<p>Understanding the multi-scale effects of habitat fragmentation on biodiversity is essential for effective conservation in a rapidly changing world. Here, we assessed plant functional composition in edge and interior plots across 28 islands in Thousand Island Lake, China. Plants were categorized into four functional groups based on life form and shade tolerance. Functional composition was defined as the proportions of functional groups in each plot, island, and virtual landscape. Differences between edge and interior plots were analyzed using the Wilcoxon test, and correlations with island area were evaluated using Spearman rank correlation. The relationship between functional composition and total habitat amounts in virtual landscapes was investigated using SLOSS analysis. We found that interior plots had higher proportions of shade-tolerant trees and lower proportions of shade-intolerant trees, regardless of whether richness- or abundance-based metrics were used. The functional composition of shrubs showed minimal variation with plot type, though edge plots had a higher proportion of shade-tolerant shrubs. Island area affected functional composition differently at the island scale, depending on whether richness-based or abundance-based metrics were used. The relationship between total habitat amounts and functional composition exhibited threshold patterns with unstable and stable phases at the landscape scale. Our study reveals a hierarchical structure in the multi-scale impacts of habitat fragmentation on plant functional composition and highlights different responses of functional groups across scales. Thus, we conclude that fragmentation research must consider ecological impacts at multiple scales and from multiple perspectives.</p>