Ecofunctionality in artificial aquatic ecosystem: linking abiotic dynamics to community stability
Author(s)
Bellisario, Bruno
Date Issued
March 15, 2010
Type
Doctoral Thesis
Abstract
The influence of environmental conditions on the structuring process of detritus-based
communities is of great importance in order to understand the consequences of
environmental changes on ecosystems structure and functioning.
Natural and human induced alterations in space and time have sparked widespread
changes in the global distribution of biota, and this results in the expansion of
allochtonous, non-native species and contractions of autochthonous, native species, the so-called "biotic homogenization". Homogenization is not a random process, because invasion success and extirpation vulnerability are defined by the interaction between species traits and environmental conditions.
Therefore, since species contribute individually and collectively to the stability of communities and ecosystems, the modification of community structure could lead to a structural and functional homogenization, involving the replacement of ecological specialists by the same widespread generalists. Homogenization of communities might also reduce ecosystem functioning, stability and resistance to environmental changes by restricting the available range of species-specific responses. The structural composition of communities defines the range of functional traits that influence ecosystem functions (such as the decomposition of organic matter), and the homogenization might limit the pool of species that can compensate for local extinctions (i.e., reduce spatial patterns in functional redundancy). Homogenized communities might therefore have a decreased resistance to environmental
perturbations, as the high degree of similarity among communities might dampen or
eliminate potential recolonizations by species with locally extirpated traits.
In this work, I wanted to assess the consequences for ecosystem structure and
functioning of changing environmental conditions over space and time. Since the effects of biotic homogenization might be particularly high in areas, such as small and
fragmented ecosystems that experience more frequent and severe disturbance events,
the Biological Reserve of Tarquinia saltern represents a suitable candidate to test
hypotheses about functional ecology.
The aim of this work is to understand how the steepest gradients of environmental
conditions influence the structure and functioning of detritus-based communities. The importance in the study of decomposition processes and dynamics lies in the ability of
detritus to sustain higher species diversity, larger predator biomass, and longer food chains than would be supported by primary productivity alone, stabilizing the dynamics of consumer populations and food webs that would be otherwise unstable.
The experimental approach carried out for this work comes from a twelve months field
experiment under non-manipulative conditions in six sites in the area of Tarquinia
saltern, to cover the full spectrum of environmental gradients, using the allochtonous leaf detritus of Phragmites australis (Cav.) Trin. ex Steud.
Here I applied the network analysis to understand how the whole community assembly
and the spatial distribution of macroinvertebrates on leaf detritus are influenced by the environmental conditions under which they are structured, and the consequence for ecosystem functionality and stability, giving useful insights for conservation and management.
Additional information
Dottorato di ricerca in Ecologia e gestione delle risorse biologiche
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