| The thesis investigated the static and dynamic soil chemical properties of a vegetation chronosequence affected by hill fire in Tai Mo Shan, Hong Kong. Five chronosequence units were studied, where fire has been absent for 0 (F0), 1 (F1), 3 (F3), 6 (F6) and 17 (F17) years. They represent the new burnt, short grassland, tall grassland, tall grassland and shrubland, and woodland sites, respectively. Four hypotheses were tested as follows: (1){A0}While the effects of fire on soil chemical properties are well documented in the literature, the morphological properties are not easily recognizable in the field. (2){A0}The soil chemical properties of the new burnt site (F0) are different from the predominantly grassland sites (F1, F3 and F6) where fire has been absent for 1 to 6 years. (3){A0}There is a build-up of soil organic matter (SOM) and nutrients with successional development of the vegetation community towards the woodland (F17) stage. (4){A0}While fire events result in a flush of mineral N in the soil system, its availability increases even more profoundly with successional development of the vegetation in the absence of fire.; To test the above hypotheses, the profile morphology, immediate effects of fire, static and seasonal dynamics soil nutrients were studied in the field and under laboratory conditions, at 0--5 cm and 5--10 cm depths. It is difficult to isolate the effects between fire and vegetation on profile morphology of the soil pits. However, the thickness of the O (1.5--6 cm) and A (4.5--21 cm) horizons decreased consistently with successional development up to the F6 stage. The corresponding values for the woodland site (F17) were 3 and 8 cm. The possible effects of fire were discussed.; Mineral N fluxes were investigated using the sequential in situ soil core technique.; The chronosequence units experienced different fire events in the last two decades. While static and dynamic nutrient status of the soils are clearly demonstrated, the findings are relevant to our understanding of ecological succession after fire disturbance and to the management of country parks in Hong Kong. (Abstract shortened by UMI.)... |
