Abstract:
The suitable stand structure is beneficial for improving the ecological and economic functions of the stands. In order to provide scientific basis for sustainable management of
Cupressus funebris plantation in hilly area of central Sichuan, hydrological effects of litter layer and soil layer under different thinning intensity were compared, and the optimal thinning intensity of soil and water conservation was discussed. In 2007,
Cupressus funebris plantations with 35−40 year-old, canopy density ≥0.8, understory shrub coverage ≤20% and herb coverage ≤30% were selected, and three thinning intensities (I: 10%−15%, II: 16−25%, III: 26−35%) and CK (no thinning) were set by random block method. Based on the field sampling in 2019, the hydrological effect indexes such as soil bulk density, capillary porosity, total porosity, maximum water holding capacity, saturated water storage capacity and litter volume, natural moisture content, maximum water holding capacity, maximum water holding capacity, maximum retaining capacity and effective retaining capacity, as well as dynamic process simulation of litter water holding and water absorption were analyzed and caculated. The results showed that: (1) After thinning, the litter volume increased significantly. The total litter volume of thinning intensity I, II and III was 1.24, 1.78 and 2.38 times of CK, respectively. The maximum water holding capacity and effective storage capacity of thinning intensity III were 3.73 and 2.59 times of CK, respectively. Except thinning intensity II and CK, there were significant differences among other treatments (
P < 0.05). (2) The variation of water holding capacity of litter layer with soaking time followed the logarithmic function
W=
a−b×ln(
t+
c),
R2>0.95, and the variation of water absorption with soaking time followed the power function
V=
mtn,
R2>0.80. (3) The soil bulk density under different thinning intensities was significantly lower than that of CK. The soil capillary porosity of thinning intensity III was the largest (35.30±2.60%) and the control was the smallest (28.19±1.29%). The maximum water holding capacity of 0−30 cm soil was the highest in thinning intensity III (105.90±2.60 mm), followed by II (103.07±3.01 mm), and the smallest was CK (84.58±1.29 mm). The saturated water storage of different thinning intensities was higher than that of CK. The 0−30 cm soil saturated water storage of thinning intensity I, II and III was 1.09, 1.21 and 1.27 times of CK, respectively. Considering the hydrological effects of soil layer and litter layer, thinning intensity III, i.e. the number of trees reserved from 1700 indv. ·hm
−2 to 2100 indv·hm
−2, was the best optimum thinning intensity. The hydrological performance of the three thinning intensities was better than that of CK, indicating that thinning had a positive effect for improving the hydrological performance of forest stand.