Response of Soil and Litter Chemical Characteristics to Simulation of Nitrogen Deposition in Quercus castaneifolia Stand

The patterns of nitrogen distribution in the world are changing and today have become a serious environmental problem. The aim of this study was to investigate the biochemical response of soil and litter to simulated nitrogen deposition in chestnut-leaved oak (Quercus castaneifolia). Four treatments in twelve plots of 20 m × 10 m2 were randomly established in the plantation stand. Four simulated nitrogen deposition treatments were considered including zero (control), 50 (low), 100 (medium) and 150 (high) kg N ha−1 year−1, with four seasons in each month. At the end of the simulated period, an increasing trend in nitrogen, phosphorus and potassium was observed in high nitrogen deposition treatment. The carbon in the litter layer at the end of the simulated period was also significant (P < 0.01) at levels of 100 and 150 kg N. At the end of simulation period, the lowest soil pH changed were observed in the high treatment and the highest in the control treatment. The highest amount of potassium and phosphorus were observed in control treatment 290±5 and 15±0.1, respectively, while in the high simulated nitrogen treatments the lowest values were 221±4 and 8.1±0.1, respectively. The results of this study showed that when the nitrogen content in the soil increased, it could decrease the rate of decomposition and microbial activity in the soil and cause a change in the chemical composition of the litter layer.