The impacts of land use changes on soil organic carbon (SoC) and soil organic nitrogen (SON) storage have been analyzed from 1990 to 2000 in China between forest, grassland and cropland based on 2473 soil profiles and Landsat TM images from the end of 1980s to the end of 1990s. Estimation of the greenhouse gasses inventory approach suggested by IPCC indicated that the losses of SoC and SON pools were 77.6±35.2 TgC (Tg = 106 t) and 5.6±2.6 TgN to a depth of 30 cm in China, in which the mean annul losses of SoC and SON were 7.76 TgC/yr and 0.56 TgN/yr, respectively. SoC and SON pools of cropland increased 79.0±7.7 TgC and 9.0±0.7 TgN, grassland lost 100.7±25.9 TgC and 9.8±2.2 TgN, and forest lost 55.9±17.0 TgC and 4.9±1.1 TgN, respectively. In order to estimate the uncertainty range of calculated results, this paper adopted the land use conversion approach to compare with IPCC's approach. The calculation of the land use conversion approach showed that the losses of SoC and SON pools were 53.7 TgC and 5.1 TgN to a depth of 30 cm, and 99.5 TgC and 9.4 TgN to a depth of 100 cm respectively, which the calculation proCedure was designed according to the conversion area and the changing rate of SoC and SON densities among forest, cropland and grassland during 10 years.
The alpine grassland in the Tibetan Plateau plays an important role in global carbon cycle and carbon balance. However, regional carbon cycle in the alpine grassland ecosystem is still not clear. In this study we selected Golog prefecture in the headwater of the Yellow River valley as a study area, which is loCated on the southeast of the Tibetan Plateau. Using field-obtained physical and chemical data from more than 50 typical soil profiles, the organic soil carbon storage in the study area is estimated. The results show that soil organic carbon sinks primarily include alpine meadow and alpine steppe soils. The mean soil organic carbon per unit area is 29.97 kg/m2. The total soil organic carbon storage is about 15×108tC. The spatial distribution of soil organic carbon is characterized by its density and storage increase from northwestern to southeastern part of the study area. The very cold environment results in the higher value of soil organic carbon density in the study area.
Soil organic carbon (SoC) is considered to be a key index in evaluation of soil quality, soil degradation and soil C sequestration. In order to discuss the temporal-spatial dynamics of SoC in reversed desertification area, Yulin County is taken as a case. Data of SoC were obtained based on the Second National Soil Survey in 1982 and re-sampling in 2003. Methods to soil sampling, SoC determination, soil organic carbon density (SoCD) and storage (SoCS) calculation are soil auger, K2Cr3O7 oxidation and FeSO4 titration and area-weighted mean values, respectively. On average, SoCD and SoCS and their changes vary between different soil groups, soil C pools and sub-areas. During 1982 and 2003, soil organic carbon density (SoCS) for arable layer (0-20 cm), 1-m depth (0-100 cm) and whole profile (100±10 cm) increase 0.15 kgm-2, 0.29 kgm-2 and 0.31 kgm-2 respectively, being equal to increments of SoCS of 10.12 Gg, 19.06 Gg and 20.10 Gg, correspondingly. As for soil C pools, arable layer is much more sensitive to climate change, land use/management and other human activities than 1-m depth and whole profile. With regard to soil group and sub-area, the change of SoCD of sandy soil distributed in the northwest is much less than that of loessal soil distributed in the southeast, thus per unit area SoCS in the northwest is lower than the southeast. As far as soil genus, the SoCD of moving sandy soil and semi-fixed sandy soil is significantly lower than that fixed sandy soil, and sandy loamy loessal soil is less than light loamy loessal soil, which indicate that there is great potential to increase SoC in the study area. These data demonstrate that afforestation, agroforestry, tillage of soil and water conservation, and other soil restoration countermeasures can enhance soil C sequestration and mitigate the atmospheric concentration of CO2.
A 20,000-years environmental record is elucidated by analyzing the environmental proxies such as grain size, ToC, TN, C/N, Fe/Mn, Sr/Ba and environmental magnetism parameters from a lake core (TC1) in Southern Tibet area. Results showed that during the period of ca. 19800-18000 Cal aBP, the decreasing temperature was reflected by all analyzed proxies. Temperature appeared a jump rise around ca. 16000 Cal aBP and then had an abrupt decrease. About 15200-12000 Cal aBP, temperature slowly re-rose. However, almost all the proxies indicated that the environment was unsuitable for lives existing during ca. 12000-9500 Cal aBP. Especially during ca. 11600-10400 Cal aBP, the environment became deteriorated. From the beginning of HoloCene, the environment experienced 3 obvious warm stages (ca. 9500-7600 Cal aBP, ca. 6800-5800 Cal aBP, ca. 4800-3800 Cal aBP) and 2 cold stages (ca.7600-6800 Cal aBP, ca. 5800-4800 Cal aBP), representing obvious alternation of warm-dry and cold-wet, having the climatic change characteristics of South Asian monsoon (southwest monsoon) zone. Some characters of the 20,000-year climatic and environmental change sequence in Chen Co area had rather good coherence with Greenland ice core records (GISP2) and other environmental records on the Tibetan Plateau, reflecting that the environmental changes in this area had certain global significance.
On the basis of the physical and chemical analyses of glacial lacustine sediment and glacial geomorphology in Diancang Mountain, the series of climate change since HoloCene is expected to be rebuilt, including 6 stages with the alternation of cold-wet and warm-dry climate. The comparison with other areas affected by southwest monsoon shows that the time when southwest monsoon arrived at Diancang Mountain was later than that of the Arabian Sea and earlier than that of the Tibetan Plateau. This fact implies that Diancang Mountain is the joint linkage of the above place. Another phenomenon is that after southwest monsoon arrived at the Tibetan Plateau, the climate of Diancang Mountain change slightly drier. The record presents that this area was influenced by southeast monsoon between 6.0 ka BP and 5.3 ka BP.
14C dating, geoChemical analysis, pollen analysis and environmental magnetism analysis are performed on samples from the Maqiao site, Shanghai. Comparitive study was conducted on the large amount of the collections from the archaeological sites and natural sedimentary stratum in the Yangtze Delta. The research results indicate that oCean degression happened 7200 aBP-5300 aBP, which made large area of land exposed, and offered good space for human activities during the Liangzhu Culture epoCh. In the Liangzhu Culture epoCh, suitable climatic conditions accelerated human activities, leading to the developed culture and unprecedented jade-article culture. At the late Liangzhu Culture, climatic transition from warm/wet climate to cold/dry climate oCcurred. This climatic transition resulted in large scale flooding periods, leading to the collapse of the Liangzhu Culture, followed by the relatively backward Maqiao Culture. Single archaeological section is not enough in reconstruction of paleo-climatic change and therefore, natural sections and archaeological sections are widely collected for further research. Comparitive research results between natural deposition sections, archaeological sections and climatic curves reconstructed from pollen analysis on samples taken from Qingfeng section, Jianhu Lake, Jiangsu Province indicate that the flooding periods in the Yangtze Delta matched well the climatic transition periods, which are also corresponding well to the strong changing fluctuations of the climatic conditions. Comprehensive research on the archaeological sections and natural sedimentary sections suggests that the cultural interruptions at the archaeological sites are the results of the flood events in the Yangtze Delta. Climatic changes, flood events and water changes play the important parts in influencing the development of human civilization in the Yangtze Delta. The research results are meaningful in further research on the climatic changes in the Yangtze Delta, esp. in research methodology.
The distribution of settlements in the Xila Mulun River Valley and its neighborhood in the Liao Dynasty is the key factor for analyzing the scope of cultivation and the disturbance of environment. This paper divides the settlements in the area into dichotomies: 1) fundamental settlements dispersing loose-footed, which were relatively small in size and population, and the surrounding cultivated land were limited; and 2) settlements centered by prefectural capitals and county seats, where the population was relatively concentrated and the scope of cultivated land was larger. Most of the latter settlements were memorial places of Khitan history rather than agriculture-fitted ones. Under very few circumstance, to some extreme extent, the county seat loCated in the centre of the desert, where the farming conditions did not exist, but due to the concentration of the population, the intermingle cultivated lands were highly developed. These areas were critical factors causing environmental problems.
Using the tree-ring width chronologies in Qumalai and Zhiduo, this study investigated the relationships between tree growth and annual runoff of Tongtian River, and reconstructed the runoff series since 1485 AD at Zhimenda hydrologic station, which is loCated on Tongtian River Basin in the source region of the Yangtze River. The variation of reconstructed runoff series was also analyzed. The results showed that the distinct high-flow period of annual runoff in Zhimenda hydrologic station oCcurred in the first 50 years of the 19th century, and the low-flow one oCcurred in the latter half of the 17th century. There are 96 years with extremely high annual runoff, and 117 years with above-average annual runoff. Moreover, the numbers of extremely low runoff years and below-average runoff years are 86 and 81, respectively. There are 138 years with normal annual runoff. The significant cycles of 43, 37, 32, 5, and 2 years exist in the reconstructed runoff series.
Based on the data from Shanghai water resources survey separately conducted at the beginning of the 1980s and the end of the 1990s, taking water conservation zone, which is generally used to manage water resources and prevent serious flood, as the basic unit for stream structure analysis, this paper discussed the characteristics of stream structure and its growth laws under the situation of rapid urbanization in Shanghai. The research showed that (1) Horton law still plays an important role in some areas with relative lower urbanization level, and stream number and average length of stream decrease in geometric series with the raising of stream order. Self-similarity of stream structure lies in different stream orders. (2) Urbanization is the dominant factor changing the structure of river system in urban area. In high-urbanized water conservancy zones, self-similarity properties of stream structure could not be observed. (3) There existed significant relationship between stream structure and its function. Because water area and stream ramification decreased obviously during the proCess of urbanization in Shanghai, it is an urgent task to pay more attention to those indicators such as water area, stream ramification, river naturalness, and try best to maintain the reasonable values for these indicators.
After dividing the source regions of the Yellow River into 38 sub-basins, the paper made use of the distributed hydrologic model--SWAT model to simulate discharge with validation of the measured yearly and monthly runoff data from the Tangnag Hydrologic Station, and simulation results are satisfactory. Five land-cover scenario models and 24 sets of temperature and precipitation combinations were established to simulate annual runoff and runoff depth under different scenarios. The simulation shows that with the increase of vegetation coverage annual runoff increases and evapotranspiration decreases in the basin. When temperature decreases by 2oC and precipitation increases by 2%, basin runoff increases by 39.69%, which is the largest among all scenarios.
With the long-term data of the geodetic sea level measurements undertaken in the Dongting Basin and the recent sediment data of Dongting Lake, we analyze the tectonic subsidence rate of the Dongting Basin and the sedimentary rate of Dongting Lake. From the point of view of geomorphology and hydrogeology, we distinguish the two different spatial concepts between "the basin of Dongting Lake" and "the Dongting Basin". Then, we discuss the influences of the tectonic subsidence and the siltation on the space of storing flood of Dongting Lake and the levees. Under the circumstance of the basin of Dongting Lake encircled by levees, the capacity of storing flood of Dongting Lake will decrease due to the tectonic subsidence. The tectonic subsidence capacity of the Dongting Basin restrains the shrinking tendency of Dongting Lake to a certain extent, but the tectonic subsidence is harmful to the situation of preventing flood disasters in the region of Dongting Lake. The better quality of levees is required due to the tectonic subsidence and the siltation, and the difficulties of preventing flood disasters are increasing in the region of Dongting Lake.
Combined with recent historical period of climate data and two periods of land use data sets from remote sensing data, we test the net primary productivity (NPP) data sets over last 20 years in North China modelled by the satellite data-driven Global Production Efficiency Model (GLO-PEM) for detecting the widespread spatial and temporal characteristics of the impacts of climate and land use change on the regional NPP. Our results shows that over the past 20 years, the average annual temperature in the research region has remarkably increased by more than 0.064oC, but over the same period, there has been a 1.49 mm decrease in annual precipitation and decrease in NPP by an annual rate of 6.9 TgC. The NPP changes in the study region were greatly affected by the average temperature and precipitation by ten-day periods as well as the seasonal temperature and precipitation. The correlation between seasonal NPP and seasonal precipitation and temperature is highly consistent with land cover spatially, and the correlation coefficient changes with the changes of vegetation types. The analysis reveals that the areas of change in land use only take up 5.45% of the whole study region, so the impacts of climate changes on the NPP dominate (90% of the total). However, land use plays an absolute dominative role in the areas with land cover changes, accounting for 97% of the total. Over the past 20 years, the NPP in the whole study region remarkably reduced due to obvious precipitation decrease and temperature rise. Between two periods of land use (about 10 years), the changes in climate are predicted to cause a decrease in NPP by 78 (±0.6) TgC, and combined impacts of climate changes and land use to cause a decrease in NPP by 87 (±0.8) TgC.
This paper describes a method of the detection for the landscape change by satellite remotely sensed data. In order to improve the accuracy of detection for the landscape change, we presented the differencing image PCA method to improve the Principal Component Analysis (PCA) and the band difference of images method using the multi-temporal remotely sensed data of TM (Thematic Mapper). And the Liaohe River Delta of China was selected as a case to validate this method. The results showed that the differencing image PCA method has higher detection accuracy compared with the conventional method--post-classification change detection and the overall accuracy of the change detection reaches 0.89 and the Kappa coefficient is 0.82. The research result also showed that the landscape changed about 22% in the Liaohe River Delta area during 1984-2000. The main change is the reduction of the reed area, the increase of the paddy field and the city area.
Modeling land use scenarios change and its impact in typical regions are helpful to investigate the interactive mechanism between land use system and terrestrial ecosystem, and optimize land use pattern and reduce potential ecological risk in the process of future land use. A System Dynamic (SD) model aims at modeling land use scenarios change and assessing its ecological impact in the northern China in the next 50 years is developed in this paper. The accuracy assessment with historical data covering 1990 to 2001 indicated the SD model is reliable. After the different "what-if" scenarios controlled by GDP, population, market and technology advancement were built, the different land use scenarios changes in the northern China from 2000 to 2050 were simulated with their ecological impact assessment. The result suggested that such factors as GDP, population, market and technology have good relationship with land use structure change in the northern China. It also indicated that such measures as strictly controlling population growth, importing proper amount of grain from other regions in addition to increasing per unit area grain yield to keep supply-demand balance in the region, and improving agricultural technology are the guarantee to the regional sustainable development with fast economic growth and obvious land use structure improvement at the same time.
Based on years of on-the-spot investigated materials and statistical data, this paper analyses the overall tendency, spatial differences and driving forces of the cultivated land change of Qira oases in the south of Tarim Basin. Based on GPS instant positioning, initial prediction of the cultivated land amount of Qira oases in 2010 and 2020 was carried out by means of establishing multiple regression mode and GIS aided spatial analysis. The result shows that dynamic changes of society and economy, improvement of agricultural technology, restrictions of water and land resources are three primary factors influencing cultivated land amount change in the arid area. The authors believe that this study will provide scientific basis for sustainable oasis agricultural development of this region.
Land use change data are mainly derived from land use data of different periods through statistical analysis or spatial analysis in GIS environment, and those land use data usually came from remote sensing images, land survey, historical maps or regional statistical information. Because of the errors in those land use data, land use change data are in dissimilar precision, but the available papers on land use change have not paid more attention to the point, but gave some descriptions of the error of land use data. Aimed at the error characteristics of land use change data, error analysis method was firstly discussed in this paper, and then the impacts from influencing factors, including the percentage of land use change and the error of periodical land use data, were analyzed in detail to a certain extent. The result showed that high precision of land use change data cannot always be guaranteed by high precision of land use data, which also depends on the error direction and the percentage of changed area. The results imply that the error of land use change data have been ignored at present and should be improved in the process of land classification, image collection, processing, interpretation and analysis.
The eco-environment restoration pattern means an integration of the policies and their matching measures in regulating the relation between human being and environment in the eco-environmentally fragile areas. This paper discussed the contents, indices and methods of the pattern evaluation. And then, based on the research results in the past ten years and the successful cases of small watersheds in the loess hilly-gully region, the characteristics of eco-environment restoration patterns including "relieving and de-farming" (RD), "rebuilding terrace and de-farming" (RTD) and "dam system and permanent control" (DSPC) were summarized. The sizes of de-farming slope farmland, rebuilding terrace, enlarging garden plot and restoring vegetation were calculated, the investment demands of eco-environment restoration on three patterns were done, benefits from those patterns were analyzed respectively and compared among each other. As a result, this paper drew the following conclusions: (1) RD pattern showed that the area of de-farming slope farmland more than 25o is 41.91×104 hm2 with 44.01×108 yuan (RMB) of policy allowance, and that of de-farming slope farmland more than 15o is 125.53×104 hm2 with 131.82×108 yuan of that. The result of RTD pattern is that the area of enlarged terraces is 69.16×104 hm2 and that of restored vegetation is 541.02×104 hm2, with 125.05×108 yuan of total investment demand. And the data from DSPC pattern included 36×104 silt-covered dams, 55.98×104 hm2 of silt-covered farmland and 554.2×104 hm2 of new woodland or grassplot, and 221.22×108 yuan of investment demand. (2) The benefit analysis of three patterns and their comparison results showed that RTD pattern ranks the first, with appropriate investment demand, better benefit and safer food supplies. Compared with RTD, RD being underway at present is a transitional pattern, with lower benefit and unsafe food supplies, and it should be replaced with RTD as soon as possible. On account of the limitation of its bigger investment demand and more uncertain factors, DSPC can be only regarded as an accessorial pattern, in despite of its profit prior to that of RTD.
Research on land use/land cover change and associated effects on eco-environment is the key content of geographical research on global change today. And ecosystem services are the hot issues of ecology and ecological economics. In this paper, we put ecosystem service values in use to weigh the ecological values of corresponding land use types, so as to evaluate the ecological effect of regional land use change. Yongsheng county, situated in the northwest of Yunnan province, also an ecotone, is taken as our research area. Based on TM images in 1988, 1994 and 1999, the landscape component maps of Yongsheng county were conducted through methods of supervised classification and interactive modification. The landscape type transition matrix and three kinds of indices for spatial patterns including patch-level index, class-level index and landscape-level index were calculated by models and GIS to examine the spatial patterns and dynamics of regional landscape in Yongsheng county. The results show that, due to human activity, the unused land decreased rapidly during the past 12 years; because of the limitation of physical geographic condition, the proportion of steady farmland is not high; the inter-changes of farmland and unused land happened frequently. And index for landscape diversity has showed a tendency of increasing, which means that the proportion of each landscape component changed to average. Also, the decreasing of fractal dimension of unused land shows that human activity effects are increasing. And land use change in Yongsheng county from 1988-1999 has got a good ecological effect, where the ecological benefit of land use is always increasing, and shows a distinct spatial difference.
