Width Identification and Spatiotemporal Change in the Landscape Ecotones in the Poyang Lake Sandy Land Based on an Advanced Remote Sensing Ecological Index

ABSTRACT The landscape ecotones at the edge of Poyang Lake Sandy Land are of critical for ecological conservation and restoration, and the spatiotemporal evolution of their location and structure indicating regional sand advancement and retreat. However, rapid changes in regional surface landscapes and complex environmental disturbances have hindered dynamic and quantitative assessments of ecotone positions and widths. This study aimed to precisely identify landscape ecotone widths and analyze their spatiotemporal variation characteristics. We focused on the ecotones between sandy land and adjacent landscapes (croplands, wetlands, and forests) at the landward edges of the Xingzi and Duobao Sandy Lands in the Poyang Lake region. An advanced remote sensing ecological index (ARSEI) was constructed, and five phases of imagery from 2000 to 2024 were applied to precisely identify the landscape ecotone width through piecewise linear fitting and habitat gradient change validation. We found that Xingzi Sandy Land's northern edge ecotone width ranged from 421 to 826 m, exhibiting a decreasing–increasing–decreasing trend. The central and southern edge ecotones were approximately twice as wide, with annual growth centrally and slow decrease southward. Duobao Sandy Land ecotone widths (279–746 m) were significantly smaller, showing initial decrease then later increase. Field investigations of vegetation and soil property factors confirmed that spatial positions and widths closely aligned with ARSEI‐derived measurements. Pronounced sand retreat phenomena occurred in Xingzi's northern area and Duobao's southern area, suitable for natural restoration. The Xingzi's central and southern areas of ecotones require priority ecological restoration due to significant width fluctuations. Human activities (sand mining, industrial construction, tourism) must be strictly regulated in these areas.