Abstract
Floodplain lakes and associated wetlands in tropical dry climates are controlled by pronounced and severe seasonal hydrologic fluctuations. We examined the plant community response to a bimodal flooding pattern in the Zapatosa Floodplain Lake Complex (ZFLC), Northern Colombia. We measured floristic and quantitative change in four sampling periods emphasizing seasonal differences in plant abundance and life-form structure. Of 79 species identified in the lake complex, 52 were used to characterize eight community types via classification and ordination procedures. Results showed that community structure does not change significantly during the flooding/receding stages. But maximum drawdown phase significantly disrupts the aquatic community structure and the exposed shorelines become colonized by ruderal terrestrial plants. Early rainfalls at the beginning of the wet season are emphasized as an important feature of plant regeneration and community development. The general strategy of the ZFLC vegetation can be framed into the flood pulse concept of river-floodplain systems. Thus, plant communities are mainly responding to disturbances and destruction events imposed by extreme water level fluctuations.
Highlights
Floodplains play an important role regarding the biogeochemistry and ecology of tropical river systems
We examined the shoreline of the Zapatosa Floodplain Lake Complex (ZFLC) with emphasis on seasonal differences in macrophyte abundances and lifeform structure
Related to objective (2), we expected that the environmental filters associated with the bimodal flooding and drawdown phases would greatly shape the seasonal plant assemblages, and hypothesize that the inundation event increases the similarity of the vegetation structure with increasing flooding
Summary
Floodplains play an important role regarding the biogeochemistry and ecology of tropical river systems. Plant and animal life of this particular system are adapted to the seasonal variations in space and time caused by extreme water level fluctuations This seasonality represents an important factor in the speciation of several aquatic and wetland plants (Haynes & Holm-Nielsen, 1989). The interactions between rivers and their surrounding floodplain motivated Junk, Bayley, and Sparks (1989) to propose the ‘flood pulse concept’ as a main force controlling the biota of tropical floodplains. They considered the floodplain as the area periodically inundated by the waters of rivers, lakes, lagoons, and/or underground water, or by direct precipitation. Related to objective (2), we expected that the environmental filters associated with the bimodal flooding and drawdown phases would greatly shape the seasonal plant assemblages, and hypothesize that the inundation event increases the similarity of the vegetation structure with increasing flooding
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