Background Many researchers have studied natural forest litter and obtained a lot of achievements. The litter plays a major role in forest soil and water conservation, this is beyond doubt. However, it is lack of study on the litter characteristics of man-made forests, especially in the suburbs of cities.

Methods Water-holding characteristics and accumulated amount of litter in 8 species city man-made forests was studied in the suburb of Nanjing. Litter thickness (d) and accumulation (M) of litter were measured by sampling, natural water content (R₀), water holding rate (R_t), maximum water holding rate (R_max) and water absorption rate(V) were analyzed in laboratory, maximum retain rate(R_拦), maximum retain capacity (W_拦) were calculated and effective retain deepness was calculated.

Results 1) The effect of forest composition on litter characteristics was significant, litter thickness and accumulated amount showed significant difference in different communities (P < 0.05). 2) The change of litter thickness ranged from 2.10 to 5.24 cm, the descending order of litter thickness was as Cinnamomum camphora forest(Ⅰ), Michelia chapensis forest(Ⅱ), Ligustrum lucidum forest(Ⅲ), Liriodendron chinense forest(Ⅳ), Phyllostachys glauca forest(Ⅷ), Celtis sinensis forest(Ⅴ), Zelkova serrata forest(Ⅶ), Acer palmatum forest(Ⅵ), and the change of accumulated amount was the similar. The correlation analysis showed it was positive between litter accumulation (M) and its thickness (N), the linear equation was M=1.405 4d+0.665 4 (R²=0.823 4, P < 0.05). The change of water-holding capacity of litter in different forests was consistent, i.e., the water-holding capacity(W) increased sequentially with the increase of immersion time (t), and showing as an inverted "J" curve with the equation W=alnt+b. The water absorption rate of all litter showed another change, that was, the water absorption rate decreased successively with the increase of immersion time, showing as a "L" curve and the equation was fitted as v=at^b. 3) The R_max of the 8 plantations were 667.56%(Ⅶ), 462.90%(Ⅵ), 341.18%(Ⅴ), 292.19%(Ⅱ), 298.01%(Ⅲ), 290.76%(Ⅷ), 191.38%(Ⅳ), and 271.99%(Ⅰ). 4) The water-holding capacity of litter varied among different forests types, Z. serrata forest(Ⅶ) was the strongest by by comparing the W_sv, which was 26.32 t/hm², A. palmatum forest(Ⅵ), and L. lucidum forest(Ⅲ)were more strong, that of which were 16.64 t/hm², 16.44 t/hm². The W_sv of the L. chinense forest(Ⅳ) was only 9.55 t/hm², which was the weakest on the effective retain deepness.

Conclusions The water-holding capacity of different plantation communities was significantly different, and the selection of tree species and community types in urban plantation construction had an important effect on the water-holding capacity and water conservation ability of forest land. Cultivating Z. elkova forest is more reasonable development direction of urban forest construction in Nanjing at present because of its strong ability of the effective retain deepness to water and soil.