Abstract: 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.

Key words: oasis edge expanding, hydrological process, trend analysis, oasis-desert ecotone, Heihe middle reaches