Yang Shengtian

Response of sediment yield to vegetation restoration at a large spatial scale in the Loess Plateau

The impact of vegetation coverage on erosion and sediment yield in the Loess Plateau has been extensively studied, but the research has been primarily based on observations from slope runoff plots or secondary forest regions; the scaling method remains unresolved when it is applied at a large spatial scale, and it is difficult to apply to regions with severe soil and water loss given the predominance of herbs and shrubs. To date, there is little data on the quantitative impact of changes to vegetation on sediment concentration at a large spatial scale. This paper is based on vegetation information from remote sensing images, measured rainfall and sediment data over nearly 60 years, and results from previous runoff and sediment variation research on the Yellow River. We introduce the concepts of a sediment yield coefficient and the percentage of effective vegetation and erodible area, analyze the impact of different vegetation conditions on the flood sediment concentration and sediment yield, and evaluate the effect of rainfall intensity on sediment yield under different vegetation conditions at the watershed scale. We propose models to evaluate the impact of vegetation on sediment yield in the loess gully hilly region, which are based on remote sensing data and support an application at a large spatial scale. The models can be used to assess sediment reduction that results from the current significant improvement of vegetation in the Loess Plateau.

The current vegetation restoration effect and its influence mechanism on the sediment and runoff yield in severe erosion area of Yellow River Basin

Since 2000, the vegetation restoration has been significant in the Loess Plateau. Almost concurrently, the measured sediment discharge of the main stem of the Yellow River has been significantly reduced. Based on the vegetation information from remote sensing images from end of 1970s to 2013, this paper introduced the concepts of erodible area, forest and grassland proportion, vegetation coverage and the percentage of effective vegetation, and analyzed the vegetation change of scale, coverage and type. By introducing the concepts of percentage of effective vegetation, sediment yield coefficient and runoff yield coefficient, the sediment and flood yield for different vegetation conditions were discussed at the watershed scale, revealed the reasons for dramatically runoff and sediment yield reduction in the study area. The results showed that compared with the late 1970s, the vegetation just changed a little before 1998. While the vegetation coverage increased from 11%-25% to 35%-55% during 1998 to 2013, this vegetation improvement process is also the sensitive stage of vegetation change and sediment yield. High sediment concentration floods would still be the common flood of tributaries in the Loess plateau in future, while the sediment concentration would be reduced.

无测站流域水文预测（PUB）的研究方法

根据国内外研究成果,结合自身的科研体会,借用＂巧妇面临无米之炊＂时可能用到的＂借、替和种米＂的应对逻辑,将无测站流域水文预测（Predictions in Ungauged Basins,PUB）的研究方法归纳为移植法、替代法和生成法。将移植法归类为两种,一是当研究地区没有测站资料（简称无资料）而周边某个地区有测站资料（简称有资料）时,如果有资料区的自然地理环境与研究地区相似,直接移用该有资料地区的资料到无资料区,即直接移植法;二是倘若周边不只一个区域有资料,那么就借用所有这些点的信息,采用插值法得到无资料区的资料,即间接移植法。定义替代法为如果本研究区域或者相似区域没有资料,但有可能＂求出＂资料的辅助信息,则挖掘这些信息的方法。将替代法分为两类,一是根据本研究区域其他信息,通过模型模拟、同化、融合、从本学科和多学科领域挖掘信息等技术,得到本研究区所需资料。二是根据其它研究区域其他信息得到本研究区所需资料,包括就地外延和对比流域法。定义生成法为通过获取第一手资料开展水文预测的方法,包括野外实验和室内实验。通过梳理PUB的这些研究途径,探索了PUB方法发展的可能突破口,旨为推动PUB的研究提供思路。

A TES algorithm based on corrected Alpha difference spectra

In this study, we start from WIENs approximation to define and derive Alpha difference spectrum, which is independent of temperature. Then, we present a correction term to remove the influence of WIENs approximation on Alpha difference spectrum. On these bases, a new temperature and emissivity separation algorithm is advanced, which combines attractive features of Alpha derived emissivity method and ASTER TES algorithm. Compared with current TES algorithm, the new algorithm is fast, simple and precise. It can be used for wide temperature and surface type ranges

A large scale LAI inversion algorithm

In this paper, a new LAI retrieval method is developed. The algorithm borrows ideas from the principles and methods of ground LAI measurements, and adopts a new frame which differs from traditional remote sensing LAI inversion methods. The ground data acquired from two field experiments are used to validate the algorithm. In order to resolve the scale exchange problem between high resolution ground observation and low resolution remote sensing data, two high resolution remote sensing images almost having the same resolutions with ground measurements are used as transitions

Natural eco-environmental evaluation of eastern Qinghai-Tibet Plateau using RS and GIS

The impact of interbasin water transfer on environment is very significant. The affected area of the west route scheme of the South to North Water Transfer Project in China (SNWT) is located in the eastern Tibetan Plateau, where the altitude is high with frigid eco-environment. In this article, remote sensing and GIS are applied to analyze the natural environment and the natural environment index is established to express the natural conditions of the study area. After the natural environment index is divided into four grades and the features of each grade are analysed, some results are obtained for reference in environmental assessment of the west route of SNWT.