Ana Silvia Rolon

Does Non-Intentional Flooding of Rice Fields After Cultivation Contribute to Waterbird Conservation in Southern Brazil?

Abstract.— Use of rice fields as complementary habitats to waterbird species was investigated. Three questions were posed (1) does waterbird richness (defined as number of species), abundance and composition differ between rice fields and natural wetlands; (2) do richness, abundance and composition of waterbird species differ between flooded and drained rice fields in the post-harvest season, and (3) do richness, abundance and composition of waterbird species change in rice fields over the rice cultivation cycle? Eight collections were made in eight rice fields with different hydrological conditions after cultivation (four dry and four flooded) and four natural wetlands. Waterbirds were censused using binoculars and one telescope. A total of 76 waterbird species were observed during the study period (2005–2006): 59 species in rice fields and 70 species in natural wetlands. The richness of waterbirds was higher in natural wetlands than flooded and drained rice fields; however, there was no difference between flooded and drained rice fields. The richness of waterbirds did not change over the rice cultivation cycle. Waterbird abundance was higher in natural wetlands than in flooded and drained rice fields. Natural wetlands showed a seasonal pattern of species composition and abundance different from rice fields. Rice fields are used for an important fraction of the waterbird richness in southern Brazil, acting as habitat complementary for biodiversity, but in lower richness and abundance when compared to natural wetlands. The non-intentional flooding of rice fields did not contribute towards waterbird conservation in southern Brazil.

Does pine occurrence influence the macrophyte assemblage in Southern Brazil ponds

The destruction of wetlands due to afforestation areas is a common activity in temperate and subtropical regions in Southern America. The expansion of pine (Pinus elliottii Engelm.) in the Coastal Plain of Southern Brazil is critical and its impacts on aquatic biodiversity are little known. We tested the hypotheses that: (1) pine occurrence diminishes the macrophyte richness and changes the macrophyte composition in ponds; (2) beta-diversity between natural and pine ponds is determined mainly by species nestedness (species loss). Sampling was carried out from 2007 to 2009 in five ponds in pine invasion matrix and five ponds in native grassland matrix. In natural ponds, the total richness was 87 species, followed by 51 species in pine ponds. From the total richness, 42 species were shared between natural and pine ponds. The natural ponds were richer than the pine ponds along the entire study, and the composition of macrophyte species was different between natural and pine ponds. Comparing natural ponds with each other and pine ponds with each other, the species turnover (species replacement) was determinant for beta-diversity, however, when we compared natural and pine ponds, we found that nestedness and species turnover were equivalent for beta-diversity. The increase in the nestedness mechanism indicates that the pine occurrence implies in species loss in Southern Brazil ponds. The change of hydroperiod may be one of the causes for the macrophyte species loss. The removal of pine from areas destined to conservation in Southern Brazil is urgent as well as a proper management of pine plantations in order to minimise its expansions and impacts in the aquatic biodiversity, since 90% of its wetlands have been already lost.

Macrophyte dynamics in an oxbow lake of the Sinos River basin in south Brazil

Wetlands are among the most important ecosystems on Earth and present enormous social and economic importance. These environments are sources of natural resources for humans, and their high productivity provides habitat for rich, unique biota (GIBBS 2000). The floodplains in the south of Brazil are important wetlands, and the flood pulse is considered an important factor in the aquatic community structure and organization of these environments (JUNK et al. 1989). Flooding is one ofthe most common natural forms of abiotic disturbance in aquatic riverine ecosystems (THOMSON et al. 2002). MAY (1974) observed that floods increase the structural variables of aquatic ecosystems, creating new habitats that facilitate related species coexistence. Studies related to hydrologic disturbance in aquatic ecosystems have concentrated their efforts on the effects of floods on aquatic communities, mainly events oflong duration (TucKER et al. 1995). However, studies that analyze the effects o f floods o f brief duration on aquatic communities are scarce. In Brazil, most of the functional studies o f floodplains were developed in the Amazon region (PIEDADE et al. 1994) and in the Upper Paraná River (AGOSTINHO et al. 200 l). Studies analyzing the effects o f flood pulse in aquatic communities are mainly concentrated on shallow lakes associated with a floodplain system (MALTCHIK et al. 2004, STENERT et al. 2003, Á VILA et al. 2004). The main goa! of this study was to analyze the effects of floods on the macrophyte community richness and biomass in an oxbow lake over an annual cycle (2003-2004) in the south of Brazil.