Manejo de duas espécies arbóreas da caatinga para a produção de estacas e mourões.

Abstract

The exploitation of the Caatinga is generally extractive, and timber products are obtained by cutting the twisted and bifurcated stems of trees. This results in them not meeting the requirements of diameter, length, and linearity for use as stakes and posts, as is the case with Mimosa tenuiflora and Libidibia ferrea. These native species, usually utilized for bioenergy production, could produce more stakes and posts if the growth of their stems were controlled. Specimens of these species without stem management were compared with plants from which branches were pruned, and the growth of their stems was guided by a tutor, according to a randomized complete block design with 2x2 factorial treatments (2 species - M. tenuiflora and L. ferrea - and 2 levels of stem management - without and with stem management) and 5 replications. Survival, increments in plant height (H) and basal stem diameter (DB), the number (n) of branches present on the plants at the end of the experiment or pruned in 17 months in the field, and the dry biomass (MS) of the branches removed from the plants were analyzed. M. tenuiflora outperformed L. ferrea in all variables. Stem management increased the number of branches emitted and decreased the mean increments in DB. Larger M. tenuiflora plants achieved average increments in H and DB of 246.1 cm and 32.6 mm in unmanaged plants and 262.9 cm and 15.4 mm in managed ones. In contrast, smaller M. tenuiflora plants resulted in average increments in H and DB of 151.3 cm and 26.5 mm in unmanaged plants and 91.1 cm and 11.6 mm in managed ones. Larger L. ferrea plants resulted in average increments in H and DB of 121.9 cm and 11.6 mm in unmanaged plants and 126.8 cm and 3.2 mm in managed ones. In contrast, smaller L. ferrea plants resulted in average increments in H and DB of 36.1 cm and 4.3 mm in unmanaged plants and 7.6 cm and 0.4 mm in managed ones. The values related to larger plants indicate the growth potential of these species, especially M. tenuiflora, and the data from smaller plants show that branch pruning should be avoided until they develop and better withstand the stress caused by this type of management. It is concluded that Libidibia ferrea and, mainly, Mimosa tenuiflora survive and have growth potential when their stems are managed. Larger plants maintain height growth, increase branch emission, and generate up to 582.4 g MS/plant, but reduce the increment in basal stem diameter. Temporary suspension of stem management is recommended, especially for plants that have not yet reached 200 cm in height after 17 months of growth, and monitoring their growth to determine when the stems will reach dimensions suitable for use as stakes and posts, and when to resume stem management.