Abstract: Abstract Aims Water depth is a critical environmental factor in wetland ecosystems, influencing plant growth, regeneration, and distribution patterns. As an essential component of natural ecosystems, litter affects the regeneration of plant seedlings through various mechanisms such as light attenuation, mechanical obstruction, and allelopathy.Wetland ecosystems tend to accumulate a larger amount of litter because of flooding and anaerobic conditions. However, few studies have paid attention to the interactive effects of litter cover and water depth changes on the regeneration of plant seedlings. Methods This research simulated the field environmental conditions in mobile rain shelters to analyze the influences of water depth variation (wet, water-saturated, and flooded) and litter cover(0, 500, 1000, and 1500 g/m2) on the seed germination rates and emergence rates of Echinochloa crus-galli, E. crus-galli var. mitis, Bidens pilosa, and Alisma plantago-aquatica. Important findings The results demonstrated that the seed germination rates and emergence rates of E. crus-galli, E. crus-galli var. mitis and A. plantago-aquatica were significantly affected by litter cover, moisture conditions, and their interactions, while B. pilosa was only significantly influenced by litter cover. Litter cover decreased the germination and emergence rates of B. pilosa by 59.4% to 96.9% and 94.4% to 100% respectively. The germination rate of B. pilosa seeds beneath the litter was significantly reduced by 94% compared to that above the litter, indicating that the shading effect resulting from litter cover was the primary cause restricting the germination of B. pilosa seeds. The germination rate of A. plantago-aquatica seeds was nearly zero under wet conditions, but increased to over 30% in water-saturated or flooded environments, suggesting that sufficient moisture is of vital importance for the germination of A. plantago-aquatica seeds. Under water-saturated or flooded conditions, 29% to 60% of the seeds of A. plantago-aquatica can germinate when covered by litter. However, only 1.5% to 17% of the seedlings can penetrate through the litter layer. It was supposed that the mechanical obstruction caused by the litter cover is the crucial factor influencing the seedling regeneration of A. plantago-aquatica.This study provides fundamental data for revealing the distribution patterns and succession dynamics of wetland vegetation under environmental changes and holds significant importance for the ecological restoration and scientific management of wetland vegetation. Key words Litter; Water depth; Wetland ecosystem; Seedling germination

Key words: Key words Litter, Water depth, Wetland ecosystem, Seedling germination