分类： 地球科学 >> 地理学 提交时间： 2021-07-23 合作期刊: 《干旱区科学》
摘要： Water availability, which enables plant growth and animal activity, regulates dryland ecosystem function. In hyper-arid ecosystems, rain cannot support vascular plant growth. Therefore, hyper-arid vegetation is restricted to the lower topography, where runoff accumulates. Typically, food resources originating from areas of dense vegetation are dispersed across the desert floor, enabling animal life in areas lacking vascular plant growth. However, certain regions, such as the hyper-arid upper topography, may be devoid of plant-derived food resources. The present study examined arthropod activity in the upper topography of a hyper-arid desert, in comparison with arthropod activity in the lower topography. Pitfall traps were utilized to compare arthropod activity along unvegetated ridges with activity in parallel, vegetated riverbeds. Surprisingly, the study revealed dense arthropod communities in the barren upper topography. Arthropods collected in the upper topography represented 26% of total arthropod abundance. In addition, the overlap between arthropod identity in the ridges and wadis (i.e., riverbeds) was low, and certain arthropods were strongly affiliated with the ridges. The upper topographic communities included high numbers of silverfish (Zygentoma: Lepismatidae), malachite beetles (Psiloderes), and predatory mites (Acari: Anystidae), and these arthropods were present at various life stages. It remains unclear how arthropod communities can persist in the unvegetated upper topography of the hyper-arid study area. These results raise the possibility that other food sources, independent from vascular plants, may play a significant role in the life history of hyper-arid arthropods.
分类： 农、林、牧、渔 >> 土壤学 提交时间： 2024-12-17 合作期刊: 《干旱区科学》
摘要： Alluvial fans possess diverse geomorphological features and have a significant impact on soil characteristics and variations in ecological stoichiometry. However, it remains unclear how alluvial fans in arid mountainous areas influence the changes in ecological chemical stoichiometry and, consequently, indirectly affect ecosystem function. Alluvial fan, with its diverse topographical features, exerts a multifaceted influence on soil formation and characteristics. Limited information exists regarding the ecological stoichiometric characteristics of the alluvial fan in arid mountainous areas. This study investigated the soil physical-chemical characteristics, enzyme activities, soil ecological stoichiometries, and its driving factors of four types of micro-topographies (alluvial mesas, high floodplain, groove beach, and striated groove) in the foothills of eastern Helan Mountains, China. Results showed that soil physical and chemical properties in the 0–20 cm soil depth was consistently higher than those in the 20–40 cm soil depth, with no changes in pH, total nitrogen, and total potassium. C:P and N:P ratios in alluvial mesas, high floodplain, and striated groove were significantly higher than those in groove beach. Redundancy analysis showed that soil nutrients played the most significant role in the variation of soil ecological stoichiometry characteristics. Topography influenced soil stoichiometry indirectly, primarily through impacts on enzyme activity and soil nutrient elements. These findings elucidate the intricate interplay between soil ecological stoichiometric characteristics and environmental factors across diverse micro-topographies in alluvial fan, contributing to our understanding of the formation and development of soil in dryland.
分类： 地球科学 >> 地理学 提交时间： 2021-07-23 合作期刊: 《干旱区科学》
摘要： Lop Sea, located at the east end of the Tarim Basin, Northwest China, dried up permanently, which is the terminal lake of the Tarim River. Lop Sea was considered as the lake basin of Lop Nor since Quaternary. However, the possibility that Lop Nor was away from the Lop Sea in historical time is crucial to be discussed to interpret the proxy records in sediment profiles. To obtain a general view of the evolution of Lop Nor and Lop Sea in a historical period, several approaches were adopted in this paper. First, the Qianlong Thirteen-Row Atlas, an ancient imperial atlas of the Qing Dynasty, which was completed around 1760, indicated that the Tarim River formed a relatively large lake at its modern upstream region. Second, a Digital Elevation Model (DEM) with a 10-m spatial resolution and a relative precision of 0.42 m was derived from TanDEM-X/TerraSAR-X satellite image pairs using the interferometry method, which was verified using ICESat-GLAS laser footprints and a local DEM acquired by a drone. Finally, based on the spatial analysis of historical documents, expedition reports, sediment profiles and archaeological evidence, it can be deduced that the lacustrine deposition was discontinued in the Lop Sea. Six episodes in the evolutionary history of the drainage system in eastern Tarim Basin were summarized. The proved depositional condition variations could be used for future interpretation of proxy records in sediment. The high-accurate DEM provided a reference for the location of further fieldwork in the Lop Sea. The method proposed in this paper may be efficient for the research of inland lakes or rivers in global arid regions.
分类： 地球科学 >> 地理学 提交时间： 2022-10-12 合作期刊: 《干旱区科学》
摘要：
Topography plays an important role in determining the glacier changes. However, topography has often been oversimplified in the studies of the glacier changes. No systematic studies have been conducted to evaluate the relationship between the glacier changes and topographic features. The present study provided a detailed insight into the changes in the two branches (east branch and west branch) of Urumqi Glacier No. 1 in the Chinese Tianshan Mountains since 1993 and systematically discussed the effect of topography on the glacier parameters. This study analyzed comprehensive recently observed data (from 1992/1993 to 2018/2019), including mass balance, ice thickness, surface elevation, ice velocity, terminus, and area, and then determined the differences in the changes of the two branches and explored the effect of topography on the glacier changes. We also applied a topographic solar radiation model to analyze the influence of topography on the incoming shortwave radiation (SWin) across the entire glacier, focusing on the difference in the SWin between the two branches. The glacier mass balance of the east branch was more negative than that of the west branch from 1992/1993 to 2018/2019, and this was mainly attributed to the lower average altitude of the east branch. Compared with the west branch, the decrease rate of the ice velocity was lower in the east branch owing to its relatively increased slope. The narrow shape of the west branch and its southeast aspect in the earlier period resulted in a larger glacier terminus retreat of the west branch. The spatial variability of the SWin across the glacier surface became much larger as altitude increased. The SWin received by the east branch was slightly larger than that received by the west branch, and the northern aspect could receive more SWin, leading to glacier melting. In the future, the difference of the glacier changes between the two branches will continue to exist due to their topographic differences. This work is fundamental to understanding how topographic features affect the glacier changes, and provides information for building different types of relationship between the glacier area and ice volume to promote further studies on the basin-scale glacier classification.
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