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Macrodetritivores, the reverse mechanism from lawn to bunch grasses

Dijk, K.M. van (2014) Macrodetritivores, the reverse mechanism from lawn to bunch grasses. Master's Thesis / Essay, Biology.

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In grazing ecosystems, tall and short vegetation patches can shift spatially and temporally, which causes heterogeneity and a mosaic pattern of structurally discrete vegetation patches. The mechanisms that drive these vegetation patterns in grazing ecosystems are still poorly understood. A recent explanation suggests that the interplay between soil macrofauna and large herbivores and their opposing influence on the abiotic soil environment could provide the conditions that are essential to maintain heterogeneity. Soil macrodetritivore bioturbation, such as digging and tunnelling, loosen up the soil thereby alleviating plant stress. Dung is highly attractive to soil bioturbating macrodetritivores; because of the herbivore avoidance, its moisture, its high abundance of microbial bacteria and the freshly digested material. The effects on soil biophysical conditions by dung associated macrodetritivores have not been given much attention yet in the literature on vegetation mosaics. This study looked at the change in vegetation structure and at the physical changes of the soil that occurred around and underneath a dung pile in the African tropical savannas. We were especially interested in the changes induced by soil organisms in reversing the effects of large grazers. To see the effect of dung on the soil and vegetation, we set up an experiment and placed dung piles at different sites that followed a rainfall gradient. We had three different treatments; the control without dung, one with dung and where we prevented the dung beetles from tunnelling underneath the dung pile and one with dung and with the tunnelling dung beetles. Although there was no difference between the two dung treatments , the results showed an uniform significant effect, for both changes in soil structure and increased tall vegetation biomass, induced by the dung treatments across the rainfall gradient. Consequently, our study provided strong evidence that the alternation between soil fauna bioturbation and grazer biocompaction dominated states may be a key component in the heterogeneity of savannas. The understanding of this mechanism and the heterogeneity could be of conservational importance, with the current decline in nature areas through the demand for agricultural land.

Item Type: Thesis (Master's Thesis / Essay)
Degree programme: Biology
Thesis type: Master's Thesis / Essay
Language: English
Date Deposited: 15 Feb 2018 08:02
Last Modified: 15 Feb 2018 08:02

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