Subjects: Biology >> Botany submitted time 2023-03-28 Cooperative journals: 《干旱区研究》
Abstract： Nitraria tangutorum nebkha is a common natural landscape in the desert- oasis ecotone of Jilantai; however, the growth characteristics of N. tangutorum shrubs and the morphological characteristics of N. tangutorum nebkhas under different background vegetation coverages remain unknown. Through the measurement of shrubs and morphological characteristics of N. tangutorum nebkhas, the variability of morphological parameters of N. tangutorum nebkhas and the relationship between the growth characteristics and morphology of N. tangutorum nebkhas were quantitatively analyzed under different background vegetation coverages. The influence of background vegetation coverage on the succession of N. tangutorum nebkhas was also discussed. Results showed that: (1) the evolution of N. tangutorum nebkhas was stable under four different background vegetation coverages. The morphological parameters of N. tangutorum nebkhas gradually developed toward large scale and small density with the increasing background vegetation coverage. (2) Overall, a good correlation was found between the morphological parameters of N. tangutorum nebkhas under different background vegetation coverages. (3) In the desert-oasis ecotone of Jilantai, the relationship between the L and W of N. tangutorum nebkhas followed a quadratic or power function, and the relationship between the A and V of N. tangutorum nebkhas followed a power function. Except for sample site 1, the relationship between A and H and between H and D followed linear trend and power function, respectively. (4) The coverage of N. tangutorum nebkhas was mainly 40%- 80%, accounting for 64.62% of total N. tangutorum nebkhas in the desert- oasis ecotone of Jilantai. This finding indicated that the N. tangutorum nebkhas in the study area is well grown, widely developed, and temporarily not a source of wind and sand damage to the oasis.
Subjects: Geosciences >> Geography submitted time 2023-02-27 Cooperative journals: 《干旱区地理》
Abstract： Although large-scale ripples (LSRs) are widely distributed in various desert regions of the globe, there are few studies on LSR in China. Through field investigations and observation, remote sensing imagery analysis by Google Earth, and a laser particle size analyzer, spatial distribution patterns and fundamental morphometric and grain size features of both individual and collective forms of LSRs in the Korqin Sandy Land of China are explored. Furthermore, coarse grain sources, differences in granulometric distribution, morphometric features, interior sedimentary structures between LSRs and common ripples, and differences between sands from LSR and common wind ripple are discussed in this study. The results are as follows: (1) LSRs are primarily concentrated on the central and northern parts of Ongniud Bannar, the western extreme of Korqin Sandy Land, and close to or surrounding nearby rocky mountains; they are also primarily distributed in the southern zone of the middle Xilamulun River, on the eastern banks of the Xiangshui River, in the area of the Songshu Mountain, and on the fluvial plain of the lower Chaganmulun River. (2) In line with the dimension, shape, and location of LSRs, plot-, patch-, and stripe-shaped LSR spatial units can be recognized, which are mainly generated on such geomorphic positions as broad interdune, central and upper stoss of a dune, and trough-like lowland, respectively. (3) The average length of LSR is 6.32 m, with an obvious spatial difference; the average strike is NE-SW, significantly perpendicular to the local predominant wind direction and with an insignificant spatial difference; the average spacing is 1.68 m, with a spatial difference; individual LSR has a dissymmetric cross-section. (4) The grains of LSR are comparatively coarser, belonging to the class of middle-coarse sand, which are, however, thinner than those in northwestern China, West Asia, and North Africa; coarse grains are mainly derived from fluvial sediments on ancient river channels, underlying fluvial-lacustrine sediments of late Quaternary, and weathering crusts and alluvial deposits on foothills of nearby denuded mountains. (5) There are considerable differences in appearance, grain composition, geometric morphology, and internal sedimentary structure between LSRs and common sand ripples, which are the smallscale perpendicular bedforms among aeolian depositional landforms and can superimpose on the surfaces of various dunes. The research will, to some extent, advance the principle theories of aeolian geomorphology and effective sand-control practice.
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