Deposition, seasonality and the effect of climate on litterfall and its components in Caatinga, a tropical dry forest: A five-year study

Litter production is an ecosystem process responsible for adding nutrients to the soil. In addition, litter contributes to increased soil fertility and respiration and prevents soil degradation and erosion. However, in the Caatinga around 40 % of the native vegetation has already been modified, resulting in the loss of this material. In this study, we evaluated the deposition and decomposition of litter, its relationship with meteorological variables, nutrient concentration, nutrient return and nutrient use efficiency in a dry forest in the semi-arid region of Brazil. Average litter production was 864.69 kg DM ha-1 year-1, with greater deposition during the dry season. The main component was the leaf fraction, which accounted for 61 % of the total litter. This fraction showed a negative correlation with global solar radiation (-0.70), net radiation (-0.75) and canopy temperature (-0.61). The remaining fractions (twigs, reproductive structures and miscellaneous items) cannot therefore be linked to the explanatory group, and present isolated effects. The average rate of decomposition was 1.60 year-1 and ranged from 0.14 to 3.99 year-1 over the five years of the evaluation, while nutrient return equalled litter production, especially for Ca2+ (39.4 kg ha-1 year-1), N (20.7 kg ha-1 year-1) and K+ (13.1 kg ha-1 year-1). Nutrient use efficiency was relatively high for P, Mg2+ and K+. Our results suggest that the Caatinga presents a unimodal seasonal pattern of litterfall, with greater production during rainier years and peaks in production during the transition between winter and autumn. Litter production led to an increase in organic matter in the soil, acting as a source of nutrients and protecting the soil from impacts caused by environmental conditions.