Vegetation chronosequence in Hong Kong: Soil properties and successional development

The soil properties of a vegetation chronosequence in Hong Kong involving a grassland, a 22-year mixed woodland, a 52-year forest and two graduation 150-year old climax (fens shui) forests were examined. The objectives were to test the three hypotheses: (1) then are no significant differences in soil chemical properties between different climax forests, (2) exotic species are inferior to native species in soil amelioration; and (3) organic carbon, nitrogen and cation nutrients tend to accumulate in the soils during successional development of the vegetation. The results show that the soils along the vegetation chronosequence are strongly acidic in reaction, contained moderate to high levels of organic carbon, high exchangeable acidity, and low levels of mineral nitrogen (NH, and NO3), available phosphorus and cation nutrients. All the three hypotheses are rejected. While the feng shui forests differed markedly in soil properties, exotic species were superior to native species in augmenting soil organic carbon, mineral nitrogen and exchangeable Ca. There was no accumulation of organic carbon, nitrogen and cation nutrients with ecological succession, due to the influence of patchy fire, species composition, parent materials and distance from the sea.