Anatomia da madeira e dendrocronologia de espécies arbóreas do gênero Machaerium Pers. (Leguminosae-Papilionoideae)

Abstract

The Machaerium genus includes 130 species, which has Neotropical distribuition and center of diversity in Brazil with approximately 80 species. The genus is distributed in all phytogeographic areas of the country, but its richness and endemism occurs in the Atlantic Domain and Amazon Forest. The Machaerium species are classified in five infrageneric sections, which is based in the presence or absence of spiny stipules and venation patterns and size of leaflets. However, the infrageneric classification of Machaerium is controversial according to some authors, mainly when it is compared with phylogenetic analyzes. Thus, there is a need to research new characters that contribute for the species delimitation and an upgrade of the infrageneric classification. Besides, there is necessity to know the dendrochronological potential of the Machaerium species in the Atlantic Rain forest, a rich and threatened biome. This study aimed to analise the wood anatomy of eleven trees species of Machaerium to verify the consistency of the infrageneric sections and identify diagnostic characters of the species. And also, to analyze the growth periodicity and the influence of the climatic factors on the growing of Machaerium incorruptibile, an endemic specie from Atlantic Rain Forest. Samples were collected with an increment borer and were processed following the usual methods for wood anatomy, scanning electron microscopy and dendrochronology. The species analyzed showed the anatomical characters for the Leguminosae and the Papilionoideae subfamily. The presence of unlignified parenchyma bands, fibres very thin-walled and rays irregularly storied were important to separated Machaerium hirtum from the other ten species. The remaining ten species were separated between them by quantitative wood characters, especially diameter and vessel frequency, and also by the morphological characters of vestured pits, as the ornamentation projections at the pit aperture. The wood anatomy did not corroborate the infrageneric sections in Machaerium, like observed in the phylogenetic studies of the genus. The dendrochronology data were analyzed using the software ARSTAN and a chronology was made for Machaerium incorruptibile. Analyses with precipitation and temperature were performed, demonstrating a positive significant correlation between the growth rings and the average temperature of spring, when the temperature is milder, and a negative significant correlation between the widths of growth rings and the average summer temperature, when the temperatures are hotter. There was also a negative correlation between the most severe El Niño events and the width of growth rings, demonstrating the effect of this phenomenon on population growth, as found in other tropical species.