Abstract: Analyzing the effects of thinning on litter storage and hydrological characteristics can provide a scientific support for the establishment of Chinese fir (Cunninghamia lanceolata) plantation and the improvement of its water-conserving function. A randomized block experiment was designed in a 13-year-old Chinese fir plantation in the Yangkou State-owned Forest Farm in Fujian Province, with four thinning intensities: no thinning (control), light, moderate, and high thinning intensity. We analyzed the litter storage capacity, water absorption characteristics, and interception capacity of each decomposition layer of the Chinese fir plantation under the four thinning intensities using field investigation and indoor immersion methods. The litter stock under the four treatments ranged from 4150 kg·hm^-2 to 7148 kg·hm^-2. The litter accumulation under the moderate thinning was 21.06% and 75.06% higher than that under light and high thinning, respectively, and the litter stock in the half-decomposed layer was 3.38 times of that in the undecomposed layer. The relationship between water capacity (W), water absorption rate (V) and immersion time of undecomposed and half-decomposed litters was described with the function models of W=a+blnt and V=kt_n, respectively. The former increased rapidly before 4 h, while the latter decreased rapidly from 0 to 4 h. The water holding capacity and water absorption rate of the half-decomposed layer were higher than those of the undecomposed layer, and were higher in the moderate thinning treatment than in the other three treatments. Thinning significantly changed the maximum water holding capacity (14011-23600 kg·hm^-2), maximum storage capacity (10450-17840 kg·hm^-2) and effective storage capacity (8340-14310 kg·hm^-2) of litter layer, with the strongest effect of the moderate thinning. The values of the hydrological characteristics of litter were greater in the half-decomposed layer than in the undecomposed layer. It is suggested that moderate thinning should be adopted in the management of Chinese fir plantations in this area to maximize the benefit of forest water conservation.

Key words: thinning, Cunninghamia lanceolata, litter, hydrological characteristics