Environmental constraints on germination and establishment of two endangered Dimorphandra species: the role of water availability, fire, and livestock

Dimorphandra exaltata and D. wilsonii are endangered species in the Atlantic Forest and Cerrado, biomes threatened by anthropogenic activities such as fire and livestock grazing. Also, in the areas where these species occur, annual rainfall tends to decrease due to climate change. Thus, this study investigated the influence of the bovine digestive tract, water, and fire on the germination and establishment of seeds from both species, to support future management and conservation plans. To address this question, we conducted experiments to assess the effects of seed passage through the bovine digestive tract, water availability (natural or irrigated), and exposure to fire on the germination and establishment of Dimorphandra species. Passage through the bovine digestive tract did not enhance germination. However, it did not impair the seeds’ viability, favoring germination over time. Daily irrigation increased germination of the two species, suggesting that natural precipitation may be insufficient to establish them under field conditions. Fire did not stimulate germination in either species, indicating that recurrent fires in native areas could impair seedling establishment. Considering changes in precipitation and increased fire occurrence due to climatic changes, as well as livestock expansion, D. exaltata and D. wilsonii may have their regeneration compromised, threatening their persistence in natural habitats. We propose that, to increase the regeneration rate of the species studied, replanting young individuals at advanced stages of development would be a viable alternative, given environmental limitations, such as water deficit and fire occurrence, which are more detrimental to the natural regeneration of seedlings of these species.