Effects of tending and management on water retention characteristics of litter layers of different types of Pinus Massoniana forest in the Three Gorges Reservoir area

Accurately grasping the effects of differences in stand structure composition and nursery management on the hydrological and ecological processes of different types of Pinus Massoniana plantation is of great significance in realising the sustainable management of Pinus Massoniana forests in the region. Taking different types of ponytail pine forests in the Three Gorges Reservoir area as the research object, and taking into account the differences in species composition and nursery management,four stand types of nurtured P. massoniana + Cunninghamia lanceolata mixed forest(Ⅰ), nurtured P. massoniana + Camellia oleifera mixed forest(Ⅱ), unmanaged P. massoniana pure forest(Ⅲ) and unmanaged P. massoniana + C.lanceolata mixed forest(Ⅳ) were selected as the research subjects by field investigation and indoor soaking method,the water-holding characteristics and water-holding capacity of litter layers of the different stand types were compared and analyzed. The results showed that the variation of litter storage in the four types of P. massoniana forest stands ranged from 16.45 to 24.67 t/hm², and the litter storage was in the order of Ⅳ > Ⅱ > Ⅲ > Ⅰ, and the storage in the semi-decomposed layer of litter was higher than the storage in the undecomposed layer. The maximum water-holding capacity of litter varied from 31.67 to 57.57 t/hm², and the maximum water-holding rate varied from 301.68% to 360.08%; the effective storage capacity of litter varied from 31.49 to 52.18 t/hm², and the effective storage rate varied from 173.74% to 227.77%. The effective storage capacity showed the order of Ⅱ > Ⅳ > Ⅲ > Ⅰ from large to small, and the effective storage rate of litter was ranked as Ⅱ > Ⅰ > Ⅳ > Ⅲ. Except for unmanaged P. massoniana + C.lanceolata mixed forest, the maximum water retention rate and effective storage rate of litter in the semi-decomposed layer were higher than those in the non-decomposed layer. The water holding capacity of dead wood was logarithmically related to the soaking time: W = alnt + b, and the water absorption rate was power-functional to the soaking time: V = at^b. In conclusion, among the four types of P. massoniana forest, the care-type nurtured P. massoniana + Camellia oleifera mixed forest has the best water retention effect in litter layer, and the P. massoniana needle-width mixed forests with strengthened nursery management could play the function of the deadfall layer in water conservation more effectively.