Padrões de germinação dos diásporos e emergência das plântulas de espécies arbóreas do cerrado, do Vale do Rio Araguari, MG

Abstract

Diaspores of tree species have peculiar characteristics, which coupled with environmental conditions, respond differently to germination and emergence. Therefore, the aim of this work is to study germination of diaspores and seedling emergence of tree species occuring in the Vale do Rio Uberlandia, MG, under controlled conditions and field conditions in an attempt to find patterns that would allow to group them. The diaspores were tested for germination or emergence under controlled conditions or under field conditions. The measures of the analyzed germination and emergence in the experiments under controlled conditions allowed a formation of two groups: one with fast species and the other with slow species. In general, the species were heterogeneous regarding the time necessary for the processes to occur and asynchronous, which also showed variability among individuals. Anadenanthera colubrina, Astronium fraxinifolium, Ceiba speciosa; Dipteryx alata, Myracrodruon urundeuva and Tapirira guianensis were the fastest and had percentage of germination between 68 and 100% and emergency between 26 and 100%. Regarding germination, A. fraxilifolium and T. guianensis took less time and were the fastest (t0 = 3 and 2; tf = 15 and 5; t = 4 and 3 days and v = 0,415 and 0,492 day-1, respectively). Regarding the emergence, A. colubrina and C. speciosa recorded the lowest values for these measures (t0 = 5 and 6; tf = 19 and 16; t = 8 and 9 days and v = 0,179 and 0,362 day-1, respectively). Aspidosperma cylindrocarpon; Cariniana estrellensis, Cedrela fissilis, Enterolobium contortisiliquum, Genipa americana, Hymenaea courbaril, Lithraea molleoides, Luehea divaricata, Machaerium acutifolium, Ormosia arborea, Plathymenia reticulata; Pouteria torta and Sterculia striata proved to be slow for both processes, with germination percentage values from 4,0 to 87,5% and emergency from 2,8 to 100%. Among these species L. molleoides and P. reticulata were the slowest to germinate (tf = 210 and 330; t = 119 and 100 days and v = 0,008 and 0,010 day-1, respectively), while H. courbaril and O. arborea were the slowest to emerge (t0 = 129 and 202; tf = 284 and 221; t = 225 and 212 days and v = 0,004 and 0,005 day-1, respectively). The species and the individuals were grouped in the dendrogram and the PCA, in two main groups according to speed and spread of germination and emergence. In field conditions, the behavior of the diasporess regarding the emergence was similar to the registered behavior in the controlled environment, where C. speciosa and M. urundeuva were the fastest (t0 = 14 and 14; tf = 24 and 18 and t = 16 and 16 days, respectively) and G. americana and S. striata the slowest (t0 = 39 and 32; tf = 85 and 53 and t = 52 and 37 days). C. speciosa, M. urundeuva, P. reticulata and S. striata had the highest percentage of plant survival in the surroundings of the semi-deciduous forest, while for the seedlings of G. americana, the survival was higher inside the forest. The spread of germination of the diaspores or seedling emergence of species in Vale do Rio Araguari was associated to dormancy in the dispersal units.