Chapter 1 - Núria BONADA

Brief introduction and objectives
INTRODUCTION
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Brief introduction and objectives
In all ecosystems, patterns and processes are highly influenced by spatial and temporal scales,
and the organization level used. The scale effect over communities has been widely discussed
either, in terrestrial and aquatic ecosystems. Very often, the choice of the correct scale has
been considered the main problem in ecology. This phenomenon is based on the idea that the
factors affecting communities can vary depending on the observation scale, and therefore,
patterns and processes do as well. Similarly, although several controversies can be found in
literature, patterns and processes can also be influenced by the organization and taxonomical
level used. The work we present here try to study macroinvertebrates from mediterranean
aquatic ecosystems at different scales, organization and taxonomical levels.
The mediterranean climate
Mediterranean climate is characterized by a high seasonality with wet and cold winters and
dry and hot summers. Overall, two factors can be used to define mediterranean climate: over
65% of the annual precipitation falling in winter (although in some areas the wet period goes
from autumn to spring), and the presence of a summer drought with length and intensity
variables. The mean annual precipitation varies between 275-900 mm/a, although sometimes
this is not as fixed, and some definitions exclude the maximum level of annual precipitation.