Deceptive Groundcover

A patch of Vernonia steetziana in flower
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The relatively good rains of the last season have produced an impression of good ground cover in most areas. However, much of this good looking cover is deceiving as it consists of ‘weeds' and there is no room for complacency. Many areas were laid bare during the last few years of low rainfall and these are going to take a long time to recover under good management. With the death of many of the perennial grasses recovery will be slow. ‘Nature's way' is to produce a ‘scab' to heal the ‘wounds'.

These healing scabs are produced in the form of hardy, unpalatable, annual grasses and ‘weeds' or forbs. Being unattractive to grazers, these pioneer plants can provide soil cover from wind, rain and heat. Under this protective cover soil nutrition can improve and more palatable grasses can be re-established. With reduced grazing pressure and informed management practice it will take many years for these areas to become productive again.

Soil

Healthy soil is a ‘living' part of our environment. As a production factory it contains millions of macro- and micro-organisms and thus requires water, oxygen and ‘food' to sustain this life. These necessities infiltrate through the soil surface, therefore a loose or ‘friable' soil surface is of prime importance. Plant roots, leaf cover and dead material (litter) are vital to this process. Plant cover also reduces water run-off and temperature, thus improving infiltration and preventing evaporation and erosion.

Bare soil surfaces become dry, hot, ‘capped' and compacted by the action of raindrops. High temperatures, lack of moisture and oxygen and hard surfaces all deter plant growth. The less plants that grow the worse the situation becomes. The only plants adapted to survival in these harsh conditions and the only ones capable of reversing the downward trend are hardy pioneers which many people consider weeds.

‘Weeds’!

The term ‘weed' is often used for ‘problem plants' which are able to multiply very successfully to the extent that they interfere with organised agriculture. Even useful plants can become ‘weeds' if they grow in, what people might consider, the wrong place. Many of the ‘pioneer' plants that grow in natural veld conditions after grass cover has been abused are ‘herbs' or ‘forbs'. Forbs are non-woody plants - other than grasses, sedges or rushes - and many damaged areas of the lowveld are covered in them at the moment.

These herbs or forbs are generally spiky or aromatic and unpalatable to ungulates. Their function, as mentioned previously, is to protect the soil rather than be eaten. They normally endure for only a couple of years until good grass cover is re-established. Being unable to compete with improved plant cover they will vanish on their own. They are a very necessary part of the rehabilitation process.

Certain woody species, such as sickle - bush (Dichrostachys cinerea), perform the same function but over a longer period of time. The ‘pod bearing' plants (e.g. - Crotalaria spp. and Indigofera spp.) are generally nitrogen fixing and fertilise the soil in addition to protecting the soil surface. They are all part of the succession process.

Ground Cover

Plants growing in a particular area are referred to as ‘ground cover' . Ground cover is measured in two ways. The part of the plant in contact with the soil is referred to as ‘basal cover' and that part above the soil as ‘aerial cover'. Basal cover cuts down water run-off and breaks the soil surface.

Aerial cover shades the soil and protects the surface from the compaction of raindrops. An area with 80 percent aerial cover would very likely have only around five percent basal cover so one must be very conservative when trying to assess ground cover.

The aerial cover will normally be drastically reduced when the leaves died off. The impression of ‘lateral cover' - i.e. viewed from the side - can be very misleading when viewed from the comfort of a vehicle seat while driving through the veld. ‘Vertical cover', which is most effective from rain and sun, can only be assessed on foot by looking straight down onto the ground and will provide a very different picture.

Although the vertical cover may be poor the lateral cover is useful in preventing wind-erosion and does provide shade when the sun is not overhead. Many animals like black rhino and bushbuck are reliant on sufficient lateral, rather than aerial, cover to provide ideal habitat. The seeds of many pioneer plants are light and dispersed by wind while others are thrown a short distance by animals walking through and bumping the springy plant stems.

One of the herb species that has been most prolific in many areas is Vernonia steetziana with its long-lasting and attractive blue flowers. The Vernonias are a large genus with approximately 1,000 species confined generally to the tropical regions of the world. In South Africa the genus is represented by about 50 species.

Certain species are large like the V.myriantha and V.amygdalina of damper areas while others are smaller than V.steetziana which grows to about 800 mm. When dry, with fluffy seed heads it gives the lateral impression of substantial cover.

Resist The Temptation To Burn

After the relatively good rains, many landowners may gain the impression that there is a lot of bulk cover and be tempted to burn the veld. The land is trying to recover after several dry years and excessive grazing pressure. If the weed cover is burned off it will set the recovery process back to square one. Resist the temptation to burn and let nature take its course.

You won't generate any grass by burning the weeds. ‘Scratching the scab' will only leave you with a permanent ‘scar'. Leave the weeds and observe the healing process. Now is not the time to build up animal numbers.

Despite the rains, grass growth was not good in most areas. Rather reduce animal numbers and take early precautions to prevent veld-fires. New legislation requires permission before burning any area of natural veld. Let nature rehabilitate the impoverished veld and give it all the assistance the land deserves.



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