OCR
142 IVIL Zoocoenological characteristics must, instead, consider biomass relations, degree of corrumpency and degree of obstancy. The relationship between presocium and insectivorous vertebrates, for example, is so complicated that this can be best expressed by the mass of food consumed, rather than by abundance values. The degree of obstancy, on the other hand, can be established - at least in individual cases - by the decrease in abundance of the target populations. The corrumpents will be related neither to individual plants nor oeci, but to whole plant stands, even if they only consume certain parts of it (e.g. granivores). Ihe degree of corrumpency manifests itself in the direction of presocia, and the food consumed can be measured by mass. 9. Dispersion Examining the spatial distribution of any zoocoenosis based on abundance, we find very uneven numbers, indicating that the spatial distribution of populations is extremely patchy. Dispersion expresses the spatial distribution of a population. This is the only characteristic that exclusively expresses spatial distribution, and can only be studied in space, without considering the inter-population relationships. Our perception of dispersion is formed through censuses of abundance. The abundance values obtained by the censuses will indicate that populations may be of heterogeneous distribution, even under similar conditions, although we can find the opposite, too. In larval populations of Operophthera, there may be no obstants in some parts of the canopy, causing different abundances of Operophthera at certain canopy levels, as the obstants are more abundant in the upper or lower canopy. It is also possible that the cynipid Eulophus abdominalis is more active on the sunny southern side of the canopy than in the shady northern one. Dispersion is, therefore, a strictly space-dependent feature, because the spatial distribution of species can be influenced by factors over and above the energy source, hinting at microclimatic influence. Hence, parts of an oecus can be suitable for the development of a different zoocoenosis. Therefore, dispersion points to the “clumped” nature of the zoocoenosis, also indicating its varied nature, and hints at additional factors influencing their association. Even where the energy source is otherwise available, dispersion constitutes an important characteristic, allowing insight of the inner life and development of the zoocoenosis. Dispersion is not a phenomenon that ceases to exist through increasing the number of samples (Balogh, 1953), but something that requires our close attention. An uneven dispersion does not become even if we perform various calculations, and this warns us about the reliability of quantitative calculations. Of course, this does not mean that such calculations are impossible in principle, only that sample size might not be great enough, and the quantitative data obtained are of uncertain precision.