Abstract:

Soil organic carbon (C) and nitrogen (N) are important components of soil nutrients. In order to explore the variation of soil nutrient contents, soil C and N contents and C:N ratio were investigated in Koelreuteria paniculata forests grown in wasted manganese mine lands in Xiangtan, Hunan for different years in an vegetation restoration program. The result showed that soil C and N contents increased with the increase of the restoration time. The soil C content was 13.36, 14.78, and 26.96 g·kg^-1 in 3-, 5- and 9-year-old stands, respectively, and they were 1.30, 1.44 ,and 2.63 times of the control plot (10.27 g·kg^-1), respectively. The N were 0.54, 0.59, and 1.12 g·kg^-1 in 3-, 5- and 9-year-old stands, respectively, which means that they were about 38%, 51% and 187% higher than the control plot (0.39 g·kg^-1), respectively. The soil C and N were significantly higher in 9-year-old stands than the control plot (P<0.05). The soil C and N varied with soil depths in the forests at different restoration stage. The C:N ratio in soil ranged from 26.60 to 23.75 at different restoration stages of forests, and decreased with the increase of the duration. The soil C:N ratio declined by 2.79 in 9-year-old stands compared to control stands. In the study site, soil pH was slightly positively correlated to soil C and N contents, as well as soil C:N ratio (P >0.05). There was a significantly positive correlation between soil C content and soil N content (P <0.01). Significantly positive correlations were found between soil C content and C:N ratio (P <0.01) while positive correlations were found between soil N content and C:N ratio (P <0.05). Our results provided scientific reference for examining the dynamics of soil nutrients during restoration and evaluating the effects of vegetation restoration in mining wastelands.

Key words: Koelreuteria paniculata, vegetation restoration, wasteland, soil, carbon, nitrogen, C/N