Ecologia de comunidades de aves associadas a plantações de arroz irrigado em Santa Catarina, Brasil

Abstract

The southern region of Brazil presents more than 90% of its wetlands altered in rice plantations. This cultivation is developed in regions of fertile and flooded lands, with organic or inorganic management, acting as substitute natural areas for several groups of birds and arthropods, also associated with each other. Due to the lack of information on the subject in the country, this study analyzed and related communities of birds and arthropods that use inorganic management during a planting cycle between July 2015 and June 2016 in the municipalities of Itajaí, Garuva and Araranguá, SC, Brazil, also observing their association with environmental variables. Birds were recorded monthly in linear transects in each locality and arthropods and environmental variables were collected. Average abundance, relative abundance, relative frequency of occurrence and the indexes of similarity, diversity and equitability were calculated. Comparative analyzes between the municipalities were performed through the ANOVA, Kruskall-Wallis, ANOSIM and RDA Tests. Birds of 107 species were registered, with resident and occasional majority, as well as vulnerable taxa, migratory species of the Northern Hemisphere and new records for the state. In general, species richness and abundance were higher at the beginning and the end of the cycle, but there were no significant differences between areas due to the common presence of a few dominant taxa. The Araranguá crops had the lowest richness and diversity, possibly due to the shorter rice cycle, which offers niches for a shorter period of time. A total of 68 families of arthropods were collected, with richness and abundance equally related to the cycle. The RDAs among birds, arthropods and environmental variables presented high explanability values, evidencing their association in these environments. It is concluded that the state's rice fields offer varied resources throughout the year, harboring distinct groups of birds and arthropods, and are therefore important for the conservation of species associated with crops. In Araranguá an organic crop was studied and compared to one of the inorganic crops of the same municipality. The same comparative analyzes were employed. There were 61 bird species and 53 arthropod families. Through the comparisons, it was verified that richness, abundance, diversity and equitability of the organic cultivation were higher, as well as more exclusive and migratory species and one of high sensitivity were registered. It is concluded that the state's rice fields offer varied resources throughout the year, harboring distinct groups of birds and arthropods, and are therefore important for the conservation of species associated with crops, especially organic farming, which has proved to be more sustainable and less impactant on biodiversity.