Plantas aquáticas em lagoas temporárias do semiárido, nordeste do Brasil

Abstract

Temporary ecosystems are characterized by having alternating hydrological phases and unstable ecological conditions influencing the composition and structure of aquatic plant communities. The potential of each species to use nutrients, organic matter, light and carbon incorporating them into their biomass as well as the ability to take advantage of favorable environmental conditions to form a viable seed bank allow us to infer the life strategies of different ecological types of these plants in temporary environments. In this context, this study had two main objectives elucidated in two manuscripts: The first, titled "What factors influence the biomass of aquatic plants in temporary ponds of the semiarid region?", aimed primarily to evaluate the influence of water and sediment parameters on the structure of aquatic macrophyte communities. For this, we assessed the biomass of aquatic plants and various parameters of water and sediment in 14 temporary ponds. The second, titled "Composition and structure of aquatic plants seed banks in temporary ponds of semiarid Brazil" aimed primarily to understand how the community of aquatic plants is reconstructed from the seed bank in the soil. For that, an experiment with seed germination was conducted which evaluated the floristic composition and density as an attribute of the structure of the seed banks formed in nine temporary ponds. In general, the results obtained through studies in these environments have shown that among the processes that shape the community of aquatic macrophytes in temporary ponds, water parameters contributed the most. Factors strongly associated with biomass of aquatic plants were total phosphorus (water), ammonia nitrogen (water), dissolved oxygen (water), pH (sediment), organic matter (sediment), iron (sediment) and zinc (sediment). Abundant species such as Heteranthera limosa and Ludwigia decurrens were associated with pH (water), Al (sediment), Fe (sediment), NO3 (water), turbidity (water) and O2 (water). The floristic composition was similar among the studied ponds whereas the structure was dissimilar. Opportunistic species were predominant and presented high values of population density in the seed bank. Most of the species that germinated in the seed bank were different from those germinated in the field.