A total of 21 typical coupled large samples were chosen from areas in the nature reserves and their surroundings on the Tibetan Plateau (TP) with large-sample-comparison method (LSCM). To evaluate the protection effectiveness of the nature reserves, we compared the alpine grassland net primary production (NPP) of these coupled samples and analyzed the differences between them before and after their establishment as protected areas. The results show that: (1) In view of alpine grassland NPP, the ecological and environmental conditions of most nature reserves were more fragile than those of their surrounding areas and also lower than the average values for the TP. (2) Of the 11 typical nature reserves selected, the positive trend of NPP in Manzetang is the most significant, while in Taxkorgan, the trend is not obvious. Moreover, with the exception of Selincuo, the annual NPP growth rate in nature reserves covered by meadow and herbaceous wetland is higher than that in nature reserves consisting of steppe and desert grassland. (3) Some notable findings existed in 21 typical coupled samples: (a) After the establishment of nature reserves, the annual NPP increase rate in 76% of samples inside nature reserves and 82% of samples inside national nature reserves are apparently higher than that of corresponding samples outside nature reserves. (b) The ecological protection effectiveness in Central Kunlun, Changshagongma, Zoige Wetland, and Siling Co nature reserves is significant; in most parts of the Three Rivers' Source and Qiangtang nature reserves, the protection effectiveness is relatively significant, while in south-east Manzetang and north Taxkorgan, the protection effectiveness is not obvious. (c) The ecological protection effectiveness is significant in nature reserves consisting of meadow; however, it is weak in nature reserves covered by steppe.
This paper presented a new conceptual framework by taking account of heat stress, social vulnerability, and population exposure. Meanwhile, an index system combining environmental data, demographics data and socioeconomic data has been built for the quantitative assessment of county-level heat stress risk pattern of China. The counties with the greatest vulnerability scores contain the Tarim Basin in Northwest China, Yudong Plain and Huaibei Plain in North China, Sichuan Basin in Southwest China, Jianghan Plain and Dongting Lake Basin in Central China, and Pearl River Basin in South China. The hot spots of heat stress risk are located in Jianghan Plain and Dongting Lake Basin in Central China, Sichuan Basin in Southwest China, the junction of Jiangsu, Zhejiang and Shanghai in East China, and Pearl River Basin in South China, especially the Pearl River Delta Region. The hot spots of vulnerability are located in counties of high heat stress or high social vulnerability level, while the hot spots of risk mainly consist of metropolitan areas with dense population and advanced economic level. The results of dominant factor partition show that heat stress dominant areas are mainly located in basins or plains which are more prone to high temperature, social vulnerability dominant areas are mainly located in less developed counties, and population exposure dominant areas are mainly located in coastal counties with dense population.
As the city social-ecological system was regarded as the risk assessment target, a 3D framework of ecological adaptive cycle was built, which extended the landscape ecological risk assessment indicators to the potential-connectedness-resilience 3D criteria from the former landscape index level. Emphasis was placed on the principle of static spatial pattern with interactive dynamic trend from a geographical spatial analysis view. It was believed that the 3D framework could describe the pattern-process interaction with specific landscape elements much more clearly. Taking Shenzhen city as a study area, this study adopted the 3D framework of ecological adaptive cycle in building a landscape ecological risk assessment index system with the help of GIS spatial analysis method. Different scenarios were established based on the ordered weighted averaging (OWA) algorithm in the risk assessment. The results show that among the three scenarios, the concrete value of landscape ecological risk showed a similar distribution trend that the Dapeng Peninsula had the lowest landscape ecological risk in Shenzhen city; Yangtai Mountain and Bijiashan Park showed relatively low risks in the city area, even though the risks in each scenario were specifically different. This indicated that the choice of the specific threshold in "development" or "protection" largely depended on the city development strategy created by decision makers under current cognition. The emphasis of scenario tradeoff was extracting the risk and uncertainty interval rather than an optimal value. The development or protection methods through each of the specific planning objectives would be the ultimate goal of the ecological risk assessment at a regional scale. The evaluation in this study improved the landscape ecological risk assessment indices and methods based on the adaptive cycle concept, which reflected the spatiotemporal dynamics and exposure disturbed by human interference. Furthermore, the preference transform in OWA method reduced the uncertainty caused by the subjective risk assessment, which could improve the theoretical basis as well as maneuverability in urban planning. This study not only extended the landscape ecological risk assessment to spatial-temporal integration perspective, but also made a significant improvement in ecological risk assessment of landscape indicator system. Therefore, the results of this study could offer a powerful quantitative support for landscape development and protective measures effectively, such as city construction and demarcation of ecological control line.
Human activity intensity is a synthesis index for describing the effect and influence of land surface. This paper presents the concepts of human activity intensity and construction land equivalent, builds an algorithm model for human activity intensity, and establishes a method for converting different land use/land cover types into construction land equivalent as well. An application in China based on the land use data from 1984 to 2008 is also included. The results are shown as follows: (1) Human activity intensity is defined as the degree of land use, transformation and exploitation by human beings. It is an effective way to determine the construction land equivalent coefficient of different land use/land cover types by taking construction land equivalent as a basic unit and identifying the alteration of land surface natural properties caused by human activities. The application in China and correlation analysis with population density indicated that it is feasible to take the ratio of the construction land equivalent area to the total area as an indicator of human activity intensity. (2) We adopted a two-level method of eight attribute labels to construct general standard of converting different land use types into construction land equivalent, and establish a method for calculating the coefficient of construction land equivalent. We also built a coefficient table for constructing land equivalent of 49 land use types based on the latest land use classification system. (3) The human activity intensity in China increased from 7.63% in 1984 to 8.54% in 2008. It could be generally divided into five levels: very high, high, medium, low and very low, according to the human activity intensity at county level in 2008, which is rated by over 27%, 16%-27%, 10%-16%, 6%-10% and below 6%. The human activity intensity in China was spatially split into eastern and western parts by the line of Helan Mountain-Longmen Mountain-Jinghong; the eastern part was characterized by the levels of very high, high and medium, while the western part was featured by the low and very low levels.
In this paper, the smooth crops growth NDVI curves from 1999 to 2013 were rebuilt by the S-G techniques, with the combination of 10-day SPOT time-series NDVI data from 1998 to 2013 with the spatial resolution of 1 km and land use data in 2000, 2005 and 2010. Spatial and temporal changes of multiple cropping index (MCI) from 1999 to 2013 in China were extracted by a difference algorithm. The results are as follows: (1) The total precision of sample validation based on visual identification was 91.95%, and the slope of linear regression of the MCI between remotely sensed data and statistical data was 0.73 (R=0.775, P<0.001), suggesting that this method is an effective way to extracting spatial information of the MCI for agricultural and land management. (2) From the north to the south of China, the MCI gradually becomes more and more complex. The percentages of the single, double and triple cropping system occupying the total cropland were 43.48%, 56.39% and 0.13%, respectively in China. (3) From 1999 to 2013, the overall cropping index increased with an annual rate of 1.29% (P<0.001) in China, while it exhibited significant differentiation in different zones. The area with a significant decreasing trend occupied 2.12% (P<0.1) of the total cropland and was found at the borders of Hebei, Beijing and Tianjin, central Anhui, the Chengdu Plain, the Poyang Lake Plain, northern and southern Hunan, and central Guangxi. The area with a significant increasing trend occupied 16.40% (P<0.1) of the total cropland and was distributed in eastern Gansu, the Weihe Plain of Shaanxi, western Shanxi, the borders of Hebei, Shandong and Tianjin, the Shandong Peninsula, and the Jianghan Plain. (4) Terrain and economic development level played an important role in the regional differentiation of MCI change. There is a positive correlation between terrain and the inter-annual changes of MCI, and a negative correlation between economic development level and the inter-annual changes of MCI.
Based on economic geography perspective and county-level statistical data, this paper examined the temporal-spatial processes of herbivorous livestock industry and its environmental pressure using GIS technology and mathematical modeling approach. The results showed that: (1) The whole breeding quantity of herbivorous livestock increased obviously, but there were significant differences between breeds. From 1978 to 2012, the quantity of herbivorous livestock increased by 92.5%, and the order of breading quantity is beef cattle > mutton sheep > cow. (2) The number of counties with an increasing herbivorous livestock quantity was larger than that with a decreasing quantity. Besides, the breeding quantity in northern China grew significantly faster than that of southern China, presenting a pattern of "the north is more active than the south". (3) Spatial Dubin-Model (SDM) showed that five indexes including per capita grain yield, productive land area proportion, per capita available income of downtown, agricultural mechanization level, agricultural labor productivity, and policies had positive effects on the development of herbivorous livestock breeding, while per capita GDP, urbanization level and non-agricultural income proportion had significantly negative effects. (4) Based on the self-organizing feature map (SOM), herbivorous livestock breeding counties in China could be divided into six types, and different measures should be taken for different priorities.
Based on the records of water level at hydrological points and flood report in the Yellow River Basin during the Qing Dynasty, we reorganized the data record of Wanjintan water level concerning Shanxian County (named Shanzhou in the Qing Dynasty, presently Sanmenxia City now), and rebuilt the areal precipitation change sequence in the middle Yellow River from May to October between 1765 and 2010. In this study, accumulative anomaly methods, wavelet analysis, and moving t-test technique were used to examine the characteristics of flood in different phases, periodicities, and mutability of precipitation in the past 246 years. Results showed that precipitation increased rapidly from 1816 to 1863, 1902 to 1918, and 1938 to 1989; the precipitation decreased from 1765 to 1815, 1864 to1901, and 1919 to 1937. According to the wavelet analysis, five types of time scales of the areal precipitation were identified, with the average periods being 72.7a, 46.8a, 30.3a, 22.5a and 11.2a, respectively. By the method of moving t-test technique, three periods of the abrupt change were found in the sequence of areal precipitation, namely 1824-1826, 1856-1874, and 1933-1937. The sequence tendency of a decadal areal precipitation coincided with other alternative indicators, which reflected the precipitation sequence alignment and external factors. The corresponding period including different phases, such as the 1810s, 1840-1850s, 1880-1900s, 1920s, 1970s and 1990s. It is shown that the reconstruction results were consistent on the basis of proxy data from historical documents and natural indicators, and that there were a lot of uncertainties in historical climate change.
Based on the boundary data of lakes, some moderate-high resolution remote sensing datasets including MODIS and Landsat TM/ETM+ images and the meteorological data, the spatial-temporal variations of lake ice in the Hoh Xil region during the period 2000-2011 are analyzed by using RS and GIS technology. And the factors affecting the lake ice phenology are also discussed. Some conclusions can be drawn as follows. (1) The freeze-up start (FUS) and freeze-up end (FUE) of lake ice appears in late October - early November, and mid-November - early December, respectively. The duration of lake ice freeze-up is about half a month. The time of break-up start (BUS) and break-up end (BUE) of lake ice is relatively dispersed, and appears in late April - early June, and early May - early June, respectively. The ice duration (ID) and the complete ice duration (CID) of lakes are 196 days and 181 days, respectively. (2) The phenology of lake ice in the Hoh Xil region changed dramatically in the last 10 years. Specifically, the FUS and FUE time of lake ice showed an increasingly delaying trend. In contrast, the BUS and BUE time of lake ice presented an advance. This led to the reduction of the ID and CID of lake ice. The average rates of ID and CID were -2.21 d/a and -1.91 d/a, respectively. (3) The variations of phenology and evolution of lake ice are the results of local and climatic factors. The temperature, lake area, salinity and shape of the shoreline are the main factors affecting the phenology of lake ice. (4) The spatial process of lake ice freeze-up is contrary to its break-up process. The type of lake ice extending from one side of lakeshore to the opposite side is dominant in the Hoh Xil region.
Based on the 0.5°×0.5° daily gridded precipitation dataset and observations at meteorological stations released by the National Meteorological Information Center, the interannual variation of areal precipitation in the Qilian Mountains during 1961-2012 is investigated using principal component analysis (PCA) and regression analysis, and the relationship between areal precipitation anomaly and drought accumulation intensity is analyzed. The results indicate that the spatial distribution of precipitation in the Qilian Mountains can be well reflected by the gridded dataset. The gridded data-based precipitation in mountainous regions is generally larger than that in plain regions. Generally, there is more precipitation in the eastern section of the mountain range than in the western section. The annual mean areal precipitation in the Qilian Mountains is 724.9×108m3, and the seasonal means in spring, summer, autumn and winter are 118.9×108m3, 469.4×108m3, 122.5×108m3 and 14.1×108m3, respectively. Summer is a season with most areal precipitation, being approximately 64.76%. The areal precipitation in summer, autumn and winter shows an increasing trend, while spring presents a decreasing trend. Among the four seasons, summer has the largest trend magnitude of 1.7×108 m3 per year.
：Based on the empirical sediment transport equation that reflects the characteristics of "more input, more output" for sediment-laden flow rivers, a general sediment transport expression was developed, which takes into account the effects of upstream sediment input, previous cumulative erosion and sedimentation, critical water volume for sediment initiation and the differences of sediment sizes between the main stream and its tributaries. Then, sediment load equations of non-flood and flood seasons for the sub-reaches from Bayangaole to Sanhuhekou and from Sanhuhekou to Toudaoguai, as well as the whole Inner Mongolia reach from Bayangaole to Toudaoguai, were obtained based on measured data from 1952 to 2010. Furthermore, the corresponding erosion and sedimentation and the cumulative values at each river reach were calculated using the proposed sediment transport equations for the period from 1952 to 2010 according to the principle of sediment conservation. Comparisons between the calculated and measured values using the proposed sediment load equations for the sub-reaches and the whole reach show that the calculated sediment load and erosion and sedimentation and corresponding cumulative values in the non-flood and flood seasons were in good agreement with measurements; the determination coefficient R2 between the calculated and measured sediment load is about 0.93 and 0.97 for the non-flood and flood season, respectively; the determination coefficient R2 between calculated and measured the erosion and sedimentation for the non-flood and flood season is about 0.80 and 0.90; and the R2 between the calculated and measured cumulative erosion and sedimentation is about 0.94 and 0.99. It is obvious that the agreement of cumulative erosion and sedimentation was higher than that of the corresponding annual values, and the agreement of flood seasons was higher than that of non-flood seasons. These results indicated that the proposed methods can be applied to calculate the sediment load and erosion and sedimentation in the non-flood and flood seasons; and they can provide a scientific basis for the analysis of sediment load and the long-term trend of sediment deposition in the Inner Mongolia reach of the Yellow River.
Field archaeological investigations were carried out in the Jianghan Plain in the middle reaches of the Changjiang River. Based on the integrated study with a comparative analysis for characteristics of the modern flood sediments, multidisciplinary approaches such as the AMS14C and archaeological dating, micromorphology of zircon, grain size, magnetic susceptibility and geochemistry are conducted to identify paleoflood sediments archived at the Zhongqiao Site. The results indicate that three paleoflood events (i.e. 4800-4597 cal. a BP, 4479-4367 cal. a BP & 4168-3850 cal. a BP) occurred at the Zhongqiao Site. Comparisons of paleoflood deposit layers at numerous Neolithic sites show that two Holocene extraordinary paleoflood events occurred over the Jianghan Plain area at approximately 4900-4600 cal. a BP (i.e. mid-late Qujialing cultural period) and 4100-3800 cal. a BP (i.e. from late Shijiahe cultural period to the Xia Dynasty). Further analysis of the environmental background for the paleoflood occurrences suggested that there was great climate variability between approximately 5000-4500 a BP and ca 4000 a BP. These two paleoflood events were closely related with the expansion of Jianghan lakes driven by the climatic change, and influenced the rise and fall of regional Neolithic Culture. Other evidences also suggested that intensified discrepancy between social development and environmental change processes (especially the hydrological process) in the end of Shijiahe cultural period might be the key factor leading to the collapse of Shijiahe Culture. The severe extraordinary floods related to the climatic anomaly at ca 4000 a BP and political conflicts from internal or other cultural areas all accelerated the collapse of the Shijiahe Culture. These results gave us a better understanding of the climate change at ca 4000 a BP, and also provide evidence for the prehistoric flood events in the Great Yu age, which is considered to be the turning point from the Neolithic Age to the Bronze Age in China.
In this study, palaeoflood hydrological and sedimentary investigations were carried out in the Yiluohe River basin. Typical loess-soil stratigraphy of the Holocene period was identified at the Longmenxia (LMX) site in the Yihe River basin. Based on the analysis of sedimentary characteristics, magnetic susceptibility and particle-size distribution, the five flood slackwater deposits were identified and interbedded into the loess-soil stratigraphy. By the stratigraphic correlation and the optically stimulated luminescence method (OSL), the four episodes of flooding events occurred at 3100-3000 a BP, 1800-1700 a BP, 770-610 a BP and 420-340 a BP, respectively, namely at the end of the mid-Holocene Climatic Optimum and the beginning of the late Holocene, the dynasties of Eastern Han to Western Jin, Song-Yuan and the Ming-Qing, respectively. These flooding events might include the AD223 and 1761 flooding events and they well corresponded to the phase of the Holocene monsoonal shift, climatic abrupt change and climatic decline. The flooding peak stages were estimated with the elevations and the depositional depths of the SWD. According to the flood peak stages and hydraulic parameters, the peak discharges were reconstructed at 14100-15800 m3/s with the slope-area method. The reconstructed peak discharges of the flooding events are much more than those of the gauged modern floods at the Longmenxia gauge station in the middle reach of the Yihe River.
Papers related to the classification and revisions aim to examine the spatial and temporal differentiation of geographical elements based on assessment indicators. The main contents include: establishing standards for reasonable classification and revisions, making revisions for geographical elements in a study area according to different levels of assessment indicators, and analyzing the results of classification and revisions in a comprehensive way.
