Physical traits are better drivers than secondary compounds for leaf litter decomposition in a tropical heath vegetation

Abstract

Litter plays a crucial role in regulating nutrient and energy flows in tropical forests, and secondary compounds, specifically phenolic compounds and tannins, have been identified as the main drivers of litter decomposition in tropical rainforests. The effect of secondary compounds could be stronger in tropical forests with high solar incidence such as tropical heath vegetation (Restinga). To investigate if the importance of secondary compounds extends to Restinga, we evaluated the effect of 14 leaf litter traits, including phenolic compounds and tannins, on the litter decomposition of 26 species for two years. We found a large interspecific variation in both traits and decomposition rate among species. Specific leaf area (SLA) and water holding capacity (WHC) were the best individual predictors of litter decomposition. When combined with C, P, Ca, Mg, and Na, they were the best predictors of litter decomposition in Restinga. However, the low explanatory power (31 %) suggests that other biotic and abiotic factors may also play a crucial role in explaining litter decomposition in Restinga. Remarkably unlike previous studies in tropical rainforests, phenolic compounds and tannins had little or no significance as drivers of litter decomposition in Restinga. Our results suggest that the importance of phenolic compounds and tannins is context-dependent, and a comprehensive understanding of litter decomposition in Restinga requires inclusion of both abiotic and biotic factors.