Land-use/land-cover changes (LUCCs) have links to both human and nature interactions. China's Land-Use/cover Datasets (CLUDs) were updated regularly at 5-year intervals from the late 1980s to 2010,with standard procedures based on Landsat TM\ETM+ images. A land-use dynamic regionalization method was proposed to analyze major land-use conversions. The spatiotemporal characteristics,differences,and causes of land-use changes at a national scale were then examined. The main findings are summarized as follows. Land-use changes (LUCs) across China indicated a significant variation in spatial and temporal characteristics in the last 20 years (1990-2010). The area of cropland change decreased in the south and increased in the north,but the total area remained almost unchanged. The reclaimed cropland was shifted from the northeast to the northwest. The built-up lands expanded rapidly,were mainly distributed in the east,and gradually spread out to central and western China. Woodland decreased first,and then increased,but desert area was the opposite. Grassland continued decreasing. Different spatial patterns of LUC in China were found between the late 20th century and the early 21st century. The original 13 LUC zones were replaced by 15 units with changes of boundaries in some zones. The main spatial characteristics of these changes included (1) an accelerated expansion of built-up land in the Huang-Huai-Hai region,the southeastern coastal areas,the midstream area of the Yangtze River,and the Sichuan Basin;(2) shifted land reclamation in the north from northeast China and eastern Inner Mongolia to the oasis agricultural areas in northwest China;(3) continuous transformation from rain-fed farmlands in northeast China to paddy fields;and (4) effectiveness of the "Grain for Green" project in the southern agricultural-pastoral ecotones of Inner Mongolia,the Loess Plateau,and southwestern mountainous areas. In the last two decades,although climate change in the north affected the change in cropland,policy regulation and economic driving forces were still the primary causes of LUC across China. During the first decade of the 21st century,the anthropogenic factors that drove variations in land-use patterns have shifted the emphasis from one-way land development to both development and conservation.The "dynamic regionalization method" was used to analyze changes in the spatial patterns of zoning boundaries,the internal characteristics of zones,and the growth and decrease of units. The results revealed "the pattern of the change process," namely the process of LUC and regional differences in characteristics at different stages. The growth and decrease of zones during this dynamic LUC zoning,variations in unit boundaries,and the characteristics of change intensities between the former and latter decades were examined. The patterns of alternative transformation between the "pattern" and "process" of land use and the causes for changes in different types and different regions of land use were explored.
The implementation of new type industrialization and urbanization and agricultural modernization strategies lacks of a major hand grip and spatial supporting platform,due to long-term existed "dual-track" structure of rural-urban development in China as well as unstable rural development institution and mechanism. It is necessary to restructure rural production,living and ecological space by carrying out land consolidation,so as to establish a new platform for building new countryside and realizing urban-rural integration development in China. This paper develops the concept and connotation of rural spatial restructuring. Basing on the effects analysis of industrialization and urbanization on rural production,living and ecological space,the mechanism of pushing forward rural spatial restructuring by carrying out land consolidation is probed. A conceptualization of the models of rural production,living and ecological spatial restructuring is analyzed combining with agricultural land consolidation,hollowed villages consolidation and industrial and mining land consolidation. Finally,the author argues that a "bottom-up" restructuring strategy accompanied by a few "top-down" elements is helpful for smoothly pushing forward rural spatial restructuring in China. In addition,the optimization and restructuring of rural production,living and ecological space will rely on the innovations of regional engineering technology,policy and mechanism,and mode of rural land consolidation,and more attentions should be paid to rural space,the foundation base and platform for realizing urban-rural integration development.
Alpine timberline,as the "ecological transition zone," has long attracted the attention of scientists in many fields,especially in recent years. Many unitary and dibasic fitting models have been developed to explore the relationship between timberline elevation and latitude or temperature. However,these models are usually on regional scale and could not be applied to other regions;on the other hand,hemispherical-scale and continental-scale models are usually based on about 100 timberline data and are necessarily low in precision. The present article collects 516 data sites of timberline,and takes latitude,continentality and mass elevation effect (MEE) as independent variables and timberline elevation as dependent variable to develop a ternary linear regression model. Continentality is calculated using the meteorological data released by WorldClim and mountain base elevation (as a proxy of mass elevation effect) is extracted on the basis of SRTM 90-meter resolution elevation data. The results show that the coefficient of determination (R2) of the linear model is as high as 0.904,and that the contribution rate of latitude,continentality and MEE to timberline elevation is 45.02% (p=0.000),6.04% (p=0.000) and 48.94% (p=0.000),respectively. This means that MEE is simply the primary factor contributing to the elevation distribution of timberline on the continental and hemispherical scales. The contribution rate of MEE to timberline altitude differs in different regions,e.g.,50.49% (p=0.000) in North America,48.73% (p=0.000) in the eastern Eurasia,and 43.6% (p=0.000) in the western Eurasia,but it is usually very high.
Assessment of vulnerability for natural ecosystem to climate change is a hot topic in climate change and ecology,and will support adapting and mitigating climate change. In this study,LPJ model modified according to features of China's natural ecosystems was employed to simulate ecosystem dynamics under A2,B2 and A1B scenarios. Vulnerability of natural ecosystem to climate change was assessed according to the vulnerability assessment model. Based on eco-geographical regions,vulnerability of natural ecosystem to climate change was analyzed. Results suggest that vulnerability for China's natural ecosystems would strengthen in the east and weaken in the west,but the pattern of ecosystem vulnerability would not be altered by climate change,which rises from southeast to northeast gradually. Increase in ecosystem vulnerable degree would mainly concentrate in temperate humid/sub-humid region and warm temperate humid/sub-humid region. Decrease in ecosystem vulnerable degree may emerge in northwestern arid region and Qinghai-Tibet Plateau region. In the near-term scale,natural ecosystem in China would be slightly affected by climate change. However,in mid-term and long-term scales,there would be severely adverse effect,particularly in the east with better water and thermal condition.
It is very important in accurately estimating the forests' carbon stock and spatial distribution in the regional scale because they possess a great rate in the carbon stock of the terrestrial ecosystem. Yet the current estimation of forest carbon stock in the regional scale mainly depends on the forest inventory data,and the whole process consumes too much labor,money and time. And meanwhile it has many negative influences on the forest carbon storage updating. In order to figure out these problems,this paper,based on High Accuracy Surface Modeling (HASM),proposes a forest vegetation carbon storage simulation method. This new method employs the output of LPJ-GUESS model as initial values of HASM and uses the inventory data as sample points of HASM to simulate the distribution of forest carbon storage in China. This study also adopts the seventh forest resources statistics of China as the data source to generate sample points,and it also works as the simulation accuracy test. The HASM simulation shows that the total forest carbon storage of China is 9.2405 Pg,while the calculated value based on forest resources statistics are 7.8115 Pg. The forest resources statistics is taken based on a forest canopy closure,and the result of HASM is much more suitable to the real forest carbon storage. The simulation result also indicates that the southwestern mountain region and the northeastern forests are the important forest carbon reservoirs in China,and they account for 39.82% and 20.46% of the country's total forest vegetation carbon stock respectively. Compared with the former value (1975-1995),it manifests that the carbon storage of the two regions do increase clearly. The results of this research show that the large-scale reforestation in the last decades in China attains a significant carbon sink.
Based on the GIMMS AVHRR NDVI data (8 km spatial resolution) for 1982-2000,the SPOT VEGETATION NDVI data (1 km spatial resolution) for 1998-2009,and observational plant biomass data,the CASA model was used to model changes in alpine grassland net primary production (NPP) on the Tibetan Plateau (TP). This study will help to evaluate the health conditions of the alpine grassland ecosystem,and is of great importance to the promotion of sustainable development of plateau pasture and to the understanding of the function of the national ecological security shelter on the TP. The spatio-temporal characteristics of NPP change were investigated using spatial statistical analysis,separately on the basis of physico-geographical factors (natural zone,altitude,latitude and longitude),river basin,and county-level administrative area. Data processing was carried out using an ENVI 4.8 platform,while an ArcGIS 9.3 and ANUSPLIN platform was used to conduct the spatial analysis and mapping. The primary results are as follows:(1) The NPP of alpine grassland on the TP gradually decreases from the southeast to the northwest,which corresponds to gradients in precipitation and temperature. From 1982 to 2009,the average annual total NPP in the TP alpine grassland was 177.2×1012 gC yr-1(yr represents year),while the average annual NPP was 120.8 gC m-2 yr-1. (2) The annual NPP in alpine grassland on the TP fluctuates from year to year but shows an overall positive trend ranging from 114.7 gC m-2 yr-1 in 1982 to 129.9 gC m-2 yr-1 in 2009,with an overall increase of 13.3%;32.56% of the total alpine grassland on the TP showed a significant increase in NPP,while only 5.55% showed a significant decrease over this 28-year period. (3) Spatio-temporal characteristics are an important control on annual NPP in alpine grassland:a) NPP increased in most of the natural zones on the TP,only showing a slight decrease in the Ngari montane desert-steppe and desert zone. The positive trend in NPP in the high-cold shrub-meadow zone,high-cold meadow steppe zone and high-cold steppe zone is more significant than that of the high-cold desert zone;b) with increasing altitude,the percentage area with a positive trend in annual NPP follows a trend of "increasing-stable-decreasing",while the percentage area with a negative trend in annual NPP follows a trend of "decreasing-stable-increasing",with increasing altitude;c) the variation in annual NPP with latitude and longitude co-varies with the vegetation distribution;d) the variation in annual NPP within the major river basins has a generally positive trend,of which the growth in NPP in the Yellow River Basin is most significant. Results show that,based on changes in NPP trends,vegetation coverage and phonological phenomenon with time,NPP has been declining in certain places successively,while the overall health of the alpine grassland on the TP is improving.
The Three-River Headwaters Region (TRHR),which is the source area of the Yangtze River,Yellow River,and Lancang River,is of key importance to the ecological security of China. Because of climate changes and human activities,ecological degradation occurred in this region. Therefore,"The nature reserve of Three-River Source Regions" was established,and "The project of ecological protection and construction for the Three-River Headwaters Nature Reserve" was implemented by the Chinese government. This study,based on MODIS-NDVI and climate data,aims to analyze the spatiotemporal changes in vegetation coverage and its driving factors in the TRHR between 2000 and 2011,from three dimensions. Linear regression,Hurst index analysis,and partial correlation analysis were employed. The results showed the following:(1) In the past 12 years (2000-2011),the NDVI of the study area increased,with a linear tendency being 1.2%/10a,of which the Yangtze and Yellow River source regions presented an increasing trend,while the Lancang River source region showed a decreasing trend. (2) Vegetation coverage presented an obvious spatial difference in the TRHR,and the NDVI frequency was featured by a bimodal structure. (3) The area with improved vegetation coverage was larger than the degraded area,being 64.06% and 35.94%,respectively during the study period,and presented an increasing trend in the north and a decreasing trend in the south. (4) The reverse characteristics of vegetation coverage change are significant. In the future,degradation trends will be mainly found in the Yangtze River Basin and to the north of the Yellow River,while areas with improving trends are mainly distributed in the Lancang River Basin. (5) The response of vegetation coverage to precipitation and potential evapotranspiration has a time lag,while there is no such lag in the case of temperature. (6) The increased vegetation coverage is mainly attributed to the warm-wet climate change and the implementation of the ecological protection project.
The Three-River Headwaters region in China is an ecological barrier providing environmental protection and regional sustainable development for the mid-stream and downstream areas,which also plays an important role in animal husbandry in China. This study estimated the grassland yield in the Three-River Headwaters region based on MODIS NPP data,and calculated the proper livestock-carrying capacity of the grassland. We analyzed the overgrazing number and its spatial distribution characteristics through data comparison between actual and proper livestock-carrying capacity. The results showed the following:(1) total grassland yield (hay) in the Three-River Headwaters region was 10.96 million tons in 2010 with an average grassland yield of 465.70 kg/hm2 (the spatial distribution presents a decreasing trend from the east and southeast to the west and northwest in turn);(2) the proper livestock-carrying capacity in the Three-River Headwaters region is 12.19 million sheep units (hereafter described as "SU"),and the average stocking capacity is 51.27 SU [the proper carrying capacity is above 100 SU/km2 in the eastern counties,60 SU/km2 in the central counties (except Madoi County),and 30 SU/km2 in the western counties];and (3) total overgrazing number was 6.52 million SU in the Three-River Headwaters region in 2010,with an average overgrazing ratio of 67.88% and an average overgrazing number of 27.43 SU/km2. A higher overgrazing ratio occurred in Tongde,Xinghai,Yushu,Henan and Zêkog. There was no overgrazing in Zhiduo,Tanggula Township and Darlag,Qumerleb and Madoi. The remainder of the counties had varying degrees of overgrazing.
This study firstly analyzed the shrinkage of winter wheat and the changes of cropping systems in the Hebei Plain from 1998 to 2010 based on the agricultural statistic data of 11 cities and meteorological data,including daily temperature,precipitation,water vapor,wind speed and minimum relative humidity data from 22 meteorological stations,and then calculated the water deficit and irrigation water resources required by different cropping systems,as well as the irrigation water resources conserved as a result of cropping system changes,using crop coefficient method and every ten-day effective precipitation estimation method. The results are as follows. 1) The sown areas of winter wheat in the 11 cities in the Hebei Plain all shrunk during the study period. The shrinkage rate was 16.07% and the total shrinkage area amounted to 49.62×104 ha. The shrinkage was most serious in the Beijing-Tianjin-Tangshan metropolitan agglomerate,with a shrinkage rate of 47.23%. 2) The precipitation fill rate of winter wheat was only 20%-30%,while those of spring maize and summer maize both exceeded 50%. The irrigation water resources demanded by the winter wheat-summer maize double cropping system ranged from 400 mm to 530 mm,while those demanded by the spring maize single cropping system ranged only from 160 mm to 210 mm. 3) The water resources conserved as a result of the winter wheat sown area shrinkage during the study period were about 15.96×108 m3/a,accounting for 27.85% of those provided for Beijing,Tianjin and Hebei by the first phase of the Mid-Route of the South-to-North Water Diversion Project.
With rapid urbanization and the socio-economic transformation,cultivated land protection has gradually become a major concern in China. The economic compensation plays a crucial role in promoting cultivated land protection and improving the utilization ratio of cultivated land. Farmer household's satisfaction has a great influence on the effectiveness of compensation. Therefore,households' willingness to select the economic compensation pattern for cultivated land protection has been considered and re-examined. By employing Participatory Rural Appraisal method (PRA),3 villages and 392 households were investigated and sampled in mesa and hilly areas of Chongqing. Then a quantitative analysis framework of household livelihood hexagon has been developed to quantify the livelihood assets of different farmer households. Finally,the Gray Relation Model and Probit Regression Model have been employed to explore the coupling relationship between the household livelihood assets and their compensation pattern options. The results show that there are both qualitative and spatial heterogeneity in household livelihood assets. We found that the inequality of livelihood assets is evident for five household types. There is a spatial trend that the higher the elevation,the less livelihood assets are. In addition,their options of economic compensation pattern vary from Chengdu Pattern to Foshan Pattern due to their difference in livelihood assets and difference in location. In detail,there is a coupling relationship between household livelihood assets and their compensation pattern;negative correlation is observed between natural assets value and household pattern options,while the other livelihood assets have positive impacts on compensation pattern in varying degrees,which from the top are psychological assets,human assets,physical assets,financial assets,and social assets respectively. A conceptual compensation pattern system has been designed to meet the demands for farmer households mainly according to their shortage in livelihood assets. In addition,compensation method,compensation standard,the basis of compensation and the source of compensation funds have been proposed accordingly.
The regional changes of daily temperature extremes in North China caused by urbanization are studied further from observed facts and model estimates on the basis of homogenized daily series of maximum and minimum temperature observations from 268 meteorological stations,NCEP/DOE AMIP-Ⅱ reanalysis data (R-2),and the data of simulations by regional climate model (RegCM3). The observed facts of regional warming on long time scales are obtained by analyzing the indices of temperature extremes during two time periods of 1961-2010 and 1951-2010. For urbanization effect,the contributions to decreases in annual and winter diurnal temperature range (DTR) are 56.0% and 52.9%,respectively,and increases in the lowest minimum temperature (TNn) are 35.7% and 26.2% by comparison of urban and rural observations. Obtained by R-2 data with observations for contrast,on the other hand,increase in the number of annual warm nights (TN90p) contributed by urbanization is 60.9%. And observed facts of regional warming in daily temperature extremes are also reflected in the simulations,but what difference is urbanization progress at rural areas in North China would be prominent in the next few years relative to urban areas to some extent from model estimates.
In addition to socio-economic factors,major landforms may affect the city structure and urban form. Here we show that landforms have significant effects on the city shape and street patterns of the fast-growing Iranian cities of Dezful (a river) and Khorramabad (mountains and valleys),but no clear effects on the cities of Yazd and Nain. Also,where the street orientation is peaked,the Gibbs/Shannon entropy (a measure of dispersion or spread) is low,but increases as the distribution becomes more uniform because of landform constraints. The streets in the old inner parts of all the cities are,on average,shorter and denser (more streets per unit area) than the streets of the newer outer parts. The entropies of the outer parts are also greater than those of the inner parts,implying that the street-length distribution gradually becomes more dispersed or spread as the city expands. All these cities have been fast growing in the past decades,with the newer outer parts expanding rapidly. As shown here,the rapidly formed outer parts (with greater dispersion in street patterns) have significantly different textures from those of the older inner parts,indicating different functionality and growth processes. These quantitative methods for street-network analysis can be used worldwide,particularly for analysing the effects of landforms on city shape and texture.