荒漠河岸胡杨(Populus euphratica)树干液流的时滞效应

以2012年4—9月树干液流速率与环境因子的实测数据,分析了荒漠河岸胡杨(Populus euphratica)树干液流的时滞效应。结果表明:不同月份胡杨树干液流速率对不同环境因子的时滞不同;4—9月,胡杨树干液流速率峰值时间比太阳辐射峰值时间晚约1h,比空气温度峰值时间早约1h,比水汽压差峰值时间早约2h,比空气相对湿度谷值时间早约2h;对影响胡杨树干液流速率的环境因子进行了主成分分析,发现胡杨树干液流速率与1h以前的第1主成分、第2主成分相关性最高,相关系数分别为0.864、0.875;对错位前后胡杨树干液流速率与环境因子进行多元线性回归分析发现,在胡杨树干液流的数值模拟中,考虑液流相对于环境因子的时滞效应可以提高模型的拟合精度。     

Capacity of soil loss control in the Loess Plateau based on soil erosion control degree

The capacity of soil and water conservation measures, defined as the maximum quantity of suitable soil and water conservation measures contained in a region, were determined for the Loess Plateau based on zones suitable for establishing terraced fields, forestland and grassland with the support of geographic information system (GIS) software. The minimum possible soil erosion modulus and actual soil erosion modulus in 2010 were calculated using the revised universal soil loss equation (RUSLE), and the ratio of the minimum possible soil erosion modulus under the capacity of soil and water conservation measures to the actual soil erosion modulus was defined as the soil erosion control degree. The control potential of soil erosion and water loss in the Loess Plateau was studied using this concept. Results showed that the actual soil erosion modulus was 3355 t?km^-2?a^-1, the minimum possible soil erosion modulus was 1921 t?km^-2?a^-1, and the soil erosion control degree was 0.57 (medium level) in the Loess Plateau in 2010. In terms of zoning, the control degree was relatively high in the river valley-plain area, soil-rocky mountainous area, and windy-sandy area, but relatively low in the soil-rocky hilly-forested area, hilly-gully area and plateau-gully area. The rate of erosion areas with a soil erosion modulus of less than 1000 t?km^-2?a^-1 increased from 50.48% to 57.71%, forest and grass coverage rose from 56.74% to 69.15%, rate of terraced fields increased from 4.36% to 19.03%, and per capita grain available rose from 418 kg?a^-1 to 459 kg?a^-1 under the capacity of soil and water conservation measures compared with actual conditions. These research results are of some guiding significance for soil and water loss control in the Loess Plateau.     

第四纪环境研究新理论

On the basis of extensive survey to the Quatemary paleosols, soils and weathering layers in the vast northern China and the Loess Plateau, we found some unusually special phenomena of chemical components such as unsuccessive illuvium, twin illuviums, unusually thick illuvium and multi-illuviums etc. According to the analysis on the content of CaCO3 and the data of penetrating experiment, a new theory of illuvial depth or removal depth of CaCO3 in weathering and leaching belt was constructed, which indicates that the time of CaCO3 removing to the illuvial depth is very short,and the effect of time factor on illuvial depth can be ignored. The theory can be taken as a credible foundation for studying many geological and geographical problems in weathering and leaching belt.When the illuvial depth of CaCO3 iS bigger than the thickness of developing belt of soil or paleosol, it can be determined that the paleosol has turned into weathering crust. When the illuvial depth of CaCO3 is bigger than the thickness of paleosol, paleosol is leaching moderately acid soil. When two, three layers or unusually thick CaCO3 illuviums exist in the same weathering section or at the bottom of the same paleosol, there were two or more periods forming paleosol and corresponding climatic stages at that time. On the basis of the equation of relationship between mean annual rainfall (y) and illuvial depth of CaCO3 (x) (y = 305.5x 168.5) determined in the paper, mean annual precipitation during the development of paleosol can be calculated.     

Numerical Experiments of Meiyu(Baiu) Rainfall by Quasi-Lagrangian Limited Area Model with Terrain

In this paper, a 10-level Quasi-Lagrangian Limited Area Model is used to simulate the process of Meiyu(Baiu) front of 1979. Some physical processes, such as large-scale condensation and cumulus convection, are included in the model. The simulation results are encouraging. 24-h numerical simulation shows that the invading of cold air from North China and rapidly northward moving of warm air from South China can be successfully reproduced. The terrain with a maximum of 4175 m is incorporated in the model. Three different kinds of terrain schemes are tested and the dynamic effect of the Plateau on the process of heavy rainfall is found to be very important.     

黄土高原发展过程中的五大转折

1 Introduction W hatim portanttransform ations have taken place during the form ation ofthe Loess Plateau in China? Research on this problem has especially im portantscientific significance forus to learn ofthe evolution oftheLoessPlateau and predictthe f…     

科尔沁沙地固定沙丘土壤水体积分数变化

利用2006-2009年5-9月科尔沁沙地固定沙丘0~150 cm土壤水体积分数监测数据及降水资料,采用偏度、峰度检验法检验了固定沙丘不同月及不同土层土壤水体积分数的正态性,并得到了其正态分布相关参数的估计值及其置信区间;同时,对不同土层、不同月及不同年间的土壤水体积分数变化和差异进行了分析。结果表明:(1)固定沙丘同一月的土壤水体积分数以显著性水平α=0.1通过正态分布的假设检验;固定沙丘土壤水体积分数的平均值范围1.82%~4.95%,主要集中在2%~4%;(2)受降水影响,固定沙丘7月土壤水体积分数较高,且与其他月的差异显著;7月土壤水体积分数均值和方差的点估计及置信水平为0.95的置信区间、统计特征均与其他月的有较大差异;(3)固定沙丘0~10 cm土壤水体积分数较低,且与其他土层有显著差异;而10~30 cm土壤水体积分数较高;(4)2008年土壤水体积分数较低,而2009年土壤水体积分数较高;除2007年与2008年土壤水体积分数没有显著差异外,其余年份间的土壤水体积分数均有显著差异。     

“四层一体”在地理研学资源开发中的运用——以哈尼梯田地理研学资源开发为例

自2016年教育部等十一部门印发《关于推进中小学生研学旅行的意见》以来,社会各界对于研学旅行的研究迅速增加。因地理学研究“人地关系地域系统”这一核心问题,无疑成为研学旅行研究和实践的重要阵地。但如何开发地理研学旅行资源,尤其是如何有机结合人文地理与自然地理研学要素成为困扰很多研学导师的难题。本文尝试使用“四层一体”分析方法,从自然地理要素、生计、制度、文化四个层面出发,探讨如何从地理学科视角挖掘和利用研学资源,发现各个地理研学要素之间的相互作用关系,增强其逻辑性。     

Changing climate affects vegetation growth in the arid region of the northwestern China

The northwestern China is a typical dry-land region of Inner Asia, where significant climate change has been observed over the past several decades. How the regional vegetation, particularly the grassland-oasis-desert complex, responds to such climatic change is poorly understood. To address this question, we investigated spatio-temporal changes in vegetation growth and their responses to a changing climate by biome and bioregion, using satellite-sensed Normalized Difference Vegetation Index (NDVI) data from 1982 to 2003, along with corresponding climate data. Over the past 22 years, about 30% of the total vegetated area showed an annual increase of 0.7% in growing season NDVI. This trend occurred in all biomes and all bioregions except Sawuer, a subregion of the study area with no significant climate change. Further analyses indicated that NDVI change was highly correlated with the current precipitation and evapotranspiration in growing season but was not associated with temperature. We also found that NDVI was positively correlated with the preceding winter precipitation. These findings suggest that precipitation may be the key cause of vegetation growth in this area, even for mountain forests and grasslands, whose growth are often regarded to be limited by low temperate in winter and early spring.