Stable isotopes in plants are widely applied in geographical and ecological studies in the recent years internationally, which combine long- term biogeochemical process and integrate different systemic components. Researches on stable isotopes of plants aim at studying temporal and spatial information of environmental factors, and revealing the trends of climate change and the geographical distribution characteristic. Abundant environmental and climatic information is recorded by stable isotopes in plants, such as information on temperature, humidity, precipitation and environment isotopes composition. The latest progresses over the world are reviewed in this paper, including the basic theories, research methods and main application areas. Review of researches on stable isotopes in plants on national and international literatures shows that stable isotopes in plants have close relation with environmental factors. The technology of stable isotopes in plants is mostly used to rebuild historical climate series, and recovers isotopes composition and concentration trends of CO2 in the atmosphere. Analysis of the features of isotopes in plants indicates that stable isotopes in plants could not only be applied to studying climate change, but also to detect regional environmental differences which has an important future for application. Study shows that the 18O in plants came only from H2O. Therefore, the origin of vapor in plants is one of the most important factors of the δ18O composition in plant, especially in typical monsoon regions. So it is possible to estimate the respective affected areas of different monsoons, and to study the spatial pattern of monsoon climate.
Based on the NOAA AVHRR - NDVI data from 1981 to 2001, digitalized China Vegetation Map (1∶1 000 000), temperature and precipitation data, DEM, and spatial people density data in 2000, the spatial patterns and characteristics along the altitude gradients of the vegetation change as well as their factors in Mt. Qomolangma Natural Reserver have been studied. The results show that: (a) there are notable spatial differences of vegetation change in Mt. Qomolangma Natural Reserver and stability is the most common status. 5.09 percent of the whole area is becoming serious degradation, 13.34 percent degraded, 54.31 percent keeping stable, 26.31 percent turning better and 0.95 percent notably turning better. The degradation and serious degradation areas mostly lie in the south of the Reserver, which are along the national boundaries. The areas of vegetation turning better lie in the north of the Reserver and the south side of the Yarlung Zangbo River. The stable areas lie between the better and worse areas. Along with the increase of elevation, the states of vegetation changes transit from degradation to stability. At the altitude from 2400m to 4000m vegetations are in degraded change condition while at the altitude from 4000m to 6000m vegetations are stable. (b) The degenerated objects in Mt. Qomolangma Natural Reserver are most composed of shrubs, needle- leaf forests and needle- leaf and broad- leaf mixed forests. Plant changes can be divided into three types: (1)Stable to growing better. They are steppes and meadows. (2)Stable to degraded. They are shrubs and alpine sparse vegetation. (3)Degraded. They are needle- leaf forests and needle- leaf and broadleaf mixed forests. (c) The temperature change affects vegetation change in space while the integration of temperature changes and slopes affects vegetation change along the altitude gradients. Spatial correlation coefficient of temperature change and NDVI change is 0.51. Correlation coefficients along the altitude gradients of temperature change and NDVI change and slope and NDVI change are 0.946 and - 0.896. (d) Unconscionable resource use mode made by human beings leads to the vegetation degeneration in some parts of Mt. Qomolangma Natural Reserver. Bio- resources are continually used to meet the need of economic development and human living, which are hard to regenerate in such a rigorous environment. Because of poverty and severe environment in Mt. Qomolangma Natural Reserver, sustainable development should be consistent with economic development. A series of adaptive policies and modes such as protecting bio- resources, altering industry structures and eliminating hunger and poverty should be taken to keep sustainable development.
Reference crop evapotranspiration (ET0) is one of important climate factors, mainly affected by local climate. As related to water balance and energy balance, it decides the shaping and evolvement of geographical environment. With 34 meteorological stations'data including minimum and maximum air temperature, wind speed, air humidity and sunlight hours from 1951 to 2000, ET0 was obtained by FAO Penman-Monteith equation (P-M) for growing season in western Songnen Plain of Northeast China. Then the authors analyzed the temporal- spatial characteristics of ET0 series with climate diagnostic analysis, and the abrupt change points through point - area integrated analyses by Jy parameter and Mann- Kendall methods. The results show that: (i) the high value of ET0 appears in southwest sandy land, and ET0 gradually decreases northeastwards; (ii) ET0 tends to increase in recent 50 years, and the north area contributes most; (iii) taking 1962 and 1982 as turning points, areal ET0 series indicates evident phase changes during period of 1951~2000; and (iv) two upward and one downward abrupt changes are examined in areal ET0 series, and the time of abrupt changes in typical stations is basically consistent with that in study area, but properties of abrupt changes show evident spatial diversity.
Zhalong wetland locates at the western part of Heilongjiang province and was developed from the terminal lake of the Wuyuer river. In this paper, the geological environment of the Zhalong area and the relationships among the Zhalong wetland, the Nenjiang river and the Songnen desert were studied by field survey, soil sample analysis and remotely sensed image interpretation. It was found that the desert from Qiqihaer to Daqi consisted of NW- extended dunes and saline, forming a NE - extended dune belt with Keerqin desert together. The desert was mainly developed from the last glacial period. After that, the Nenjiang river flowed through the dune area and rebuilt the dunes and a lot of yoke lakes were left in Zhalong area. Because of the crustal tectonic uplift in the Zhalong area, the Nenjiang river moved westwards and Wuyuer river became an inner river which terminal lake evolved and developed as the present Zhalong wetland eventually. So the environmental evolution of the Zhalong area since the last glacial period was concluded as: the wind- blown dune belt formed → the Nenjiang river rebuilt the dune belt → the Nenjiang river westwardly migrated and the Wuyuer river became an inner river → the terminal lake of the Wuyuer river evolved to the Zhalong wetland. Therefore, the Zhalong wetland and the Lianhuan lake developed on an once- existed desert, suggesting that the ecoenvironment of the area is the frailest in the whole Nenjiang watershed. It means that the salinification and desertation in the area would rapidly develop and severely affect the eco- environment of the Qiqihaer- Daqi area if the Zhalong wetland disappeared.
At present, air pollution draws attention of many researchers and officials from all countries to the latent impacts to human health in the world, along with the development of industrialization and urbanization. Study focus is to assess health effects of exposure to pollutants. Recently health risk assessment of air pollution is being developed at home and abroad. The full risk assessment process includes identification of pollutant concentration, exposure assessment, dose and effect assessment and expression of human health risk. The authors introduce research progress in urban air quality simulation, human exposure, air pollutant toxicology and health effect, and GIS operation in health risk assessment in recent years. Having analysed existing researches, the authors find some research limits, including: 1. Research scale are restricted to small regions, and data from limit inspect stations can't assess broad regions, such as megapolis; 2. Applied methods usually are qualitative although some are semi- quantitative assessment on the basis of WHO air quality health effect standard; 3. Indexes of human effect mainly are morbidity and mortality, and seldom research touches on health risk of exposed population; 4. Some researches focus on conventional pollutants health effect in short term, and little involve comparatively sensitive traffic pollutant health effect. In order to serve population, future research should concentrate on simulating microscopic urban air quality, structuring quantitative assessment based on exposure- dose relationship and developing long- term pollutant health effect models according to actually absorbed dose.
With the development of computer and GIS, distributed model for soil erosion and sediment yield has become the developing direction in the field of soil erosion. This paper discussed the technical route and realization of distributed model based on the analysis of the main distributed models home and abroad at present. Finally, the paper indicated some problems of the distributed models for soil erosion and sediment yield in our country: ( 1) there are many problems in the developing of distributed models for soil erosion and sediment yield which are based on the distributed hydrological models, although the latter provides many references for study of the former; ( 2) the distributed models for soil erosion and sediment yield are mainly based on the loess plateau and the models are regional at present in our county; ( 3) most relational expressions of soil erosion and sediment are mainly empirical and the process of soil influx is simply beginning to be considered nowadays; ( 4) the spatial and temporal change of single rain event was ignored in most distributed models for soil erosion and sediment yield at present. In the future, the above problems should be solved in the constructing of distributed model for soil erosion and sediment yield in our country.
As one of the consequences of historical fluvial evolution, river terrace has recorded some information about environmental changes during river processes. It is the significant geomorphologic complex for analyzing river' s historical evolution. This work gives a review on the origin, geomorphologic characteristics, causes of formation, environment responses and the datemeasure technology of river terraces as well as its significance in reconstruction of environment during terrace formation. It shows that river terraces are the integrative consequence of the river system and related environment influences. Researchers should consider the entire river system and its environment syntheses to study river terraces. The geological tectonic and climate characteristics and ancient river dynamics may be revealed according to research of river terraces. River terraces are the crucial geomorphologic elements used to reveal the environmental information in study areas. With the development of the meterage instruments, the date - measure technology will be more accurate and sensitive. The dynamic simulation and the quantitative analysis for the formation and evolution of river terraces need more exploration.
Spatial distributing of census data is an effective way to integrate statistical data and natural factors. Land- cover and land- use change (LUCC) is the effect of human activities, and spatial distribution of population has close relationship with LUCC pattern both at regional and global scales. Population can be redistributed onto geo- referenced square grids according to this relation. Since there exist efficient approaches for monitoring LUCC with remote sensing and GIS, geo- referenced population data can also be updated conveniently. According to existing methods, it is found that the population density is directly related to land use types and the residential area is the best index for population distribution. Residential areas could be reclassified into three sub classes: urban residential, rural residential, and commercial- industrial. The paper presented an enhanced method for spatial distributing census data: re- classification of rural residential areas. On the basis of the relationship of various kinds of indexes and inhabitation density, several indexes were selected for re- classifying rural residential areas. Using these re- classified rural residential data, the precision of census redistributing pattern was improved obviously. Methods and main algorithms used in these studies were presented in the paper. Characters and prospect of this study were also discussed.
It is a great challenge to retrieve aerosol optical thickness over bright surface from remotely sensed data, because it is very difficult to estimate the reflectance of the complicated surface accurately, and the radiance is not sensitive to the aerosol change when the surface reflectance is high. To overcome the difficulties of aerosol optical thickness retrieving in the bright areas, many methods were provided. We introduced some significant methods: 1) contrast reduction algorithm. This method applied in a sequence of satellite images which contain a clear image; 2) high contrast surfaces algorithm. This method can retrieve aerosol optical thickness from two closely located, high contrast surfaces; 3) two or more sensors cooperation method, which can retrieve aerosol optical thickness together with surface reflectance; 4) methods which are based on surface reflectance database/model, which need to ascertain the surface reflectance accurately. We analyzed the advantages and disadvantages of each method. At last, we provided the prospect of the aerosol optical thickness deriving over bright surface. The construction of surface reflectance database and the development of the BRDF model make the surface reflectance more accurate, the increasing aerosol measuring stations advance our quantitative understanding of aerosol characteristics, and the design of many new satellite sensors which can derive the aerosol optical thickness becomes more perfect. All of the above factors can help aerosol optical thickness retrieving a lot.
Owing to the fragile eco- environment, terrain fragmentation, and serious soil erosion, the karst area in Southwest China is one of the distinct poor regions. Selecting Maotiaohe watershed as study area, taking villages and towns as studying unit, and using GIS and ANN model, this paper simulates the spatial distribution of natural impoverishing index and socio- economic alleviating impoverishing index, calculates the poverty degree of villages and towns, and reveals the spatial distribution of poverty in order to provide scientific basis for eliminating poverty and ecological reconstruction. The results show that the natural factors such as soil erosion and so on are the main impoverishing indexes, and socio- economic factors are the main alleviating impoverishing indexes. The villages and towns with smaller poverty degree are mainly distributed in the middle and east area of Maotiaohe watershed, and those with larger poverty degree are mainly distributed in the southern and northern area of Maotiaohe watershed. The results also indicate that application of BP neural network to simulating regional poverty is convenient, precise and feasible, which can be an alternative approach to simulating regional poverty.
International and USDA's soil texture classification systems are prevalent in the world, which adopt additional manual inquiring of triangle coordinate diagram to realize the naming of soil texture. This takes a lot of time and energy and lacks precision control. To apply computer program can perform the same task easily, conveniently and fast. According to the oversea research status quo in soil texture automatic classification based on computer graphics, using Visual Basic (VB) a as platform, soil texture automatic classification system (STAC) is built the better practicability in China. The theories of STAC are mainly based on the fact that each point in the textural triangle represents a unique combination of clay, sand and silt content. For a given textural class, all combinations of clay, sand and silt content are bound by a polygon. Therefore, finding the textural class is equivalent to finding the polygon where the particular combination of clay, sand and silt content is located. The algorithm of the program is point - in - polygon algorithm, which can determine whether a point of known coordinates (clay percentage and sand percentage) lies inside a polygon in the textural triangle. STAC is simple, convenient, fast and explicit. STAC can be used in a Windows 95 console program and above without requiring installation. It realizes texture automatic naming of single as well as batch soil data and provides graphical display, statistics and analysis function, and user - defined classification, and can classify several thousands of soil samples in about a second.
Land surface temperature (LST) is of considerable importance for many applications, notably global climatic, hydrological, ecological and biogeochemical studies. In the past two decades, a large number of methods and algorithms have been developed to retrieve cloud free LST from thermal infrared data. As for all optical remote sensing, the Earth observation can only be realized for cloud free condition. In order to get LST for all weather conditions, microwave remotely sensed data, instead of thermal infrared data, from space is commonly used due to its capability to penetrate clouds and to some extent rain. Although the passive microwave remote sensing has some advantages compared to the thermal infrared, there are few algorithms developed to retrieve LST from it, mainly because there are various factors affected the microwave signal. In this paper, we review almost all existing algorithms found in literature, which can be roughly categorized into the statistical- based and physics- based retrieval algorithms, to retrieve LST from passive microwave remotely sensed data. The merits and the disadvantages are summarized for each method respectively. Finally further possible improvement and development directions on the scaling transfer, the microwave radiative transfer modeling and the combination of the different remote sensing data are given for LST retrieval from passive microwave data.
Varied demands of society for the limited land are leading to an overlay of interests and thus to land use conflicts. Moreover, the conflicts are exacerbated by the rapid increase of population and urban expansion on both regional and global scale, which is an obstacle for sustainable land use. It is becoming increasingly challenging for local and national government over land management. Thereby, the study of land use conflicts plays an important role in the realization of sustainable land use. This article examines the causes of land use conflicts from both physical and social - economic dimensions, and regards that scarces of land resource and increasing conflicting demands for land should be responsible for land use conflicts. Conflicts among economical, environmental and social objectives are this articles main contents. Farmingpastoral region, water - land ecotone and urban - rural fringe are the three hotspots of multiple conflicts. The article also describes familiar methods used in the study of resource use conflicts, with a hope to help the study of land use conflicts. There is still a long way to define and understand the concept of land use conflict and its connotation, to pursue its driving forces and countermeasures. In the future the emphases of land use conflicts study should focus on tracing and monitoring the dynamics of land use conflicts in order to create a better basis for understanding the conflicts and also on the contrast of internal and external conflicts from the context of occurrence and evolution. The models or tools should also be developed at the same time in order to reduce land use conflicts in terms of a regional management of environment and natural resources.
Huge press on natural resources and environment in China requires the study of the regional land quality pertinent to land degradation. Land use, which is exhibited as patches in space, has a close relationship with land quality. The research of the relationship between land use and land quality at patch scale can improve our under standing of the effects land use changes on land quality. The Ministry of Land and Resources implemented “Remote Sensing Monitoring on Land Resources and Eco - environment in Area around Beijng”and“Remote Sensing Monitoring Study for Distribution of Cultivated Farmland and Grain for Green in Typical Regions around Beijing”projects from 2002 to 2004. With the help of the project's achievements, the cultivated farmland changes in Zhangbei County, Hebei province, from 1999 to 2003 were analyzed by using the SPOT2/4 and SPOT5 remote sensing data. The degradation character of changed patches from cultivated land in 1999 to grassland and forest land in 2003, from grassland and forest land in 1999 to cultivated land in 2003 and unchanged cultivated land were analyzed by the application of GIS and statistical methods. The cultivated land decreased by 20229.5ha in 2003 compared to 1999, most of which turned into grassland and forest land, and the main type is the change of farmland to man- made grassland. The most of newly increased cultivated land came from grassland. The area of un- degraded patches in all types from cultivated land to grassland and forest land, except the change from farmland to low- density forest land, are larger than degraded patches, indicating these change types could lead to a higher land quality. The changed patches from forest land to farmland and from grassland to irrigated farmland have an obvious degradation inclination; however, the proportion of changed patches' area and quantities from grassland to farmland, from other land to farmland and from grassland to vegetable land is not large. Compared to un- changed cultivated patches, the area proportion of undegraded patches to total changed patches from farmland to grassland is larger and the quantity proportion is similar; the area and quantity proportion from farmland to grassland is not different largely. Both area and quantity proportions of un- degraded patches from farmland to forest land are larger than those from forest land to farmland. These results indicate the transition from farmland to forest land and grassland can improve the regional land quality.
Soil macro- organic matter (MOM) with a rapid turnover rate plays a dominant role in soil nutrient dynamics, especially soil nitrogen. MOM is a significant component of light organic matter in soils. It can be a sensitive index to reflect the short- term effects of the management on soil organic matter. This paper reviews the concepts of various soil organic matter (SOM) fractions by different physical fractionations, details the fractionation methods for soil macro- organic matter (MOM), discusses the factors which have influences on the content of the soil MOM, factors which include management, land use, soil texture and climate. In the end, this paper points out the existing problems about the study of MOM: (1) The dynamic mechanism of soil organic matter is still puzzling. (2) The procedure for the separation of the soil MOMfraction needs to be studied further. (3)Many researchers'opinions diverge from each other on the contribution of MOM to soil nitrogen mineralization. In future, the study should focus on the mechanism of MOM responding to affecting factors, separating methods and the contribution of MOMto soil nitrogen mineralization.
