The effect of farmland abandonment on dung beetle diversity and function in the Nama-Karoo, Northern Cape, South Africa.

Steed, Adam John (2020-03)

Thesis (MScConsEcol)--Stellenbosch University, 2020.

Thesis

ENGLISH ABSTRACT: Agricultural land abandonment has cascading effects on native biota. When badly managed, pressures on native biota can increase leading to reduced ecosystem function. Conversely, increased ecosystem function can result after decreasing anthropogenic pressures. This phenomenon has received little attention in the often-overexploited arid rangeland areas of the world. Here, I used a keystone taxon, dung beetles, as a bioindicator of the effect of farmland abandonment in the Nama-Karoo of South Africa. I documented changes in dung beetle abundance, richness, community assemblage composition, and their functional diversity as a result of ceasing large-scale sheep farming and evaluated differences in these factors across different biotopes. Dung beetles were sampled using baited pitfall traps on farms that were abandoned a long time ago (>10 years), recently (ca. 1 year ago) and on active farms, as well as from three dominant biotopes (hills, flatlands and ephemeral riparian zones) using three dung types (omnivore = pig; ruminant non-pelleted = cow; and ruminant pelleted = sheep). In general, riparian systems and flatlands had greater dung beetle richness, abundance, biomass and functional richness in comparison with hills, and each had a unique assemblage composition. Therefore, the flatland and ephemeral riparian areas that are generally most severely impacted by anthropogenic actions (since rocky slopes inhibit grazing activities) are particularly important for conserving dung beetle ecosystem functions and services. Dung beetle richness, abundance, and functional richness was higher in abandoned farmland areas due to greater dependence on omnivore and cow dung than on sheep dung, and reduced pressures on remaining native vertebrates. However, large-bodied dung beetles became rare after farmland abandonment. I therefore strongly encourage the reintroduction of native meso-herbivores to enhance dung resources in these abandoned areas, which will support higher dung beetle diversity, greater ecosystem function and increased ecosystem services.

AFRIKAANSE OPSOMMING: Die staking van veeboerdery kan 'n effek hê op inheemse biota. Indien dit sleg bestuur kan die druk op inheemse biota toeneem tot 'n verminderde ekosisteemfunksie. Tog kan 'n verhoogde ekosisteemfunksie ontstaan na so 'n afname in antropogeniese druk. Hierdie verskynsel het min aandag geniet in die dikwels oorbenutte droë gebiede van die wêreld. Hier het ek 'n sleutelsteen takson, miskruiers, as bioindikator gebruik om die effek van landbougrondverlating in die Nama-Karoo van Suid-Afrika te bestudeer. Ek het veranderinge in die volopheid van miskruiers, spesies-rykheid, samestelling van gemeenskappe asook hul funksionele diversiteit gedokumenteer as gevolg van die staking van grootskaalse skaapboerdery en die verskille tussen hierdie faktore oor verskillende biotope geëvalueer. Ek het miskruiers gevang deur gebruik te gebruik van lokvalle op plase wat al 'n geruime tyd gelede (> 10 jaar) ontruim is, onlangs ontruim is (ongeveer 1 jaar gelede) of steeds aktief is, en dan ook in drie dominante biotope (klipkoppies/heuwels, platvlaktes en efemerale oewersones) met behulp van drie soorte mis (omnivore = vark; herkouer = koei; en nie-herkouer = skape). Oor die algemeen het oewerstelsels en platvlaktes groter miskruier rykheid, volopheid, biomassa en funksionele rykdom in vergelyking met klipperige heuwels gehad, elkeen met 'n unieke spesies samestelling. Daarom is die plat vlaktes en efemerale oewergebiede, wat meestal die ergste geraak word deur antropogeniese optrede (aangesien klipperige hellings weidingsaktiwiteite belemmer) veral belangrik vir die behoud van ekosisteemfunksies en dienste van miskruiers. Interessant genoeg was die rykheid, oorvloed en funksionele rykheid van miskewers hoër in verlate landbougebiede as gevolg van 'n groter afhanklikheid van herkouer mis as van nie-herkouer (skaap) mis, asook druk op die inheemse soogdiere wat verminder het. Die grootste miskruiers het egter skaars geword ná die verlating van landbougrond. Ek moedig die herinvoering van inheemse meso-herbivore sterk aan om mis kwaliteit in hierdie verlate gebiede te bevorder, wat 'n groter diversiteit van miskewers, groter ekosisteemfunksie en verhoogde ekosisteemdienste sal ondersteun.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/108412
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