Abstract: Although the forest floor plays important roles in water-holding and nutrient cycling, there is not enough knowledge of the functional changes of the forest floor resulting from changes in vegetation. To evaluate the effect on the hydrological properties of forest floor by the substitution of plantation species for native coppice, we selected four species substituting plantations and one native coppice (secondary native broad-leaved forest, dominated by Quercus liaotungensis and Corylus heterophylla var. sutchuenensis) (QC) as a comparison forest. The substituting plantations were Cercidiphyllum japonicum (Cj), Pinus tabulaeformis (Pt), Pinus armandi (Pa), Larix kaempferi (Lk). These were established in 1987 with a stocking density of approximately 2500 stem ha^-1. Thickness and the amount of floor in coniferous plantations were significantly higher compared to secondary native broad-leaved forest and pure broadleaved plantation. The maximal water-holding capacity of the floor showed the same trend as thickness and amount of litter. Main contributors to the difference in hydrological characteristics in the plantations were the quantity of forest floor and the maximal water holding capacity per unit weight of the floor. The relationships between water absorption processes, water absorption rate and the immersion time for litter, fitted to logarithmic and exponential regressions, respectively. Water absorption processes differed significantly between the various plantations and different decomposition floor horizons. Water absorption characteristics were influenced by leaf structure in various tree species and the degree of decomposed litter. Our results showed that litter amount in coniferous plantations were significantly higher than in deciduous broad-leaved plantation. This suggests that a large amount of nutrients are held in the litter horizon, delaying return to the soil and utilization by plants. At the same time, maximal water-holding capacity of the forest floor in F [fermentation] and H [hummus] horizons was significantly higher than that in L [fresh litter] horizon. Therefore, improving litter transformation from L horizon to F and H horizons by promoting forest floor environment would be one of the best methods for plantation management.

Key words: forest floor, plantation substitution, water absorption rate, water-holding capacity, ecology restoration, eastern Tibetan Plateau