Fenologia reprodutiva de espécies estivais da familia poaceae em pastagem nativa do bioma pampa, Rio Grande do Sul, Brasil

Abstract

In Rio Grande do Sul, the Pampa biome presents large areas of country vegetation, being characterized mainly by grasses, one of the main families that compose the fields of this biome. This group stands out for its great economic importance, including the main cereals used in human food and important forage for use in agriculture. Phenology studies the occurrence of repetitive biological events and their relation to climate. This study is of fundamental importance for understanding the ecology of the plant community. The objective of this study was to describe the reproductive phenological patterns of summer grasses native to the Pampa biome, in the city of São Gabriel, RS, Brazil, and the relation between phenophases and climatic variables, mean temperature and mean precipitation. The study was conducted at the Anacreonte Ávila de Araújo Research Center - DDPA Forrageiras, and at the Federal University of Pampa, São Gabriel municipality: Axonopus affinis Chase, Calamagrostis viridiflavescens (Poir.) Steud, Cynodon dactylon (L.) Pers, Eragrostis plana Nees, Mnesithea selloana (Hack) of Koning and Sosef, Paspalum notatum Flugge, Paspalum plicatulum Michx, Paspalum urvillei Steud, Piptochaetium montevidense (Spreng.) Parodi and Schizachyrium microstachyum (Desv.) Roseng. For the phenological study ten individuals of each species were tagged, which were followed biweekly during the period from November/2016 to October/ 2017, and recorded the following phenophases: flowering, fruiting and dispersion. Circular statistics were used to analyze the data, to determine the period of occurrence of each phenophases. In addition, the Spearman correlation coefficient (rs) test was performed to evaluate the existence or not of the relationship between reproductive phenophases with mean temperature and mean precipitation. In general, flowering, fruiting and dispersal occurred in the period from September to March, with November being the period with the highest peak of activity for all phenotypes analyzed. The mean temperature variable showed a significant correlation with at least one of the reproductive phenophases of each species, the only species that did not show correlation with this variable was Axonopus affinis Chase. Mean precipitation did not correlate with any of the species. Therefore, the climatic variable average temperature is a conditioning factor for the reproductive phenophases of the studied species