What happens when a patch enters into contact with another patch? This condition is the rule and not the exception in a mosaic. The distinctive characteristic of a patch is in contact with other characteristics of the neighboring patches and it is possible that it receives a negative reaction (for instance a different pH of soil in the case of a patch of vegetation). On the other side the patch encounters a favorable condition and expands damaging the neighboring patch. For instance, a clone of bamboo spreading into grassland. This case is typical for invader plants. An intermediate reaction is also possible.
Borders of any type are critical areas, either for the physical characteristics of objects or for biological and ecological entities.
Organisms have created barriers at the border of their bodies such as cellular membranes or specialized tissue (tegument). Borders also play an important role in informing the organism that it is at the limits or margin. For this reason, a border (or ecotone), is a very informative area of an individual or of a patch (Fig. 6.1).
Fig. 6.1 Ecotones can be created by contraction of a patch due to fragmentation or substitution with another patch type. In this case we have considered the case of a woodland that has been progressively reduced by cultivations to a narrow band of natural vegetation assuming the role of an edgerow. The diversity along an edgerow increases due to the margin effect a diversity a diversity
A. Farina, Ecology, Cognition and Landscape, Landscape Series 11,
DOI 10.1007/978-90-481-3138-9_6, © Springer Science+Business Media B.V. 2010
The information available to an individual (plant, animal, microbe, fungi, virus) is quite different compared to the information that is collected by a patch (population, community), but in the end the result seems the same. The limits of a favorable area or the possibility for a new area of expansion are detected by sensors in individuals and by the different behavior of components in the population and community patches.
Ecotones have received great attention from ecologists for over 100 years, especially in the context of transition between biomes, geographic vegetation unit, movement of tree lines, and wildlife habitat (Fig. 6.2).
Since 1905, Clements used the term "ecotone" from the combination of two words (eco) oikos (home) and tonos (tension). The American naturalist Leopold (1933) described the greater richness of wildlife at the edges (across the ecotone).
Ecotones contribute to the complexity of the environmental mosaic as well as to the local complexity, either in terrestrial or in fresh and salt water bodies.
It is not easy to study ecotones because of their fuzzy character when observed at a fine scale, and their temporal and spatial instability increases such difficulties.
Ecotones can be observed across many scales, and we can consider the ecotones inside the paradigm of the hierarchy (Gosz 1993, Wiens 1992).
Initially these were considered as static entities like new habitats, but later, and especially during the past two decades, they were considered edges of a dynamic mosaic. Ecotones have been recognized as important structures regulating the flux of nutrients, alerting to the border of the individual species habitat. They contain high levels of biological diversity in addition to primary and secondary productivity.
Their importance in the functioning of species and also of ecosystems and landscapes has been largely recognized (Risser 1995).
Ecotones are considered interruptions of physical or biological structures along a gradient (Fig. 6.3).
Fig. 6.2 When a patch (population, community) meets another patch the transition zone is characterized by uncertainty; an ecotone is located there
Fig. 6.3 Ecotone properties largely depend on their environmental context (A). The direction of the dominant wind or the gravitational force can produce severe changes in ecotone function. For instance in image (B) the gravitational effects are depicted as the main constraint for the fluxes of matter and nutrients
According to the theory of the mosaic, ecotones represent the margin of expansion or reduction of every patch, the transitional point between different conditions.
We can locate ecotones everywhere in a landscape according to the type of mosaic perceived. So also for ecotones we have to adopt the paradigm of a subjective mosaic strictly linked to the cognitive component of each living organism.
Ecotones exist on all scales, from the biome to a few centimeters in space and from the long term of thousands of years to the ephemeral life of temporary ponds.
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