in heavily grazed areas. We examine these issues in catchments where farm reservoirs provide sediment stores with 137Cs, 210Pb, geochemical and mineral magnetic signatures. Rainfall data and stocking numbers are reported and current erosion rates are estimated. Sediment accumulation in the reservoirs increases between 1935 and 1940, probably due to rises in the frequency of rainfall events of >25mm day. Significant increases in sedimentation rates (×8) occur during rain-fed wheat cultivation. In an uncultivated catchment, sediment yields remain relatively high and reflect increases in erosion from hillslopes, colluvial storage, and cultivated land sources. Gully systems have acted as transport routes rather than sediment sources over the last ～70 years. Badland erosion rates average ca. 50t ha?1 yr?1. At Ganora, their development in the 1920s strongly influences peak sedimentation between 1970 and 1980. Any delay between badland initiation and increased sediment yield appears to be a function of landscape connectivity. Recovery following disturbance is occurring slowly and is likely to take >100 years. De-stocking and better management systems are reducing erosion rates but may be offset by increases in rainfall intensity. 相似文献
18.
Juan Ortiz Sanz Maria de la Luz Gil Docampo Santiago Martínez Rodríguez María Teresa Rego Sanmartín Gonzalo Meijide Cameselle 《Journal of archaeological science》2010
In the present study a simple method is described for obtaining 3D digital models of petroglyphs of different sizes and characteristics and its usefulness, in the study of this cultural heritage, is evaluated. For this research we used low-cost photogrammetric software and consumer-grade digital cameras, without any other surveying techniques. In order to test this methodology, three field research studies were carried out in Galicia (Spain). 相似文献
19.
20.
John Boardman 《Transactions (Institute of British Geographers : 1965)》2003,28(2):176-196
The South Downs in southern England have been farmed for 5000 years: the initial loess cover is now a thin, stony remnant as a result of erosion. During the 1980s, field monitoring of erosion events in an area of 36 km2 showed that average rates of erosion are low (0.5–5.0 m3 ha−1 yr−1 ), but that occasional storms result in losses of over 200 m3 ha−1 yr−1 on individual fields. On soils that are only 15 cm thick, such rates pose a threat to future farming. Almost all recent erosion has been on fields of winter cereals, which are bare in the wet autumn period. Of greater significance in the short term are the effects of soil-laden runoff (or muddy floods) on urban areas. Flood damage to property has been a regular event since the conversion of this area to winter cereals in the 1970s. Soil conservation measures have been negligible and flood protection has consisted mainly of engineering works and limited land-use change at sites where property damage has occurred. Conversion to grass under the Set Aside, and an Environmentally Sensitive Area (ESA) scheme, could be an effective soil conservation and flood protection approach. In the longer term, increasing stoniness of soils, the economic incentives for arable farming in marginal areas, and the success of legal proceedings relating to flood damage, will determine the future of erosion on the South Downs. Current farming systems clearly are unsustainable and would become more so under future climates without substantial site-targeted land use change. 相似文献