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Li G.,Hulunber State Station of Grassland Ecosystem Field Observation and Scientific Research | Li G.,Key Laboratory of Resource Remote Sensing and Digital Agriculture | Li G.,Chinese Academy of Agricultural Sciences | Zhang H.,Chinese Academy of Agricultural Sciences | And 6 more authors.
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2010

The accuracy validation of the MODIS/FAPAR product is a prerequisite for using it to estimate local net primary production (NPP), and to supply service for monitoring the balance of region carbon and arranging production of grassland animal husbandry rationally. For this purpose, we designed and carried out in-situ measurements of FAPAR in two 2 km×2 km areas within the temperate meadow-steppe grassland in Hulunber during growing season in 2008, and analyzed heterogeneity of the two sites using image of Beijing-1 satellite with resolution of 32 m, and then scaled up and validated MODIS/FAPAR products with in-situ measured data in grassland area. The results showed that the MODIS FAPAR product reflected very well the seasonal dynamics of in-situ FAPAR, but tended to overestimate the value with averaged relative error of 13.7% in the Stipa Baicalensis site and 18.7% in the Leymus Chinensis site. The MODIS/FAPAR algorithm was derived based on the global land cover map, which may be too broad for local areas. More fieldworks for various types of the grasslands are necessary. Source


Yan Y.,Hulunber State Station of Grassland Ecosystem Field Observation and Scientific Research | Yan Y.,Key Laboratory of Resources Remote Sensing and Digital Agriculture | Yan Y.,Chinese Academy of Agricultural Sciences | Wu L.,Rothamsted Research | And 9 more authors.
Geoderma | Year: 2015

There have been few studies on the formation and resistance of physical crusts to wind erosion for typical steppe soils in Inner Mongolia, China. The objectives of this study were to 1) examine the effects of rainfall quantity on soil crust thickness, 2) investigate the effects of soil crust on wind erosion, 3) determine the crust thickness (crust formed by various rainfall quantities) able to most effectively resist wind erosion, and 4) evaluate the differences between the responses of soils with different treatment histories to crust formation and subsequent wind erosion at given rainfall quantities. To this end, we simulated five light rainfall levels to investigate the impact of light rainfall on soil crusting and subsequent wind erosion for soils of a semi-arid steppe via a unique approach. The results show that the soil crust thickness increases linearly with an increasing amount of rainfall for all four soils. The soil crust formed by rainfall of more than 0.5. mm was able to nearly completely prevent wind erosion during the experimental period; soil losses of only 0.1-2.4% were observed for the high rainfall treatments (>. 0.5. mm) for all four soils. In contrast, soil losses of 9.4-33.1% occurred in the non-rainfall treatments for the four soils. The results show that the soil loss ratio increased with increasing clay plus silt content and SOC content for the non-rainfall treatment and 0.2. mm rainfall treatment. © 2015 Elsevier B.V. Source


Yan Y.,Hulunber State Station of Grassland Ecosystem Field Observation and Scientific Research | Yan Y.,Key Laboratory of Resources Remote Sensing and Digital Agriculture | Yan Y.,Chinese Academy of Agricultural Sciences | Xin X.,Hulunber State Station of Grassland Ecosystem Field Observation and Scientific Research | And 15 more authors.
Plant and Soil | Year: 2013

Many studies reported the influence of wind erosion on soil degradation and the effect of vegetation coverage on preventing wind erosion. However, fewer studies have quantitatively measured the grassland soil particle size fractions and nutrients' loss caused by wind erosion under different vegetation coverage. Aims: We conducted a field experiments to (1) to explore the effect of vegetation coverage on soil wind erosion; (2) examine quantitatively the effects of wind erosion on soil texture, and determine the most erodible particles fraction of soil; (3) to examine quantitatively the soil carbon, nutrients such as nitrogen and phosphorus loss caused by wind erosion under different vegetation coverage. Methods: Six vegetation coverage treatments (0 %, 15 %, 35 %, 55 %, 75 % and 95 %) were constructed. To be able to monitor wind erosion status under more diverse weather conditions, three consecutive repeat experiments under different weather condition were conducted. Results: The results show that all the residue soil samples after wind erosion became coarser than that of original soil samples. The degree of change for the soil particle size distribution before and after wind erosion gradually increased with the less of vegetation coverage. The critical particle size for distinguishing the original soil sample and the residue soil after wind erosion occurred in the range of 125 μm and 210 μm depending on the vegetation cover. The fractions below or above the critical particle size are either easy to deplete or favoured by wind erosion, respectively. The most reduction occurs between 50 and 90 μm depending on the different weather condition and vegetation coverage. Due to the disproportionately greater amounts of nutrients in the fine soil particles, the preferential depletion of fine particles directly lead to a preferentially significant depletion of organic carbon and nutrients. The organic carbon and nutrient contents in the residue soil after erosion decreased significantly compared to that in the original soil. The soil nutrient loss ratio decrease significantly with the increase of vegetation coverage. Conclusions: Wind erosion is an important factor to affect the evolution of soil texture and soil nutrient. Vegetation coverage has a major impact on both preventing wind erosion and decreasing loss ratio of fine particles and nutrients. If we want to effectively protect the fine particles and nutrients, the vegetation cover should be maintained at least above 35 %. © 2013 Springer Science+Business Media Dordrecht. Source

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