Effects of Typhoon Disturbances on Soil Microbial Activities in an Uplifted Coral Reef Tropical Forest, Southern Taiwan

Two sites of an uplifted coral reef forest in southern Taiwan were chosen, and soil microbial
activities were analyzed by considering typhoon disturbances during 2004 and 2005. The aims of
this study in the Kengting Uplifted Coral Reef Nature Reserve (KUCRNR) were to illustrate the
effects of typhoon disturbances upon the spatial and temporal variations in soil microbial biomass
and respiration. The vegetation of the ridge site on the exposed coral reef was dominated by Aglaia
formosana and Pouteria obovata, and that of the valley site at the bottom between reefs was
dominated by Pisonia umbellifera. Regarding microbial activities, the seasonal monitoring of soil
microbial biomass carbon (MBC) and nitrogen (MBN) and basal respiration (CO2-C evolution)
was conducted for surface soils at the 2 sites including the onsets of typhoon events. Six typhoons
occurred in the study area in the 2 yr. The soil microbial activities significantly varied at the 2 sites.
The effects of the disturbance events upon the soil system by the typhoons were highly variable in
terms of temporal changes in MBC, MBN, and basal respiration for both sites. The MBC values
in summer, autumn, and winter with typhoons were significantly (p < 0.05) lower than those in
spring without typhoons in both two sites during 2004, but these differences caused by typhoons
were not found in 2005. These contradictory results in seasonal differences of MBC by typhoon
disturbances were also found in MBN and basal respiration. Furthermore, the values of the above
soil microbial activities at the ridge site are generally lower than those at the valley site, because of
larger nutrient losses through runoff at the ridge site than at the valley site. The major driving force
of runoff is the heavy rainfall during typhoon events associated with steep slopes of the ground
surface. Nevertheless, the typhoon events disturbed these soil microbial activities which did not
show discernible seasonal trends.