Espécies arbóreas e suas relações com variáveis climáticas sob influência de deficiência hídrica no solo da floresta de terra firme em Caxiuanã, Pará, Brasil.

Abstract

The intensity and frequency of severe droughts in the Amazon region are increasing due to global climate change and may intervene with botanical factors. Thus, this thesis analyzed the floristic composition, richness, diversity, and species’ distributionabundance, besides diametric plant species group increase over time in forestry areas with and without water exclusion in the soil, also relating growth in groups’ dynamics of species with climatic variables. Data were collected in 98 subplots in area A (without water exclusion) and in 98 subplots in area B (with water exclusion), each measuring 10 m x 10 m, in which all plant species with the diameter at breast height (DBH≥10 cm) were inventoried. in both areas, 378 and 356 plant individuals were monitored, respectively, through dendrometric bands that allowed the monthly increment diameter measure of species. The Fabaceae, Sapotaceae, Chrysobalanaceae, Burseraceae families were the most representative in the study areas, especially Fabaceae, which displayed the highest richness. A small variation was found in the observed richness in area A, and the community evenness and the diversity index remained constant, while in area B, the variation in richness was greater, which may have contributed to a small change in the diversity index over time. The best ecological models adjusted were Zipf and Zipf-Mandelbrot for areas A and B plant communities, respectively. The average diametric behavior increment of the trees was different between the diameter and the wood density classes in the two analyzed areas. In areas A and B, it was observed that individuals who grouped in the upper diameter class tended to have a higher average annual diameter increase compared to the other medium and low diameter classes, and individuals grouped within the low and high wood density classes’ which presented the highest and lowest average annual increment value, respectively. The meteorological variables‘ wind speed and average temperature showed negative and significant correlations with the monthly diametric increase by diameter and density classes, whereas the active photosynthetic radiation did not present a significant correlation. Considering the high diameter class trees and those grouped within the low- density class since even being submitted to water deficit they continued to have a higher average with a smaller variation of diametric increase concerning the other classes, it is possible to infer that they are more resistant to water deficiency than trees belonging to other diametric and wood density classes. Therefore, it can be concluded that the forest appears to be well established, with high species richness and diversity, and that the water restriction in the soil over the time of ten years of study was not enough to interfere in the conservation status of the environment expressively.