Gobabeb Training and Research Internship Programme 2012
Project 1: The Recovery of Hypolithic Cyanobacteria after disturbance and attempted rehabilitation in the Central Namib Desert –Omagano Shooya
Hypolithic Cyanobacteria (HLC) are part of biological soil crusts (BSC) which are complicated communities of cyanobacteria, lichens, fungi, algae and other bacteria. These HLC communities are critical to ecosystem functioning in the gravel plains of the Namib Desert. HLC grows on the underside of transparent rocks, like quartz, where it can absorb sufficient moisture and light while still avoiding intense and fatal direct sunlight. These bacterial communities help stabilize soils against wind and water erosion, improve soil texture, and enhance plant growth through fixing nitrogen in the soils. Unfortunately, HLC is highly susceptible to surface disturbances and is suffering under the increasing amount of vehicular traffic and uranium mining in the Namib.
With the relatively new understanding of the importance of HLC, companies have been raking their tracks in order to try and rehabilitate HLC after off-road driving.Building on previous studies on the topic of impacts on HLC in 2010 and 2011, this study observed the rehabilitation rates of HLC in three treatment areas (un-raked tracks, raked tracks, control/undisturbed) and compared data to data from 2011 on the same disturbed sites. The amount of HLC in raked areas had lower cover than the undisturbed (control) sites, suggesting that raking may actually be hindering HLC re-growth. Additionally, the overall amount of HLC cover was lower in 2011 than 2012. This may have been due to lower rainfall and fog in this study than in the 2011 study. Following these results, further studies should observe how frequency and timing of disturbance and weather impact the recovery rate of HLC in the Namib’s gravel plains.
Two studies on the effects of zebra dung on soil abiotic properties, herbaceous plant growth, and insect communities:
Plants, animals, and insects in the desert ecosystems have adapted to nutrient-poor, dry soils; however, much of the ecological functioning in this region may rely on larger ungulates, like the Hartmann’s Mountain Zebras. Large ungulates, like zebras, may play critical roles, as they disperse seeds and recycle nutrients through their dung and urine. Dung and urine both provide high levels nitrogen in the forms of ammonium and nitrates and therefore provide a natural fertilizer for plants. Additionally, zebra dung provides food and shelter for insects and small animals, and resources for bacteria in the area. Unfortunately, increased mining in the Namib-Naukluft Park is limiting the zebras’ refuge and water resources, making them vulnerable to habitat loss. The loss of zebra in this area could upset the balance of nutrients, food, and shelter for other members of this ecosystem. The following two studies observed how zebra dung affect soil properties, plant growth, and plant and belowground invertebrate communities.
Project 2: The spatial extent of the effect of Hartmann’s mountain zebra dung on soil abiotic properties at Zebra pan in the Namib-Naukluft Park –Wilson Muyenga
Within the Zebra Pan of the Namib-Naukluft Park, soil samples were taken from up to 35cm away and up to 10cm deep at ten random zebra dung sites to observe the differences in soil properties (pH, electrical conductivity (EC), nitrates) in an area surrounding recent zebra droppings. Different from a similar, but more limited study in 2011, soil analyses and controlled greenhouse experiments revealed no differences in soil pH, EC, or nitrates near or far away from the zebra dung sites. The homogenous soil properties may be due to nutrient leaching or urine deposition near the dung, or, paradoxically, to a lack of leaching from the dung into the soil (very little rain had fallen in 2012 compared to 2011). This study was limited to 35cm radii surrounding the dung sites; further studies should study plant growth and soil conditions from samples further from dung sites.
Project 3: Impacts of Hartmann’s mountain zebra dung on herbaceous plant and ground dwelling invertebrate communities, central Namib –Titus Shuuya
Using one hundred paired samples of dung and no-dung sites, this study compared the above-ground biomass, species richness, abundance, and diversity of herbaceous plants. Dung sites had a higher amount of biomass than the no-dung sites but there was no difference in the number of plant species (richness) or the number of plants (abundance). One meter quadrates with fresh zebra dung placed experimentally and four pitfall traps in close proximity to the dung, were used to assess the ground invertebrate community. The study found no association between invertebrate communities and zebra dung. Future studies should use a calibrated scale for zebra dung age and observe potential correlations between the amount of zebra dung and herbaceous biomass. Additionally, the vegetative community could be assessed by analysing the seedbank and germination rates within the dung. Further, invertebrate communities may be more reliant on fresh dung and, thus, future studies should replenish zebra dung during the invertebrate community study.