Aspectos fitossociológicos e produção de fitomassa pastável da jurema-preta (mimosa tenuiflora [willd.] poir) em área de caatinga sucessional.

Abstract

The objective of this study was to evaluate the phytosociological parameters of woody vegetation, growth and phytomass production of the Jurema-preta (Mimosa tenuiflora (Willd.) Poir submitted to the control of the number of regrowth in areas of silvopastoral system in the caatinga of the Sertão Paraíba. The experiment was carried out at Fazenda Lameirão, in the municipality of Santa Terezinha-PB. An experimental area of 4.0 ha was used, being divided in 4 pickets (1, 2, 3 and 4) with approximately 1 ha each. The experimental area was submitted to silvopastoral management in the year 2016. The plots were selected to apply four forms of control of the number of Jurema-preta regrowths, distributed as follows: 1 regrowth; 2 regrowths; 3 regrowths and plants lowered and managed to allow the growth of all regrowths (without control). For this, each plot (45m x 45m) was drawn 5 jurema-preta plants. Two evaluations were carried out, in the final third of the rainy season of 2017 and 2018, which comprised between the months of March / April. The phytosociological parameters evaluated were: Frequency, Density, Shannon-Wiener diversity index (H ') and Pielou equability index (J) of the woody species. To estimate the growth, the number of sprouts (NS) was counted, and the measurements of the plants when to the diameter of the trunk (D), basal diameter of the sprouts (DBS) and height of the largest sprout (HLS). As the production per hectare was: stem phytomass, leaf and total (PSP, PLP and PTP). The design was randomized blocks (DBC), with the control form in the plots (without control, 01 regrowth, 02 regrowth, and 03 regrowth) and the seasons in the subplots, with the plants as replicates. For the phytosociological parameters, 640 individuals were found in the experimental area during the two seasons, seven of which were endemic to the caatinga. The total Density (TD) ranged from 194 to 564 and 552 to 1057 (plants / ha) in the four treatments for 2017 and 2018, respectively. The equability value (J) for the 2017 season was 0.81; 0.83; 0.76 and 0.84, and 2018 was 0.86; 0.82; 0.85 and 0.81, in the treatments without control, 1, 2 and 3, respectively. Regarding the growth of the juremas NS, with the exception of the control, was higher in 2017, differing NS obtained in 2018. For the production of stem phytomass (PSP) and leaf phytomass production (PLP), it was observed that there was similarity to the results found for NR. Thus, the control of the number of regrowths of the jurema-preta over 2 years does not have a direct influence on the presence of woody species of the caatinga. But the populations of these species increased in all the studied areas, which can be used within the silvopastoral system. There was an increase in trunk diameter and a reduction in the number of rebrites remaining, with a reduction in leaf and stem production, but with uniform growth and greater basal diameter of the shoots.