Rules Governing Structure and Dynamics of the Ecological Mosaics

The distribution of energy, matter, and organisms on the environmental sub-stratum can appear in at least two different forms:

a - gradient-like, in a fuzzy system (Fig. 3.6) b - border-like, distinguishing separate discrete units (Fig. 3.7).

Fig. 3.4 The resolution at which a mosaic is observed can greatly change its appearance; for instance if we select 200 classes the image is indistinct, and if we select two classes the information is too compressed. Thirty-four classes is too much again but ten classes allows us to observe objects (shrubs) like in the b/w image

Fig. 3.4 The resolution at which a mosaic is observed can greatly change its appearance; for instance if we select 200 classes the image is indistinct, and if we select two classes the information is too compressed. Thirty-four classes is too much again but ten classes allows us to observe objects (shrubs) like in the b/w image a: The gradient distribution pertains to many physical phenomena, such as the air and water temperature, sea water salinity, water content in the soil, and noise levels around an urban environment. Gradient means that particles are distributed according to a concentration threshold and that particles have the capacity to migrate following a dispersion behavior. b: The sharp border between an entity and the neighboring one creates a mosaic, a puzzle of objects with different shapes, internal structures, and cognitive

Fig. 3.5 The mosaic may be created moving from order to disorder and vice versa, but the functions of these two types are completely different

3 Toward a Theory of the Mosaic Disorder Order

3 Toward a Theory of the Mosaic Disorder Order

Fig. 3.5 The mosaic may be created moving from order to disorder and vice versa, but the functions of these two types are completely different

o o

Fig. 3.6 Example of distribution of an event along a gradient, for instance the thermic behavior of an exposed soil

Fig. 3.7 In this figure we can observe a mosaic of large bands (6) and inside each band we can observe a gradient of ten tones characters. The sharp border means that two different objects do not have the capacity to prevail one over the other, at least in the adjacencies, and that their distinct characters are homogeneous when observed. An example is from the patchy distribution of clonal plants like Prunus spinosa or nettles.

These two designs (gradient and sharp border), when observed at a different scale, modify their aspect and can interchange such characters. It is evident that a mosaic appears beyond the limit of a gradient, and that a gradient may appear when we reduce the scale of observation inside a patch of the mosaic, or when we enlarge the scale of observation.

In this case, the geographical distribution of Prunus spinosa is based on a gradient when locally it has a patchy distribution. And the gradient distribution of temperature shows patchy mechanisms when observed at the scale of climatic regions. Some conclude that, gradients and mosaics are a matter of scale. I think rather that they are two different conditions in which energy, matter, and life forms can be observed. The behavior of entities like temperature, water, and noise changes according to the level of scale at which we observe; different mechanisms are involved according to the spatial or temporal scale. How and when the different patterns (patchiness or gradient) shift is an openly disputed argument and, in my opinion, the key to understanding relevant parts of ecological complexity.

In general, it is reasonable to hypothesize that gradient patterns appear when a physical or biological entity is under the first stage of organization or when the dynamics are so strong so as to reduce the inherent behavior of a system.

The elements responsible for patchiness are local uniqueness, phase difference, and dispersal (Levin 1976). The mosaic appears when the system is under self-organizing control and the entropic state is moving toward a mature state. For instance, after heavy rains a stream can receive enough water to move in a chaotic (s.l.) way stones, gravel, sand, and particulate consistently. The more the flush is intense and short in time - for instance after a summer thunderstorm - the more the material is accumulated in a highly disordered way.

A mosaic appears when disturbance and recovery processes act contemporarily at different spatial and temporal scales independently. Observing the movement of stream deposits along the entire water body we can recognize zones with different dimensions of detritus. Moving from the head to the mouth the dimension of sediments change creating a "linear" mosaic of elements (Fig. 3.8).

A further example can be used. For instance, a recent seeded field with different types of grasses shows a mixed distribution of plants emerging from the random distribution of seeds during the seeding. In one or two years it is quite common to observe the appearance of a mosaic in which patches of dominant species are growing. This means that the system, in this case the plant community, moves to

Fig. 3.8 In (A) the distribution of objects is random, a mixing of different objects is assembled by chance like during a short flush of a montane stream. In (B) a sequence of events, like annual floods distributes eroded material of a stream bed according to dimension and shape creating a linear, or gradient mosaic. In the first case time was the limiting factor in creating order in the system. In the second example order is much improved and the system shows self-organization

n A O n O O

□ □ □ □ □

° o ° o° o

* A A Ä » A A A

Fig. 3.8 In (A) the distribution of objects is random, a mixing of different objects is assembled by chance like during a short flush of a montane stream. In (B) a sequence of events, like annual floods distributes eroded material of a stream bed according to dimension and shape creating a linear, or gradient mosaic. In the first case time was the limiting factor in creating order in the system. In the second example order is much improved and the system shows self-organization a coalescence in which the competition between plants, nutrients available, and micro-climatic constraints imposes order on the system.

0 0

Post a comment