Soil macroinvertebrate communities and ecosystem services in deforested landscapes of Amazonia

Abstract

Land use changes in the Amazon region strongly impact soil macroinvertebrate communities, which are recognized as major drivers of soil functions (Lavelle et al., 2006). To explore these relations, we tested the hypotheses that (i) soil macrofauna communities respond to landscape changes and (ii) soil macrofauna and ecosystem services are linked. We conducted a survey of macrofauna communities and indicators of ecosystem services at 270 sites in southern Colombia (department of Caqueta) and northern Brazil (state of Pará), two areas of the Amazon where family agriculture dominates. Sites represented a variety of land use types: forests, fallows, annual or perennial crops, and pastures. At each site we assessed soil macroinvertebrate density (18 taxonomic units) and the following ecosystem service indicators: soil and aboveground biomass carbon stock; water infiltration rate; aeration, drainage and water storage capacities based on pore-size distribution; soil chemical fertility; and soil aggregation. Significant covariation was observed between macrofauna communities and landscape metric data (co-inertia analysis: RV=0.30, p<0.01, Monte Carlo test) and between macrofauna communities and ecosystem service indicators (co-inertia analysis: RV=0.35, p<0.01, Monte Carlo test). Points located in pastures within 100m of forest had greater macrofauna density and diversity than those located in pastures with no forest within 100m (Wilcoxon rank sum test, p<0.01). Total macroinvertebrate density was significantly correlated with macroporosity (r2=0.42, p<0.01), as was the density of specific taxonomic groups: Chilopoda (r2=0.43, p<0.01), Isoptera (r2=0.30, p<0.01), Diplopoda (r2=0.31, p<0.01), and Formicidae (r2=0.13, p<0.01). Total macroinvertebrate density was also significantly correlated with available soil water (r2=0.38, p<0.01) as well as other soil-service indicators (but with r2<0.10). Results demonstrate that landscape dynamics and composition affect soil macrofauna communities, and that soil macrofauna density is significantly correlated with soil services in deforested Amazonia, indicating that soil macrofauna have an engineering and/or indicator function.