Pedosphere 15(2): 181--, 2005
ISSN 1002-0160/CN 32-1315/P
©2005 Soil Science Society of China
Published by Elsevier B.V. and Science Press
| Nitrogen mineralization in soils along a vegetation chronosequence in Hong Kong |
L. M. MARAFA and K. C. CHAU |
| Centre for Environmental Policy and Resource Management, Department of Geography and Resource Management, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong (China). Email: lmmarafa@cuhk.edu.Hk |
| ABSTRACT |
| This research examined nitrogen mineralization in the top 10 cm of soils along a vegetation gradient in Hong Kong at sites where fire has been absent for 0, 1, 3, 6 and 17 years (at the time of the study), and the relationships between N mineralization and successional development of vegetation in the absence of fire. The sites including a newly burnt area (S1), short grassland (S2), tall grassland (S3), mixed tall grassland and shrubland (S4), and woodland (S5) were selected, and the in situ core incubation method was used to estimate nitrogen mineralization. Throughout the 60-day incubation in four periods, more nitrogen was mineralized at the S3 and S4 sites, the predominantly grassland sites, which contained the highest levels of soil organic matter (SOM) and total Kjeldahl nitrogen (TKN), than the S1 site, while immobilization occurred at the S2 and S5 sites. Leaching loss decreased with successional development of the vegetation, in the order of S1 > S2 > S3 > S4 > S5. The pattern of nitrogen uptake with ecological succession was less conspicuous, being complicated by the immediate effect of fire and possibly the ability of the woodland species to extract nitrogen from the deeper ground. In the absence of fire for 3 to 6 years, the build-up of SOM and TKN was accompanied by active mineralization, thus paving the way for the invasion of shrub and tree species. A close relationship existed between nitrogen mineralization and ecological succession with this vegetation gradient. Inherent mechanisms to preserve nitrogen in a fire-prone environment including immobilization and uptake and the practical relevance of nitrogen mineralization to reforestation are discussed. |
| Key Words: fire impact, immobilization, nitrogen mineralization, successional development, vegetation chronosequence |
| Citation: Marafa, L. M. and Chau, K. C. 2005. Nitrogen mineralization in soils along a vegetation chronosequence in Hong Kong. Pedosphere. 15(2): 181-. |
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