Litter decomposition and nutrient release dynamics of leaves and roots of the babassu palm in eastern Amazonia

Abstract

The ruderal babassu palm (Attalea speciosa) is expanding on large areas of degraded Amazon landscapes. Decomposition of leaves and roots is in the center of plant:soil interactions. We evaluated decomposition and nutrient concentrations of leaves and fine roots of babassu in comparison with two exotic reference species, Acacia mangium (slow degradability) and Leucaena leucocephala (fast degradability), in a 138-day litterbag assay carried out in secondary forest stands of different age and babassu abundance. We chose 4-mm over 2-mm mesh litterbags based on a pilot study. Babassu leaves degraded slower than leaves of A. mangium and L. leucocephala, and also had lower nitrogen, phosphorus and calcium concentrations in all stages of decomposition. By contrast, potassium concentrations in babassu leaves were higher than in both reference species at 0 and 50 days. Roots of all three species decomposed slower than leaves. Compared to the leaves, both biomass loss and nutrient concentrations differed less between babassu and reference-species roots, except for lower nitrogen concentration in babassu roots. Leaf-litter decomposition of all three species was significantly faster in old than in young secondary forest, suggesting an acceleration of decomposition along succession. Babassu leaves decomposed faster in old babassu-dominated than non-dominated secondary forest, pointing to the existence of specialized decomposer communities in babassu-dominated stands.

Belowground competition and niche partitioning between the Babassu palm and Urochloa grass in eastern Amazonian pastures

“…Babassu and Urochloa have in common an accumulation of soil organic matter (SOM) in their surroundings, reported for Babassu by Gehring et al (2020), and in Urochloa pastures by Santos et al (2013) and Silva Neto et al (2012). The pathways for such SOM buildup, however, likely differ between the two, with high root exudation from the C4 grass Urochloa (Louw‐Gaume et al, 2017), as opposed to high Babassu litter inputs with high C:N ratios (Gehring et al, 2020) and slow litter decomposition (Luz et al, 2020).…”