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Ma F.,Province Ministry Co Constructed Ministry of Education Key Laboratory of Humid Subtropical Eco geographical Process | Ma F.,Fujian Normal University | Ma H.-L.,Province Ministry Co Constructed Ministry of Education Key Laboratory of Humid Subtropical Eco geographical Process | Ma H.-L.,Fujian Normal University | And 4 more authors.
Chinese Journal of Applied Ecology | Year: 2015

An incubation experiment was conducted to investigate the effects of the additions of different nitrogen forms on nitrogen transformation in red soils of subtropical forest under soil moisture conditions with 40%, 70% and 110% of water holding capacity (WHC). The results showed that soil net mineralization and ammonification rates were maximum at 70% WHC and minimum at 40% WHC. Compared with the control, the addition of NO3 -N decreased the soil net mineralization and ammonification rates by 56.1% and 43.0% under 70% WHC condition, and decreased by 68.2% and 19.0% under 110% WHC, respectively. However, the proportion of ammonification to mineralization increased at 70% and 110% WHC, which suggested that nitrate addition inhibited the nitrification. With addition of NO3 -N at 110% WHC, the net nitrification rate was lowest while N2O emission was highest with the concomitant decrease of nitrate content, indicating that N2O emission was largely derived from denitrification. However, at 40% WHC and 70% WHC, the maximum N2O flux was found at the early stage of incubation. Even with addition of NH4 +-N and NO3 -N, N2O flux did not change much at the latter stage of incubation, indicating that autotrophic nitrification was dominant for N2O production at the early stage of incubation. Under 40% WHC condition, soluble organic carbon increased more and it increased largely with NH4 +N addition, which meant NH4 +N addition could enhance the mineralization of soil organic matter. Under 40% and 110% WHC conditions, the addition of NH4 +N increased significantly the soil soluble organic nitrogen (SON) by 73.6% and 176.6% compared with the control, respectively. A significant increase of 78.7% for SON was only found at 40% WHC under addition of NO3 -N compared with the control. These results showed that high soil moisture condition and addition of NH4 +N were of benefit to SON formation. ©, 2015, Editorial Board of Chinese Journal of Applied Ecology. All right reserved. Source

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