Biomass production by tree species is negative affected by decreased precipitation and chronic anthropogenic disturbance in a Caatinga dry forest

Abstract

Tropical dry forests are currently exposed to slash-and-burn agriculture, livestock production, exploitation of forest products and increasing aridity, with impacts on primary productivity still to be investigated. In this study, we investigated how chronic anthropogenic disturbance and reduced rainfall affect the woody biomass of Pityrocarpa moniliformis in a Caatinga dry forest, Brazil. Using tree-ring analysis for a total of 50 individuals, we addressed tree age, radial growth rates, and accumulated woody biomass across sites exposed to varying levels of human disturbance and average rainfall. Accumulated woody biomass ranged from 4.31 to 219.26 kg per individual (22 and 27 years, respectively). The highest values were found in wetter, less disturbed sites (90.41 ± 54.75 kg), while the lowest were observed in drier but also less disturbed sites (36.40 ± 18.39 kg). Growth and biomass were positively correlated with rainfall but negatively affected by drought and disturbance. Trees in drier areas required at least eight additional years to reach biomass levels comparable to those in wetter areas. Considering the extremes of the precipitation gradient, drier sites exhibited, on average, 59.74% less biomass. These findings highlight the impacts of aridity and chronic disturbance on tree growth and biomass, ultimately influencing dry forest productivity.