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

Ronildson Lima Luz,Christoph Gehring,Robert Michael Boddey,Marcelo Correa Zelarayán,Márcio Fernandes Alves Leite

doi:10.1590/1809-4392201903171

Ronildson Lima Luz, Christoph Gehring + Show 3 more

Open Access

https://doi.org/10.1590/1809-4392201903171

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Abstract

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.

Highlights

In the humid tropics, including the Amazon, repeated cycles of slash-and-burn agriculture with shortening fallow periods promote the persistence and dominance of aggressive ruderal plants (Loehle 1988; Chai et al 2016; Schweiger et al 2017)
We evaluated the effects of stand age and babassu dominance on leaf and root decomposition rates for each species via ANOVA model fitting, with three levels of hierarquical nesting along time, with four or three replications per factor
We explored species-specific changes in mass and nutrient concentrations along time with the Marcus-test (Marcus 1976), a one-way ANOVA with decomposition time aligned in an ordinate scale

Summary

Introduction

In the humid tropics, including the Amazon, repeated cycles of slash-and-burn agriculture with shortening fallow periods promote the persistence and dominance of aggressive ruderal plants (Loehle 1988; Chai et al 2016; Schweiger et al 2017). Typical features are earlier reproduction and great dispersal capacity (Brooks et al 2004), and the production of allelopathic compounds (Souto et al 2001) They shape soil chemical properties in their surroundings to their favor (Ehrenfeld 2003), governing nutrient cycling (Blank 2008) and microbial communities (Kourtev et al 2003). Home-field advantages and other forms of positive plant:soil feedbacks are often key for the ecological success of megadominant species (Kulmatski et al 2008)

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