ABSTRACT A new species of Rhynchospora (Cyperaceae) only known from the Parecis plateau, on the southwestern edge of the Brazilian Amazon, is described here. Rhynchospora parecisensis was found growing only in open environments of deciduous seasonal forest and savanna enclaves in the midst of seasonal evergreen forest, in the state of Mato Grosso, western Brazil. Rhynchospora parecisensis differs from the other species of Rhynchospora sect. Pluriflorae subsect. Subebracteatae by the distally puberulent to pubescent glumes. The new species resembles Rhynchospora acanthoma, but differs from it by the subtriangular to quadrangular scapes in cross-section and the distally puberulent to pubescent glumes, with ciliate to ciliolate margins. Taxonomic comments, illustrations and a distribution map are also provided.

RESUMO Uma nova espécie de Rhynchospora (Cyperaceae), conhecida apenas para o Planalto dos Parecis, no sudoeste da Amazônia brasileira é descrita. Rhynchospora parecisensis foi encontrada apenas em ambientes abertos de floresta sazonal decídua e enclaves de savana, em meio a áreas de floresta estacional sempre verde, estado do Mato Grosso, centro-oeste do Brasil. Rhynchospora parecisensis difere das outras espécies de Rhynchospora sect. Pluriflorae subsect. Subebracteatae pelas suas glumas puberulentas a pubescentes distalmente. A nova espécie é semelhante a Rhynchospora acanthoma, porém difere pelos escapos subtriangulares a quadrangulares em secção transversal, e pelas glumas puberulentas a pubescentes distalmente, com margens ciliadas a cilioladas. Comentários taxonômicos, ilustrações e mapa de distribuição são apresentados.

Abstract Palm trees are striking elements of tropical forests and provide many jobs for Amazonian populations. The research's objective was to identify the palm trees present in the local way of life, the one with the highest consensus value for use in two riverside communities in Abaetetuba, Pará, and evaluate traditional knowledge and implications for residents' way of life. The study was carried out in Rio Urubueua de Fátima (R.U.F) and Nossa Senhora dos Anjos (N.S.A). The interviewees' selection was made by non-probabilistic sampling. The data were obtained through participant observation, semi-structured interview, non-specific induction, annotation in a field diary, and audiovisual record. Of the total palm trees cited, the Ethno-species Inajá was chosen due to its consensus use-value with values of 0.438 for R.U.F. (with 36 citations) and 0.484 N.S.A. (27). Three categories of use were identified: food, construction, and utensils. The high consensus of service is justified by the wide use from its various parts, being a reference as a plant of full use for making it possible to obtain food, protection, shelter, and utensils. Its use is related to the vast repertoires of the interlocutors received from their ancestors. This implies the importance of a species for maintaining people's social lives in two Amazonian riverside communities that depend on nature for their livelihood and quality of life.

Resumo Este estudo trata das Cyperaceae ocorrentes na Serra dos Martírios-Andorinhas (Parque Estadual Serra dos Martírios Andorinhas e Área de Proteção Ambiental de São Geraldo do Araguaia), no município de São Geraldo do Araguaia, Pará, Brasil. A Serra está no “Arco do Desmatamento”, uma área de elevada vulnerabilidade ambiental com os maiores índices de desmatamento da Amazônia. A fitofisionomia predominante é a de Savana Amazônica, caracterizada pelos ambientes abertos com o predomínio de herbáceas, como as Cyperaceae, representadas por apenas quatro espécies em inventário florístico prévio. Estudar a diversidade de Cyperaceae nos permite compreender melhor a dinâmica do estrato herbáceo, contribuindo para a conservação, monitoramento e manejo destes peculiares e fascinantes ambientes. Para tanto, foram analisadas 276 amostras de Cyperaceae da Serra das Andorinhas provenientes de coletas de campo e de acervos de herbários. Atualmente, Cyperaceae é representada por 12 gêneros e 72 espécies na área de estudos, das quais, sete são novos registros para o estado do Pará. São apresentadas chave de identificação, descrições sucintas com caracteres diagnósticos, distribuição geográfica, hábitat, ilustrações de espécies e gêneros.

Abstract This study focuses on the Cyperaceae occurring in the Serra dos Martírios-Andorinhas (Serra dos Martírios- Andorinhas State Park, and São Geraldo do Araguaia Environmental Protection Area), in the São Geraldo do Araguaia municipality, state of Pará, Brazil. The Serra is in the “Deforestation Arc”, an environmentally vulnerable area with the highest deforestation rates in the Amazon Forest. The predominant phytophysiognomy is the Amazonian savanna, characterized by open environments dominated by herbaceous plants, such as Cyperaceae, represented by only four species in a previous floristic inventory. Studying the diversity of Cyperaceae allows us to a better understanding of the herbaceous layer’s dynamics and assisting in the conservation, monitoring, and management of these fascinating and peculiar environments. Therefore, 276 field and herbarium samples of Cyperaceae from Serra dos Martírios-Andorinhas were examined. Now, Cyperaceae are represented by 12 genera and 72 species in the study area, of which seven represent new records for the State of Pará. A taxonomic identification key, short descriptions with main diagnostic characters, geographic distribution, habitat data, and illustrations for all species and genera are provided.