In conjunction with data-based reconstructions,
another source of information on environmental
variability and ecosystem response comes from
climate, ecosystem and bioclimatic vegetation
models. Studies on a range of terrestrial and
aquatic ecosystems show that changes in ecosystem
character can be described by sudden switches to
contrasting states (Rietkerk and von der Koppel,
1997). The presence of stable states, and what
character may signal a transition in ecosystem
state, has profound implications for understanding
ecosystem response to environmental changes.
Collaboration within KITE will fully integrate the
skills of palaeoecologists and modellers to develop
two main modelling initiatives to simulate and
investigate ecosystem response to environmental
change, the presence, and character, of stable
states and signals of transitions ensure
compatibility of research results. Firstly, we will
apply a developing a bioclimatic model of present
day plant distribution and their climatic
tolerances. Work at the University of York, U.K. has
been developing a bioclimatic model that constrains
individual tree species within envelopes of climatic
tolerance via a genetic algorithm this allows
present, past and future climatic modelling of
continental scale sub-Saharan African plant
distributions in a GIS (La Ferla et al., 2001;
Tokumine et al., in press). Standard GIS software is
used for the manipulation of the present and future
climate surfaces. By manipulating the climatic and
environmental parameters we will be able to match
communities derived from the palaeoecological
research projects to quantify the degree and nature
of climate change. For example, the current
environmental variables used to define the climatic
envelope can be substituted with those derived from
atmospheric general circulation models such as
HadCM3 (Gordon et al. 2000), potential spatial
changes in a species distribution can be determined.
Secondly, we will develop and apply
‘state-transition’ models that have hitherto been
used to investigate Sahelian ecosystem dynamics in
Tanzania (Rietkerk and von der Koppel, 1997). This
type of modelling approach will be used to
understand more generic ecosystem response signals.
The results will be contextualised in light of
current debates regarding long term ecological
functioning, ecosystem behaviour and add to the
ecological understanding on a range of issues such
as is the high biodiversity of the Eastern Arc
Mountains is related to global climatic changes, or
is it a response to such change?
References
Gordon, C., Cooper, C., Senior, C., Banks, H.,
Gregory, J., Johns, T., Mitchell, J., Wood R., 2000.
The simulation of SST, sea-ice extents and ocean
heat transport in a version of the Hadley Centre
coupled model without flux adjustments. Climate
Dynamics 16, 147-168.
La Ferla, B., Taplin, J., Ockwell, D., Lovett,
J.C. 2002. Continental scale patterns of
Biodiversity: can higher taxa accurately predict
African plant distribution? Botanical Journal of
the Linnean Society 138, 225-235.
Rietkerk, M., van der Koppel, J. 1997. Alternate
stable states and threshold effects in semi-arid
grazing systems. Oikos 79, 69-76.
Tokumine, S., McClean, C. J., Lovett, J. (in
press). Genetic algorithm based climate modelling of
continental scale sub-Saharan African plant
distributions in a GIS. Computers, Environment
and Urban Systems.
