Reproductive phenology of critical native plant species for mineland restoration in the eastern Amazon

Amazon ironstone outcrops vegetation, or canga, is a remarkable environment in which the plants are adapted to peculiar circumstances. Knowledge regarding different aspects of this ecosystem remains modest, including necessary insights for its conservation and recovery, such as the reproductive phenology of priority species that form the plant community. This study aimed to monitor the reproductive phenology of critical native species that are categorized as rare, endemic, and/or threatened in the canga of the Amazon Rainforest, in Para, Brazil. During February 2016 and May 2017, eleven species were evaluated regarding the presence or absence of flowering and fruiting phenophases, and these were associated with environmental variables. Phenological data were evaluated through circular statistical analysis. All studied species flowered and produced fruit during the monitoring period. The evaluated species have an annual reproductive cycle marked by seasonality and flowering peaks between March and April, during the wet season, and fruiting peaks during May, at the beginning of the dry season. The best period for collecting ripe seeds, a primary tool for the restoration of degraded areas, is June. Water availability may be essential for the establishment of annual plants and to induce flowering in both annual and perennial species. The reproductive phenophases of the studied species are concentrated within a short period and are synchronized, which may increase the possibility of cross-pollination and minimize flower and seed predation. We discuss the challenges in including annual plants and the importance of having them and perennial species in conservation and restoration of degraded areas projects.