A review of the structure and dynamics of araucaria mixed forests in southern Brazil and northern Argentina

The Araucaria Mixed Forests (AMF) are subtropical conifer-hardwood mixed forests that are part of the Atlantic forest floristic dominion in Brazil and Argentina. The AMF is dominated by the coniferAraucaria angustifolia(hereafter araucaria), accompanied by a diversity of angiosperms. Its distribution largely corresponds to the 13 degrees C isotherm and is associated with overall lower temperature, frost-prone, and wetter climates than neighboring vegetation types. Palynological research and bioclimatic modelling have yielded somewhat conflicting results but suggest intense forest-grassland dynamics, with grasslands possibly dominating the landscape during the drier and colder last glacial maximum. Araucaria is a cultural keystone species whose distribution has been greatly fostered by Amerindian activity in the last few millennia. Angiosperms form a lower layer beneath araucaria canopies, and they seem to be geographically structured into a wetter and colder eastern and a drier and hotter western portion. Araucaria attain large sizes and high longevity but is unable to regenerate under the shade cast by angiosperm canopies and need large-scale disturbances for successfully complete their life-cycles. This cycle has been synthesised in the non-equilibrium Lozenge model of forest dynamics. Regeneration opportunities arise from the frequent multiple treefall gaps produced by the tornado and windstorm-prone climate of subtropical South America and by the grazing-, fire-, and nurse-plant successional dynamics of the forest-grassland mosaic. Dispersal is mediated by a complex web of interactions with birds and mammals. A review of the dynamics of southern Oceanic Temperate Forests indicates that the dynamics of the AMF fits a prevailing pattern in these forests that corresponds to the Lozenge model. Deforestation and degradation by logging and cattle grazing have impacted most of the AMF original range. Similarly to what happened toAgathis australisin New Zealand, the establishment of commercial plantations still need incentives and research to thrive and produce large-scale environmental benefits.

Automated summary

The Araucaria Mixed Forests are subtropical forests dominated by Araucaria conifers in Brazil and Argentina, with a diversity of angiosperms. The distribution is associated with lower temperature, frost-prone, and wetter climates. The forest dynamics are influenced by a mix of natural disturbances and human activities.