Factors affecting fruit set in Aizoaceae species of the Succulent Karoo

Gesine Pufal; Carolin Mayer; Stefan Porembski; Norbert Juergens

doi:10.1016/j.baae.2007.06.001

Factors affecting fruit set in Aizoaceae species of the Succulent Karoo

Gesine Pufal
, Carolin Mayer
, Stefan Porembski
, Norbert Juergens

Publikation: Beiträge in Zeitschriften › Zeitschriftenaufsätze › Forschung › Begutachtung

6 Zitate (Scopus)

Abstract

Allgemein wird angenommen, dass intensive Weidewirtschaft in der Sukkulenten-Karoo Südafrikas negative Effekte auf die Reproduktion und Verjüngung mehrjähriger Pflanzen hat, indem domestizierte Herbivoren die Zahl von Blüten und Früchten schmälern. In der vorliegenden Studie wurde der Fruchtansatz bei sechs perennierenden Arten der Aizoaceae unter zwei unterschiedlichen Beweidungsintensitäten untersucht. Ferner sollte die eingehendere Betrachtung zweier Arten (Cheiridopsis imitans und Leipoldtia schultzei) Aufschluss darüber geben, ob neben der Beweidung auch andere Faktoren die Fruchtproduktion dieser Pflanzen beeinflussen. Zusätzlich wurde in stark und gering beweideten Gebieten die Populationsstruktur dieser beiden Arten analysiert.

Für die untersuchten Arten erwies sich die Beweidung durch Nutzvieh als einer der wesentlichen Gründe für die Verringerung der Fruchtproduktion. Extreme Witterung in einem Dürrejahr führte zu Abweichungen von diesem Muster, da durch erheblich verringerte Weidetierbestände der sonst starke Beweidungsdruck nur geringfügig war. Die detaillierten Untersuchungen zeigten allerdings, dass neben Beweidung andere biotische Faktoren noch größere Blüten- und Fruchtverluste verursachen können. Als Blüten- und Fruchtfresser erwiesen sich die Raupen des Nachtfalters Diaphone eumela (Noctuidae), sowie zwei Nagetierarten, Otomys unisulcatus und Rhabdomys pumilio. Experimente mit Pflanzen in Käfigen, die nur Nutzvieh ausschlossen, bestätigten jedoch, dass Beweidung durch Ziegen zweifellos für den kontinuierlichen Verlust von Früchten verantwortlich ist. Unzureichende Bestäubung verringerte ebenfalls den Fruchtansatz, spielte jedoch fast ausschließlich bei geringem Weidedruck eine Rolle.

Originalsprache	Englisch
Zeitschrift	Basic and Applied Ecology
Jahrgang	9
Ausgabenummer	4
Seiten (von - bis)	401-409
Seitenumfang	9
ISSN	1439-1791
DOIs	https://doi.org/10.1016/j.baae.2007.06.001
Publikationsstatus	Erschienen - 01.07.2008

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SDG 15 – Lebensraum Land

Fachgebiete und Schlagwörter

Ökosystemforschung

ASJC Scopus Sachgebiete

Ökologie, Evolution, Verhaltenswissenschaften und Systematik

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10.1016/j.baae.2007.06.001

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title = "Factors affecting fruit set in Aizoaceae species of the Succulent Karoo",

abstract = "By reducing the number of flowers and fruits, intense grazing activities of domestic livestock are considered to have negative effects on the plant recruitment of perennial plants in the Succulent Karoo, South Africa. In the present study, the fruit set of six perennial species belonging to the Aizoaceae was investigated under two different grazing intensities. Two species (Cheiridopsis imitans and Leipoldtia schultzei) were examined more closely to determine whether factors other than grazing impact fruit production of these plants. Apart from reproductive output, the population structure of these two species was explored in heavily and slightly grazed areas. For all investigated species, heavy livestock grazing was identified as a major threat to fruit production. Deviations from this pattern were recorded in a drought year, when harsh weather conditions reduced herd sizes dramatically and the usually high grazing pressure was alleviated. However, detailed analyses revealed that also other biotic factors can cause severe fruit and flower losses even exceeding that caused by grazing. Caterpillars of the noctuid moth, Diaphone eumela, and two rodent species, Otomys unisulcatus and Rhabdomys pumilio, proved to be further important herbivores of flowers and fruits. Experiments with caged plants, excluding livestock from grazing, confirmed though that livestock grazing definitely accounts for a continuous reduction of fruit production. Insufficient pollination success was another parameter reducing fruit set; however, this was almost exclusively observed under low grazing pressure.",

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author = "Gesine Pufal and Carolin Mayer and Stefan Porembski and Norbert Juergens",

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AU - Mayer, Carolin

AU - Porembski, Stefan

AU - Juergens, Norbert

PY - 2008/7/1

Y1 - 2008/7/1

N2 - By reducing the number of flowers and fruits, intense grazing activities of domestic livestock are considered to have negative effects on the plant recruitment of perennial plants in the Succulent Karoo, South Africa. In the present study, the fruit set of six perennial species belonging to the Aizoaceae was investigated under two different grazing intensities. Two species (Cheiridopsis imitans and Leipoldtia schultzei) were examined more closely to determine whether factors other than grazing impact fruit production of these plants. Apart from reproductive output, the population structure of these two species was explored in heavily and slightly grazed areas. For all investigated species, heavy livestock grazing was identified as a major threat to fruit production. Deviations from this pattern were recorded in a drought year, when harsh weather conditions reduced herd sizes dramatically and the usually high grazing pressure was alleviated. However, detailed analyses revealed that also other biotic factors can cause severe fruit and flower losses even exceeding that caused by grazing. Caterpillars of the noctuid moth, Diaphone eumela, and two rodent species, Otomys unisulcatus and Rhabdomys pumilio, proved to be further important herbivores of flowers and fruits. Experiments with caged plants, excluding livestock from grazing, confirmed though that livestock grazing definitely accounts for a continuous reduction of fruit production. Insufficient pollination success was another parameter reducing fruit set; however, this was almost exclusively observed under low grazing pressure.

AB - By reducing the number of flowers and fruits, intense grazing activities of domestic livestock are considered to have negative effects on the plant recruitment of perennial plants in the Succulent Karoo, South Africa. In the present study, the fruit set of six perennial species belonging to the Aizoaceae was investigated under two different grazing intensities. Two species (Cheiridopsis imitans and Leipoldtia schultzei) were examined more closely to determine whether factors other than grazing impact fruit production of these plants. Apart from reproductive output, the population structure of these two species was explored in heavily and slightly grazed areas. For all investigated species, heavy livestock grazing was identified as a major threat to fruit production. Deviations from this pattern were recorded in a drought year, when harsh weather conditions reduced herd sizes dramatically and the usually high grazing pressure was alleviated. However, detailed analyses revealed that also other biotic factors can cause severe fruit and flower losses even exceeding that caused by grazing. Caterpillars of the noctuid moth, Diaphone eumela, and two rodent species, Otomys unisulcatus and Rhabdomys pumilio, proved to be further important herbivores of flowers and fruits. Experiments with caged plants, excluding livestock from grazing, confirmed though that livestock grazing definitely accounts for a continuous reduction of fruit production. Insufficient pollination success was another parameter reducing fruit set; however, this was almost exclusively observed under low grazing pressure.

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KW - Cheiridopsis imitans

KW - Herbivory

KW - Lack of pollination

KW - Land use

KW - leipoldtia schultzei

KW - livestock exclusion

KW - population structure

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Factors affecting fruit set in Aizoaceae species of the Succulent Karoo

Abstract

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