Base metal fluxes from fig trees to soil on Barro Colorado Island, Panama: potential contribution of the common frugivorous bat Artibeus jamaicensis

Abstract

The contribution of animals to element fluxes in ecosystems is little known. We therefore estimated the contribution of a common frugivorous bat species (Phyllostomidae: Artibeus jamaicensis) to the base metal fluxes (Ca, Mg, and K) from fig trees to soil in a tropical lowland forest on Barro Colorado Island (BCI) because figs provide large parts of the Ca required by these mammals. We chose three individual old-growth fig trees on each of four geological units of BCI varying in soil exchangeable base metal concentrations. To assess element fluxes, we determined internal base metal cycling via canopy exchange and litterfall, external input through bulk and dry deposition, and contributions of bats through pellets and bat faeces as well as element absorption in bats. Assuming a consumption of 20 % of the total fig production by A. jamaicensis, total mean fluxes from fig trees to soil were 24 ± 7 g m−2 year−1 for Ca, 4.6 ± 1.6 for Mg, and 21 ± 4 for K, respectively. The largest part of Ca and Mg was cycled as bulk litterfall (79 ± 9 and 62 ± 15 %, respectively) and of K as canopy leaching (56 ± 12 %). A. jamaicensis contributed 1.7 ± 0.5, 2.3 ± 0.6, and 6.1 ± 1.8 % to the total fluxes of Ca, Mg and K under fig trees, respectively. The contribution of A. jamaicensis to the base metal fluxes below the fig canopy was similar to that of bulk deposition. Our results demonstrate that the contribution of a single frugivorous mammal species to internal base metal cycling in a tropical ecosystem may be similarly important as bulk deposition and can have measurable effects on local soil fertility.