Effects of soil moisture and soil depth on nitrogen mineralization process under Mongolian pine plantations in Zhanggutai sandy land, P. R. China

The rates of soil N mineralization at soil depths of 0–15, 15–30, 30–45 and 45–60 cm and moisture regimes were measured at three sand-fixation plantations ofPinus sylvestris var.mongolica by laboratory aerobic incubation method. The results showed that average rates of soil net N-mineralization across soil depth varied from 1.06 to 7.52 mg·kg−1·month−1 at soil depths from 0 to 60 cm. Statistical analyses indicated that the effects of different soil depths, moistures and their interactions on net N-mineralization rates were significant (P<0.05). The net N-mineralization rates significantly decreased with increasing soil depths and at depth 0–15 cm accounted for 60.52% of that at depth of 0–60 cm. There was no difference in soil net N-mineralization rates between half and fully-saturated water treatments, however these rates were substantially higher than that without water treatment (P<0.05). The factors influencing N mineralization process have to be studied further in these semiarid pine ecosystems.