Characteristics of Sand Dune Pattern and Fluvial-aeolian Interaction in Horqin Sandy Land, Northeast Plain of China

The interaction between fluvial and aeolian processes can significantly change surface morphology of the Earth. Taking the Horqin Sandy Land as the research area and using Landsat series satellite remote sensing images, this study utilizes geomorphology and landscape ecology to monitor and analyze the aeolian geomorphology characteristics of the Horqin Sandy Land. Results show that the sand dunes of the Horqin Sandy Land are mainly distributed on alluvial plains along the banks of the mainstream and tributaries of the Western Liao River, and the sand dune types tend to simplify from west to east and from south to north. The aeolian geomorphology coverage tend to be decreasing in the past 40 years, with an average annual change rate of 0.31%. While the area of traveling dunes decreased, the area of fixed and semi-fixed dunes increased. The fractal dimensions of various types of sand dune have all remained relatively constant between 1.07 and 1.10, suggesting that they are experiencing a relatively stable evolutionary process. There is a complex interaction between fluvial and aeolian processes of the Horqin Sandy Land, which plays a central role in surface landscape molding. Sand dunes on both sides of different rivers on the Horqin Sandy Land present certain regularity and different characteristics in terms of morphology, developmental scale, and spatial pattern. There are six fluvial-aeolian interaction modes in this area: supply of sand sources by rivers for sand dune development, complete obstruction of dune migration by rivers, partial obstruction of dune migration by rivers, influence of river valleys on dune developmental types on both sides, influence of river valleys on dune developmental scale on both sides, and river diversion due to obstruction and forcing by sand dunes. This study deepens our understanding of the surface process mechanism of the interaction between fluvial and aeolian processes in semi-arid regions, and provides a basis for researches on regional landscape responses in the context of global environmental change.

Evaluation of Spectral Scale Effects in Estimation of Vegetation Leaf Area Index Using Spectral Indices Methods

Spectral index methodology has been widely used in Leaf Area Index(LAI) retrieval at different spatial scales. There are differences in the spectral response of different remote sensors and thus spectral scale effect generated during the use of spectral indices to retrieve LAI. In this study, PROSPECT, leaf optical properties model and Scattering by Arbitrarily Inclined Layers(SAIL) model, were used to simulate canopy spectral reflectance with a bandwidth of 5 nm and a Gaussian spectral response function was employed to simulate the spectral data at six bandwidths ranging from 10 to 35 nm. Additionally, for bandwidths from 5 to 35 nm, the correlation between the spectral index and LAI, and the sensitivities of the spectral index to changes in LAI and bandwidth were analyzed. Finally, the reflectance data at six bandwidths ranging from 40 to 65 nm were used to verify the spectral scale effect generated during the use of the spectral index to retrieve LAI. Results indicate that Vegetation Index of the Universal Pattern Decomposition(VIUPD) had the highest accuracy during LAI retrieval. Followed by Normalized Difference Vegetation Index(NDVI), Modified Simple Ratio Indices(MSRI) and Triangle Vegetation Index(TVI), although the coefficient of determination R^2 was higher than 0.96, the retrieved LAI values were less than the actual value and thus lacked validity. Other spectral indices were significantly affected by the spectral scale effect with poor retrieval results. In this study, VIUPD, which exhibited a relatively good correlation and sensitivity to LAI, was less affected by the spectral scale effect and had a relatively good retrieval capability. This conclusion supports a purported feature independent of the sensor of this model and also confirms the great potential of VIUPD for retrieval of physicochemical parameters of vegetation using multi-source remote sensing data.

Sandy Land-lake-vegetation Landscape of Songnen Sandy Land of China:Pattern,Process and Mechanism

In order to investigate the dynamic evolution of the sandy land-lake-vegetation landscape in Songnen Sandy Land(SSL)and its response to climate change and human activities,the distribution pattern,evolution,and driving mechanisms of the landscape were analyzed based on Landsat satellite images and meteorological and socio-economic data during 1980–2020.The results indicate that the area of sandy land exhibited an upward fluctuation during the last 40 yr,with a net increase of 251.75 km^(2) at an increment rate of 3.80%/10 yr.The lake area also exhibited an upward fluctuation,with a net increase of 1200.95 km^(2) at an increment rate of 20.42%/10 yr.Vegetation coverage decreased by 2633.30 km^(2),with areas of low vegetation coverage exhibiting a trend of initial decline and subsequent increase,areas of medium vegetation coverage showed an upward fluctuation,and areas of high vegetation coverage showed a trend of initial increase and subsequent decrease,with overall changes of–0.67%/yr,1.12%/yr,and 0.17%/yr,respectively.The relationships between sandy land,lakes,and vegetation coverage were significant,with areas of sandy land and low vegetation coverage showing the strongest correlation.The dynamic evolution of landscape is controlled by regional climatic and socio-economic factors,with socio-economic factors as the first principal component contributing up to 59.64%.

GIS Applications and Development Trends in China

Since its conceptualization and creation in the 1960 s, Geographic Information System(GIS) has considerably developed. As a combination of traditional and modern technology, GIS has become an important part of modern management, decision-making, and command, contributing greatly to social progress and development. This article introduces the concepts of GIS, expounds on the GIS applications in China, and looks forward to developments in GIS technology in the future while reviewing the issues that GIS application development faces. GIS has evolved into an important branch of the information technology industry, with great vitality and broad development prospects.

1980年以来5个时期松嫩沙地湖泊群分布及其变化研究

以松嫩沙地湖泊为研究对象,利用1980年、1990年、2000年、2010年和2015年的Landsat MSS/TM/OLI影像数据,采用面向对象分类、景观指数和数理统计方法,研究5个时期湖泊的分布和面积及其变化特征。研究结果表明,1980年、1990年、2000年、2010年和2015年研究区的湖泊总面积分别为1 470.22 km2、3 493.64 km2、3 963.17 km2、2 671.17 km2和1 505.52 km2;与1980年相比,2015年湖泊群质心向东北东方向迁移了46.28 km;1980~2015年,松嫩沙地湖泊群景观破碎化加剧;湖泊群聚集性与连接性逐步加强,湖泊演变过程趋于稳定;社会经济因素对松嫩沙地湖泊变化的影响作用较大。