Abstract
ABSTRACT Myracrodruon urundeuva, Handroanthus impetiginosus and Amburana cearensis are Caatinga tree species that produce valuable timber, but little is known about their ecology. The objective of this study was to evaluate the seed distribution of these species on the forest floor before and after seed dispersal; and seedling emergence, survival, and growth during the rainy season after dispersal of seeds. There were no remaining viable seeds of these species in the seedbank before seed dispersal. The average numbers of seeds after seed dispersal were 188 seed m-2 in a 30 m radius around M. urundeuva, 9 seed m-2 in a 10 m radius around H. impetiginosus, and 5 seed m-2 in a 20 m radius around A. cearensis. The distance of seed dispersal reached 30, 20, and 10 m for M. urundeuva, H. impetiginosus, and A. cearensis trees, respectively, due to differences in tree height, seed weight, forest density, and wind intensity. Seedling emergence was observed during 4 (M. urundeuva) and 9 (H. impetiginosus and A. cearensis) weeks. High mortality predominated at the beginning and end of the rainy season for M. urundeuva and A. cearensis, respectively, while practically all H. impetiginosus seedlings survived. M. urundeuva showed the highest mortality but had higher number of established seedlings than the other species. Seedling survival peaked around 5 m from the tree base. Seedling recruitment and natural regeneration of these trees are assured in the Caatinga site evaluated.
Highlights
The Caatinga Biome covers most of the Brazilian northeast region; it is characterized by semiarid climate and high levels of biodiversity and endemism
According to Fernandes and Queiroz (2018), the natural regeneration process is determined mainly by the seedbank and seed rain, which are affected by the vegetation composition and disperser agents, such as wind and animals; many Caatinga sites are clear cut without considering the autecology and contribution of each species to the ecosystem, and other ecological factors that interfere with forest regeneration, such as patterns and ranges of seed dispersal
No seedlings emerged from the forest floor material collected at different distances around the studied tree species before seed dispersal, but seedlings emerged from the forest floor material sampled after seed dispersal
Summary
The Caatinga Biome covers most of the Brazilian northeast region; it is characterized by semiarid climate and high levels of biodiversity and endemism. According to Fernandes and Queiroz (2018), the natural regeneration process is determined mainly by the seedbank and seed rain, which are affected by the vegetation composition and disperser agents, such as wind and animals; many Caatinga sites are clear cut without considering the autecology and contribution of each species to the ecosystem, and other ecological factors that interfere with forest regeneration, such as patterns and ranges of seed dispersal They consider that the failure to minimally understand the effects of these factors on the vegetation composition may result in large land areas without a proper source of propagules, quantitatively and qualitatively hindering the natural processes of vegetation regeneration. Smith, (Fabaceae) species, locally known as aroeira, ipê-roxo, and cumarú, respectively These are xerophilous, long-lived tree species that, according to the Red Book of Brazilian Flora, deserve attention due to their declining populations resulting from heavy wood exploitation (MARTINELLI; MORAES, 2013). Their phenology is similar in many aspects: the onset of the dry season triggers flowering and anemochorous dispersal of their winged seeds; and, at the beginning of the following moist season, the seeds germinate (GOMES; QUIRINO, 2016; LIMA et al, 2008)
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