Estudos fitossociológicos e dendrométricos em um fragmento de caatinga, são josé de espinharas – PB

Abstract

The present study aimed to analyze the floristic composition, characterize the parameters of the internal structure, adjust volumetric models in order to obtain stem volume estimates as well as estimate a form factor for stems in a stretch of caatinga vegetation. The study area is located in ‘Cachoeira’ settlement, in the municipality of São José de Espinharas, PB state. Forty-nine samples, with an area of 400 m2 (20 × 20 m), were used and systematically distributed with the spacing between plots of 300 × 300m. In order to collect the inventory data, regeneration and the internal structure (class of vitality, quality of stem and crown position), it was followed the Measurement Protocol of Caatinga Forest Management Network. For the study of volumetric estimates, it was used a 225-sample stem, with measurements of the circumference of the stem at 0.30m and 1.3 m of soil and overall height of the largest stem. In the rigorous scaling procedure, the stem was measured in 1 m sections by the adapted Smalian method. The total volumes by stem were obtained with six linear and nonlinear models, with two options for the diameter at 0.3 m and equivalent diameter. The form factor was estimated by the ratio between the actual volume obtained by stem rigorous scaling and cylindrical volume, which base was the sectional area obtained by the DAP at 1.30m and height of the stem. We found, in the study area, 22 species, 11 families and 20 genera, and the species Luetzelburgia bahiensis, had its first record in the state of Paraiba. The internal structure of community indicated that above 71% of stems showed to be healthy and 89.40% of the stems have low quality, namely, they are stems with branch, fork and very askew stems. Eight species showed rectilinear stem and without fork and only 14.99% of the stems are part of the ruling class of the forest. The obtained value was 0.87 for the studied form factor, however, it suggests the use of two form factors for the calculation of individual volume stems, stems with a diameter < 5 cm and with a diameter ≥ 5 cm, use medium form factor 0.80 and 0.885, respectively. Four volumetric models showed good performance for volume estimates of stems. Therefore, they can be used for areas with the same silvicultural similarities in the same region.