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1.
Driving forces responsible for aeolian desertification in the source region of the Yangtze River from 1975 to 2005 总被引:1,自引:1,他引:0
The Yangtze River is the China’s longest river and the third-longest river in the world. The river’s source region in the
Qinghai-Tibet Plateau is especially sensitive to global environmental change because of its high elevation and cold environment.
Under the influence of global warming, aeolian desertified land has expanded rapidly in this area. To assess the trends in
aeolian desertification from 1975 to 2005, remote-sensing and GIS technology were used to monitor the extent of aeolian desertification
in 1975, 1990, 2000, and 2005. The data sources included Landsat multi-spectral scanner images acquired in 1975, Enhanced
Thematic Mapper (ETM+) images acquired in 2000, and Thematic Mapper (TM) images acquired in 1990 and 2005. Images recorded
between June and October were selected, when vegetation grew well, because aeolian desertified land was more easily recognized
during this period. Thematic maps, including land use and geomorphologic maps, were used as supplementary data. Aeolian desertification
maps (1:100000) were produced for each year from the Landsat images through visual interpretation. The area of aeolian desertified
land increased by 2,678.43 km2 from 1975 to 2005, accounting for 8.8% of the total area of aeolian desertified land in 1975, an increase of 89.28 km2 a−1. Increasing mean annual temperature and the combination of a dry, cold, and windy climate in winter and spring were mainly
responsible for the expansion of desertified land. 相似文献
2.
Rocky desertification and its causes in karst areas: a case study in Yongshun County,Hunan Province,China 总被引:9,自引:0,他引:9
Rocky desertification, a process of land degradation characterized by soil erosion and bedrock exposure, is one of the most
serious land degradation problems in karst areas, and is regarded as an obstacle to local sustainable development. It is well
known that human activities can accelerate rocky desertification; however, the effects of climate change on rocky desertification
in karst areas are still unclear. This study focused on the effects of temperature and precipitation changes and human activities
on rocky desertification in karst areas to determine the impacts of climate change and human disturbances on rocky desertification.
Areas of different level of rocky desertification were obtained from Landsat TM (1987) and Landsat ETM+ (2000) images. The
results show that, although the total desertification area increased by only 1.27% between 1987 and 2000, 17.73% of the slightly
desertified land had degraded to a moderate or intense level, 2.01 and 15.71%, respectively. Meanwhile, between 1987 and 2000,
the air temperature increased by 0.7°C, and precipitation increased by 170 mm. Statistical results indicate that the increase
in precipitation was caused by heavy rainfall. In addition, under the interactive influences of heavy rainfall and temperature,
the average karst dissolution rate was about 87 m3 km−2 a−1 during the 14 years in the study area. Further analysis indicated that rocky desertification was positively related with
the increase in temperature and precipitation and especially with the heavy rainfall events. Climate change accelerated rocky
desertification in the karst areas.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
3.
Guangyin Hu Huijun Jin Zhibao Dong Junfeng Lu Changzhen Yan 《Environmental Earth Sciences》2013,70(7):3245-3254
The source region of the Yellow River, located in the northeastern portion of the Qinghai–Tibet Plateau, plays a critical role in water conservation, biodiversity protection, and wetland conservation. Aeolian desertification of this area is an important concern. Remote sensing and GIS technology were employed to assess the trends in aeolian desertification from 1975 to 2005. The monitoring results showed that, aeolian desert land increased from 15,112 to 17,214 km2 during 1975–2005. In addition, it was found that the area of aeolian desertification increased rapidly from 1975 to 1990, was stable from 1990 to 2000, and slightly decreased from 2000 to 2005. Increasing temperature, overgrazing, and drainage of wetlands have been key driving factors of aeolian desertification. Thus, to control the expansion of aeolian desert lands in the source region of the Yellow River and to rehabilitate existing desert areas, the priority should be given to altering human behavior in these areas. 相似文献
4.
Estimation of areas of sand and dust emission in the Hexi Corridor from a land cover database: an approach that combines remote sensing with GIS 总被引:1,自引:0,他引:1
The present study combined remote sensing with geographical information system (GIS) technology to interpret Landsat TM images
from 1996 to 2000 and establish a land cover database for the Hexi Corridor of China’s Gansu Province. The areas of sand and
dust emission and trends in their change were extracted by analyzing the database, with the following results: In 2000, the
source area for sand and dust storms totaled nearly 170,000 km2, accounting for 75.1% of the study region. The emission area decreases from as much as 70,000 km2 in winter and spring to around 58,000 km2 in summer and autumn, accounting for 41.1 and 34.1% of the source area, respectively. During the 4 years of the study period,
the emission area decreased by nearly 57 km2 in winter and spring (a 0.1% change); however, the vulnerability of the land surface to wind erosion increased in ca. 190 km2 and decreased in ca. 102 km2. Although the area of dust emission decreased from 1996 to 2000, the area vulnerable to wind erosion increased by ca. 87 km2, and the increased number of sand and dust storm days in the region between 2000 and 2003 appears to be correlated with this
increase. 相似文献
5.
Relationships between rocky desertification and spatial pattern of land use in typical karst area,Southwest China 总被引:7,自引:4,他引:3
Yongjun Jiang Linli Li Chris Groves Daoxian Yuan Pat Kambesis 《Environmental Earth Sciences》2009,59(4):881-890
Karst rocky desertification is a typical type of land degradation in the Southwest China. An attempt was made to study quantitatively
the relationships between rocky desertification and spatial pattern of land use through applying spatial analysis of Geographical
Information System in Nandong underground river system, a typical karst area, Southwest China. The spatial distribution of
rocky desertification and spatial pattern of land use were obtained from interpreting Landsat Images in Nandong area in 2007
by supervised classifications, and verified and rectified through field survey. The results indicate that: (1) the total land
deserted area covers 378.3 km2, or 23.4% of the total area, of which intense, moderate and slight rocky desertification covers 269.46, 54.2, and 54.63 km2, respectively, in Nandong area. (2) There is an obvious effect of spatial pattern of land use on rocky desertification. With
the increase of elevation and slope, there is a higher occurrence ratio of rocky desertification in the cultivated land and
grass land. Also, more than half of total rocky desertification was dominated within the areas of 4 km from the construction
land, and 97% of total rocky desertification was dominated within the areas of 10 km from the construction land in Nandong
area. And what can be known from the data is that the primary effect distance of human on rocky desertification from the construction
land is 4 km, and the farthest effect distance of human on rocky desertification from the construction land is 10 km in Nandong
area. 相似文献
6.
An analysis, over historical times, of the influence of natural factors such as climate, geological activity, existing landforms,
and the activity of aeolian sands on the desertification of oases and other lands in the Heihe River basin of northwestern
China revealed that desertification occurred more or less quickly according to whether the prevailing climate was cold or
warm, respectively. In the 1990s, the area of desertified lands in the lower reaches of the Heihe River (Ejin region) was
29.1% greater than in the mid 1980s. However, the rate of desertification in the middle reaches of the Heihe River basin was
relatively slower, only 9.4% from 1949 to 1990 (or 0.27% per year). Since 1990, the rate of desertification has been stable.
By 2000, the total area of land desertification in the mid to lower reaches of the Heihe River basin was 13,508.4 km2, or 11.8% of the region monitored. Of the total land desertification area, the regions of Linze, Gaotai, Sunan, Jiuquan,
Jia Yuguan, and Jinta accounted for 1.70, 1.71, 1.43, 0.85, 0.28, and 9.39%, respectively, whereas the Ejin region’s 11,434.64 km2 accounted for 84.65%, indicating that land desertification in the lower Heihe River basin was particularly severe. The causes
responsible for the occurrence and development of land desertification in the Heihe River basin were analyzed. 相似文献
7.
Assessment of sediment and erosion rates by using the caesium-137 technique in a Chinese polygonal karst depression 总被引:4,自引:0,他引:4
Xiaoyong Bai 《Environmental Earth Sciences》2011,64(8):2151-2158
Karst depressions comprise geomorphologically important sources and sinks for sediments and associated pollutants; yet the
sedimentology of many depressions is not well understood in the world. In this paper, the 137Cs technique was employed to estimate recent sedimentation rates in a Chinese polygonal karst depression. The results indicate
that the sediment deposition rates ranged from 0.91 to 1.97 mm year−1 from 1963 to 2007, and the average sediment deposition rate and specific deposit yield were estimated to be 1.47 mm year−1 and 20 t km−2 year−1, respectively. These results are consistent with the local monitoring data of runoff fields, which confirms the validity
of the overall approach. This shows that the soil loss rate is very low in some karst areas of Southwest China. Above all,
the approach appears to offer valuable potential to study surface erosion by estimating sediment deposition rates of karst
depressions, rather than the assessment of complicated soil erosion in stony soils of carbonate rock slopes. In addition,
the space distribution of surface soil and 137Cs inventories are affected remarkably by the inhomogeneous dissolution of limestone under the soil. It may be an important
phenomenon, which exists widely in karst areas, and it is significantly different from other places. 相似文献
8.
The qanat water supply technology, which gravity drains mountain aquifers into valleys, is considered as a culturally appropriate
and ecological sustainable design to meet northern Cyprus’ drinking water development needs. This research estimates the boundary
and water budget for the proposed qanat recharge area of 370 km2, which is in the upper elevations of the limestone dominated Five Finger Mountain Range. The mountain drainage was analyzed
using global elevation data from the Shuttle Ranging Topography Mission (SRTM). Efforts to use Tropical Rainfall Measuring
Mission (TRMM) annual precipitation for water budget inputs failed due to extreme error when tested against 10–30 years of
meteorological station data; TRMM under-estimated depths on the narrow mountain peaks. Gage records, while few in number,
were area averaged to set average annual precipitation inputs at 530 mm year−1. Evaporation was estimated using a complementary relationship areal evapotranspiration (CRAE) model, setting average atmospheric
outputs at 221 mm year−1. Recharge to the qanat aquifer was set by subtracting evaporation from precipitation, and then allocating 50% of the remaining
water to environmental services. At 25% development, the qanat system supplies 14 mm3 year−1 of water, meeting the drinking water deficit of 13 mm3. 相似文献
9.
M. M. Saç E. Yumurtaci G. Yener B. Camgöz A. Uğur B. Özden 《Environmental Geology》2008,55(3):477-483
Gediz Basin is one of the regions where intense agricultural activities take place in Western Turkey. Erosion and soil degradation
have long been causing serious problems to cultivated fields in the basin. This work describes the application of two different
137Cs models for estimating soil erosion rates in cultivated sites of the region. Soil samples were collected from five distinct
cultivated regions subject to soil erosion. The variations of 137Cs concentrations with depth in soil profiles were investigated. Soil loss rates were calculated from 137Cs inventories of the samples using both proportional model (PM) and simplified mass balance model (SMBM). When PM was used,
erosion and deposition rates varied from −15 to −28 t ha−1 year−1 and from +5 to +41 t ha−1 year−1, respectively; they varied from −16 to −33 t ha−1 year−1 and from +5 to +55 t ha−1 year−1 with SMBM. A good agreement was observed between the results of two models up to 30 t ha−1 year−1 soil loss and gain in the study area. Ulukent, a small representative agricultural field, was selected to compare the present
data of 137Cs techniques with the results obtained by universal soil loss equation (USLE) applied in the area before. 相似文献
10.
Climate change and local adaptation strategies in the middle Inner Mongolia,northern China 总被引:2,自引:1,他引:1
According to records of 17 meteorological stations distributed in the study area, climate change of the middle Inner Mongolia
in northern China was analyzed in this paper. Based on SPOT VGT data, combined with field investigation, local vegetation
change was detected in the last 10 years. The results show that annual mean air temperature obviously rose, while precipitation
slightly decreased in fluctuation in the study area during the last 50 years. Air temperature increasing rates are +0.318°C 10 year−1 during 1960-2009 and +0.423°C 10 year−1 during 1980–2009, while precipitation decreasing rates are −2.91 mm 10 year−1 during 1960–2009. There were five different dry or wet periods from the 1960s to the 2000s in order, and the wetter 1990s
and the drier 2000s changed dramatically in the study area. Local climate totally tend to warm–dry conditions during the last
50 years. According to coefficient of variation (Cv) of yearly growing-season cumulative NDVI value and yearly NDVI maximum in pixel scale, vegetation had experienced huge temporal
and spatial variation during the last 10 years. Recently, frequent droughts and dust storms seriously affected local agriculture
and grazing activities, and resulted in heavy economic loss, especially over the drought period of 1999–2001. Faced with those
drought disasters accompanied with strong dust storms, the local authorities proposed the enclosing-transferring strategy
and made great efforts to adapt overt climate change and improve environment, including making selective emigration, decreasing
livestock numbers, fencing grasslands and building forage production bases with irrigation instruments and actively adjusting
industry structure. However, some effects and potential problems of this adaptation strategy still need to be comprehensively
assessed further in longer time scales and aimed at different sub-regions. 相似文献
11.
Studying spatial and temporal variation of soil loss is of great importance because of global environmental concerns. Understanding
the spatial distribution of soil erosion and deposition in the high-cold steppe is important for designing soil and water
conservation measures. Measured 137Cs losses (Bq m−2) from long-term high altitude (4,000 m above sea level) watershed plots on the Qinghai–Tibet plateau and derived soil erosion
estimates (Mg ha−1 year−1) were significantly correlated to directly measured soil losses from the same plots, over the same period (1963–2005). The
local reference inventory was estimated to be 2,468 Bq m−2. The result of analyzing 137Cs distribution and its intensity in the soil profiles in this area shows similarities to 137Cs distribution in other areas. 137Cs is basically distributed in the topsoil layer of 0–0.3 m. Soil erosions vary greatly in the entire sampled area, ranging
from 5.5 to 23 Mg ha−1 year−1, with an average of 16.5 Mg ha−1 year−1 which is a moderate rate of erosion. 相似文献
12.
荒漠化是指人类历史时期以来,由于人类不合理的经济活动和脆弱生态环境相互作用造成土地生产力下降,土地资源丧失,地表呈现类似荒漠景观的土地退化过程。在中国北方荒漠化形成因素中过度放牧占30.1%,过度农垦占26.9%,过度樵采占32.7%,水资源利用不当占96%,工矿交通建设中不注意环境保护占0.7%,在地区上以北方农牧交错及旱农地区荒漠化最为严重。要采取因地制宜措施和建立健全而完善的治理实施系统以达到生态、经济和社会三个效益的目的。 相似文献
13.
Urban expanding pattern and soil organic, inorganic carbon distribution in Shanghai, China 总被引:2,自引:0,他引:2
Soil carbon stock changes induced by land-use change play an essential role in the global greenhouse effect and carbon circulation. This paper studies the urban expanding patterns and spatial characteristics of soil organic carbon (SOC) and soil inorganic carbon (SIC) distribution and evolution during the urbanization process of Shanghai, China, based on the data of the regional geochemical survey. Urbanization process in Shanghai, China, has been quickening greatly since the 1980s. The urban area expanded from 193.08 km2 in 1980 to 1,570.52 km2 in 2005, or up from 3.05 to 24.77% in the past 25 years, and the urban expansion circled the central city region according to the RS images acquired in the periods of 1980, 2000 and 2005. The urban topsoil is slightly enriched with SOC and SIC, which shows obvious spatial variability. By comparison of SOC and SIC distribution in the central urban area, urbanized area during 1980–2000, 2000–2005 and the suburban area, the SOC obviously accumulates in the central urban area, while SOC density in the urbanized area decreases; similarly, the SIC obviously accumulates in central urban area; furthermore, the SIC density increases with urban land use duration extending and urban ecosystem evolving. This paper provides the characteristics of SOC and SIC distribution and evolution during the course of urbanization, which may be useful for assessing the impact of land use and urban development on SOC and SIC pools in urban ecosystem. 相似文献
14.
Using Multitemporal Remote Sensing Imagery and Inundation Measures to Improve Land Change Estimates in Coastal Wetlands 总被引:1,自引:0,他引:1
Remote sensing imagery can be an invaluable resource to quantify land change in coastal wetlands. Obtaining an accurate measure
of land change can, however, be complicated by differences in fluvial and tidal inundation experienced when the imagery is
captured. This study classified Landsat imagery from two wetland areas in coastal Louisiana from 1983 to 2010 into categories
of land and water. Tide height, river level, and date were used as independent variables in a multiple regression model to
predict land area in the Wax Lake Delta (WLD) and compare those estimates with an adjacent marsh area lacking direct fluvial
inputs. Coefficients of determination from regressions using both measures of water level along with date as predictor variables
of land extent in the WLD, were higher than those obtained using the current methodology which only uses date to predict land
change. Land change trend estimates were also improved when the data were divided by time period. Water level corrected land
gain in the WLD from 1983 to 2010 was 1 km2 year−1, while rates in the adjacent marsh remained roughly constant. This approach of isolating environmental variability due to
changing water levels improves estimates of actual land change in a dynamic system, so that other processes that may control
delta development such as hurricanes, floods, and sediment delivery, may be further investigated. 相似文献
15.
Puyu Wang Zhongqin Li Huilin Li Min Cao Wenbin Wang Feiteng Wang 《Environmental Earth Sciences》2012,66(1):265-273
RTK-GPS data, aerial photographs and Aster images were used to quantify volume, surface elevation, terminus position and area
changes of Glacier No. 4 of Sigong River over Mt. Bogda, Tianshan during the period from 1962 to 2009. Glacier surface elevation
of the tongue area decreased by 15 ± 8 m (0.32 ± 0.17 m a−1) and ice volume loss reached 0.014 ± 0.008 km3 (0.013 ± 0.007 km3 w. e.). The glacier terminus retreated at a rate of 8.0 m a−1 and the area decreased by about 0.53 km2, accounting for 15.8% of the glacier area in 1962 (3.33 km2). The changes can be primarily attributed to the significant increase in temperature in this region. A comparison with glacier
changes by field measurements in other regions of eastern Tianshan showed obvious spatial differences in the magnitude of
the changes, owing to a combination of regional climate change and topographical factors. 相似文献
16.
Spatio-temporal patterns of agricultural expansion and its effect on watershed degradation: a case from the mountains of Nepal 总被引:1,自引:1,他引:0
K. C. Krishna Bahadur 《Environmental Earth Sciences》2012,65(7):2063-2077
Expansion of agricultural at the cost of forested land is a common cause of watershed degradation in the mountain zones of
developing countries. Many studies have been conducted to demonstrate land use changes in such regions. However, current knowledge
regarding the changes, driving forces and implications of such change within the context of watershed development is limited.
This study analyses changes in spatial patterns of agricultural land use and their consequences for watershed degradation
during the 1976–2000 period along an altitude gradient in a watershed in Nepal, by means of remote sensing, GIS and the universal
soil loss equation. Estimated soil loss ranged from 589 to 620 t ha−1 y−1, while areas of extreme hazard severity (>100 t ha−1) increased from 9 to 14.5% from 1990 to 2000. Spatial distribution of soil loss in 2000 was characterized by 88% of total
soil losses being from upland agricultural areas. The study determined that without considering other forms of land degradation,
only water erosion was responsible for erosion of a substantial area in a short timeframe. Areas under upland cultivation
are in an extremely vulnerable state, with these areas potentially no longer cultivable within a period of 6 years. As sustainability
of the watershed is dependent on forests, continued depletion of forest resources will result in poor economic returns from
agriculture for local people, together with loss of ecosystem services. Thus, in order to achieve the goal of watershed development,
remaining forest lands must be kept under strict protection. 相似文献
17.
本文根据类似荒漠境况的出现是判断荒漠化发生与否的重要标志这一原则,并结合在中国南方开展的一些研究,对湿润地区的荒漠化进行了初步的探讨。研究表明,湿润地区的荒漠化并不包含所有存在侵蚀作用的退化土地,而专指人为侵蚀作用导致的出现了具类似荒漠境况的退化土地。中国南方湿润地区土地荒漠化分布最显著的特征为斑点状分布于丘陵山区或河、湖、海滨的冲积平原,面积为1.98×105km2,其中流水作用导致的荒漠化面积为1.78×105km2,风力作用的为0.11×105km2,其它0.09×105km2。自然因素,特别是气候和地貌因素对荒漠化的形成和发展起着积极的影响作用,但不是决定作用。人为不合理的经济活动,才是造成荒漠化的主要原因。文章最后还简要介绍了湿润地区荒漠化的防治问题。 相似文献
18.
Ana Carolina Ruiz-Fernández José Luis Marrugo-Negrete Roberth Paternina-Uribe Libia Hascibe Pérez-Bernal 《Estuaries and Coasts》2011,34(6):1117-1128
With the aim of evaluating temporal changes in sedimentation and organic carbon (Corg) supplied over the last ~100 years, a sediment core was collected at Soledad Lagoon, a costal ecosystem surrounded by mangroves,
located in the Cispatá Estuary (Caribbean coast of Colombia). The core sediments were characterized by low concentrations
of calcium carbonate (0.2–2.9%), organic matter (3–8%), total nitrogen (0.11–0.38%), and total phosphorus (0.19–0.65 mg g−1). Fe and Al concentrations ranged from 4% to 5%, and Mn from 356 to 1,047 μg g−1. The 210Pb-derived sediment and mass accumulation rates were 1.54 ± 0.18 mm year−1 and 0.08 ± 0.01 g cm−2 year−1, respectively. The sediment core did not provide evidence of human impact, such as enhancement of primary production or nutrient
enrichment, which may result from recent land uses changes or climate change. The Corg fluxes estimated for Soledad Lagoon core lay in the higher side of carbon fluxes to coastal ecosystems (314–409 g m−2 year−1) and the relatively high Corg preservation observed (~45%) indicate that these lagoon sediments has been a net and efficient sink of Corg during the last century, which corroborate the importance of mangrove areas as important sites for carbon burial and therefore,
long-term sequestration of Corg. 相似文献
19.
The development and utilization of water and land resources in the Shiyang River basin are the highest among the inland rivers
in northwestern China. Using GIS and the landscape structure analysis program FRAGSTATS, landscape metrics of a study area
in the lake-district in Minqin Oasis in the lower reaches of Shiyang River basin were calculated and analyzed based on TM
images from 1987 to 2001 at class level and landscape level, respectively. Transformation matrix of the landscape mosaics
was also examined. The driving forces of landscape changes were analyzed, including the dynamics of runoff and groundwater
resources and their exploitation, and influences of policies and market economy. The results showed that: (1) Patch number
of farmland and desert decreased, but their mean patch area increased, indicating that reclamation and desertification was
very serious in the study area. Contagion index for oasis increased and edge density and landscape diversity were reduced.
(2) Farmland and desert areas have enlarged by 1,520.46 and 4,941.27 hm2, respectively. This increase was at the cost of woodland and grassland, which shrank by 1,520.46 and 4,941.27 hm2, respectively. (3) The net utilization of surface water decreased by 50% in the last 10 years, and dropped to 22.3 × 106 m3 in the later 1990s. Exploitation of groundwater increased remarkably, up to 80 × 106 m3 per year in the last 5 years. (4) The capability of the economic structure to withstand pressures of the market economy has
depressed distinctly because of the simplified planting pattern, which is dominated by salinity-enduring cash crops, such
as cotton. Based on the above analysis, strategies of ecological reconstruction in the lake-district were suggested. 相似文献
20.
The production of organic matter and calcium carbonate by a dense population of the brittle star Acrocnida brachiata (Echinodermata) was calculated using demographic structure, population density, and relations between the size (disk diameter)
and the ash-free dry weight (AFDW) or the calcimass. During a 2-year survey in the Bay of Seine (Eastern English Channel,
France), organic production varied from 29 to 50 gAFDW m−2 year−1 and CaCO3 production from 69 to 104 gCaCO3 m−2 year−1. Respiration was estimated between 1.7 and 2.0 molCO2 m−2 year−1. Using the molar ratio (ψ) of CO2 released: CaCO3 precipitated, this biogenic precipitation of calcium carbonate would result in an additional release between 0.5 and 0.7 molCO2 m−2 year−1 that represented 23% and 26% of total CO2 fluxes (sum of calcification and respiration). The results of the present study suggest that calcification in temperate shallow
environments should be considered as a significant source of CO2 to seawater and thus a potential source of CO2 to the atmosphere, emphasizing the important role of the biomineralization (estimated here) and dissolution (endoskeletons
of dead individuals) in the carbon budget of temperate coastal ecosystems. 相似文献