Browsing by Author "Luo, Lihui"

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    Are the shoreline and eutrophication of desert lakes related to desert development?
    (Springer, 2021-01) Luo, Lihui; Zhao, Wenzhi; Wang, Lixin; Ogashawara, Igor; Yang, Qiyue; Zhou, Hai; Yang, Rong; Duan, Quntao; Zhou, Chenglin; Zhuang, Yanli; Earth Sciences, School of Science
    Desert lakes are unique ecosystems found in oases within desert landscapes. Despite the numerous studies on oases, there are no reports regarding the spatiotemporal distribution and causes of eutrophication in the desert lakes that are located at the edge of the Linze Oasis in northwestern China. In this study, the seasonal shoreline and eutrophication of a desert lake were monitored using an unmanned aerial vehicle (UAV) and water sampling during three crop growth stages. The spatial extents of the shoreline and algal blooms and the chromophoric dissolved organic matter (CDOM) absorption coefficient were derived through UAV images. The desert lake shoreline declined during the crop growing stage, which exhibited the largest water demand and began to expand after this stage. The estimated CDOM absorption coefficient measurements and classified algal bloom area showed seasonal variations that increased from spring to late summer and then decreased in autumn. The first two crop growth stages accounted for most of the water and fertilizer requirements of the entire growth period, which may have contributed to large amounts of groundwater consumption and pollution and resulted in peak eutrophication of the lake in the second growth stage. However, the CDOM absorption coefficient of the third stage was not well correlated with that of the first two stages, suggesting that the lake may be affected by the dual effects of groundwater and precipitation recharge in the third stage. These results indicate that the water quality of desert lakes may be affected by agricultural cultivation. The agricultural demands for water and fertilizer may change the spatiotemporal changes in water quality in the lake, especially in the middle and early stages of crop growth.
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    Dew formation characteristics in the gravel desert ecosystem and its ecological roles on Reaumuria soongorica
    (Elsevier, 2021-12) Zhuang, Yanli; Zhao, Wenzhi; Luo, Lihui; Wang, Lixin; Earth Sciences, School of Science
    As an additional source of water to plants besides rainfall, dew may have a positive impact on vegetation in the arid ecosystems. Knowledge regarding dew formation characteristics and its ecological effects on vegetation water status and photosynthetic performance in the gravel desert ecosystem is still lacking. In this study, the dew variability and formation frequency on a gravel desert were measured by microlysimeters. We quantified dew formation characteristics, investigated vegetation water response to dew events in the gravel desert ecosystem at the edge of a desert oasis, Northwestern China. The results showed water adsorption was a primary pathway of dew formation in such system, and the average daily amount of dew is 0.06 mm. Dew occurred on 36% of growing season days, the number of days with dew amounts >0.03 mm accounted for 82% of the total dew events, and the cumulative amount of dew for those days was 3.41 mm. Relative humidity, air temperature, wind speed, the difference between air temperature and soil surface temperature had significant effects on dew formation. A threshold of RH ≥30% is taken to mark possible condensation in the gravel desert ecosystem. A significant positive correlation between dew amounts and the relative moisture in the near-surface air was found when RH ≥30%. The moderate wind velocity (1–1.8 m/s) was favorable to dew formation, and when wind speed >5.47 m/s, there was no dew formation. Because of the water-absorbing scales on the leaves of Reaumuria soongorica, dew events significantly improved their relative water content, water potential, and photosynthetic performance in the early morning and ameliorating the adverse effects of plants exposed to prolonged drought. The study highlights dew is an important supplementary source of water in the gravel desert ecosystem. Although the absolute dew amounts were found not high, it can be a frequent and stable water resource. Furthermore, this study provides a comprehensive understanding of the effects of dew on plant water status in the gravel desert ecosystem.
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    The hidden costs of desert development
    (SpringerLink, 2020-08) Luo, Lihui; Zhuang, Yanli; Zhao, Wenzhi; Duan, Quntao; Wang, Lixin; Earth Sciences, School of Science
    Economic benefits and ecological restoration are the leading drivers of desert development through man-made oasis expansion. However, the sustainability of oasis expansion in combating desertification while promoting economic growth remains unclear, though such knowledge is critical for future desert development across the globe. To address this knowledge gap, a comprehensive assessment integrating meteorological, groundwater and remote-sensing data as well as groundwater simulation datasets was conducted to evaluate the spatial-temporal changes in the desert-oasis ecotone of northwest China over the past six decades. Desert development causes a rapid decline in the surrounding groundwater table, increases pollution in soil and groundwater and is associated with an increased frequency of strong sandstorms. Desert development seems to have improved the environment and promoted the economy, but there is a huge cost for the overexploitation of water resources and the transfer of pollution from surface to underground, which could cause deserts to degrade further.
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    Increased human pressures on the alpine ecosystem along the Qinghai-Tibet Railway
    (Springer, 2020) Luo, Lihui; Duan, Quntao; Wang, Lixin; Zhao, Wenzhi; Zhuang, Yanli; Earth Sciences, School of Science
    Construction of the Qinghai-Tibet Railway (QTR) increased the links between inland China and the Qinghai-Tibet Plateau (QTP). The QTR accelerated surrounding tourism, boosted the local economy and led to rapid development of livestock raising. To assess how distance from the railway and different regions has influenced the impact of the QTR on the alpine ecosystem, human footprint maps were produced to indicate human pressures, and the normalized difference vegetation index (NDVI), an index of vegetation greenness, was used to characterize the growth of alpine vegetation. The construction and operation of the QTR have increased human pressures, while the establishment of nature reserves has effectively reduced human pressures. The QTR contributes significantly to the increased human pressures in the Tibetan region compared with the Qinghai region and exerts negative impacts on alpine vegetation. Although the warmer and wetter climate trend has proven beneficial in enhancing alpine vegetation greenness, the declining trend of alpine vegetation has been stronger in regions with more intensive human pressures, especially in the grazing areas and the tourist areas around Lhasa. These results suggest that the impact of the QTR on alpine vegetation in Tibet is greater than that in Qinghai and that the spatial extent of the indirect impact of the QTR in Tibet is confined to approximately 30 km from the railway. These results will provide guidance and a theoretical basis for the protection of the alpine environment on the QTP under intensified anthropogenic influence.