When blooming, we recycle faster! Reciprocal intraspecific litter-mixing effects of floral and leaf litter decomposition.

The form and function of plant organs influence plant decomposition. Floral litter typically decomposes faster and is of higher quality than conspecific leaf litter. However, how intraspecific differences in litter quality between plant organs drive litter-mixing effects on decomposition remains unclear. We hypothesized that: (i) floral and leaf litter decompose faster when mixed than when decomposed alone, (ii) these synergistic effects are stronger for leaf litter decomposition, and (iii) litter-mixing effects are mediated by multivariate litter trait complementarity. To test these hypotheses, we conducted a common garden field experiment using floral and leaf litter from 28 tropical woody species. As predicted, synergistic effects were common and mutual for both litter types, with stronger effects observed in leaf litter decomposition. Different functional traits predicted litter-mixing effects for each litter type, supporting the hypothesis of multivariate trait complementarity. Autochthonous traits (inherent to the litter itself) accounted for two-thirds of the variation in litter-mixing effects for both litter types, while allochthonous traits (from associated litter) explained one-third of the variation. These findings highlight that functional differences between plant organs influence litter-mixing effects on decomposition. This advances our understanding of the litter diversity-decomposition relationship and its implications for nutrient cycling and plant-soil feedback.