During field trips around Ongava, we see some termite mounds surrounded by areas of bare ground, while other mounds have shrubs, trees and grasses growing nearby. Why the difference, and could the soil around the bare mounds contain a substance that inhibits plant growth?
Between November and December 2021, we ran some experiments to test this hypothesis. We sampled 9 mounds from different areas of Ongava, taking soil from 7 locations at each mound: 1 from the center of the mound, 2 samples at its bare base, 2 where grass was growing closest to the mound, and 2 control samples 10 m away from the mound. The 2 paired samples were on opposite sides of each mound. After sieving the soil samples to remove any seeds already present, we split each sample equally among 4 pots and planted 20 seeds of Enneapogon cenchroides (a common, vigorous grass growing on Ongava) in each pot. A total of 252 pots were planted this way and kept in a greenhouse kindly constructed by our technician Simeon Naholo, to preserve moisture in the air and prevent the soil from drying out and compacting. The pots were frequently watered.
We predicted that there will be little or no germination nor growth in the pots containing soil from the center and base of the mounds, but we expected high rates of germination in the pots containing soil sampled from the grassy and control areas.
We now need to give time for germination to occur and be sure that no more germination can take place before analyzing the results. Perhaps the sampling, choice of grass seeds and growing conditions could be improved, and so this experiment might be seen as a trial-error to guide us in designing better experiments.
Author: Elizabeth Nelao Shangano