Variabilidade espacial da chuva de sementes em área ciliar da caatinga no semiárido paraibano.

Abstract

The research aimed to analyze the spatial variability of seed rainfall in a riparian area of Caatinga in the Paraíba Semi - arid. In the Serra Branca experimental area destined to the studies of the Laboratory of Ecology and Botany - LAEB / CDSA / UFCG, 100 plots of 10x10 m were marked in which 50 collectors of 0.25 cm² were intercalated. The material was collected monthly and sent to the Ecology and Botany Laboratory of the CDSA / UFCG, where the leaves, branches, fruits, seeds, flowers, bark and miscellaneous and heavy fractions were separated. The study period was from August 2015 to April 2017. The data obtained from the weighing were manipulated in a Microsoft Excel spreadsheet to analyze the spatial variability of the seed rain in the area. For the analysis of the spatial variation, the area was divided into three bands. The first comprised the Margin, with a total of 15 collectors; the second the Medium with 20; and the third was the Borda, also with 15. The total weight was 92.43 g of seeds in 12.5 m², which corresponded to the density of 7.4 g / m². During this period, the month with the highest seed production was March of 2016, with 18.20 g, and the one with the smallest contribution was April of 2017, with 0.54 g of seeds. Relating precipitation to seed production, it is observed that during the monitoring period, the months with the highest precipitation, from December 2015 to February 2016 and March 2017, corresponding to the rainy season in the region, presented low values in the production of seeds, while the highest values were observed in the dry period. Regarding the spatial variation, it was observed that in the driest months, the highest rainfall values were obtained in the Margin and Borda, with the exception of November 2015 and June and December 2016. The only environment that did not seed production was Borda, in August 2016, and the peak with 10.20 g was recorded at the Margin in March 2016. The highest value of density was observed in the Margin, and the values of seed densities were decreasing as it was directed towards the Middle. In general, seed rain values were considered low and some factors may have contributed to the results obtained, such as the small number of adult individuals, the low rainfall.