Leaf economics traits predict litter decomposition of tropical plants and differ among land use types

Abstract

1. Decomposition is a key ecosystem process that determines nutrient and carbon cycling. Individual leaf and litter characteristics are good predictors of decomposition rates within biomes worldwide, but knowledge of which traits are the best predictors for tropical species remains scarce. Also, the effect of a species’ position on the leaf economics spectrum (LES) and regeneration light requirements on decomposition rate are, until now, unknown. In addition, land use change is the most immediate and widespread global change driver, with potentially significant consequences for decomposition. 2. Here we evaluate 14 leaf and litter traits, and litter decomposition rates of 23 plant species from three different land use types (mature forest, secondary forest and agricultural field) in the moist tropics of lowland Bolivia. 3. Leaf and litter traits were closely associated and showed, in line with the LES, a slow–fast continuum ranging from species with tough, well-protected leaves (high leaf density, leaf dry matter content, force to punch and litter C : N ratio) to species with cheap, productive leaves [high specific leaf area (SLA) and nutrient concentrations in leaves and litter]. 4. Fresh green leaf traits were better predictors of decomposition rate than litter traits, and leaf nitrogen concentration (LNC) was a better predictor of decomposition than leaf phosphorus concentration, despite the widely held belief that tropical forests are P-limited. 5. Multiple regression analysis showed that LNC, SLA and chlorophyll content per unit leaf area had positive effects on decomposition, explaining together 65–69% of the variation. Species position on the LES and regeneration light requirements were also positively related to decomposition. 6. Plant communities from agricultural fields had significantly higher LNC and SLA than communities from mature forest and secondary forest. Species from agricultural fields had higher average decomposition rates than species from other ecosystems and tended to be at the fast end of the LES. 7. Both individual traits of living leaves and species’ position on the LES persist in litter, so that leaves lead influential afterlifes, affecting decomposition, nutrient and carbon cycling