Spatio-temporal changes in the structure of the ant, bee, and tree communities in the brazilian cerrado

Abstract

In this study, we described the changes in land cover and land use, in climate, and in the incidence of fires that have occurred over the last decades within the region of the “Triângulo Mineiro and Southeastern Goiás” site (TMSG) of the Long-term Ecological Program (PELD-CNPq). We also evaluated to what extent some stressors, such as habitat fragmentation, fire events and the creation of artificial dams, are related to temporal changes in the communities of euglossine bees, ants and trees. We detected abrupt changes in climate, fire frequency and land use in the TMSG region. Since 2000, the area occupied by native vegetation has declined from 34.5 to 25.5 % while the incidence of fires increased exponentially. Moreover, the annual maximum temperature is 2.5 °C higher than it was about 30 years ago. Temporal changes in the composition of the euglossine community in forest fragments (varying in size from 16 to 200 ha) were gradual and non-directional, suggesting that the community is at equilibrium. For arboreal ants associated with savannas, our data also indicate an absence of directionality in the community trajectory. However, there is evidence that changes are no longer gradual in the presence of recurrent fire events. In contrast, the tree communities showed gradual and directional changes, indicating the existence of a successional process in these communities. These changes started, in one case, by the construction of a reservoir along the margin of the forest fragment and, in the other, by the suppression of anthropic disturbances when the fragment became part of a protected area.