Riparian vegetation provides the nutrient and energy input that maintains the metabolism and biodiversity in tropical headwater streams. In the present study, it was hypothesised that ~30% of riparian plant species contribute over 70% of coarse particulate organic matter and, because tropical plants are perennial and semi-deciduous, it was expected that leaf fall would occur year round. The aims of the present study were to evaluate the composition and structure of the plant riparian zone and the input and associated benthic stock of organic matter. The riparian vegetation was composed of 99 taxa. The most abundant plant species were Tapirira obtusa, Sclerolobium rugosum, Croton urucurana, Byrsonima sp. and Inga sp. The input and benthic stock showed a seasonal pattern, with higher values recorded at the end of the dry season and at the beginning of tropical storms. The biomass contributed monthly by the vegetation ranged from 28 ± 6 g m–2 to 38 ± 11 g m–2, and the mean monthly benthic standing stock was 138 ± 57 g m–2. The results illustrate the importance of riparian vegetation as an energy source to tropical streams and how individual plant species contribute to organic matter inputs in these ecosystems.
Aquatic plants have great influence on the structure and dynamics of aquatic ecosystems, thereby contributing considerably to biodiversity. In Brazil, knowledge of the biodiversity of aquatic macroflora is still limited. We present a checklist of aquatic macrophytes occurring in the northeastern region of Brazil through a bibliographic search. We recorded a total of 412 species, 217 genera and 72 families. The most representative families were Cyperaceae (70 species), Poaceae (38), Fabaceae (27) and Asteraceae (20). The States with highest number of species were Pernambuco (370), Bahia (360), Ceará (267) and Paraíba (261). The best-represented life forms were amphibious (193 species) and emergent (100). The aquatic flora of Northeastern Brazil exhibits high species richness; however, there is a scarcity of records of aquatic macrophytes for the States of Alagoas, Rio Grande do Norte, Maranhão, Sergipe and Piauí.
Evaluation of the eff ects of fl ooding on seedling recruitment from seed banks helps in understanding vegetation regeneration in fl oodplains. We studied the eff ects of simulated fl ooding on richness and abundance of, and temporal variation in, seedling recruitment from the soil seed bank of a fl oodable savanna of the Pantanal wetland, under two conditions: 1) Post-fl ood = inundated for 30 days followed by irrigation; 2) Non-fl ooded = only irrigated. We recorded emerged seedlings biweekly for 120 days and found a total of 124 species for the two treatments, the most abundant species were annual herbs (e.g., Richardia grandifl ora and Euploca procumbens) and annual graminoids (e.g., Digitaria ciliaris and Cyperus haspan). Flooding positively infl uenced seedling richness and abundance, while seedling emergence from the non-fl ooded soil was slower, but continued during all periods. Th e diff erent temporal patterns between treatments showed that fl ooding increases the abundance of emerged seedlings and acts as a trigger for explosive recruitment shortly after water depletion.
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