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1.
Food safety and its related influencing factors in China are the hot research topics currently, and cultivated land conversion is one of the significant factors influencing food safety in China. Taking the North China Plain as the study area, this paper examines the changes of cultivated land area using satellite images, estimates land productivity from 1985 to 2005 using the model of Estimation System for Land Productivity (ESLP), and analyzes the impact of cultivated land conversion on the land production. Compared with the grain yield data from statistical yearbooks, the results indicate that ESLP model is an effective tool for estimating land productivity. Land productivity in the North China Plain showed a slight decreasing trend from 1985 to 2005, spatially, increased from the north to the south gradually, and the net changes varied in different areas. Cultivated land area recorded a marginal decrease of 8.0 × 105 ha, mainly converted to other land uses. Cultivated land conversion had more significant negative impacts on land production than land productivity did. Land production decreased by about 6.48 × 106 t caused by cultivated land conversion between 1985 and 2005, accounting for 91.9% of the total land production reduction. Although the land productivity increased in Anhui and Jiangsu provinces, it can not offset the overall adverse effects caused by cultivated land conversion. Therefore, there are significant meanings to control the cultivated land conversion and improve the land productivity for ensuring the land production in the North China Plain.  相似文献   

2.
Energy crops are a basic material in the bioenergy industry, and they can also mitigate carbon emissions and have environmental benefits when planted on marginal lands. The aim of this study was to evaluate the potential productivity of energy crops on marginal lands in China. A mechanistic model, combined with energy crop and land use characteristics, and meteorological and soil parameters, was used to simulate the potential productivity of energy crops. There were three main results. 1) The total marginal land in China was determined to be 104.78 × 10~6 ha. The 400-mm precipitation boundary line, which is the dividing line between the semi-humid and semi-arid zones in China, also divided the marginal land into shrub land and sparse forest land in the southeast and bare land, bare rock land, and saline alkali land in the northeast. 2) The total area of the marginal land suitable for planting energy crops was determined to be 55.82 × 10~6 ha, with Xanthoceras sorbifolia and Cerasus humilis mainly grown in the northern China, Jatropha curcas and Cornus wilsoniana mainly grown in the southwest and southeast, and Pistacia chinensis mainly grown in the central area, while also having a northeast-southwest zonal distribution. 3) Taking the highest yield in overlapping areas, the potential productivity of target energy crops was determined to be 32.63 × 10~6 t/yr. Without considering the overlapping areas, the potential productivity was 6.81 × 10~6 t/yr from X. sorbifolia, 8.86 × 10~6 t/yr from C. humilis, 7.18 × 10~6 t/yr from J. curcas, 9.55 × 10~6 t/yr from P. chinensis, and 7.78 × 10~6 t/yr from C. wilsoniana.  相似文献   

3.
As the important reserve land resources for food production,saline-alkali land should play a significant role to ensure the national food security in the context of global food crisis. The western Songnen Plain is one of main distribution regions of saline-alkali land in China,with great potential in agricultural development. In this study,the extent,transformation,spatial distribution and temporal change of saline-alkali land in the western Songnen Plain during 1954–2005 were investigated by using remote sensing and GIS spatial analysis methods. Saline-alkali land change was detected from a temporal series of topographic maps in 1954,satellite images of Landsat MSS in 1976,Landsat TM/ETM in 1988,2000 and 2005 through artificial visual interpretation. The results indicated a significant expansion in saline-alkali land area and aggravation in salinization. The area of saline-alkali land had increased from 401.48×103 ha in 1954 to 1 097.45×103 ha in 2005. While the ratio of light,moderate and serious salinized land areas changed from 6.72︰2.92︰1.00 to 1.25︰1.06︰1.00 in the study period. Grassland,cropland,swampland and water body were the major land use and land cover types from which saline-alkali land transformed. And the secondary salinization occured mainly in Da′an City,Tongyu County,Changling County,Daqing City,Dorbod Mongolian Autonomous County and Zhaoyuan County. Finally,seven large ecoregions and 14 corresponding sub-ecoregions were delineated out based on spatio-temopral dynamic characteristics of saline-alkali land and geo-relational environmental attributes. According to the results,measures of amelioration and ways of development of saline-alkali land in the western Songnen Plain were put forward.  相似文献   

4.
This study investigated the regional differences of China′s urban land expansion from the late 1980s to the year of 2008, based on the spatio-temporal analysis of CLCD (China′s land cover/land use database) datasets which were mainly produced from remote sensing imagery data. A newly defined urbanization level index (UI), based on urban land area, is proposed to describe Chinese urban expansion process at 1 kilometer, provincial, regional, and na-tional scales, together with the absolute urban expansion index (UEa) and the relative urbanization expansion index (UEr). The results indicate that the percentages of total land area occupied by urban in the late 1980s, 1995, 2000, 2005, and 2008 were approximately 0.25%, 0.32%, 0.33%, 0.43% and 0.52% of China′s total land area, respectively. Between the late 1980s and 2008, the total urban expansion in the mainland of China was 2.645 × 104 km2, resulting in an annual urban expansion area of about 1322.7 km2/yr, with the UEr of 111.9%. This study also finds that there has been an obvious spatial gradient of urbanization ratio running from the east coast to the west inland, and the urbanization gaps among different regions have persisted over the past two decades. The study also reveals obvious temporal varia-tions of the urbanization rates. There was very little urban growth during the period of 1995-2000 due to the governmental policy factors.  相似文献   

5.
Wetland Is an important landscape existing almost DEFINITIONS OF WETLANDall over the world．In China，wetlands are distributedeverywhe。加mfrlgld－tern。。。ie zone to tropical zone，XU QI et al．dehned wetland as the soil which isfrom lmoral！o Inland from paln to pforeau and moisten by under－ground water or Is permanently ormountains．＞ome ot the wetlands share the sam。char－temno。rllv soak。d by ground。ater（XU，1995）．Thisacterlstlcs of other countries，and some are un…  相似文献   

6.
Based on the simulation with the Ocean-Atmosphere Coupled Model CCSM and Ocean Model POP under the greenhouse gas emission scenario of the IPCC SRES A2 (IPCC, 2001), and on the earth crust subsidence and glacier melting data, the relative sea level change is obtained along the coast of China in the 21st century. Using the SRTM elevation data the submergence of coastal low land is calculated under the extreme water level with a 100-year return period. The total flooding areas are 98.3×103 and 104.9×103 km2 for 2050 and 2080, respectively. For the three regions most vulnerable to extreme sea level rise, i.e., the coast of Bohai Bay, the Yangtze River Delta together with neighboring Jiangsu Province and northern Zhejiang Province, and the Pearl River Delta, the flooded areas are 5.0×103, 64.1×103 and 15.3×103 km2 in 2050 and 5.2×103, 67.8×103 and 17.2×103 km2 in 2080, respectively.  相似文献   

7.
PRESSURE OF WATER SHORTAGE ON AGRICULTURE IN ARID REGION OF CHINA   总被引：2，自引：0，他引：2  
1INTRODUCTIONWiththedevelopmentoftheworld,waterdemandisincreasing,especiallywiththegrowthofpopulationinthelast50years,waterdemandforirrigationhasgreatlyincreasedforfoodproduction.Inthearidandsemi-aridareas,watershortagebecomesaheavierproblemtorestrictfoodproduction,localeconomyandenvironmentalprotection.China,with22%ofthetotalpopulationintheworld,hasonly8%offreshwaterintheglobe;watershortagehasaffectedagricultureandresident'slifeinthenorthernChina.SomescientistsindicatedthatChina'swaters…  相似文献   

8.
During the last 30 years,China has witnessed rapid economic growth and dramatic urbanization,with about 1.2 × 107rural people migrating annually into urban areas.Meanwhile,especially since 1995,the rural population has been declining,which is closely linked to land circulation and the increase in farm size in many villages.Increasing scale of farming operations is often regarded as a key to avoiding the abandonment of farmland and to increasing the income of rural farmers.However,until now,there has been little research on the spatial and temporal variability of farm size at the national level in China.Using data from the national agricultural census and rural household surveys,this study examines the characteristics of land use circulation and the consequent changes in the area of farmland per household.The results show that: 1) 12.2% of rural households were involved in land circulation at the national level.The highest amounts of land circulation have occurred in those provinces where the farmland per capita is more than 0.2 ha or less than 0.1 ha;2) over 80% of households operate less than 0.6 ha of farmland;3) the proportion of mid-sized farms(between 0.2 ha and 0.6 ha per household) has decreased while the smallest and the largest farms have increased.This bears some similarity with the phenomenon known as the ′disappearing middle′,referring to the changes in farm size.This study establishes a framework for interpreting the factors affecting the changes in farm size in China,which include two promoting factors(urbanization and agriculture) and four hindering factors(agricultual land system,household registration,stable clan system,and farmland loss).  相似文献   

9.
1 THE NATURAL ENVIRONMENTAL CHARACTERISTICS The Sanjiang Plain is located in the northeast of Heilongjiang Province, China. Russia borders this region in the north and east. Its total area is 1.088×107ha. The area of plain occupies 61.21％of the total land area and that of hill and mountain amounts to 38.79％of the total land area. It is not only one of the most important regions with large area of fresh water wetlands and with varieties of rare migratory waterfowls, but a…  相似文献   

10.
LAND RECLAMATION PROCESS IN NORTHEAST CHINA SINCE 1900   总被引：2，自引：1，他引：1  
Landuse/coverchange(LUCC)isafocalthemeandemergingissueinthestudyofglobalenvironmentalchange.Humanmodificationsandalterationstotheenvironmentcauseimpactsonthesurfaceoftheearth,threatenglobalsustainabilityandlivelihoodsystems,andcontributetochangeinthebiogeochemicalcyclesoftheearth,whichinturnaffectatmosphericlevelsofgreenhouseandothertracegases.ConsequentlytheInternationalGeosphere-BiosphereProgram(IGBP)andtheInternationalHumanDimensionsProgram(IHDP)initiatedLUCCProgramtodevelopabette…  相似文献   

11.
It is important to understand how land use change impacts groundwater recharge,especially for regions that are undergoing rapid urbanization and there is limited surface water.In this study,the hydrological processes and re-charge ability of various land use types in Guishui River Basin,China(in Beijing Municipality) were analyzed.The impact of land use change was investigated based on water balance modeling,WetSpass and GIS.The results indicate that groundwater recharge accounts for only 21.16% of the precipitation,while 72.54% is lost in the form of evapotranspiration.The annual-lumped groundwater recharge rate decreases in the order of cropland,grassland,urban land,and forest.Land use change has resulted in a decrease of 4 × 106 m3 of yearly groundwater recharge in the study area,with a spatially averaged rate of 100.48 mm/yr and 98.41 mm/yr in 1980 and 2005,respectively.This variation has primarily come from an increase of urban area and rural settlements,as well as a decrease of cropland.  相似文献   

12.
GPS measurement,an effective method for surveying glacier surface topography,has been applied in some glaciers for many years.The Shuiguan River No.4 glacier,a small glacier with its area of 1.84 km2 in 1972,located in the east of the Qilian Mountains,China,was selected to study its ice elevation change using GPS measurement in 2007.This study was conducted on the ablation area with GPS-measured area 0.5 km2.The ice elevation change of the glacier was obtained by comparing the DEM obtained by a 1:50 000 topographic map made in 1972 with the DEM by GPS-measured data acquired in 2007.The differences of the two DEMs showed the thinning condition of the glacier was apparent.The mean thinning was 15±8 m with the mean thinning rate of 0.42±0.22 m a-1 for 1972-2007 in the measurement area,which equaled 0.38±0.20 m yr-1 in water equivalent(w.e.).The prominent thinning occurred on the south part of the glacier,which was the area near the glacier terminus with the maximum thinning of 41±8 m.Assuming the thinning value of 15±8 m for the glacier area below 4640 m a.s.l.,the wasting ice mass was calculated to be 6.4±3.2×10-3 km3 for 1972-2007,corresponding to 5.7±2.8×10-3 km3 w.e.,which meant that the montane runoff released by the glacier was at least 5.7±2.8×106 m3 between 1972-2007.  相似文献   

13.
Wetlands in China: Feature, value and protection   总被引：2，自引：1，他引：1  
The estimated total area of wetland in China is more than 25.9 million hectares including about 11.9 million hectares of marshes and bogs, 9.1 million hectares of lake and about 2.2 million hectares of coastal salt marshes and mudflats. The area of wetland is equivalent to 2.7% of the land surface. China also has 2.7 million hectares of shallow sea water (less 5m in depth at low tide). Marshes and bogs are equivalent 1.3% of the land surface. Only three provinces (regions)—Qinghai, Xizang (Tibet) and Heilongjiang — have a larger total area of marsh and bog. According to the structure, type and development of wetland in different river basins, wetland can be classified nine main regions. The experiments indicate that the coefficient of the marsh to regulate flood is similar to that of lakes. Wetlands occupy 17.8% of the Sanjiang Plain area, the annual carbon contribution is 0.78 × 104t. Carbon released from marsh soil return into atmosphere is 3.95 × 106t/a. At present there is a sharp contradiction between population growth and natural resources shortage, causing wetland to be exerted with huge pressures and serious threats. Foundation item: Under the auspices of the Key B Item of the Chinese Academy of Sciences (KZ951-B1-201-02). Biography: LU Xian-guo (1957 —), male, a native of Changchun City, Jilin Provice, professor. His research interests include wetland process and environmental effect.  相似文献   

14.
The Hexi Corridor is an important base of agriculture development in Northwest China. According to recent statistics, there are 65.94×108m3 of water resources available in the Hexi Corridor. At present, net consumption in development and utilization is 43.33×108m3. Water supply and demand reach a balance on the recent level of production, but loss of evaporation and evapotranspiration is as much as 25.69×108m3. So net use efficiency of water resources is 59%. Based on analyzing balance between water and land considering ecological environment at present, there exists the serious water shortage in the Shiyang River system where irrigation lands have overloaded. There is a comparative balance between supply and demand of water resource in the Heihe River system; and the Sule River system has some surplus water to extend irrigation land. Use of agriculture water accounts for 83.3% and ecological forest and grass for 6.9%. The Hexi Corridor still has a great potential for water saving in agriculture production. Water-saving efficiency of irrigation is about 10% by using such traditional technologies as furrow and border-dike irrigation and small check irrigation, and water-saving with plastic film cover and techniques of advanced sprinkler and drip/micro irrigation etc. cansave more than 60% of irrigated water. Incremental irrigation area for water-saving potential in the Hexi Corridor has been estimated as 56% – 197% to original irrigation area. So the second water sources can be developed from water saving agriculture in the Hexi Corridor under Development of the Western Part of China in large scale. This potential can be realized step by step through developing the water-saving measures, improving the ecological condition of oasis agriculture, and optimizing allocation of water resources in three river systems. Foundation item: Under the auspices of the Key innovation Project Engineering of Chinese Academy of Sciences (KZcx-1-10-03) Biography: GAO Qian-zhao (1942 –), male, a native of Changzhou, Jiangsu, Professor and supervisor of Ph. D students. His research interests include hydrology and rational utilization of water resources in the arid zone.  相似文献   

15.
The research on the present situation of soil and water development and utilization in Shiyang River Basin shows that water resources and eco-environment situation in this area are near the edge of collapse. Since the water crises occurred in the 1970s, problems caused by continuous decrease of water resources have been becoming serious year by year and eco-environment crisis occurred as a consequence. Up to now, 10 380ha of irrigated lands have been abandoned due to sand coverage and water shortage in the basin. Ground water was over exploded in Wuwei and Minqin because of water shortage. Ground water table in many places dropped under 5m (which is the ecology water table level), thus about 3000ha of Elaeagnus angustifolia forest come to dead and another 5800ha become feeble, and wind-drift sand near the oasis become alive. According to the current situation, if water utilization scope was not enlarged, a water transfer volume of 600×106m3/a from other areas will be suitable to keep water resources and eco-environment safety in the basin, and also 70×106m3/a will be left as spare water. Under this condition the water resources and eco-environment of the basin can reach the critical safety line of 2.032×109m3/a; or if 180×106m3 of water can be transferred from other areas, the water resources can reach the safety warning line of 1.732×109m3/a. Foundation item: Under the auspices of the National Natural Science Foundation of China (No. 40235053) and Lanzhou Jiaotong University "Qinglan" Foundation Biography: ZHANG Ji-shi (1963-), male, a native of Tongwei of Gansu Province, senior engineer, specialized in water resources and climate change in Northwest China. E-mail: zjs1963@yahoo.com.cn; hangjs@mail.lzjtu.cn  相似文献   

16.
Mollisols are common in South America. They cover about 8.87 × 10 7 ha, 1.3 × 10 7 ha and 4.3 × 10 6 ha in Argentina, Uruguay and Southern Brazil respectively, which is 11.5% of the world total. Most of South American Mol- lisols were developed on Pleistocene and Holocene sediments and lie within the limits of the temperate zone, though the extreme north is bordering subtropical and the extreme south is within a cold-temperate zone. All suborders of Mollisols occur in Argentina, the most extensive being Udolls followed by Ustolls, whereas only Udolls, Aquolls and Albolls occur in Uruguay. Vertisols in Uruguay have many properties similar to Mollisols, and the occurrence of Vertisols is strongly associated with Mollisols. The Pampean Mollisols are a significant component of the global breadbasket of modern times. The main Argentine crops are wheat,corn,sorghum, barley, soybeans and sunflower, while Mollisols in Uruguay remain mostly dedicated to cattle and sheep grazing though crop production has been increasing very rapidly in the last decade. Throughout South America, research has shown that Mollisols are experiencing losses of soil organic matter and nutrients, and degradation of physical properties after long cropping periods, resulting in soil scientists calling for increased conservation practices to reduce future losses and a deterioration of soil quality, and thus a more sustainable agriculture in the region.  相似文献   

17.
Valuation of lake and marsh wetlands ecosystem services in China   总被引：1，自引：0，他引：1  
Wetlands are highly productive natural ecosystems, providing valuable goods and services. There is growing interest in transferring ecosystem service value from the existing wetlands studied to other wetlands ecosystems at a large geographic scale. The benefit transfer method uses the known values from wetlands to predict the value of other wetland sites. This methodology requires only limited time and resources. The present study calculated the value of the ecological services provided by lake and marsh wetlands in China in terms of biodiversity indices, water quality indices and economic indices. Basic data on wetlands were obtained through remote sensing images. The results show that: 1) The total ecosystem service value of the lake and marsh wetlands in 2008 was calculated to be 8.1841 × 1010 United States Dollars(USD), with the marsh and lake wetlands contributing 5.6329 × 1010 and 2.5512 × 1010 USD, respectively. Values of marsh ecosystem service were concentrated in Heilongjiang Province(2.5516 × 1010 USD), Qinghai Province(1.2014 × 1010 USD), and Inner Mongolia Autonomous Region(1.1884 × 1010 USD). The value of the lakes were concentrated in Tibet Autonomous Region(6.223 × 109 USD), Heilongjiang(5.810 × 109 USD), and Qinghai(5.500 × 109 USD). 2) Waste treatment and climate regulation services contributed to 26.29% and 24.74% respectively, of the total ecosystem service value of the marsh wetlands. Hydrological regulation and waste treatment contributed to 41.39% and 32.75%, respectively, of the total ecosystem service value of the lake wetlands. 3) The total ecological service value of the lake and marsh wetlands was 54.64% of the total service value of natural grassland ecosystems and 30.34% of the total service value of forests ecosystems in China.  相似文献   

18.
Compared the total agricultural production (TAP) of the 5 counties in Huizhou City with that of the corresponding 5 counties in Zhaoqing City during the period from 1980 to 1996, it can be seen that the TAP growth rate of the 5 counties in Huizhou City had been a little higher than that of the 5 corresponding counties in Zhaoqing City before 1983, but has been becoming lower than the latter since 1984, and the agricultural production in Huizhou City has been gradually becoming lag behind that in Zhaoqing City since then. The TAP loss in Huizhou City kept above 3×108 yuan every year since 1986. Detailed investigation shows that the acid rain caused by the atmospheric pollution may be the main cause for the lower productivity of the land in Huizhou City. The atmospheric pollution arisen from rapid and extensive development of the economy in the Zhujiang(Pearl) River Delta Region has already greatly reduced the load capacity of the natural resources in Huizhou City and severely affected the sustainable development of the region.  相似文献   

19.
The objective of this study is to quantify the values of greenhouse gases (GHGs) exchange in carbon equivalents of marshes and paddy fields in the Sanjiang Plain, Heilongjiang Province, China. We obtained the GHGs exchange values based on comparable price by calculating the carbon sequestration values and the GHGs emission values of marshes and paddy fields respectively in four periods of 1982, 1995, 2000 and 2005. It is noted that the GHGs emission values are always negative. In this study, the marshes areas decreased from 1438977.0 to 775,132.2ha and the paddy fields areas increased from 417195.8 to 934205.0ha. The values of GHGs exchange of marshes varied from 135877.156×106 to 136882.534×106 yuan (RMB) and those of paddy fields varied from 1006.256×106 to 2767.645×106 yuan. The GHGs exchange values of marshes decreased from 1982 to 2005 on the whole, reversely, those of paddy fields increased, but those in 2005 were lower than those in 2000. In different periods, the GHGs exchange values were always higher in marshes than in paddy fields. The contribution rate of GHGs exchange values per unit area of marshes was also very high in different periods, and the maximum was up to 98.35% in 2005. As far as the whole wetland ecosystem (including marshes and paddy fields), assuming a linear change in GHGs exchange values, it represented a cumulative increase of 20926.757×106 yuan from 1982 to 2005. By adding GHGs exchange values increased during those four periods, we obtained a cumulative net increase values of GHGs exchange of wetland ecosystem of 18200.860×106 yuan. The results will be useful for understanding the indirect services provided by marshes and paddy fields.  相似文献   

20.
Survey on PCDDs and PCDFs in sediments and soils in Ya-Er Lake area, China   总被引：1，自引：0，他引：1  
INTRODUCTIONOverthepastseveralycars,considerableinteffethasbocenteIdontheenvir0nmentalbehaviouroftoxicandpersistritcomP0undssuchashalogenatalaromat-ies,inparticularthepolychiorinataldibopdioxins(PCDDe)andpolydil0rinateddi~fUtansrpCDFs).ManyofthesecomPounds,espedllythosewithahighdegere0fchiorinesubstitution,arehighlylipophiliccontawhnantSwithlowWhtersolubility,highre-sistancet0chdricaltransformationsandlowwhcrobiologhaldegradatfonpeatnnann,l988,Bromanetal.,l989,Hites,l990)whichexplain…  相似文献   

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