Elephant megacarcasses increase local nutrient pools in African savanna soils and plants

African elephants (Loxodonta africana) are the largest extant terrestrial
mammals, with bodies containing enormous quantities of nutrients. Yet we
know little about how these nutrients move through the ecosystem after an
elephant dies. Here, we investigated the initial effects (1-26 months
post-death) of elephant megacarcasses on savanna soil and plant nutrient
pools in Kruger National Park, South Africa. We hypothesized that: (H1)
elephant megacarcass decomposition would release nutrients into soil,
resulting in higher concentrations of soil nitrogen (N), phosphorus (P),
and cations near the center of carcass sites; (H2) carbon (C) inputs to
the soil would stimulate microbial activity, resulting in increased soil
respiration potential near the center of carcass sites; and (H3)
carcass-derived nutrients would move from soil into plants, resulting in
higher foliar nutrient concentrations near the center of carcass sites. To
test our hypotheses, we identified 10 elephant carcass sites split evenly
between nutrient-poor granitic and nutrient-rich basaltic soils. At each
site, we ran transects in the four cardinal directions from the center of
the carcass site, collecting soil and grass (Urochloa trichopus, formerly
U. mosambicensis) samples at 0, 2.5, 5, 10, and 15 m. We then analyzed
samples for CNP and cation concentrations and quantified soil microbial
respiration potential. We found that concentrations of soil nitrate,
ammonium, δ15N, phosphate, and sodium were elevated closer to the center
of carcass sites (H1). Microbial respiration potentials were positively
correlated with soil organic C, and both respiration and organic C
decreased with distance from the carcass (H2). Finally, we found evidence
that plants were readily absorbing carcass-derived nutrients from the
soil, with foliar %N, δ15N, iron, potassium, magnesium, and sodium
significantly elevated closer to the center of carcass sites (H3).
Together, these results indicate that elephant megacarcasses release
ecologically consequential pulses of nutrients into the soil that
influence soil microbial activity and are absorbed by plants into the
above-ground nutrient pools. These localized nutrient pulses may drive
spatiotemporal heterogeneity in plant diversity, herbivore behavior, and
ecosystem processes.