Increased forest cover reduced alpha diversity and reshaped the taxonomic and functional composition of riverine diatom communities

Résumé fourni par la source

Landscape changes, particularly variations in forest cover, significantly alter riverine environments. Yet, their impact on the taxonomic and functional patterns of benthic diatoms remains poorly understood. This study examines how forest cover gradients influence benthic diatom community composition and functional traits. It also evaluates the effects on taxonomic and functional diversity while identifying the primary environmental influencing factors. We conducted surveys at 385 river sites across landscape gradients in Ningbo, China. By collecting and analyzing benthic diatom samples, we assessed community structure and functional trait categories at high and low forest cover sites, identifying key influencing factors of diatom communities under these conditions. High forest cover sites exhibited lower nutrients and faster flow, favoring small-sized, highly attached, and profile taxa. Conversely, low forest cover sites supported motile, filamentous, and large-sized taxa under elevated nutrient conditions. Both taxonomic and functional alpha diversity were surprisingly higher in low forest cover sites. Influencing factors of diversity shifted markedly along this gradient. Natural factors, such as elevation and temperature, governed communities in high forest cover areas. Meanwhile, anthropogenic stressors, including nutrients and heavy metals, primarily shaped communities in low forest cover areas. Diatom assembly shifts from natural environmental filtering under high forest cover to pollution influenced filtering under low forest cover. Maintaining upstream riparian forests while mitigating downstream nutrient inputs is essential for supporting riverine ecological resilience.

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