Biodegradable mulching and nitrogen fertilization differentially affect AM fungal community structure and functioning in a semi-arid maize agroecosystem.

Arbuscular mycorrhizal (AM) fungi are central to plant nutrient acquisition and soil functioning, yet how biodegradable mulching and nitrogen (N) fertilization jointly regulate AM fungal communities and maize productivity remains poorly understood. We conducted a factorial field experiment combining biodegradable mulching with five N fertilization rates ranging from 0 to 300 kg N ha⁻¹. Soil properties, plant nutrient status, AM fungal richness and community composition, root length colonization (RLC), and maize yield were assessed across the jointing, silking, and filling stages. N fertilization markedly increased RLC but reduced AM fungal richness, revealing a decoupling between taxonomic diversity and root colonization. Neither mulching nor N fertilization had a significant main effect on AM fungal community composition across the three growth stages, although their interaction was significant at the jointing stage. Beta-diversity partitioning further showed that community dissimilarity was dominated by taxon turnover rather than nestedness. Environmental associations with community composition were growth-stage dependent and strongest at the jointing stage. Partial least squares structural equation modeling further showed that fertilization promoted maize yield through enhanced root colonization and plant N acquisition, whereas mulching affected N uptake through contrasting effects on soil hydrothermal conditions and soil fertility. Collectively, these findings suggest that integrating optimized N fertilization with biodegradable mulching can improve maize productivity while supporting mycorrhizal functioning in water-limited agroecosystems.