Abstract: We measured soil moisture and other soil physicochemical factors in depths of 0-10, 10-20, 20-40, 40-60, 60-80, 80-100 cm in different aged (13, 25-27, 42, 56 a) Pinus sylvestris var.mongolica plantations and adjacent grasslands (as control) on sandy land in non-rainfall seasons. We further analyzed the variation patterns of soil moisture of different aged  P. sylvestris var. mongolica plantations in non-rainfall season. The results showed that soil moisture in the 0-100 cm layer of young forest was higher than that of grassland. Soil moisture of middle-aged and mature forests decreased gradually across the soil profile. Soil moisture of middleaged forest in the 20-100 cm layer was lower than that of grassland, whereas soil moisture of mature forest was higher than that of grassland. Soil moisture in the over-mature forest showed an Sshaped curve in the soil profile. Soil moisture in the 0-10 cm layer did not change with the stand age, while that in the 10-20 cm layer was negatively correlated with stand age. The soil moisture in the 20-100 cm layer showed a trend of decreasing first and then increasing over stand age. Soil moisture in over-mature forest was higher than that of middle-aged and mature forests. The soil moisture was significantly positively correlated with the alkali hydrolyzable nitrogen in the 10-40 cm layer, significantly positively correlated with the available potassium in the 40-60 and 80-100 cm layers, but did not correlate with other physicochemical factors in the 0-10 and 60-80 cm layers.

Key words: Pinus sylvestris var. mongolica forest in sandy land, stand growth, non-rainfall season, soil moisture.