Background Forest litter is the second layer of hydrological cycle in forest ecosystem and plays an important role in forest eco-hydrological process. The purpose of this study is to clarify the hydrological functions of the litter layer in the urban forest ecosystem of Jiangsu province.

Methods Based on the current research results on the function of natural forest litter layer, this study took the Wushan area of Nantong city as the research area in 2024, and selected five urban plantations such as Platycladus orientalis, Zelkova serrata, Cunninghamia lanceolata, Cinnamomum camphora, Koelreuteria paniculata in Jiangsu province. Field plots were set up, measurement, sampling and indoor immersion experiments were carried out to study the water-holding capacity and process of litter in five plantations. By analyzing the quantity of litter, the water-holding capacity of the litter layer and the water-absorbing rate, the water-holding characteristics of litter in several typical artificial forests were obtained, thereby further summarizing the tree species with better hydrological functions of litter in Jiangsu province.

Results 1) The litter accumulation of five typical plantations ranged from 2.17 t/hm² to 10.86 t/hm², and the litter accumulation in the undecomposed layer of litter was significantly higher than that in the semi-decomposed layer, and the proportion of undecomposed layer was in the range of 56.68 %–75.79 %, among which the proportion of undecomposed layer of C. lanceolata forest was the smallest.2) The water-holding capacity of the semi-decomposed layer of litter in the plantation was significantly stronger than that of the undecomposed layer, the maximum water-holding capacity of the undecomposed litter was in the range of 1.79–20.92 t/hm², and semi-decomposed layer was in the range of 2.50–21.98 t/hm². The water-holding capacity was P. orientalis forest < C. lanceolata forest < C. camphora forest < Z. serrata forest < K. paniculata forest. The water-holding capacity of Z. serrata forest and K. paniculata forest was significantly better than that of other tree species. The maximum water-holding capacity and effective storage capacity of Z. serrata forest were 28.55 t/hm² and 22.61 t/hm². The maximum water-holding capacity and effective storage capacity of K. paniculata forest were 37.49 t/hm² and 27.88 t/hm². 3) The water-holding capacity of litter in different plantations increased rapidly in the first 0.5 h and gradually stabilized after 2 h. The fitting relationship between litter water-holding capacity and time satisfied the logarithmic function relationship. The water-absorbing rate of litter decreased with time and kept approaching 0. The water-absorbing rate was the highest in 0–0.5 h, and the fitting relationship between water-absorbing rate and time satisfied the power function relationship.

Conclusions Among the typical urban forests, Z. serrata and K. paniculata forests have better water-holding capacity and are more suitable tree species for urban water conservation, sponge city construction and water balance regulation in Jiangsu province.