Positive effects of invertebrate communities: soil layers are more important than soil type for leaf litter breakdown in a subtropical forest fragment

Plant litter breakdown sustains nutrient cycling in forest soils, yet the relative importance of soil type, soil depth, and detritivore access remains uncertain in subtropical Atlantic Forest fragments. We quantified mass loss of Garcinia gardneriana leaf litter in two forest fragments in southern Brazil, one on Cambisol and one on Argisol. Litterbags (3 g; 30 × 30 cm) with coarse mesh (10 mm; microbes plus detritivores) or fine mesh (0.05 mm; microbes only) were incubated at the soil surface and at 30 cm depth. Litterbags were retrieved after 30, 60, and 90 days during spring and summer. Argisol showed higher pH, nutrient availability, moisture, and bulk density, whereas Cambisol had higher organic matter, Al concentration, aggregate stability, and penetration strength. Leaf litter decomposition rate coefficients ( k ) ranged from 0.005 to 0.010 d -1 , and mass loss averaged 41% in coarse-mesh and 33% in fine-mesh litterbags across all retrieval times. Soil type did not affect remaining mass, but remaining mass was higher in subsurface than surface incubations and higher in fine than coarse mesh, indicating strong effects of depth constraints and detritivore access. The edaphic fauna comprised 3,161 individuals, richness and density did not differ between soils, but community composition differed, with distinct indicator families for each soil type. In Cambisol, indicator families included Muscidae, Nitidulidae, and Calliphoridae, whereas Formicidae, Philosciidae, Curculionidae, and Pteromalidae were associated with Argisol. Overall, litter breakdown was primarily regulated by detritivore access and soil depth, while soil type mainly structured assemblage identity rather than decomposition rates.