Zur Dispersion der Lepidopterenlarven in einem Eichenbestand

Lotz, Guntram; Moeller, Jürgen

doi:10.1111/j.1439-0418.1967.tb02070.x

Cited by 4 publications

(1 citation statement)

References 4 publications

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“…Es gilt zunachst zu prufen, ob in der qualitativen Zusammensetzung der Lepidopterenfauna der untersuchten Latenz-und Gradationsgebiete Unterschiede bestehen. Tabelle 2 bringt eine Zusammenstellung der gefundenen Arten in beiden Gebieten, wobei fur den Bramwald auch die Funde aus den Dispersionsuntersuchungen 1963und 1964(LOTZ und MOELLER 1967 1965und 1966(19631964: 54;1965: 41;1966: 24 Arten Es zeigt sich also, dai3 sich in der qualitativen Zusammensetzung der Lepidopterenfauna der untersuchten Latenz-und Gradationsgebiete kein wesentlicher Unterschied nachweisen lie&…”

Section: Avteninventar In Den Untevsuchten Gebietenunclassified

Vergleichende Untersuchungen an der Kronenfauna der Eichen in Latenz‐ und Gradationsgebieten des Eichenwicklers (Tortrix viridana L.)

Schwerdtfeger¹

1971

Zeitschrift für Angewandte Entomologie

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Studies on the top‐fauna of oaks in outbreak‐ and non‐outbreak‐areas of Tortrix viridanaL. 3. Importance of parasites for the local fluctuation type of the oak Tortricid. Based on investigations of Moeller‐Lotz 1968 and Betz‐Schwerdtfeger 1971 carried out in a latency area of Tortrix viridana (where the species always remains on a low population level) and in comparison with it in a gradation area (where temporary outbreaks occur), the following model concerning the importance of parasites for the local fluctuation type of the Oak Tortricid could be developped: In the latency area, the population density of the Oak Tortricid is regularly held on a low level by bad temporal coincidence between the hatching of the caterpillars and the swelling of the oak buds as well as by relatively strong activity of parasites together with other mortality factors. In the gradation area, owing to local climatic conditions the coincidence between caterpillar hatching and bud swelling becomes better from time to time; then the mortality of the freshly hatched larvae decreases and the density of the Tortricid population increases. More hosts are offered to the parasites, and they increase too. The plurivoltine species attack in greater numbers the lepidoptera needed as alternate hosts in the late summer, they nearly extinguish them thus bereaving themselves of the possibility to survive. The efficiency of parasites is reduced thereby hastening the move upward of the Tortricid abundance. Zusammenfassung Zur Frage, welche Bedeutung den Parasiten für den lokalen Fluktuationstyp des Eichenwicklers Tortrix viridana zukommt, konnte auf Grund geschilderter Untersuchungen in jc einem seiner Latenz‐ und Gradationsgebiete folgendes Denkmodell entwickelt und rechnerisch untermauert werden: Im Latenzgebiet des Eichenwicklers halten regelmäßig schlechte zeitliche Koinzidenz zwischen dem Schlüpfen der Raupen und dem Treiben der Eichenknospen sowie eine vergleichsweise starke Tätigkeit von Parasiten zusammen mit anderen Mortalitätsfaktoren seine Dichte ständig auf niedrigem Niveau. Im Gradationsgebiet ist die Koinzidenz zwischen Raupenschlüpfen und Knospentreiben zeitweise besser, die Sterblichkeit der frischgeschlüpften Räupchen wird geringer, die Dichte des Wicklers steigt an. Dank dem erhöhten Wirtsangebot vermehren sich auch die plurivoltinen Parasiten; sie befallen verstärkt die im Spätsommer als Zwischenwirte benötigten Lepidopteren, löschen sie nahezu aus und nehmen sich damit selbst die Daseinsmöglichkeit. Die Wirksamkeit der Parasiten läßt nach, wodurch die Aufwärtsbewegung der Wicklerdichte sich beschleunigt.

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Section: Avteninventar In Den Untevsuchten Gebietenunclassified

Vergleichende Untersuchungen an der Kronenfauna der Eichen in Latenz‐ und Gradationsgebieten des Eichenwicklers (Tortrix viridana L.)

Schwerdtfeger¹

1971

Zeitschrift für Angewandte Entomologie

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Eine integrierte Theorie zur Abundanzdynamik tierischer Populationen

Schwerdtfeger

1968

Oecologia

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Since the twenties of our century, at least 15 theories worth discussing have been developped which intend to explain the causes of natural control of animal populations (for details see SCHWERDTFEGER, 1968). An attempt is made to integrate the different-partly contrary-ideas and new results into a general theory. The basis to start from is the cybernetic principle of feed-back mechanism introduced into population dynamics by WILBERT (1962): an actual value (e.g. the inside temperature of a refrigerator) is permanently changed by perturbances (the always higher outside temperature); through a regulator (a thermostat), each change puts in action a regulating variable (a cooling device) which alters the actual towards the index value (required inside temperature).The often complicated processes that take part in the natural control of populations are summarized in Fig. 6. The actual value is the existing population density (Abundanz). The perturbances primarily causing its fluctuations (Fluktuation) are fertility and immigration which raise the abundance, mortality and emigration which lower it.The amplitude of the fluctuation must be limited, if the population is not to die out or to destroy its habitat by continuous increase. It is determined (Determination) as a sort of index value, the lower limit of which corresponds in the extreme to the minimal density guaranteeing the existence of the population, while the upper limit is formed by the environmental capacity. The latter is determined either by the total supply of requisites and the ability of the animals to use it or by the local minimum of adverse effects. The capacity of the environment and therewith the amplitude of fluctuations can be fixed or variable. It is fixed in a population of Great Tits with territorial behaviour: in an oak stand, the number of breeding pairs cannot be higher than the number of territories fitting in. It is variable in the case of bark beetles living in wind thrown spruce trees: they may find 2 suitable trees this year, 100 the next after heavy winter storms and 10 the year after next. In this case, the change of determination was a change of environment, specifically of the supply of a requisite; it can as well be a change in the constitution of the population characterized by its demands and efficiencies: in the final effect it makes no difference wether more breeding space is offered or less is demanded. The variability of the amplitude in the case of the bark beetles is caused by chance; it can also be governed or self-induced. It is governed e.g. by the seasonal rhythm of climate: the average level of density in tsetse flies is higher during the rain season than during the dry season. It is self-induced in the case of an entomophagous parasite changing the density of its host insect and by this varying the supply of a requisite.Fertility permanently tends to raise the density of populations. Processes of limitation (Limitation) work against this tendency. With increasing abundance, density dependent factors become more effec...

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The distribution pattern of herbivory in a beech canopy

Nielsen

Ejlersen

1977

Ecological Entomology

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Abstract. (1) The spatial distribution pattern of herbivory by phyllophagous canopy arthropods in a 90‐year‐old beech stand was analysed.(2) Two main patterns of spatial distribution were recorded. The leaf mining moths Phyllonorycter maestingella and Stigmella hemargyrella and the adult weevils Rhynchaenus fagi and Phyllobius argentatus mainly attacked the under‐story and the latter species especially the low canopy in the central part of the stand. Mines of R. fagi chiefly occurred in the top of the overstory canopy or at the fringe of the stand. However, comparable distribution patterns are only expected in mature beech stands composed of distinct overstory and understory layers.(3) The effect of the actual spatial distribution pattern of herbivory on photosynthesis, productivity, and transpiration of beech in the research stand is discussed. It is suggested that in some cases the shade leaves of the understory canopy may cushion the effect of herbivory in the beech stand.

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Zur Dispersion der Lepidopterenlarven in einem Eichenbestand

Cited by 4 publications

References 4 publications

Vergleichende Untersuchungen an der Kronenfauna der Eichen in Latenz‐ und Gradationsgebieten des Eichenwicklers (Tortrix viridana L.)

Vergleichende Untersuchungen an der Kronenfauna der Eichen in Latenz‐ und Gradationsgebieten des Eichenwicklers (Tortrix viridana L.)

Eine integrierte Theorie zur Abundanzdynamik tierischer Populationen

The distribution pattern of herbivory in a beech canopy

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