Hydrology Drives Vegetation Succession in a Tidal Freshwater Wetland of Subtropical Taiwan

Abstract

The relationships between vegetation communities and environmental variables in tropical/subtropical tidal freshwater wetlands are poorly understood. We tracked the vegetation succession of the Huajiang wetland in northern Taiwan for 10 years since its emergence in 2000, likely due to massive sediment deposition caused by typhoon floods. The aquatic plant Phragmites australis expanded and dominated the wetland within the first four years, after which terrestrial herbaceous plants appeared. In 2007, woody plants were found scattered in the wetland. In 2010, the vegetation communities became more diverse. Along the gradient of increasing elevation with decreasing soil water content, three vegetation zones were distinguished: aquatic, terrestrial, and transitional. Along the second gradient of distances from the nearest tidal creek, the transitional zone could be further differentiated into more aquatic and more terrestrial zones. Our results indicate that hydrology engaging soil moisture and sedimentation was the major force driving the vegetation succession in the tidal freshwater wetland. These findings suggest that the vegetation community in tidal freshwater wetlands can be used as an indicator to monitor management measures and assess the impacts within the wetland and catchment.