Based on the results of water sample measurements of nutrient concentrations at the Datong Station of the Changjiang River from 1998 to 1999, combined with historical data of water quality, seasonal variations of nutrient concentrations and nutrient transports are discussed.The following results have been obtained: (1) the fluxes of the nitrate nitrogen, ammonium nitrogen and nitrite nitrogen increased by time-series from 1962 to 1990, even if runoff volume had a little variation; (2) the concentrations and fluxes of the dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP) increased notably with time, but those of the dissolved silicon (DSI) decreased pronouncedly; and (3) the concentrations and fluxes changed synchronously with time between the Datong Station and the Changjiang Estuary.
Based on biomass investigations, soil respiration and plant photosynthesis measurement of dominant trees in Hailuogou valley of Mt. Gongga, Southwest China, the carbon (C) storage, absorption and release for several typical woodlands in sub-alpine zones have been discussed. For Abies fabri forest of 3,000 m above sea level, the C storage amount is 177.4 t/ha for above-ground biomass and 143.2 t/ha for soil below-ground biomass. The annual gross C fixed by vegetation photosynthesis is 20-24 t/ha. The C release by canopy respiration is 3.0-5.5 t/ha for arbors and 10-19 t/ha for surface soil and roots. The annual net C fixed of forest ecosystem is about 6.0-7.1 t/ha. At lower elevations, the amount of C released by woodlands is higher than that of woods at higher elevations. The C fixed capacity of renewed forest with middle-aged trees is higher than that of mature forest. Before becoming over-matured forest, woodland is an important sink of C whereas bareland in woods is the source of atmospheric C.
The ecological footprint of China's provinces is calculated in this paper. In general, China's development is not sustainable because its ecological footprint is beyond its bio-capacity. The sustainability status of each province in China is presented. Ulanowicz's development capacity formula was introduced to discuss the relationship of development and ecological footprint's diversity. The diversity of ecological impacts is related to the efficiency with which an economy uses the source and sink services of the environment and, in this view, should be a factor in economic output. Development capacity, calculated from the ecological footprint and its diversity, is used to examine the relationship of economic output with the structure of the ecological footprint. China and its provinces are presented as a case study to investigate this relationship. The analysis shows that footprint capacity is significant in predicting economic output. Increasing the ecological footprint's diversity is presented as another way to increase development capacity.
Using static chamber technique, fluxes of CO2, CH4 and N2O were measured in the alpine grassland area from July 2000 to July 2001, determinations of mean fluxes showed that co2 and N2O were generally released from the soil, while the alpine grassland accounted for a weak CH4 sink. Fluxes of CO2, CH4 and N2O ranged widely. The highest co2 emission occurred in August, whereas almost 90% of the whole year emission occurred in the growing season. But the variations of CH4 and N2O fluxes did not show any clear patterns over the one-year-experiment. During a daily variation, the maximum co2 emission occurred at 16:00, and then decreased to the minimum emission in the early morning. Daily pattern analyses indicated that the variation in co2 fluxes was positively related to air temperatures (R2=0.73) and soil temperatures at a depth of 5 cm (R2=0.86), whereas daily variations in CH4 and N2O fluxes were poorly explained by soil temperatures and climatic variables. co2 emissions in this area were much lower than other grasslands in plain areas.
The regional characteristics of dust events in China has been mainly studied by using the data of dust storm, wind-blown sand and floating dust from 338 observation stations through China from 1954 to 2000. The results of this study are as follows: (1) In China, there are two high frequent areas of dust events, one is located in the area of Minfeng and Hotan in the South Xinjiang Basin, the other is situated in the area of Minqin and Jilantai in the Hexi Region. Furthermore, the spatial distributions of the various types of dust events are different. The dust storms mainly occur in the arid and semiarid areas covering the deserts and the areas undergoing desertification in northern China. Wind-blown sand and floating-dust not only occur in the areas where dust storms occur, but also extend to the neighboring areas. The range of wind-blown sand extends northeastward and southeastward, but floating-dust mainly extends southeastward to the low-latitude region such as the East China Plain and the area of the middle and lower reaches of the Yangtze River. Compared with wind-blown sand, the floating-dust seldom occurs in the high latitude areas such as North Xinjiang and Northeast China. (2) The affected areas of dust storms can be divided into seven sub-regions, that is, North Xinjiang Region, South Xinjiang Region, Hexi Region, Qaidam Basin Region, Hetao Region, Northeastern China Region and Qinghai-Xizang (Tibet) Region. The area of the most frequent occurrence of dust storms and floating-dust is in South Xinjiang Region, and of wind-blown sand in the Hexi Region. In general, the frequency of dust events in all the seven regions shows a decreasing tendency from 1954 to 2000, but there are certain differences between various dust events in different regions. The maximum interannual change and variance of dust events during this time happened in South Xinjiang Region and Hexi Region. The dust events generally occur most frequently in April in most parts of China. The spring occurred days of dust events occupied 60-70% of the whole year in Hetao Region and Northeastern China Region. However, in South Xinjiang Region and North Xinjiang Region, which was less affected by monsoon climate, dust events may occur at any time of the year, less than 50% of the events in this region occur during spring. In the remaining three regions 50-60% of the dust events occur in spring of a year.
Reputed as a wonderful achievement of the world's highway construction history, the Taklimakan Desert highway is now facing serious sand drift encroachment problems due to its 447- km-long passage of sand sea consisting of crescent dunes, barchan chains, compound transverse dune ridges and complex megadunes. To solve some technical problems in the protection of the highway from sand drift encroachment, desert experts have been conducting the theoretical and applied studies on sand movement laws; causes, severities and time-space differentiation of sand drift damages; and control ways including mechanical, chemical and biological measures. In this paper the authors give an overall summary on the research contents and recent progress in the control of sand drift damages in China and hold that the theoretical research results and practices in the prevention of sand drift encroachment on the cross-desert highway represent a breakthrough and has an epoch-making significance. Since the construction of protective forest along the cross-desert highway requires large amount of ground water, what will be its environmental consequence and whether it can effectively halt sand drift encroachment on the highway forever are the questions to be studied urgently.
With the objectives to acquire the fundamental data of the territorial resource, understand the impacts of human activities on the land use and cover patterns and evaluate the potential of the future exploitation, an intensive land cover classification with an accuracy of 93% has been completed for North Ningxia by remote sensing technique based on the adoption of a combination method composed of texture training, maximum likelihood classification and post-processing such as re-allocation and aggregation. This classification result was incorporated with the contemporaneous socio-economic and meteorological data for cross-sectional regression modelling to reveal the spatial determinants of the land cover patterns and understand the human-environmental relationships. A tentative evaluation on the potential of soil exploitation in the near future was carried out in combination with our land use and cover change detection results aiming at supplying some useful references for the central and local governments in their sustainable land use planning.
With the classification data covering American land-use/land-cover (LUCC) with 30 m resolution from the project of National Land Cover Data (NLCD), we normalized them and made their resolution changed into 1 km ×1 km, created the data of American land-use grade and analyzed the spatial distribution and features of American LUCC as well as the influence of population and altitude on the land-use grade in light of methods of sampling analysis and correlation study. Based on the analysis, we concluded that forestry and grassland, accounting for 71.24% of the whole country, has taken the main part of American land cover, and besides, construction and arable land has occupied 19.22% of the total land, the rest of land cover types, including water area, wetland and underdeveloped land, is 9.54% of the country's total. The developing potential of American land resources is enormous with less destroyed and disturbed ecological environment. Although, in some sense, the population and altitude influence the spatial variation of American land-use grade respectively, the influence of spatial variation of altitude and population density on that of land-use grade is not significanct.
Taking two false color composite Landsat 5 TM (Thematic Mapper) images of band 4,3,2 taken in 1995 and 2000 as data resources, this paper carried out study on LUCC of Zhangye oasis in recent five years by interpretation according to land resources classification system of 1:100,000 Resources and Environmental Database of the Chinese Academy of Sciences. The results show that great changes have taken place in landuse/landcover in Zhangye oasis since 1995: (1) Changes of landuse structure show that cropland and land for urban construction and built-up area increased, on the contrary, water area and grassland decreased. These changes reflect the deterioration of eco-environment and the acceleration of urbanization, and also indicate the problems existing in the arrangement of water and land resources between the upper and lower reaches of the Heihe River. (2) Regional differences of landuse/landcover are evident, characterized by following aspects: in Sunan County located in Qilian Mountain area, unused land and grassland decreased, but cropland and land for urban construction and built-up area increased. In Minle and Shandan counties located in foothills, unused land, water area and cropland decreased, but grassland and land for urban construction and built-up area increased. In Zhangye City, Linze County and Gaotai County located in plain area of the middle reaches of the Heihe River, unused land, water area and grassland decreased, while woodland, cropland and land for urban construction and built-up area increased.
Waterfront resources are important and special kind of natural resources in the marginal area between land and water. The Yangtze River, the longest river in China, is not only rich in waterfront resources, but also has favorable development conditions with great potentiality. Aided by large-scale underwater topographic map, the major factors of the waterfront resources in the middle and lower reaches of the Yangtze River, such as the stability, the water depth and the natural conditions for port construction, are assessed in this paper respectively on the basis of the overall investigations. The results show that: (1) the waterfront resources are abundant in the middle and lower reaches of the Yangtze River, but lack of perfectly combined high grade waterfront; (2) there exists an obvious regional difference in the natural quality of the waterfront along the Yangtze; (3) the fore-bank water depth and waterfront stability are the main natural factors related to the waterfront quality in the middle and lower reaches of the Yangtze River; (4) the waterfronts along the Yangtze are mainly used for port, warehouse and industrial purposes; and (5) the waterfronts near important cities are highly used, especially the high-quality waterfronts. In addition, some suggestions for the development and utilization of the waterfront resources are presented in this paper.
The dual-nuclei spatial structure is composed of a regional central city, a port city and their spatial relations in certain regions. In general, this spatial structure could be found in most of the coastal regions or regions along big rivers. In terms of the mechanism, the dual-nuclei structure is the result of the spatial interaction and the complementary characteristics of the center city and the port city. The "marginal function" of the port city and its relationship with the central city has long been discussed in the literature. On the one hand, drainage area is the main natural geographical background of the formation of the dual-nuclei spatial structure; therefore, we can build a theoretical geographic structure that is based on the drainage area. On the other hand, vicissitude of the coastline also has important influence on the formation of the dual-nuclei spatial structure. It is especially meaningful if we can notice this when we examine deeply the research on the spatial structure of delta.
The data utilized in this analysis consisted of extraterrestrial radiation, global radiation, diffuse radiation, direct radiation, total cloud cover and relative sunshine. The annual variations and trend were analyzed for monthly mean daily total global, direct, and diffuse radiation on a horizontal surface and for the relations between global, direct, diffuse radiation and relative sunshine, total cloud cover. The climatological calculation equations of global and direct radiation are put forward. The results show that global and direct radiations are characterized by decrease and diffuse radiation by increase. The main causes are due to the increase of concentration of suspended particles and atmospheric turbidities rather than cloud cover variations.
Firstly, the hydrological and meteorological features of the upper reaches of the Yellow River above Tangnag are analyzed based on observation data, and effects of EI Nino and La Nina events on the high and low flow in the upper Yellow River are discussed. The results show El Nino and La Nina events possess consanguineous relationship with runoff in the upper Yellow River. As a whole, the probability of low flow occurrence in the upper Yellow River is relatively great along with the occurrence of El Nino event. Moreover, the flood in the upper Yellow River occurs frequently with the occurrence of La Nina event. Besides, the results also show dissimilarity of El Nino event occurring time exerts greater impact on high flow and low flow in the upper Yellow River, that is, the probability of drought will be greater in the same year if El Nino event occurs in spring, the high-flow may happen in this year if El Nino occurs in summer or autumn; the longer the continuous period of El Nino is, the lower the runoff in the upper Yellow River is.
Complex adaptive system theory is a new and important embranchment of system science, which provides a new thought to research water resources allocation system. Based on the analysis of complexity and complex adaptive mechanism of water resources allocation system, a fire-new analysis model is presented in this paper. With the description of dynamical mechanism of system, behavior characters of agents and the evaluation method of system status, an integrity research system is built to analyse the evolvement rule of water resources allocation system. And a brief research for the impact of water resources allocation in beneficial regions of the Water Transfer from South to North China Project is conducted.
