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Doctorat
Australie
2007
How communities influence ecosystem processes : the role of species diversity, functional diversity, and functional identity
Titre : How communities influence ecosystem processes : the role of species diversity, functional diversity, and functional identity
Auteur : Mokany, Karel
Université de soutenance : Australian National University
Grade : Doctor of Philosophy (PhD)
Résumé
Many biological communities are currently experiencing rapid changes in their
diversity and composition, due largely to the intensification of human impacts on
natural ecosystems. Alterations to the structure and diversity of communities have the
potential to influence a broad range of ecosystem processes (biogeochemical pools
and fluxes) which are of key importance to the integrity of natural systems and the
well-being of humans. Consequently, increasing research attention is being given to
understand how the diversity and composition of biological communities influences
key ecosystem processes. This thesis examined how ecosystem processes are related
to a broad range of community attributes, using native grasslands as a study system. I
investigated this topic, and associated issues, using a variety of approaches, including
conceptual and theoretical explorations, pot based experiments, mechanistic
modelling, and a major field study of a native grassland system. Importantly, I applied
a functional trait approach to gain a greater understanding of how the functional
diversity and composition of communities may influence ecosystem processes.
The results presented in this thesis overwhelmingly support Grime’s (1998) mass ratio
hypothesis, which proposes that the functional attributes of the dominant species in a
community largely determine the effect of the biota on ecosystem processes. In the
native grassland system I studied, the functional identities of the dominant species
were the most important community attribute influencing the magnitude and
variability of ecosystem processes. Functional trait diversity also had significant
effects on ecosystem processes, although it was generally found to be weaker than the
functional identities of the dominant species in predicting ecosystem processes.
Functional trait diversity essentially represents the degree of complementarity
between species, or the diversity of ways in which species access and utihse
resources. My results suggest that complementarity can be important in influencing
ecosystem processes, but in most cases it is not as important as the functional
identities of the dominant species. In contrast, ecosystem processes tended to be
poorly related to traditional measures of community diversity, such as species richness
and functional group richness. These results suggest that major changes in the
dominance hierarchies of communities are likely to have the greatest impact on
ecosystem processes, with only minor effects expected following the loss of rare
species.
Page publiée le 25 janvier 2021