Oldal 106 [106]
OCR
104 lv. The dynamics of the animal communities § DAILY ASPECTS There are other within-aspect phenomena that characterise the incessant movements in an animal community, and that can cause temporary changes. Not all animals are continuously active, even during their periods of activity. Animals living above ground are influenced by the alternating days and nights, and while most of them are active at daytime, there exist crepuscular and night-active ones, too, and they are either hiding or not apparent during daytime. While the existence of aspects can enrich a zoocoenosis (for example, due to the swarming of an obstant element during a given period), the reaction to the daily periodicity of light does not cause a change in the composition of a zoocoenosis, but causes a dynamic in activity that needs to be considered during censuses. The time-of-day assemblages include animals that are active in a given part of the day. From this definition one can see that this is not a coenological term, and such a group can be recognised at the level of assemblage. It reflects the zoocoenosis only when one or another population is only active at certain times of the day. The day-active populations rest during night-time, and the night-active ones during the day, and often at places that are difficult to find, thus they remove themselves from the visible life of the biocoenosis. The larvae of Gonioctena fornicata withdraw to the base of alfalfa stems during the day, and chew on the top leaves only during the night (Manninger, 1949). The adults of Tropinota hirta disappears from the meadow during the night, and become active sometime after sunrise (Szelényi, 1934). Weather events can, likewise, influence the activity of apparent populations, as it is known that cold, rainy days are bad for collecting. The weather influences even the soil-living populations (Jahn, 1951). It is also certain that the litter is populated by night-active animals during the day, and day-active ones during the night. Although the composition of the zoocoenosis is not altered by it, daytime is relevant for the census methods used and, if one or more of the constituent populations are active at other times than when the census was made, the quantitative relationship of the zoocoenosis will be grossly distorted. Already, we can state here that a zoocoenological survey cannot be restricted to the sampling of adults (or larvae) during daytime. The daytime has no further impact on the life of a zoocoenosis; it has less influence than an aspect, even though that is not a structural part of a zoocoenosis, either - a community is not composed of aspects and one can compare them to spikes ofa rotating wheel. The relationship of the aspects and zoocoenological categories can be conceptualised so that, occasionally, among the permanent and sub-permanent populations, stenochron and mesochron elements appear, that will, after a shorter or longer period of activity, again return to a latent phase, giving space to other, similar populations. These changes are characteristics of the
