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As herbáceas aquáticas são indicadoras da composição nutricional dos corpos de águaamazônicos e de suas áreas alagáveis, pois sua riqueza e abundância refletem as características físicas e químicas da bacia onde estão inseridas. Elas possuem diversas funções ecológicas, como proporcionar abrigo e alimento para organismos aquáticos e terrestres. Neste estudo, foi analisada a riqueza, diversidade e composição de espécies de herbáceas aquáticas e sua distribuição em nove igapós de água preta na Amazônia brasileira, dentro e fora de unidades de conservação (UCs). Os resultados foram obtidos por meio de inventários realizados entre os anos de 2009 e 2017, nos rios Negro, Jaú, Aracá, Cuiuni, Uatumã e Abacate. Foram amostradas 148 parcelas retangulares de 100 x 1m, distribuídas em nove pontos amostrais (6 a 29 parcelas por ponto). O levantamento florístico revelou 174 espécies, distribuídas em 99 gêneros e 46 famílias botânicas, predominando as famílias Cyperaceae (43 ssp.), Poaceae (33 ssp.) e Marantaceae (10 ssp.). As áreas apresentaram baixa similaridade florística, sendo que nenhuma espécie ocorreu em todas as áreas amostradas. As espécies Montrichardia arborescens (L.) Schott (Araceae) e Scleria secans (L.) Urb (Cyperaceae) foram as mais frequentes, ocorrendo em seis das nove áreas amostradas. Apenas 49,2% das espécies de herbáceas aquáticas amostradas estão presentes nas UCs inventariadas, indicando que estratégias de conservação que envolvam mais áreas de igapó de águas pretas precisam ser consideradas para a proteção desse importante grupo de plantas.

No abstract

Aquatic macrophytes are a key group in flooded areas due to their high primary productivity, and several species present in the Amazonian floodplains have potential for human food use. This study evaluated biomass production and nutrient levels in fronds of Ceratopteris pteridoides (Pteridaceae), under the following nutritional treatments: (T1) artesian well water, (T2) natural lake water, and (T3) artesian well water with a nutritive solution. Each replicate had 25 plants of 25 g total fresh biomass each. The experiment lasted for 35 days and total fresh biomass weight, root system length, leaf dry biomass weight, root dry biomass weight and sprout number were assessed. The plants from T3 had the greatest increase in total fresh biomass with an average of 430.02 g, showing that the nutritive solution used in the experiment provided the best conditions for plant growth. The daily ingestion of C. pteridoides could contribute to mineral supplementation, in addition to diversifying existing crops and contributing to sustainable agriculture.

Aquatic herbaceous plants are especially suitable for mapping environmental variability in wetlands, as they respond quickly to environmental gradients and are good indicators of habitat preference. We describe the composition of herbaceous species in two oligotrophic wetland ecosystems, floodplains along black-water rivers (igapó) and wetlands upon hydromorphic sand soils (campinarana) in the Parque Nacional do Jaú and the Reserva de Desenvolvimento Sustentável Uatumã in Central Amazonia, both protected areas. We tested for the potential distribution range (PDR) of the most frequent species of these ecosystems, which are the ones that occurred in at least two of the sampled wetlands, using species distribution models (SDMs). In total, 98 aquatic herbaceous species were recorded, of which 63 occurred in igapós and 44 in campinaranas. Most igapó species had ample PDRs across the Neotropics, while most campinaranas species were restricted to the Amazon Basin. These results are congruent with studies that described similar distribution patterns for tree and bird species, which emphasizes a high degree of endemism in Amazonian campinarana. However, we also found differences in the potential distribution of species between the two protected areas, indicating high environmental variability of oligotrophic ecosystems that deserve further investigation to develop effective measures for their conservation and protection.