Spatiotemporal characteristics,patterns and causes of land use changes in China since the late 1980s简

Land-use/land-cover changes （LUCCs） have links to both human and nature inter- actions. China＇s Land-Use/cover Datasets （CLUDs） were updated regularly at 5-year inter- vals from the late 1980s to 2010, with standard procedures based on Landsat TM／ETM＋ im- ages. A land-use dynamic regionalization method was proposed to analyze major land-use conversions. The spatiotemporal characteristics, differences, and causes of land-use changes at a national scale were then examined. The main findings are summarized as fol- lows. Land-use changes （LUCs） across China indicated a significant variation in spatial and temporal characteristics in the last 20 years （1990-2010）. The area of cropland change de- creased in the south and increased in the north, but the total area remained almost un- changed. The reclaimed cropland was shifted from the northeast to the northwest. The built-up lands expanded rapidly, were mainly distributed in the east, and gradually spread out to central and western China. Woodland decreased first, and then increased, but desert area was the opposite. Grassland continued decreasing. Different spatial patterns of LUC in China were found between the late 20th century and the early 21st century. The original 13 LUC zones were replaced by 15 units with changes of boundaries in some zones. The main spatial characteristics of these changes included （1） an accelerated expansion of built-up land in the Huang-Huai-Hai region, the southeastern coastal areas, the midstream area of the Yangtze River, and the Sichuan Basin; （2） shifted land reclamation in the north from northeast China and eastern Inner Mongolia to the oasis agricultural areas in northwest China; （3） continuous transformation from rain-fed farmlands in northeast China to paddy fields; and （4） effective- ness of the ＂Grain for Green＂ project in the southern agricultural-pastoral ecotones of Inner Mongolia, the Loess Plateau, and southwestern mountainous areas. In the last two decades, although climate change in the north affected the change in cropland, policy regulation and economic driving forces were still the primary causes of LUC across China. During the first decade of the 21st century, the anthropogenic factors that drove variations in land-use pat- terns have shifted the emphasis from one-way land development to both development and conservation. The ＂dynamic regionalization method＂ was used to analyze changes in the spatial patterns of zoning boundaries, the internal characteristics of zones, and the growth and decrease of units. The results revealed ＂the pattern of the change process,＂ namely the process of LUC and regional differences in characteristics at different stages. The growth and decrease of zones during this dynamic LUC zoning, variations in unit boundaries, and the characteristics of change intensities between the former and latter decades were examined. The patterns of alternative transformation between the ＂pattern＂ and ＂process＂ of land use and the causes for changes in different types and different regions of land use were explored.     

气候变化对海河流域主要作物物候和产量影响简

基于海河流域30 个气象站点1960-2009年的实测资料,分析该流域1960年以来农业气象指标的变化趋势,并利用VIP模型模拟分析大气CO₂浓度增加、温度、降雨和日照时数变化对作物产量的影响。结果显示：冬季温度的显著上升使冬小麦种植北界在50年间向北移动大约70 km;在品种和灌溉条件不变的前提下,小麦产量平均每10年上升0.2%~3.4%,其中CO₂浓度增加、温度、降雨及日照时数变化对其产量的影响分别为11.0%、0.7%、-0.2%和-6.5%;大气CO₂浓度增加的产量正效应大于日照时数减少的负效应。气候变化使夏玉米产量呈下降趋势（0.6%~3.8%/10年）,其中大气CO₂浓度增加、温度、降雨及日照时数变化对其产量的影响分别为0.7%、-3.6%、-1.0%和-6.8%,温度上升和辐射下降是玉米产量下降的主要原因。研究结果可为气候变化影响的评估和适应性对策制定提供科学依据。     

Changes in temperature extremes in the Yangtze River Basin, 1962–2011简

Based on daily maximum and minimum temperature observed by the China Mete- orological Administration at 115 meteorological stations in the Yangtze River Basin from 1962 to 2011, the methods of linear regression, principal component analysis and correlation analysis are employed to investigate the temporal variability and spatial distribution of tem- perature extremes. Sixteen indices of extreme temperature are selected. The results are as follows： （1） The occurrence of cold days, cold nights, ice days, frost days and cold spell du- ration indicator has significantly decreased by -0.84, -2.78, -0.48, -3.29 and -0.67 days per decade, respectively. While the occurrence of warm days, warm nights, summer days, tropi- cal nights, warm spell duration indicator and growing season length shows statistically sig- nificant increasing trends at rates of 2.24, 2.86, 2.93, 1.80, 0.83 and 2.30 days per decade, respectively. The tendency rate of the coldest day, coldest night, warmest day, warmest night and diurnal temperature range is 0.33, 0.47, 0.16, 0.19 and -0.07~C per decade, respectively （2） The magnitudes of changes in cold indices （cold nights, coldest day and coldest night） are obviously greater than those of warm indices （warm nights, warmest day and warmest night）. The change ranges of night indices （warm nights and cold nights） are larger than those of day indices （warm days and cold days）, which indicates that the change of day and night tem- perature is asymmetrical. （3） Spatially, the regionally averaged values of cold indices in the upper reaches of the Yangtze River Basin are larger than those in the middle and lower reaches. However, the regionally averaged values of most warm indices （except warm spell duration indicator） and growing season length in the middle and lower reaches are larger than those in the upper reaches. （4） The extreme temperature indices are well correlated with each other except diurnal temperature range.     

Combining LPJ-GUESS and HASM to simulate the spatial distribution of forest vegetation carbon stock in China简

It is very important in accurately estimating the forests＇ carbon stock and spatial distribution in the regional scale because they possess a great rate in the carbon stock of the terrestrial ecosystem. Yet the current estimation of forest carbon stock in the regional scale mainly depends on the forest inventory data, and the whole process consumes too much labor, money and time. And meanwhile it has many negative influences on the forest carbon storage updating. In order to figure out these problems, this paper, based on High Accuracy Surface Modeling （HASM）, proposes a forest vegetation carbon storage simulation method. This new method employs the output of LPJ-GUESS model as initial values of HASM and uses the inventory data as sample points of HASM to simulate the distribution of forest carbon storage in China. This study also adopts the seventh forest resources statistics of China as the data source to generate sample points, and it also works as the simulation accuracy test. The HASM simulation shows that the total forest carbon storage of China is 9.2405 Pg, while the calculated value based on forest resources statistics are 7.8115 Pg. The forest resources statistics is taken based on a forest canopy closure, and the result of HASM is much more suitable to the real forest carbon storage. The simulation result also indicates that the southwestern mountain region and the northeastern forests are the important forest carbon reservoirs in China, and they account for 39.82% and 20.46% of the country＇s total forest vegetation carbon stock respectively. Compared with the former value （1975-1995）, it mani- fests that the carbon storage of the two regions do increase clearly. The results of this re- search show that the large-scale reforestation in the last decades in China attains a signifi- cant carbon sink.     

Spatial and temporal variability in the net primary production of alpine grassland on the Tibetan Plateau since 1982简

Based on the GIMMS AVHRR NDVI data （8 km spatial resolution） for 1982-2000, the SPOT VEGETATION NDVI data （1 km spatial resolution） for 1998-2009, and observa- tional plant biomass data, the CASA model was used to model changes in alpine grassland net primary production （NPP） on the Tibetan Plateau （TP）. This study will help to evaluate the health conditions of the alpine grassland ecosystem, and is of great importance to the pro- motion of sustainable development of plateau pasture and to the understanding of the func- tion of the national ecological security shelter on the TP. The spatio-temporal characteristics of NPP change were investigated using spatial statistical analysis, separately on the basis of physico-geographical factors （natural zone, altitude, latitude and longitude）, river basin, and county-level administrative area. Data processing was carried out using an ENVI 4.8 platform, while an ArcGIS 9.3 and ANUSPLIN platform was used to conduct the spatial analysis and mapping. The primary results are as follows： （1） The NPP of alpine grassland on the TP gradually decreases from the southeast to the northwest, which corresponds to gradients in precipitation and temperature. From 1982 to 2009, the average annual total NPP in the TP alpine grassland was 177.2x1012 gC yrl（yr represents year）, while the average annual NPP was 120.8 gC m^-2 yr^-1. （2） The annual NPP in alpine grassland on the TP fluctuates from year to year but shows an overall positive trend ranging from 114.7 gC m^-2 yr^-1 in 1982 to 129.9 gC m^-2 yr^-1 in 2009, with an overall increase of 13.3%; 32.56% of the total alpine grassland on the TP showed a significant increase in NPP, while only 5.55% showed a significant decrease over this 28-year period. （3） Spatio-temporal characteristics are an important control on an- nual NPP in alpine grassland： a） NPP increased in most of the natural zones on the TP, only showing a slight decrease in the Ngari montane desert-steppe and desert zone. The positive trend in NPP in the high-cold shrub-meadow zone, high-cold meadow steppe zone and high-cold steppe zone is more significant than that of the high-cold desert zone; b） with in- creasing altitude, the percentage area with a positive trend in annual NPP follows a trend of ＂increasing-stable-decreasing＂, while the percentage area with a negative trend in annual NPP follows a trend of ＂decreasing-stable-increasing＂, with increasing altitude; c） the varia- tion in annual NPP with latitude and longitude co-varies with the vegetation distribution; d） the variation in annual NPP within the major river basins has a generally positive trend, of which the growth in NPP in the Yellow River Basin is most significant. Results show that, based on changes in NPP trends, vegetation coverage and phonological phenomenon with time, NPP has been declining in certain places successively, while the overall health of the alpine grassland on the TP is improving.     

The provincial pattern of the relationship between urbanization and economic develop-ment in China简

Understanding the relationship between China＇s urbanization and economic de- velopment on a provincial scale is of profound theoretical and practical significance. Based on data from 124 countries or regions throughout the world and 31 provinces or autonomous regions in China, applying improved methods using the quadrant map approach, this paper analyzed the spatial pattern of the relationship between China＇s urbanization and economic development level. The study identified the following results. （1） The 31 province-level re- gions fall into six categories： only one region is in the category of sharp over-urbanization, 3 regions are in medium over-urbanization, 11 slight over-urbanization, 8 basic coordination, one medium under-urbanization, and seven slight under-urbanization. （2） There are signifi- cant regional differences on a provincial scale in the relationships between urbanization and the level of economic development. （3） The provincial pattern of urbanization and economic development is significantly different between east and west. The eastern coastal areas are mainly over-urbanized, while the central and western regions are mainly under-urbanized. （4） The relationship between urbanization and the level of economic development is similar to the Matthew effect. Hence, two important insights are proposed. First, the phenomenon of over-urbanization in some developed regions should be viewed with some concern and vigi- lance. Second, urbanization needs to be speeded up moderately in the central and western regions.     

Sources and transport of organic carbon from the Dongjiang River to the Humen outlet ofthe Pearl River,southern China简

Transport of organic carbon via rivers to estuary is a significant geochemical proc- ess in the global carbon cycle. This paper presents bulk total organic carbon （TOC） from the Dongjiang catchment to the adjacent Humen outlet, and discusses the applicability of 613C and ratio of carbon to nitrogen （C/N） as indicators for sources of organic matter in the surface sediments. Survey results showed that organic carbon concentration in summer were higher than in the winter. An elevated trend of TOC occurred along the river to the Humen outlet in both surveys, and the highest mean values of dissolved and particular organic carbon （DOC-279 μmol L-1 and POC-163μmol L-1） were observed in the urban deltaic region in summer flood flow. Winter samples had a wide range of b＇13C and C/N （5-3C -24.6%o to -30.0%o, C/N 4-13）, and summer ones varied slightly （8-3C -24.2%o to -27.6%0, C/N 6-18）. As results suggest that POC in the three zones of upstream-delta-outlet dominantly came from riverbank soil, phytoplankton and agricultural C3 plants in winter, whereas main sources were from the riverbank and mangrove soil in summer. Moreover, anthropogenic sewage inputs had 11% and 7% contribution to POC in the deltaic and outlet. Transport accompanied with seasonal freshwater variation, phytoplankton production and degradation, and removal be- havior caused variation of organic carbon concentration. The results also discovered that TOC export bulk in Dongjiang was approximately one quarter of Humen flux in the dry flow, and anthropogenic activity significantly impacted the river export contribution.     

Livestock-carrying capacity and overgrazing status of alpine grassland in the Three-RiverHeadwaters region,China简

The Three-River Headwaters region in China is an ecological barrier providing en- vironmental protection and regional sustainable development for the mid-stream and down- stream areas, which also plays an important role in animal husbandry in China. This study estimated the grassland yield in the Three-River Headwaters region based on MODIS NPP data, and calculated the proper livestock-carrying capacity of the grassland. We analyzed the overgrazing number and its spatial distribution characteristics through data comparison be- tween actual and proper livestock-carrying capacity. The results showed the following： （1） total grassland yield （hay） in the Three-River Headwaters region was 10.96 million tons in 2010 with an average grassland yield of 465.70 kg/hm2 （the spatial distribution presents a decreasing trend from the east and southeast to the west and northwest in turn）; （2） the proper livestock-carrying capacity in the Three-River Headwaters region is 12.19 million sheep units （hereafter described as ＂SU＂）, and the average stocking capacity is 51.27 SU [the proper carrying capacity is above 100 SU/km2 in the eastern counties, 60 SU/km2 in the cen- tral counties （except Madoi County）, and 30 SU/km2 in the western counties]; and （3） total overgrazing number was 6.52 million SU in the Three-River Headwaters region in 2010, with an average overgrazing ratio of 67.88% and an average overgrazing number of 27.43 SU/km2 A higher overgrazing ratio occurred in Tongde, Xinghai, Yushu, Henan and Z~kog. There was no overgrazing in Zhiduo, Tanggula Township and Darlag, Qumerleb and Madoi. The re- mainder of the counties had varying degrees of overgrazing.