Changed plant types associated
with loss of elephants in Ugandan national park
Date: September 12, 2016
Source: University of Utah
Loss of megaherbivores such as
elephants and hippos can allow woody plants and non-grassy herbs and flowering
plants to encroach on grasslands in African national parks, according to a new
University of Utah study, published Sept. 12 in Scientific Reports. The study
used isotopes in hippopotamus teeth to find a shift in the diet of hippos over
the course of a decade in Uganda's Queen Elizabeth National Park following
widespread elephant poaching in the 1970s.
Study first author and U
postdoctoral scholar Kendra Chritz says that her method of using hippo enamel
isotopes could help scientists reconstruct past changes in vegetation in
Africa's national parks, areas with relatively little ongoing scientific
observation. The results could give ecologists an idea of what could happen to
Africa's grasslands if elephants, whose populations are steeply declining, went
extinct or reached near-extinction.
"We have a window into what
these environments could look like without megaherbivores, and it's kind of
grim," Chritz says.
Competing plant classes
Grasslands are an important
ecosystem in Africa, hosting many animals and serving as corridors for wildlife
movement. Lowland tropical grasses, such as those in elephant ecosystems, are
part of the C4 class of plants, a reference to the enzyme used to process
carbon dioxide into sugars during photosynthesis. Corn and sugarcane are also
C4 plants. C3 plants, which use a different enzyme, include trees, shrubs,
flowering plants and herbs. C3 plants compete for resources with C4 grasses in
African savannas, including sunlight. Elephants and other megaherbivores help
keep woody plant encroachment in check by browsing seasonally on shrubs and
trees. But without that herbivore control, C3 plants can advance on grasslands
unimpeded.
The presence of shrubs and trees,
which can be seen in aerial photographs, give only a partial picture of the
balance of power between C3 and C4 plants. Observing herbs and flowering plants
requires ground-level observation, and records of such observations in Uganda's
Queen Elizabeth National Park, and many national parks in Africa, is sparse.
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