The Dynamic Land Ecosystem Model (DLEM) was developed to meet critical needs for understanding and predicting the large-scale patterns and processes of terrestrial ecosystems and continental margins, and complex interactions among climate, ecosystem and human in the context of multifactor global change. The DLEM couples major biophysical, biogeochemical, vegetation dynamical and land use processes, and works at multiple scales in time step ranging from daily to yearly and spatial resolution from meters to kilometers, from region to globe. The DLEM is characterized by the following features: 1) multiple factors driven; 2) fully-coupled cycles of carbon, nitrogen and water; 3) concurrently simulation of major greenhouse gases (CO2, CH4, N2O, & H2O); 4) dynamically tracking changes in land cover/use and vegetation distribution. The model has been validated against site-specific measurements across the globe and applied at various scales. In this paper, we have briefly addressed model structure, parameters, key processes and major input/output variables. As a case study, we presented the simulated global fluxes of net primary productivity, evapotranspiration and methane during 1948-2005 and their spatial patterns in the year 2000. We also identified major gaps in terrestrial ecosystem modeling and field observations, and further discussed some critical future research needs.
Using energy consumption and land use data of each region of China in 2007, this paper established carbon emission and carbon footprint model based on energy consumption, and estimated the carbon emission amount of fossil energy and rural biomass energy of different regions of China in 2007. The main conclusions are as follows: (1) The total amount of carbon emission from energy consumption of China in 2007 was about 1.65 GtC, in which, the proportion of carbon emission from fossil energy was 89%. (2) Carbon emission intensity of industrial space of China in 2007 was 1.98 t/hm2, in which, carbon emission intensity of living & industrial-commercial space and of transportation industrial space was 55.16 t/hm2 and 49.65 t/hm2 respectively. (3) Carbon footprint caused by industrial activities of China in 2007 was 522.34×106 hm2, which brought about ecological deficit of 28.69×106 hm2. (4) The per unit area carbon footprint of industrial spaces in China was about 0.63 hm2/hm2 in 2007.
Using a static opaque chamber method, the rates of soil microbial respiration, soil respiration, and ecosystem respiration were measured through continuous in-situ experiments in semiarid Leymus chinensis steppe in Xilin River Basin of Inner Mongolia, China. Soil temperature and moisture are the most important factors affecting CO2 flux. Soil temperature was the main factor influencing respiration rates. Exponential models based on soil temperature can explain large percent of CO2 efflux variations (R2 = 0.375-0.655) excluding data of low soil water conditions. Soil moisture can also effectively explain some variations of soil and ecosystem respiration (R2 = 0.314-0.583), but it can not explain much of variation of soil microbial respiration (R2 = 0.063). Low soil water content (≤5%) inhibited CO2 efflux though soil temperature was high. Rewetting the soil after a long drought resulted in substantial increases in CO2 flux at high temperature. Bi-variable models based on soil temperature at 5 cm depth and soil water content at 0-10 cm depth can explain about 70% of variations of CO2 effluxes. The contribution of soil respiration to ecosystem respiration averaged 59.4%, ranging from 47.3% to 72.4%; the contribution of root respiration to soil respiration averaged 20.5% , ranging from 11.7% to 51.7% . The contribution of soil to ecosystem respiration was a little overestimated and root to soil respiration underestimated because of increased soil water content that occurred as a result of plant removal.
Based on 1961-2005 observed winter precipitation data in Northeast China, the temporal and spatial variations of precipitation concentration degree (PCD) and precipitation concentration period (PCP) are computed and analyzed, together with the circulation characteristics when there is a higher PCD. Results show that the PCD in Northeast China presents a yearly rising tendency and the PCP decreases obviously. In terms of decadal variation, there is a 12-year periodic variation in PCP, and since the mid-1970s there has been an 8-year short periodic variation. As to spatial variation, the PCD in winter of Northeast China has increased gradually from the eastern to western part, and the minimum value of PCD occurs in the east of Jilin Province, while the high value center is observed in the central part of the province. For the whole Northeast China, the variation tendencies are consistent in the eastern and central parts. The PCD presents a rising tendency and the PCP shows a decreasing tendency. The PCD in the southwestern and northern parts has a slight rising tendency, with the PCD in the southwestern part having the slightest increasing tendency, and the PCP in the northern part showing the slightest decreasing tendency. When a high PCD value is observed, the areas are controlled by the East Asian deep trough at 500 hPa, and the trough becomes deeper in the western part, while a high pressure, which is easily formed and intensified in the eastern part, makes the East Asia deep trough move eastward slowly. Upper-level jet stream and low-level jet stream co-exist, and the former is stronger and takes more of a southwestward position than the latter. Over the Pacific the high value extent of water vapor transport is intensified obviously, and the extent also increases. Northeast China is influenced by the water vapor transported to the northwest along the north of the high value center.
In this paper, the actual evapotranspiration in the Yangtze River Basin is calculated by the advection-aridity (AA) model with parameters validation during 1961-2007 and simulated by the general circulation model (ECHAM5/MPI-OM) from 1961 to 2000. The linear regression method and nonparametric Mann-Kendall test are used to examine the trends of annual, inter-decadal and seasonal estimated actual evapotranspiration. The results show that the annual actual evapotanspiration estimated by the above two methods presents the same decreasing trends in the upper and the mid-lower reaches of the Yangtze River, and this decrease is more significant in the mid-lower than in the upper Yangtze. The significance of decreasing annual actual evapotranspiration calculated by AA model is higher than that simulated by ECHAM5/MPI-OM, and the decreasing rate is about -9.3 mm/10a and -3.6 mm/ 10a respectively. The former is attributed to the significant decreasing trend in summer actual evapotranspiration, while the latter is caused by a significant decreasing trend in autumn and spring actual evapotranspiration. In the mid-lower Yangtze River, the seasonal actual evapotranspiration estimated by the two methods displays consistent changing trends, i.e. decreasing actual evapotranspiration in spring, summer, autumn, and increasing in winter. In the upper Yangtze River, the seasonal actual evapotranspiration estimated by the two methods shows similar downward trends in spring and autumn; the summer and winter actual evapotranpiration estimated by the two methods shows upward changing trends.
Taking Sichuan Province and Chongqing Municipality as an example, this paper studies the relationship between socio-economic factors and sediment yield in the Upper Yangtze River based on section data in 1989 and 2007. The results show that sediment yield is significantly correlated with population density and farmland area, in which the former appears to be more closely related to sediment yield. Moreover, in the relation of sediment yield vs. population density, a critical value of population density exists, below which the sediment yield increases with the increase of population density and over which the sediment yield increases with the decrease of population density. The phenomenon essentially reflects the influence of natural factors, such as topography, rainfall and soil property, and that of some human activities on sediment yield. Regions with higher population density than critical value are located in the east of the study area and are characterized by plains, hills and low mountains, whereas regions with lower level are located in the west and are characterized by middle and high mountains. In the eastern region, more people live on the lands with a low slope where soil erosion is slight; therefore, sediment yield is negatively related with population density. In contrast, in the western region, the population tends to be concentrated in the areas with abundant soil and water resources which usually lead to a higher intensity of natural erosion, and in turn, high-intensity agricultural practices in these areas may further strengthen local soil erosion.
The quarrying culture in Zhejiang is formed and developed by the combined effect of factors such as geology, geomorphology, river system and climate. The geological condition is the prerequisite for the occurrence and development of the regional quarrying culture. The landscape pattern of "seven tenths of mountains, one-tenth of water and two tenths of fields" has an important influence on the emergence and development of quarrying culture. Mountains and hills rich in stone resources are potential quarries. And hills of the plains, transitional zones of plains and hills, as well as the edges of basin areas are generally distributed with quarries, while the special estuary landscape, long and tortuous coastlines and a large number of islands all have a certain impact on quarrying culture. The rivers across the land provide a favorable condition for the transport of stone, which is conducive to the spread of quarrying culture, and certainly the construction of water conservancy projects for rivers also have an impact on quarrying culture. The special climatic conditions along the coast also have some impact on quarrying culture. Quarrying culture has a certain reaction on natural environment, changing the local landscape, hydrology, vegetation and other physical geographical elements. Quarrying activity changes the natural environment, mainly by two ways: the formation of the landscape and the stone uses.
In this paper, the research is conducted based on the geographic information TUPU analytic methods and Markov model of space probability. With the support of ARC/INFO software, this paper has compounded a series of varying TUPU of the land-use pattern by using spatial data covering four periods (1969, 1979, 1992 and 2001) in the Xinkai River basin. We can comprehend the changes of land-use pattern in the Xinkai River basin through the TUPU. The result shows that great changes have taken place on the land-use pattern in this basin during the past 33 years. The farmland has a net increase of 1357.2 km2 (exceeding 32% of the total basin), and most of it was converted from grassland, sandy soil, marsh and woodland. The changes of sandy soil somewhat oscillated. The area of sandy soil accounted for less than 23% of the total basin area. Although the sandy soil tended to decrease on the whole, the desertification of grassland and farmland is still serious in this basin. The grassland has decreased greatly. It has a net reduction of 1582.6 km2 from 36.2% to 18.5% of the total basin area. The main reasons are summarized in three respects: first, grassland has been cultivated into farmland; second, grassland has degenerated into sandy soil, marsh and saline land; third, grassland has been transformed into plantable woodland. The residential land and saline land show a decreasing trend while the wetland and woodland present an increasing trend.
Urban land use allocation has been the top concern for city planners in the process of urban strategy planning for a long time. In the past, most of urban land-use layout schemes were formed by city planners' intuition, simply layers-overlapping and limited public participation. These methods just considered very few main factors and neglected many other factors that may also determine the spatial background differences, so schemes were often modified time and time again. With economic and social development, urban planning has become more and more complicated, and previous methods cannot meet our demand now. What's more, China' new urban planning law stresses that the land-use layout scheme should be made scientifically and accurately, so it is very necessary to find a more efficient method for urban land-use layout scenario simulation and scheme evaluation. Taking Taicang City as an example, this study discusses the technical process of this method by exploring the spatial analysis function of GIS: Firstly, based on the existing research of Urban Future Model, it builds a more practical model for urban spatial expansion simulation, considering Chinese characteristics especially the real situation of the study area, Then it generates three land-use layout schemes on the basis of land use evaluation, scenario analysis and urban spatial expansion simulation. Finally, the study evaluates these land-use layout schemes by introducing multiple-target-arrive-matrix method from the aspects of agricultural safety, ecological safety, geological hazards and flood disasters, and then chooses the most optimal plan as the reference scheme of the urban strategy planning. Results show that this method has greatly improved the efficiency of urban land-use layout scheme making， and the outcome of selected reference scheme is very similar to that of the final planning scheme.
This paper studies the evolution process of coastline in the Yancheng coastal plain. First, image dodging and threshold segmentation are carried out based on the 1975 MSS image. So the "zebra-stripe" image has been obtained which reveals the evolution of ancient coast. And then, bottom characteristics samples are analyzed. The result shows that sandy soil and silt soil present alternating distribution in the Yancheng coastal plain. The distribution is compatible with the "zebra-stripe" image. In addition, the overall trends of the historical coastline and the stripes of the interpretation map is the same. To sum up, the "zebra-stripe" should be the indicator of the coastline change. A total of 10 sand hills and 10 silt flats are found in the "zebra-stripe" image. Therefore we get a better understanding of the coastal evolution in the Yancheng coastal plain.
Rapid urban expansion in China has caused the significant loss of agricultural land. Specific efforts are made by the country to protect its scarce and valuable agricultural land. The State Council promulgated the Ordinance for the Protection of Primary Agricultural Land in 1994 to promote the zoning of agricultural conservation areas. However, the agricultural land still underwent a rapid loss due to the urgent demand of local economic development. The conflict between protection and local development calls for solution. This paper provides a new thought of integrating urban development into the zoning of agricultural conservation areas, and Panyu district in Guangdong province is selected for a case study. The proposed Agent-based Land Allocation (AgentLA) model is used to automatically generate the spatial distribution of agricultural conservation areas. Compared to conventional methods, the resulted pattern from AgentLA is more compact that favors routing maintenance of the conservation areas. Moreover, the future development of the region is predicted using Geographical Simulation and Optimization System (GeoSOS), a platform for geosimulation. Finally, GIS provides the function to combine the zoning result and the predicted development pattern in order to recognize the spatial distribution of the conflict areas.
