Scale-dependent mechanisms of karst ecosystem service drivers revealed by landscape pattern indices

Identifying driving factors is fundamental for ecosystem service management, yet these relationships exhibit strong scale dependence. While previous studies have recognized this scale effect, the underlying mechanisms governing how driving factors respond to scale variations remain poorly understood. To address this knowledge gap, we conducted a comprehensive multi-scale analysis of dominant factors affecting soil conservation and water yield services across 11 distinct grid sizes (ranging from 30 m to 1000 m) and three hierarchical spatial extents (provincial, municipal, and county levels) in Guizhou Province, a typical karst region. By incorporating landscape pattern indices, particularly the Interspersion and Juxtaposition Index (IJI), we elucidated the fundamental mechanisms behind differential scale responses. Our results reveal that IJI serves as a robust predictor of scale sensitivity: (1) Slope (high IJI > 70) exhibited strong grid-size dependence as the primary driver of soil conservation, with its explanatory power decreasing dramatically from 0.24 (30 m) to 0.05 (1000 m); (2) Precipitation (low IJI < 55) dominated water yield but showed greater sensitivity to extent changes, particularly in the transition from municipal to county-level analysis. This is due to the diminishing spatial heterogeneity of precipitation as the extent decreases. This study establishes IJI as a powerful diagnostic indicator for predicting scale-dependent behaviors of ecosystem service drivers, providing a scientific basis for multi-scale ecosystem management and conservation planning.