Abstract: To clarify water conservation capacity of forests in water source area of the Middle Route of South to North Water Transfer Project in flood season, we estimated water conservation capacity of Pinus massoniana plantations with different stand densities in Longkou Forest Farm of Danjiangkou Reservoir area. Three densities (i.e., high, medium and low) of P. massoniana plantations were chosen, and the waterholding capacity of the canopy, litter and soil layers for each density was examined from June to September 2018, using field observations and laboratory analysis. The canopy interception of three densities of P. massonianaplantation ranged from 56.13 to 77.68 mm, which increased with the increasing stand density, while the penetrating rainfall showed an opposite trend. Litter biomass increased with the increasing stand density with a range of12.76-19.56 t·hm^-2. Litter biomass was greater in the non-decomposition layer than that in the semidecomposed layer. The total litter thickness under high density was the largest, followed by medium and low density. The maximum and effective water holding capacity of litter varied from 21.32 to 28.24 mm and from 16.82 to 22.51 mm, respectively. Both parameters showed the following trend: medium density>high density>low density. The water holding capacity and water absorption rate of litter had a logarithmic and power function with soaking time, respectively. Soil bulk density inP. massoniana plantation with low density was the largest, followed by high and medium density, with a range of 1.45-1.54 g·cm^-3 at the depth of 0-30 cm. The rank of total soil porosity for the three stand densities was opposite to that of soil bulk density, with a mean ranging from 42.18% to 45.71%. The effective water holding capacity of soil varied from 2.94 to 4.81 mm, and ranked in the order of medium density>low density>high density.The overall water conservation capacity of P. massoniana plantation was 204-237.55 mm, with an order: medium density>high density>low density. In summary, the medium density ofP. massoniana plantation exhibited the highest water conservation capacity. Reasonable density of P. massoniana stand should be maintained in forest management in the future.

Key words: landscape pattern, ecological risk, scale effect, corridor cutting, plateau railway.