Survival and growth of planted and naturally established trees in a degraded caatinga area

Abstract

The Semiarid region in the Northeast of Brazil is characterized by Caatinga tropical forests, adapted to 8-to-9 months of annual water stress. Human activities have resulted in environmental degradation due to tree removal and soil exposure to erosion factors; however, planting native trees, such as Mimosa tenuiflora and Cnidoscolus quercifolius, may accelerate environmental recovery. Tree recovery was evaluated in a degraded areas under a 14-year period of grazing exclusion (2005 to 2019) and planting of M. tenuiflora (2005 and 2009) and C. quercifolius (2007 and 2009) and under natural regeneration. Data on survival, height, and diameter of planted seedlings, and the number, species, height, and diameter of naturally regenerating trees were collected. The absence of grazing allowed for the establishment of 50.5% and 44.6% of the 204 M. tenuiflora and 204 C. quercifolius planted seedlings, which presented mean heights of 395 and 355 cm and mean basal diameters of 92 and 76 mm. Naturally regenerated M. tenuiflora and C. quercifolius totaled 190 and 7 plants, with heights of 95 and 139 cm, and basal diameters of 10 and 26 mm. A naturally established specimen of Cenostigma pyramidale with a height of 175 cm and basal diameter of 36 mm was found. This denotes the positive effect of seedling planting on tree cove compared to a nearby continuously grazed area; however, full recovery, especially regarding diversity of the tree community, requires more than 14year grazing exclusion, tree planting, and natural regeneration.