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| 1 | Spatial heterogeneity for grain size distribution of eolian sand soil on longitudinal dunes in the southern Gurbantunggut Desert显示文摘The grain size composition, distribution characteristics and spatial variation of eolian sand soil on distinct positions across two longitudinal dunes and interdune areas were studied by means of conventional grain size analysis and geostatistical methods. In the study, 184 samples of eolian sand soil from the 0-30cm layer were systemically collected and measured from two longitudinal dunes and interdunes in the southern Gurbantunggut Desert. The results show that the dominant grain sizes are fine and very fine sands, and the differences of grain size compositions between the distinct geomorphologic positions are significant. The contents of clay and silt are highest on the interdune areas and lowest on the crests, and higher on the leeward slopes than on the windward slopes. The contents of very fine and fine sands are highest on the windward slopes and lowest on the crests. The contents of medium, coarse and very coarse sands are lowest on the interdune lands, and highest on the crests, and are identical on the two slopes. The coarser sizes (φ1) and mean sizes (Mz) for eolian sand soil all have a varying tendency from fine to coarse sizes with interdune area → leeward slope → windward slope → crest, and the sorting (σ) are poorly to well sorted. The results of geostatistical analysis reveal that φ1, Mz and σ values are moderately to strongly spatially autocorrelated. The values of the spatially correlated ranges are φ1<σ | Qian, YiBing Wu, ZhaoNing Yang, HaiFeng Jiang, Chao | 2009 | Journal of Arid Land2009，1，1： | 9 |
| 2 | 我国耕地土壤相对湿度时空分异(英文)显示文摘Based on the data of relative soil moisture in 653 agricultural meteorological stations during the period of 1993-2013 in China, the characteristics and regularity of spatial and temporal variation of relative soil moisture in China's farmland were analyzed and discussed using geostatistical methods. The results showed that the relative soil moisture of China's farmland has shown a fluctuant increasing trend since 1993. The relative soil moisture of China's farmland is more than 60% in general, its distribution area has been expanded northward and westward with the summer monsoon since mid-April and began to shrink eastward and southward in late October. The value of relative soil moisture increases with the increase of soil depth. On an interannual scale, the relative soil moisture of farmland increased fastest in summer and autumn, and its variation range decreased with the increase of soil depth. The relative soil moisture was positively correlated with precipitation, and negatively correlated with potential evaporation and temperature. The correlation between relative soil moisture and various meteorological factors weakened as soil depth increased. The meteorological factors have a great influence on relative soil moisture of dry land in spring, summer and autumn and they also have a greater impact on relative soil moisture of paddy fields in winter. | 朱国锋 潘汉雄 张昱 郭慧文 雍磊磊 万巧卓 马惠莹 李森 | 2019 | Journal of Geographical Sciences2019，29，3： | 1 |
| 3 | Groundwater Nitrate Contamination and Driving Forces from Intensive Cropland in the North China Plain显示文摘High nitrate in groundwater is a serious problem especially in highly active agricultural areas.In this paper,the concentration and spatial distribution of groundwater nitrate in cropland area in the North China Plain were assessed by statistical and geostatistical techniques.Nitrate concentration in groundwater reached a maximum of 526.58 mg/L,and 47.2%,21.33%and 11.13%of samples had levels in excess of nitrate safety threshold concentration(50 mg/L)in shallow,middle-deep and deep groundwater,respectively.And NO-3 content significantly decreased with groundwater depth.Groundwater nitrate concentrations under vegetable area are significantly higher than ones under grain and orchard.And there are great differences in spatial distribution of nitrate in the North China Plain and pollution hotspot areas are mainly in Shandong Province.Based on both multiple regressions combined with principal component analysis(PCA),significant variables for nitrate variation in three types of ground water were found:population per unit area,percentage of vegetable area,percentage of grain crop area,livestock per unit area,annual precipitation and annual mean temperature for shallow groundwater;population per unit area and percentage of vegetable area for middle-deep groundwater;percentage of vegetable area,percentage of grain crop area and livestock per unit area for deep groundwater. | Jing LIU Chengjun ZHANG Peng LI Shunjiang LI Maoting MA Guoyin ZHANG Xianbiao GAO Changlin KOU Lihua JIANG Tongke ZHAO | 2019 | Asian Agricultural Research2019，11，9： | 1 |
| 4 | Seasonal Variation and Land-Use/Land-Cover Type Impacts on the Correlation of Urban Heat Island Intensity and Difference Vegetation Index with Satellite Data in Xi’an,China显示文摘 | ZHAO Wenting ZHU Xinming JIANG Guangxin GAO Zhiyuan | 2018 | Wuhan University Journal of Natural Sciences2018，23，5： | 0 |
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