Simulating the impacts of vegetation structure on the occurrence of a small mammalian carnivore in semi-arid savanna rangelands
Authored by Niels Blaum, Florian Jeltsch, Alexander Popp, Monika Schwager
Date Published: 2007
DOI: 10.1016/j.ecolmodel.2007.06.017
Sponsors:
German Federal Ministry of Education and Research (BMBF)
Platforms:
C++
Model Documentation:
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Abstract
In arid and semi-arid savannas, species diversity is strongly influenced
by structural diversity, which in these systems is characteristically
formed by woody vegetation. Shrub encroachment, associated with
overgrazing by domestic livestock, changes the structural diversity and
hence affects biodiversity. Many investigations have been carried out
with focus on the structure building trees, but little is known about
the importance of shrubs. Here, we present a spatially explicit and
individual-based population model for analysing the influence of shrub
encroachment on the occurrence of yellow mongooses (Cynictis
penicillata) in the Southern Kalahari, South Africa. This analysis is
based on field investigations in Southern Africa. The results of the
modelling study are in line with the results of a field study, in which
the same unimodal relationship between shrub cover and yellow mongoose
abundance was found. The model could explain this relationship by the
need of shrubs as protective structures on the one hand, and the need of
foraging habitat in the grass matrix on the other hand. To evaluate the
factors influencing the population dynamics at different levels of shrub
encroachment we carried out an extensive sensitivity analysis. Finally, we determined a range of existence of the yellow mongoose for various
shrub covers. Model results indicate a lower and an upper limit of
critical shrub densities at 1\% and 38\%, respectively. These limits
indicate the range in shrub cover allowing the persistence of the yellow
mongoose in the Southern Kalahari. (C) 2007 Elsevier B.V. All rights
reserved.
Tags
Land-use
Shrub encroachment
long-term
South-africa
Species-diversity
Seed
dispersal
Grassland
Mongoose cynictis-penicillata
Arid savanna
Habitat structure