The installation was formed by three containers with the same characteristics; square containers with dimensions of 40x40 cm. The density of the population is 100% since the beginning of the experiment, so that the relationships between the species can be directly assessed by inter and intraspecific competition. The initial proportion of individuals of each species is of a 1/3 and these are introduced randomly, in the same way that the digital model starts from a random disposition. The culture conditions for the three containers are identical, so that the obtained results from the three samples are equally representative.

The purpose of this experiment was to study the growth of three floating water plants in order to prove that the interaction of the 3 species generates a recognizable pattern, that the difference of the growing characteristics between species can be codified and parameterized digitally and that the pattern of the plants that has been generated naturally coincides with the digital simulation implemented using the Cellular Automata algorithm.

The analog/digital comparison seeks to demonstrate if it is possible to establish a digital model that is assimilable to the development of a series of species. To evaluate this, we proposed the use of three species of floating plants of rapid development, and the establishment in parallel of a digital model with a series of simple rules in the relation plant-plant and plant-environment.

The conditional rules in the CA are established in relation to the competition for the space and form of development of these species, considering that all three present a similar growth rate and that is mainly influenced by the available space and their capacity to replace or not the specimens that are around each individual. The three species used are Lemna minor, Azolla caroliniana and Spirodela polyrrhiza, all three showing a size from 0,5 to 1cm per specimen.

The three species used are Lemna minor, Azolla caroliniana and Spirodela polyrrhiza, all three showing a size from 0,5 to 1cm per specimen.

The digital model has been implemented with Processing after observing their behaviour. For example, Azolla caroliniana tends to form large carpets of individuals that remain attached between them, as the plant grows and multiplies itself in a dichotomous way. Lemna minor multiplies itself by scission of the individuals, therefore the group has the tendency to be laxer, giving also the possibility to the plants to fill the spaces between the other species. Spirodela polyrrhiza multiplies itself also by scission, but the individuals, a part from being larger, are more sessile than Lemna.

Relations between the three species were considered in order to define the rules. Azolla tends to dominate over Lemna and to occupy its place. Also, when Azolla grows forming large groups, the intraspecific competition, particularly in environments with scarce phosphorus like the experiment, tends to leave empty spaces that can be occupied by other species, especially by Lemna. Spirodela is little affectedly the development of Azolla and even less from Lemna, but requires more nutrients that the others, specially than Azolla that can fix nitrogen from the atmosphere because its symbiosis with Anabaena. Therefore, the population of Spirodela is limited also by intraspecific competition. Lemna is the more ubiquitous specie therefore can occupy large patches and is less affected than the others by intraspecific competition.

The relation between species has been codified, defining the following rules:

·         If Azolla has more than 6 neighbours Azolla >> Azolla becomes Lemna, else stays Azolla.

·         If Spirodela has more than 4 neighbours Spirodela >> Spirodela becomes Lemna, else stays Lemna.

·         If Spirodela has more than 5 neighbours Azolla >> Spirodela becomes Azolla, else stays Spirodela.

In order to obtain conclusions from the analog experiment the images have been digitally processed, grouping the different species and enabling the comparison with the digital model.