荒漠绿洲交错区绿洲扩张与主要水文过程

干旱区绿洲扩张主要发生在荒漠绿洲交错区(边缘区),绿洲空间变化对地表主要水文过程有直接影响。为了更好地了解这一变化机制,以绿洲与沙漠、荒漠、石质裸山交错分布的张掖绿洲边缘区为对象,采用F显著性检查和Mann-Kandell趋势分析对1987年以来绿洲与不同生态系统之间转化特点与趋势进行了研究,同时分析了绿洲扩张与主要水文过程关系。结果表明:1987-2017年来荒漠绿洲交错区不同生态系统空间变化主要发生在绿洲与沙漠和荒漠3种生态系统之间。转化以绿洲扩张为主要特点,累积扩张了1 696.86 hm^2,平均每年56.56 hm^2。其中,沙漠和荒漠分别转化了31.73 hm^2·a^-1和24.83 hm^2·a^-1。黑河中游干流用水量在研究时段内无显著性突变,多年平均为7.68×108 m^3,对绿洲面积扩张无显著性影响。但是地下水埋深在1998年发生显著性突变,突变周期发生在1997-2000年。总体来看,绿洲面积每增加520 hm^2,地下水埋深下降1 m。地下水位埋深对绿洲扩张有显著性影响,是绿洲扩张最敏感的水文过程要素。

Assessment of Oasis Expanding and Hydrological Process in Oasis-desert Ecotone

Oasis expanding, which is most active on oasis-desert ecoton, is frequently occurring during past decades in arid zone of China. Its change directly induces hydrological process consequently. To best understand relationship between them, we selected the ecosystem ecotone as a case study area that include oasis, sand dune, desert, and the nude stone mountain in northern edge area of Zhangye oasis and employed statistic method to analyze different ecosystem expanded and transferred trends from 1987 to 2017. And, the relationships between them and major hydrological process have been illustrated by using F significant check and Mann-Kandell trend analysis. Finally, results showed that the distribution pattern changing of different ecosystems mainly occurred on oasis, sand dune, and desert and rarely occurred on the mountain in past decades. The change trait was oasis expanding amount to 1 696.86 hm, respectively. More detail trend analysis indicated that the average water consumed amount of main stream of Heihe was 7.68×10⁸ m³ and no significantly abrupt change during study period, and the change was also no significant impact on oasis expand. However, the change trend of underground water table had an abrupt change point significantly in 1998 and maintained period from 1997 to 2000 during the entire temporal series. In general, there was a phenomenon the oasis area expanded 520hm² with UWT decreased 1m. It indicated that the UWT significantly influenced on the oasis expanded and it was a sensitive indicator during hydrological change process in oasis-desert ecotone.