Abstract
ABSTRACTThis study examined the species richness, diversity, biomass of grasses and herbaceous plants and seed germination in plots with contrasting disturbance regimes established in a dambo garden, in Chiota, Zimbabwe. The disturbance regimes were burning, clipping, clearing and conventional tillage and were applied annually to each subplot from 2010 to 2012. It was hypothesised that burning increases biomass, species richness and diversity of plants while reducing seed bank diversity. Clearing, clipping and conventionally tilling negatively affect biomass, species richness and diversity. The Shannon–Wiener Index was used to estimate species diversity and the average values obtained ranged 0.53, 0.85, 0.91, 1.3 and 1.70, for the undisturbed, burnt, conventionally tilled, clipped and cleared plots, respectively. The biomass in the experiment ranged from 0.92t ha–1 for the ploughed plot to 20.92t ha–1 for the undisturbed plot. The species richness for the plants decreased in the following order; clearing>conventional tillage>burning>clipping>undisturbed. These results show that disturbance regimes increased species richness but however decreased plant biomass. It is apparent that the management practice that ensures maximum biomass of grasses and herbs in dambos is maintaining them in their natural state. However, clearing seemed to improve species diversity compared to maintaining the dambo in its natural state.EDITED BY Alexander van Oudenhoven and Patricia Balvanera
Highlights
‘Dambos’ are seasonally waterlogged, predominantly grass-covered, low-lying areas that border headwater drainage lines (Akayombokwa Mukanda 1998)
The change in vegetation composition was evidenced by the differences in species found in the different treatments when compared to the undisturbed control
There was no significant difference in the species diversity of the plants between the different disturbance regimes
Summary
‘Dambos’ are seasonally waterlogged, predominantly grass-covered, low-lying areas that border headwater drainage lines (Akayombokwa Mukanda 1998). Conservation practices like reduced tillage and vegetation management that removes undesirable species can help increase dominance by wetland species and thereby maintaining plant diversity and biomass (USDA 2015). Biodiversity is the variety of plants, animals and other species in different ecosystems and helps in maintaining the biological functions of the environment (Naeem et al 1999). Dambos provide grazing for livestock and at times farmers burn to control pests and remove unpalatable grass species. Burning is a very common method used in Africa for clearing fields, because it is an easy and fast way of clearing large areas of land It improves soil fertility and controls pests (Ojeniyi & Adejobi 2002; Waters 2007). In some instances, burning negatively affects species diversity and richness of grasses by eliminating some species of plants that are not fire tolerant and promoting the dominance of fire-tolerant species (Whitlow 1985)
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