分类： 农、林、牧、渔 >> 土壤学 提交时间： 2024-05-15 合作期刊: 《干旱区科学》
摘要： The clay–sand barriers in Minqin desert area, China, represent a pioneering windbreak and sand fixation project with a venerable history of 60 a. However, studies on evaluating the long-term effectiveness of clay–sand barriers against aeolian erosion, particularly from the perspective of surface sediment grain size, are limited and thus insufficient to ascertain the protective impact of these barriers on regional aeolian activities. This study focused on the surface sediments (topsoil of 0–3 cm depth) of clay–sand barriers in Minqin desert area to explain their erosion resistance from the perspective of surface sediment grain size. In March 2023, six clay–sand barrier sampling plots with clay–sand barriers of different deployment durations (1, 5, 10, 20, 40, and 60 a) were selected as experimental plots, and one control sampling plot was set in an adjacent mobile sandy area without sand barriers. Surface sediment samples were collected from the topsoil of each sampling plot in the study area in April 2023 and sediment grain size characteristics were analyzed. Results indicated a predominance of fine and medium sands in the surface sediments of the study area. The deployment of clay–sand barriers cultivated a fine quality in grain size composition of the regional surface sediments, increasing the average contents of very fine sand, silt, and clay by 30.82%, 417.38%, and 381.52%, respectively. This trend became markedly pronounced a decade after the deployment of clay–sand barriers. The effectiveness of clay–sand barriers in erosion resistance was manifested through reduced wind velocity, the interception of sand flow, and the promotion of fine surface sediment particles. Coarser particles such as medium, coarse, and very coarse sands predominantly accumulated on the external side of the barriers, while finer particles such as fine and very fine sands concentrated in the upwind (northwest) region of the barriers. By contrast, the contents of finest particles such as silt and clay were higher in the downwind (southeast) region of the sampling plots. For the study area, the deployment of clay–sand barriers remains one of the most cost-effective engineering solutions for aeolian erosion control, with sediment grain size parameters serving as quantitative indicators for the assessment of these barriers in combating desertification. The results of this study provide a theoretical foundation for the construction of windbreak and sand fixation systems and the optimization of artificial sand control projects in arid desert areas.
分类： 地球科学 >> 地球科学史 提交时间： 2018-10-29 合作期刊: 《干旱区科学》
摘要： Launched in 2002, the Beiing–Tianjin Sand Source Control Project (BTSSCP) is an ecological restoration project intended to prevent desertification in China. Evidence from multiple sources has confirmed increases in vegetation growth in the BTSSCP region since the initiation of this project. Precipitation and essential climate variable-soil moisture (ECV-SM) conditions are typically considered to be the main drivers of vegetation growth in this region. Although many studies have investigated the inter-annual variations of vegetation growth, few concerns have been focused on the annual and seasonal variations of vegetation growth and their climatic drivers, which are crucial for understanding the relationships among the climate, vegetation, and human activities at the regional scale. Based on the normalized difference vegetation index (NDVI) derived from MODIS and the corresponding climatic data, we explored the responses of vegetation growth to climatic factors at annual and seasonal scales in the BTSSCP region during the period 2000–2014. Over the study region as a whole, NDVI generally increased from 2000 to 2014, at a rate of 0.002/a. Vegetation growth is stimulated mainly by the elevated temperature in spring, whereas precipitation is the leading driver of summer greening. In autumn, positive effects of both temperature and precipitation on vegetation growth were observed. The warming in spring promotes vegetation growth but reduces ECV-SM. Summer greening has a strong cooling effect on land surface temperature. These results indicate that the ecological and environmental consequences of ecological restoration projects should be comprehensively evaluated.
分类： 生物学 >> 植物学 提交时间： 2018-07-05 合作期刊: 《干旱区科学》
摘要： Climate change is shifting the amount and frequency of precipitation in many regions, which is expected to affect seedling recruitment across ecosystems. However, the combined effects of precipitation amount and frequency on seedling recruitment remain largely unknown. An understanding of the effects of precipitation amount and frequency and their interaction on seedling emergence and growth of typical desert plants is vital for managing populations of desert plants. We conducted two experiments to study the effects of variation in precipitation on Reaumuria soongarica (Pall.) Maxim. First, greenhouse experiments were conducted to examine the effects of three precipitation amount treatments (ambient, +30%, and 30%) and two precipitation frequency treatments (ambient and 50%) on seedling emergence. Second, the morphological responses of R. soongarica to changes in precipitation amount and frequency were tested in a controlled field experiment. Stage-specific changes in growth were monitored by sampling in different growth seasons. Our results showed that precipitation amount significantly affected germination, seedling emergence, and growth of R. soongarica, and there was a larger effect with decreased precipitation frequency compared with ambient. Germination and seedling emergence increased as precipitation increased under the same frequency of precipitation. The highest emergence percentage was obtained with a 30% increase in precipitation amount and a 50% reduction in precipitation frequency. Compared with ambient precipitation, a 30% increase in precipitation amount increased above- and below-ground biomass accumulation of R. soongarica during the growth season. A decrease of 30% in precipitation amount also resulted in an increase in below-ground biomass and root/shoot ratio in the early stages of the growth season, however, above- and below-ground biomass showed the opposite results at the end of the growth season, with larger effects on above-ground than below-ground biomass under decreased precipitation frequency. When precipitation frequency decreased by 50%, values of all growth traits increased for a given amount of precipitation. We concluded that precipitation frequency may be as important as precipitation amount to seedling emergence and growth of R. soongarica, and that understanding the effects of precipitation variability on seedling recruitment requires the integration of both precipitation amount and frequency. In particular, the combination of a 30% increase in precipitation amount and 50% reduction in precipitation frequency increased the emergence and growth of seedlings, suggesting that alteration of amount and frequency of precipitation caused by climate change may have significant effects on seedling recruitment of R. soongarica.
分类： 地球科学 >> 地理学 提交时间： 2017-11-07 合作期刊: 《干旱区科学》
摘要： Precipitation chemistry analysis is essential to evaluate the atmospheric environmental quality and identify the sources of atmospheric pollutants. In this study, we collected a total of 480 precipitation samples at 6 sampling sites in the northern and southern slopes of Wushaoling Mountain from May 2013 to July 2014 to analyze the chemical characteristics of precipitation and to identify the main sources of ions in precipitation.
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