Taking the amount of soil conservation as the assessment indicator, with the application of the Revised Universal Soil Loss Equation, the soil conservation function of the ecosystem services on the Loess Plateau in China was assessed. The spatial distribution of the amount of soil conservation and its dynamic changes on the Loess Plateau in nearly 20 years was analyzed, which has significantly scientific and practical values in ecological benefits for vegetation reconstruction under the warming and drying climate. The results showed as follows. The per unit area soil conserved on the Loess Plateau was 305 t·hm-2·a-1 between 1990 and 2010, and the total amount of annual soil conserved was 190×108 t. The per unit area soil conserved amounts of farmland, grassland and forest ecosystems in 1990-2000 were 249, 285 and 640 t·hm-2·a-1, respectively, increased by 14.6%, 2.9% and 7.4% in 2000-2010. The percentage of soil retention rate of grassland ranged from 83% to 88%, for forest from 94% to 97% in 1990-2010 on the Loess Plateau. The characteristics of spatial distribution of soil conservation for farmland ecosystem showed that it was the highest in hilly and gully region of the Loess Plateau, and the lowest in agricultural irrigation region and the plain area. The spatial distribution characteristics of soil conservation for grassland and forest ecosystems showed a reduced trend along the southeast to northwest. Compared in 1990-2000, the amount of soil conservation for farmland, grassland and forest ecosystems showed an obvious increment in 2000-2010, especially in the hilly region in Yulin and Yan'an in Shaanxi Province and Lüliang Mountain areas in Shanxi Province.
Large-scale construction of high-standard farmland with high capacity for resisting drought or water logging prime farmland is an important task of the current land consolidation in China. The purpose of this paper is to analyse the anti-disaster ability of farmland. The method for comprehensive evaluation of the natural disaster risk of agricultural production is selected to zone the well-facilitied capital farmland. Based on the variable fuzzy sets theory, this article uses GIS technical to divide comprehensive risk level and zone construction area of well-facilitied capital farmland according to risk intensity and feasibility of land consolidation. Taking Guanzhong region as an example, some conclusions are drawn: 1) The uncertainty of risk assessment can be reduced by using the variable fuzzy sets theory. 2) The risk assessment result was jointly determined by hazard and vulnerability, which provide the basis for selecting high-standard construction of prime farmland suitable areas. 3) Comprehensive risk level, the extent of concentrated contiguous and consolidation potential jointly determine the timing of land consolidation. It can provide a reference for zoning the construction area of well-facilitied capital farmland and for a better land consolidation plan.
As an important and basic research on regional industrialization and urbanization development, study on calculation and assessment of the potential suitable construction land is an essential work. Based on multifactor distributed algorithm and extracting process of potential suitable construction land and GIS spatial analysis techniques, by using 1:50000 DEM data, 1:100000 land use data, county-level administrating data and distribution data of all kinds of nature reserves, the article assessed the amount, grade and the spatial distribution characteristics of potential suitable construction land of Xijiang River within a range of 20 km in Guangxi Zhuang Autonomous Region and seven urban areas along Xijiang Riverside. The results show:
1) As an essential component and axis of industry and population agglomeration of Guangxi Xijiang River Economic Belt, there is plenty of potential suitable construction land along the Xijiang Riverside, which is able to meet the demand for cities or towns' expansion, as well as the distribution of local industry parks and the infrastructure construction. Therefore, it is necessary to evaluate the regional differentiation of potential suitable construction land, especially specific development and construction project.
2) The area of the available construction land in Xijiang River within a range of 20 km is 1962.64 km2, which is 4.82% of the region's total. The area of the potential suitable construction land of Xijiang River with the ranges of 5 km, 5－10 km, and 10－20 km are respectively 617.30 km2, 495.31 km2, and 850.03 km2. Overall, the potential suitable construction land of the east coast of Liujiang River is plentiful, allowing the development of the future industry and population agglomeration.
3) The senven urban areas along Xijiang Riverside in Guangxi have considerable potential suitable construction land, which needed to implement classification guiding principle. The area of the potential suitable construction land of Nanning and Liuzhou along the Xijiang River within a range of 16 km is 205.49 km2 and 203.01 km2, with more than 70% being the most suitable construction land of the total and best-quality, hence possibly for the further large-scale development and construction. While there are limited potential suitable construction lands in Baise, Chongzuo, Laibin, Guigang and Wuzhou along the Xijiang Riverside within a range of 12 km, with areas ranging between 40－60 km2. This means appropriate controls are necessary for government to restrict the expansion of cities and towns.
Global climate change has led to significant vegetation changes in recent decades. The Qaidam Basin, most of which was located in hyper-arid areas, is undergoing a process of prominent warming. It is necessary to investigate the response of vegetation to the climatic variations for a better understanding of the accumulated consequence of climate change. Vegetation NDVI is an important indicator for evaluating terrestrial eco-system change. Based on MODIS NDVI and climate data during the period 2001-2010, we analyzed spatial and temporal variation of vegetation change and its reasons for that by using methods of linear regression, partial correlation, the Hurst index and other methods. Results were shown as follows: 1) During 2001-2010, the growing season NDVI (NDVI) of the study area was improved progressively, with a linear tendency of 0.041/10 a. Trends in NDVI of shrubs, grasslands and shrub-deserts were +0.043/10 a, +0.034/10 a and +0.028/10 a respectively. The shrubs improved most significantly. 2) Vegetation restoration was characterized by two fast-growing periods, with an "S-shaped" increasing curve. 3) Vegetation restoration and degradation area accounted for about 12.43% and 0.35% of the whole study area. The restoration area was mainly distributed in high altitudes of the Burhan Budai Mt., Qimantag Mt., Ela Mt., Qaidam Mt. and Zongwulong Mt. surrounding areas of the Donggi Conga Lake and core areas of oasis. The degradation area was mainly distributed in margins of oasis, especially in the middle and lower reaches of the Qaidam and Leningrad rivers. 4) Vegetation NDVI was most positively related with average temperature (January to May) and available precipitation (May to August). The significant positive region between vegetation growth and temperature occupied about 8.36% of the vegetated lands and was mainly distributed in core areas of oasis and high latitude mountains. The significant positive region between vegetation growth and available precipitation made up about 30.95% of the vegetated lands and was mainly distributed in low latitude mountains and mountain valleys. Vegetation growth was more sensitive to hydrological conditions than to thermal conditions. 5) Vegetation growing season extension and growth acceleration were the main reasons for vegetation restoration in the Qaidam Basin. Warmer and wetter climate was the main driving force to promote vegetation growth in the Qaidam Basin. 6) The Hurst index of NDVI time series showed vegetation restoration was persistent. It is expected that promotion in vegetation growth will expand to the most parts of the region. This finding not only underlines the importance of temperature for vegetation growth in high latitudes, but also verifies the effects of precipitation on vegetation growth in low attitudes.
It is significant to make a reasonable assessment of ecological risk to optimize the landscape pattern, establish the ecological risk alarm mechanisms, minimize the risk of ecological environment and maintain the ecological function in river basin. The study, based on the remote sensing data of 1987, 2000 and 2010, chooses the typical arid inland river basin as the subject, divides the study area into 20 km×20 km risk area and analyzes the temporal-spatial distribution pattern of ecological risk in Shiyang River Basin. Proceeding from the structure of landscape ecological system, the landscape disturbance degree index, the fragile index and the loss degree index are used to build the integrated ecological risk index (ERI) in the study with the help of spatial analysis of GIS. The results show that: 1) Great changes of landscape have taken place in the study area during 1987－2010, arable, woodland and grassland area have respectively reduced by 2.46×104 hm2, 4.77×104 hm2 and 12.73×104 hm2, while the residential land, water and unused land area have increased by 1.79×104 hm2, 2.58×104 hm2 and 15.59×104 hm2, which mean that the predominant of arable land, woodland and grassland decrease gradually, while the predominant of water, unused land and residential land increase gradually. 2) According to scope of ERI, 5 ecological risk grades are separated by ‘natural breaks’. If 0.12 ≤ERI ≤0.17, then the ecological risk grade is extremely low; if 0.17 <ERI ≤0.22, the ecological risk grade is low; if 0.22< ERI ≤ 0.27, the ecological risk grade is medium; and if 0.27
Polder is an important geographic unit of the water net plain areas in South China, the study of the polder ecosystem service functions is of great significance to the optimization of land use, ecological environmental protection and restoration. This study selected polders in the Western Taihu Basin as a case and calculated four types of ecosystem services functions in terrestrial ecosystems including water regulation, environmental purification, soil conservation and habitat maintenance. The results show: 1) The polder terrestrial ecosystem can regulate water amount of 43.71×108 m3, reduce a total nitrogen of 6079.72 t, and a total phosphorus of 734.99 t, as well as retain 150.76×104 t of soil per year. The landscape composite index ranges from 0.96 to 1.11, reflecting relative great value of service. 2) The total quantity of terrestrial ecosystem service functions have difference in space, as well as the amount of per unit area. From the total quantity, the ecosystem service function of Yixing, Liyang, and Jintan is higher, but for Dantu, Danyang and Wujin, it is lower. Topography and water distribution are the main reasons for the differences. From the amount of unit area, Dantu and Danyang are high, Liyang, Jintan and Yixing are at a general level, Wujin is the minimum. The land use patterns in the polders are the main reasons for the differences. 3) The management and recovery of ecosystem service functions in polders should refer to the results of assessment and be suited to the local conditions. The counties which have strong ecosystem service functions should bring into playing their advantages. And certain measures should be taken to restore the weak ecosystem service functions. 4) The study has reference value for the ecological environmental protection and improvement and the optimization of land use in polders.
In recent years, eco-water requirement has been a new and hot spot in the study of ecology, hydrology and science of water resources. In this study, an eco-hydrological model is constructed to simulate the vegetation eco-water in the Yellow River Basin, China. The structure of vegetation ecological water during a series of land use changes in the Yellow River Basin were studied by using a combination of Remote Sensing and GIS technology, along with the meteorological data and in situ field survey, vegetation and soil texture data. The results show that: in terms of interannual changes, the vegetation ecological water fluctuations are mainly affected by climatic factors such as precipitation, the vegetation ecological water of the Yellow River Basin in the 1960s and 1980s were more than the 1970s and 1990s, and in 2000, vegetation ecological water consumption was 263.5 mm; the maximum value of vegetation ecological water was in June, July and August; in terms of vegetation types, grassland had the minimum value, followed by shrubland, and the largest was woodland; and in terms of water resources division, the mainstream of the Lanhe River Basin had the smallest (240 mm) and the Yiluo River Basin had the largest (563.1 mm) green water flows, respectively. Among the basins, the mainstream of the Lanhe River Basin, the mainstream of the Helong River Basin, the Inner-flow Section, the Huangshui River Basin, the mainstream of the Long-Lan River Basin, the upwards section of the Longyang Gorge and the Taohe River Basin generally had less than 400 mm of green water flow. In contrast, the Fenhe River Basin, the lower Yellow River Basin, the Jinghe River Basin, the Bei Luohe River Basin, the Qinhe River Basin, the Weihe River Basin, the mainstream of the Sanhua River Basin and the Yiluo River Basin generally had over 400 mm of green water flow.
Based on the meterological monthly rainfall dataset of 97 stations and ISCCP D2 data, using the SVD, statistical analysis and synthetic analysis methods, the relationships between nimbostratus, altostratus, deep convective cloud and precipitation and rain days are analyzed for 85 stations in Southwest China during summer of 1984 to 2005. The research results show that the summer nimbostratus is positively correlated with precipitation and rain days in Guizhou and Chongqing, especially the correlation coefficient with rain days reaches as high as 0.73. Except western and central Yunnan, there are obviously positive relations between summer altostratus and precipitation and rain days in the remaining parts of Southwest China, and the correlation coefficient is consistent with that of nimbostratus with percipitation and rain days. The results reflect that the pattern of altostratus and nimbostratus coexistence may favor the flood of those areas. At the same time, the correlation coefficients between deep convective cloud and precipitation and rain days are obvious in summer, and the correlation coefficients between deep convective cloud and precipitation is the bigger among those correlation coefficients and this correlation coefficient reaches as high as 0.86. It maybe because that deep convective cloud usually generates heavy rain showers and it makes a greater contribution to precipitation.
Water resource security is one of the core issues in resource and environment security and capacity in mountain areas. However, the model of water resource security assessment is still under-explored. Aiming at the current situation of water resource utilization and its temporal-spatial distributions in Yunnan Province, this paper establishes the index system for integration assessment on water resource security, and the analytic hierarchy process (AHP) method was used to compute the weights of the index system. So, a regional water resource security assessment model for Yunnan Province which could also be applied to other mountain areas was constructed. The result showed that water resources were unevenly distributed in time and space in Yunnan Province. Especially, the situation of water resources shortages is very serious in the central part where the conditions for social and economic development are better. Taking Kunming city for example, the water resources amount per capita was only 611 m3 under the assuring rate of 95%. The result of the assessment of water resources security showed that the difference was obvious in different place. The situation is better in south and southwest of Yunnan Province, but worse in the eastern part. The water resources security situation of Zhaotong city which is located in the northeastern part of the province is most serious, and the water resources security index is only 0.24, occupying 55.68% of the average value of Yunnan. Additionally, the Yi Autonomous Prefecture of Chuxiong which is located in central Yunnan Province has also a serious water shortage situation, mainly because of the climate of dry-hot valley. Water resources amount is the most important factor in water resources security in Yunnan Province, and the water shortages resulting from lack of water conservancy and drought is also very important in Yunnan Province. So, the following measures should be taken to enhance the resistance to drought and shortage of water resources capacity, such as strengthening the construction of water conservancy project, focusing on resolving the difficult problems in drinking water of people and large live stocks, improving farmland drought and flood insurance rate, paying attention to water environmental protection and development, and raising the utilization efficiency of water resources.
Northeast China (NC) is an important commodity grain base with strategic role in China. The variations of heat resources and their influences on agriculture in this region are greatly of concern under global warming conditions. Here the spatial and temporal distributions of variations and trends in heat resources are analyzed using datasets including homogeneous daily mean and minimal air temperature observations at 88 sites in NC during the period from 1960 to 2011. The Kendall-Theil robust line method is employed to estimate the slopes of the daily mean and minimal air temperature time series. The results show that accumulated temperature steadily above 0 ℃ increased by 25-95 ℃·d/10 a. The magnitude of increasing trends of the accumulated temperature in Three Rivers Plain area in NC are obviously larger than corresponding values in eastern mountain regions. The starting dates have been brought forward significantly in northern region (including Heilongjiang Province and Hulunbeier city and Xinganmeng area in Inner Mongolia Autonomous Region) and central region (including Jilin Province) of NC. The end date has been delayed significantly in northern part of NC. The number of days in which daily mean temperature steadily above 0 ℃ significantly increased by 2-4 d/10 a in northern and central parts of NC. The starting date of frost-free period has been significantly advanced and end date significantly delayed over most of NC. The number of frost free days significantly increased by 3-5 d/10 a. The accumulated temperature steadily over 10 ℃ increased by 30-110 ℃/10 a. This change is more prominent in northern part of NC than that in the southern of NC. The beginning date of daily mean air temperature steadily over 10 ℃ has been brought forward significantly in northern part of NC. The end date of daily mean air temperature steadily over 10 ℃ has been delayed significantly in southern part of NC. The effective growing seasons have been significantly lengthened by 2-4 d/10 a in northern and central part of NC.
Based on the daily data of the 13 meteorological stations in Hexi Area of Gansu Province from 1960 to 2009, we calculate the surface humid indexes of months and years, as well as the extreme drought and wet events frequency. With the method of ArcGIS IDW interpolation, Mann-Kendall, Morlet wavelet, etc, the temporal and spatial variations of extreme drought and wet events frequency are discussed, along with its impact factors. The results show: frequency of the overall trend of extreme drought and wet events fluctuantly decreased and increased from 1960 to 2009, respectively. After the year 2000, the trend became more obvious. The linear trend of the extreme drought and wet events frequency were about -0.009/a and 0.019/a, respectively. For spatial variation, the space difference of extreme drought event tendency was not obvious, especially during 2000-2009. In the 1960s, the area that extreme drought events increased corresponded to the area which extreme wet event reduced and the area that extreme drought events reduced corresponded to the area which extreme wet event increased. The abrupt change of extreme drought events frequency and extreme drought events frequency happened in 1998 and 1986, respectively. The annual mean wind speed, annual mean temperatures and relative humidity were the dominant factors in influencing extreme drought and wet events. The major cycle of extreme drought and wet events frequency were changing respectively with 19 a and 26 a.
Biological soil crusts (BSCs) are a widespread ground living cover in arid and semi-arid areas, which serve as an important ecological function in ecosystems of arid areas. To study its development characteristics and formation mechanism is the basis of effective management and utilization of these resources. Since the implementation of Grain for Green Project, the ecosystem of the Loess Plateau recovered extensively, and BSCs widely developed. However, the related researches are still deficient compared to those in the desert area. Due to the complexity of BSCs' development process and its spatial differentiation, many results of researches carrying out in desert areas can not be directly extrapolated to the loess area. In view of this, this paper chose a typical small watershed in the Loess Plateau, carried out a comprehensive survey, made lots of calculation and analysis by using GIS software, discussed the distribution characteristics of the BSCs and its influencing factors. The results showed that: 1) a total of 13 species of mosses belonging to eight genera under two families were found in the watershed. Of which Bryum algovicum Sendt., Bryum argenteum Hedw. and Didymodon constrictus (Mitt.) Saito. are most widely distributed. 2) Moss crust had the absolute advantage with an area of 4.18 km2, accounting for 60.7% of the watershed area, which are mainly distributed on the hill slope or slope top for less erosion or less disturbance, and better soil water conditions. 3) Soil, vegetation and slope aspect had a significant effect on the development of BSCs. Compared with the loess area, BSCs in sandy area had a high coverage and showed a continuous distribution. The development of BSCs under the tree and shrub vegetation was superior to those under herbaceous communities, and the vegetation coverage promoted first and then inhibited the development of BSCs (inflection point at 30% of the coverage). Overall, the coverage and thickness of the BSCs were greater on shady slope than those on sunny slope.
Based on the integrated research and statistical analysis on historical data,using the mean trophic level, this paper analyzed the variation characteristics of primary catch structure and its influencing factors. Results showed that there was an linear relationship between the mean trophic level of primary catch (Y) and the year (X) during 1956－2000 (Y = -0.008X+19.777; R = -0.710, n=41, Sig.=0.000), and that the mean trophic level of primary catch decreased with an average ratio of about 0.01 per year. Results also showed there was significant positive correlation between the freshwater input amount and the mean trophic level of primary catch, the mechanism of which was that freshwater input affected the fishery structure by changing the relative composition of the larvae of fishery species. In recent years, the increased N/P ratio and decreased concentration of silicon (Si) affected the fishery structure in the Bohai Sea via the transfer of the food chain. The change of biomass ratio between zooplankton and benthos corresponded well with the variation of ratio of fishery biomass of the pelagic food chain to that of the benthic food chain, indicating that the bottom-up effect played an important role in variation of catch structure in the Bohai Sea.
Information of forest vegetation types is very important for ecological planning, protection and construction. In this paper, we discussed a method to extract vegetation types from multi-temporal MODIS imageries in order to overcome the limitation of singletemporal imagery in identifying vegetation types. The forest vegetation was classified into five types: the evergreen and deciduous mixed forest, the evergreen broadleaf forest, the evergreen coniferous forest, the deciduous broadleaf forest and the deciduous coniferous forest in Sichuan Province. The multi-temporal MODIS feature data were selected based on analyzing the growth difference of the vegetation types through a year. The multi-temporal Normalization Different Vegetation Index (NDVI) was calculated using the red band and near infrared band of MODIS images acquired on January 9, February 26, April 22, July 19 and October 23, which were respectively presented as NDVI(1-9), NDVI(2-26), NDVI(4-22),NDVI(7-19) and NDVI(10-23).
The knowledge "NDVI(1-9) > T1 and NDVI(10-23) > T2" for evergreen forest was discovered by multi-temporal image analysis, which was used to formulate model of extracting the evergreen feature of forest. The knowledge"NDVI(7-19) > T3, NDVI(2-26)< T4 and NDVI(4-22)> T5"for deciduous forest was discovered, which was used to formulate model of extracting the deciduous feature of forest. The knowledge"NDVI(1-9) > T6 and B2 < T7"for coniferous forest was discovered, which was used to create model of extracting coniferous forest. B2 is near infrared band of MODIS images acquired on January 9. The evergreen feature, deciduous feature and coniferous forest were obtained by using the models, multi-temporal NDVI and B2. The five vegetation types were obtained by judging and combining evergreen feature, deciduous feature and coniferous forest. The overall accuracy was about 84%. The lowest accuracy of vegetation type was 76%. It was shown that the method proposed here is labor-saving and cost-effective, which is of high application value in investigating and monitoring vegetation types in large extent. It was also shown that forest vegetation covered 28.43% of the total area of Sichuan Province in 2005. According to their percentage, vegetation types arranged in descending order were the deciduous broadleaf forest, the evergreen coniferous forest, the evergreen broadleaf forest, the deciduous coniferous forest and the evergreen and deciduous mixed forest, and the percentages were respectively 32%, 29%, 18%, 14% and 7%. The vegetation type data are of important value in protecting and utilizing the forest vegetation in Sichuan Province.
Unlike traditional studies about the spatio-temporal characteristics and its evolution law of urban encroachment on cropland on landscape scale, this paper proposes agent-based Urban Encroachment on Cropland Dynamic Model (UECDM) from the micro-level, exploring in depth the mechanism and dynamics of urban encroachment on cropland from diverse perspectives, so as to bring forward sustainable development countermeasures for reconciling both balance. UECDM introduces viewshed analysis, which applies quantitative assessment results of the visual landscape to residential decision-making processes by simulating terrain and observation point. The model consists of cell automata layer of viewshed to fully characterize the various environmental elements along with their internal relations and agent layer containing the interactions among different kinds of agents, which takes account of human decision-making and self-organization of urban growth. It is applied to simulate and analyze the spatio-temporal dynamics of Tianjin's urban encroachment on cropland and validation follows. The Kappa coefficient is up to 0.795 and based on four landscape indices, the average relative error of the simulation result is about 3.86%, both indicating a high credibility of this model. Analysis of the simulation and prediction results of different periods indicates that the spatial pattern of Tianjin's urban encroachment on cropland is mainly outward expansion of the "pie" type as well as "satellite towns" of the "jump" type, which makes it possible to provide decision support for future urban development planning and cropland protection.
Snowmelt process is an important part in hydrological analyses. Many hydrology models have interduced snowmelt model in order to simulate the snowmelt processes in the catchment ranging from simple temperature-index method to sophisticated process-based model. In this paper, we make a comparison of the two approaches to identify the performances of temperature-index and process-based snowmelt approaches which coupled with the SWAT model in Juntanghu watershed of northern slope of Tianshan Mountains, Xinjiang, China. The result indicates insignificant differences between the temperature-index methods and physically energy budget based snowmelt approaches. The simulation performance from the original SWAT model in calibration period (2000-01-01-2004-12-31) was worse than that from the developed SWAT-JTH model; in validation period (2006-01-01-2010-12-31), the original SWAT model provided a better performance than the SWAT-JTH model. The simulation results are acceptable for snowmelt runoff simulation for both models. Through comparison, the structure of temperature-index method is simple and can achieve good simulation performance if the model is well calibrated. Although it is hard to meet the data requirement of the physically-based model in current observation and experiment approaches and some uncertainties associated with physical processes, there are some advantages for the physically-based model which can simulate the extreme weather conditions. In this study, the physically-based distributed snowmelt runoff model was developed and has a promising future.
As an important climate resource, near surface air temperature plays an essential role in driving the vegetation growth, monitoring agro-meteorological disasters and global change. The spatially continuous air temperature images, which can be better derived from remotely sensed data than interpolated of meteorological data from limited ground stations, are required as the important input parameters by several environmental models at the regional scale. To serve and support the scientific research and business work concerning the distribution of air temperature at regional scale, in this paper, we firstly introduced the main five categories of methods to estimate air temperature from remotely sensed thermal data, including simple statistical approaches, the advanced statistical approaches, the temperaturevegetation index (TVX), the method based on surface energy balance and the one based on temperature lapse rate. Then, the approaches of maximum, minimum and mean air temperatures estimation were discussed in more details, followed by the comparison of air temperature estimation at different temporal and spatial scales. Finally, the problems and prospects for remotely sensed estimation of air temperature were summarized.
