Pedosphere 18(6): 775--784, 2008
ISSN 1002-0160/CN 32-1315/P
©2008 Soil Science Society of China
Published by Elsevier B.V. and Science Press
Soil inorganic nitrogen and microbial biomass carbon and nitrogen under pine plantations in Zhanggutai sandy soil
YU Zhan-Yuan1, CHEN Fu-Sheng2, ZENG De-Hui1, ZHAO Qiong1 and CHEN Guang-Sheng3
1 Daqinggou Ecological Station, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016 (China). E-mail:
2 Life College, Nanchang University, Nanchang 330029 (China)
3 Ecosystem Sciences and Regional Analysis (ESRA) Lab., School of Forestry & Wildlife Science, Auburn University, Alabama 36849 (USA)
      The dynamics of soil inorganic nitrogen (NH4+-N and NO3--N) and microbial biomass carbon (Cmic) and nitrogen (Nmic) under 30-year-old fenced Pinus sylvestris L. var. mongolica Litvin (SF), unfenced P. sylvestris L. var. mongolica Litvin (SUF), and unfenced Pinus densiflora Siebold et Zucc. (DUF) plantations in the Zhanggutai sandy soil of China were studied during Apr. to Oct. 2004 by the in situ closed-top core incubation method. All mentioned C and N indices in each stand type fluctuated over time. The ranges of inorganic N, Cmic, and Nmic contents in the three stand types were 0.7-2.6, 40.0-128.9, and 5.4-15.2 μg g-1, respectively. The average contents of soil NH4+-N and Cmic under the three 30-year-old pine plantations were not different. However, soil NO3--N and total inorganic N contents decreased in the order of SUF ≥ SF ≥ DUF, the Nmic content was in the order of SF = SUF > DUF, and the Cmic:Nmic ratio was in the order of SUF = DUF > SF. Seasonal variations were observed in soil inorganic N, microbial biomass, and plant growth. These seasonal variations had certain correlations with microbe and plant N use in the soil, and their competition for NH4+-N was mostly regulated by soil N availability. The influence of tree species on inorganic N and Nmic were mainly because of differences in litter quality. Lack of grazing decreased the Cmic:Nmic ratio owing to decreased carbon output and increased the ability of soil to supply N. The soil N supply under the P. sylvestris var. mongolica plantation was lower than under the P. densiflora plantation.
Key Words:  ecosystem management, Horqin sandy land, soil nitrogen availability, Pinus densiflora, Pinus sylvestris var. mongolica
Citation: Yu, Z. Y., Chen, F. S., Zeng, D. H., Zhao, Q. and Chen, G. S. 2008. Soil inorganic nitrogen and microbial biomass carbon and nitrogen under pine plantations in Zhanggutai sandy soil. Pedosphere. 18(6): 775-784.
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