The Spatially Dynamic/Static Microhabitat - a Concept appropriate to Elucidate the Cological Demands of Soil living Beetles (Coleoptera: Carabidae)
The habitat of soil arthropods has been considered to be static in space which often is reflected in the choice of sampling methods and procedures. Based on studies of soil living beetles it has been found necessary to operate with a more flexible concept: the spatially dynamic/static microhabitat. Species with a spatially dynamic microhabitat are guided to an indefinite number of positions depending upon the simultaneous abiotic conditions there (especially moisture and temperature, but also vegetation coverage, light, etc). Species with a static microhabitat do not move on the surface according to changes in the environmental variables. They live in fixed locations although they may move vertically in response to microclimatic changes. These two types of microhabitats with their species are extremes of a possible continuum. Species living within the same environment may have spatially dynamic or static microhabitats dependent upon their mode of life. The dynamic concept often applies to epigeal beetles whereas the static concept is more or less applicable to subterraneous (often burrowing) arthropods. Epigeal species living at freshwater fringes mostly have dynamic microhabitats, whereas the static microhabitat generally is realized among species living in more predictable environments, e. g open, dry habitats and the littoral zone of seashores. The concept seems to be necessary to achieve a correct picture of the microhabitat breadth and overlap of species and hence to understand the community structure and the determinants of species richness within communities. The microhabitat concept has consequencies as to choice of collecting methods and procedures.