April field notes
The Lowveld has been blessed with welcome rains in most of the central regions over the past two months. Although the rainfall coverage seemed to encompass most of our operational areas, the rains were sporadic and varied with some areas receiving substantially more than others. The picture of the landscape from above is very different to that of a few months ago. After the rains, many of the bushveld trees have emerged from their drab winter guise, putting on a magnificent show. As one looks out to the horizon and beyond we are greeted with a kaleidoscope of colours that vary from hues of brilliant greens to the first shades of russet and orange at the onset of the coming autumn months.
The bush is slowly starting to recover after a prolonged period of drought and intense heat. At first glance the bush looks beautiful and lush, but it is actually dominated by mostly pioneer plant species.
Pioneer species play an extremely important role in veld recovery. These are the first plant and grass species that inhabit disturbed areas caused by recent drought or overgrazing. This phase of plant succession is nature’s way of protecting disturbed areas and allowing them to eventually recover. Plant succession is a natural process where disturbed areas are colonised by pioneer species, which have a relatively short lifespan (also known as annuals). They produce a large amount of seed, which establishes quickly after the first rains and improves growing conditions for the next stage. They also create better soil conditions for the more long-lived species to settle. These species, recognised by their narrow leaves, are normally unpalatable to grazers, which increases their chances of survival. Veld condition improves when the final stage of succession is reached with more palatable climax species. These long-living plants are more palatable and contain more nutrients, and after several seasons will replace the weed-like pioneer species.
With these grasses becoming more attractive to grazers, animal droppings and hoof action further improve water infiltration, nutrition, and other conditions for growth. Where grass plants survive through successive seasons in vegetative form they are termed ‘perennial’.
With improved soil and moisture conditions, grasses may survive the dry season and annual species will appear. These will compete successfully for light and shade-out pioneer species, changing the species composition of the grassland.
April is a favourite time of the year in the bush. It’s a complete change of seasons with moderate, balmy daytime temperatures and crisp evenings as autumn creeps into the Lowveld.
The constant sound of rutting impala as they challenge each other for dominance is a sure indicator that autumn has arrived. The impala rutting (mating season) starts with the moon waxing around its first quarter in April and will continue through to May.
The rut takes place at this time of the year so that the ewes give synchronous birth to their lambs some weeks after the onset of the rainy season. Synchronised birthing determines that with all the lambs being born together, predators may have a field day, but enough lambs survive to maintain a viable population of this key food-chain antelope. The first rains usually fall in October in the Lowveld, prompting vegetation growth to provide cover for the newborn lambs in addition to providing the nutrients their mothers need for lactation. The impala gestation period varies from 194 to 200 days and the arrival of the newborn lambs is determined by the date of mating. We normally see the first flush of newborn lambs appearing in the park within the first week of November or thereabouts.