TY - JOUR

T1 - Factors affecting fruit set in Aizoaceae species of the Succulent Karoo

AU - Pufal, Gesine

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.

KW - Ecosystems Research

KW - Cheiridopsis imitans

KW - Herbivory

KW - Lack of pollination

KW - Land use

KW - leipoldtia schultzei

KW - livestock exclusion

KW - population structure

UR - http://www.scopus.com/inward/record.url?scp=44449141390&partnerID=8YFLogxK

U2 - 10.1016/j.baae.2007.06.001

DO - 10.1016/j.baae.2007.06.001

M3 - Journal articles

VL - 9

SP - 401

EP - 409

JO - Basic and Applied Ecology

JF - Basic and Applied Ecology

SN - 1439-1791

IS - 4

ER -