Sazonalidade do aporte e eficiência de utilização biológica de micronutrientes em espécies florestais da caatinga em Pernambuco

Abstract

The relationships between the nutrients present in forest species of the Caatinga and the soil are little studied, mainly for micronutrients. These nutrients are required in small quantities by plants, but are mostly enzymatic activators of complex physiological systems essential for the sustainability of plant species. Studying the nutritional efficiency of these micronutrients by the forest species and their contribution in the litter, relating them to the humidity and temperature cycles of the semiarid can generate very useful information for several studies, mainly for forest restoration programs. This work aimed to estimate leaf biomass by species and area and to determine the nutritional efficiency of Cu, Fe, Zn and Mn in ten species of highest importance value in a hypoxerophilic Caatinga fragment and to monitor their contents and contents to study the monthly variability And evaluate the seasonal influence of precipitation and temperature on the contribution of these micronutrients associated with litter. Data collection was performed in a remnant forest fragment of Hypoxerophilic Caatinga in Arcoverde, Pernambuco. For leaf sampling, freshly mature leaves were collected from the middle third of the crown of the ten largest VI species, from the four cardinal points of each plant. Three specimens of each species were sampled in the fragment, with the selection criteria for repetition being the similarity of the size and vegetative development of the species sampled. Cu, Fe, Zn and Mn contents were determined in these sheets. The nutrient content in leaf biomass was obtained by multiplying the leaf biomass content of each species in the fragment. The efficiency of biological utilization of each nutrient in the species was calculated by the ratio between the leaf biomass of the species and the nutrient content accumulated in that biomass. Twenty collectors were used to collect the litter, and the plant material was collected monthly for one year. The litter was separated into leaf, twig, reproductive structure and miscellaneous fractions. In these fractions were determined the contents and contents of Cu, Fe, Zn and Mn. The largest leaf biomass were of the species Poincianella pyramidalis and Mimosa ophthalmocentra; The efficiency of biological utilization of the nutrients of the species of greatest importance value of the fragment followed the following decreasing order: Mn> Cu> Zn> Fe. In reforestations of restrictive environments the availability of Fe and Mn can be used the species Piptadenia stipulacea and Mimosa ophthalmocentra. It was verified that in hypoxerophilic Caatinga environments the litter constitutes an important source of Mn and Fe, the leaves and branches being the main fractions in the contribution of micronutrients. There was also an increase in Cu, Fe and Mn contents as the pluviometric volume increased. The contribution of Fe and Mn occurred mainly during the wetter and colder months.