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Jonkershoek summary essay
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This is on the afforestation that took place in Jonkershoek to see what the affects were on stream flow.
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Geography and Environmental studies 358Summary
Jonkershoek and afforestation in South Africa
Afforestation in South Africa took place due to the fact that there are not a large number of
indigenous forests in South Africa. During the period of colonisation, the indigenous forests were
overexploited and used for timber alongside the fact that colonisers wanted to tame the landscape of
South Africa. Therefore, afforestation programmes were implemented in order to compensate for the
detrimental affects that were taking place. There was a great amount of afforestation in the 1930s.
This was due to the occurrence of the great depression and the afforestation was implemented in order
to provide employment opportunities for a large part of the population that was unemployed. However
the farmers in the surrounding catchments of the afforestation programmes were complaining that the
increase in forests was resulting in the decrease of stream flow in the catchments. Therefore the
Jonkershoek Forestry Research Committee was put in place to determine if this was the case and to
look at the affects. This was a 40 year experiment that used multiple catchments to attain the affects.
The catchments were biesievlei, tierskloof, bosboukloof, lambragtbos and langriver which was used
as the control in this experiment in which the natural vegetation of the fynbos biome remained. They
used rain gauages with niper shields to determine the input into the system through rainfall and they
used the niper shields that were at the same gradient as the slope to account for any water that could
have been lost due to the wind presence. In order to measure the output of the stream flow, the use of
v-notch weirs with a rectangular section on top was used to accurately measure the discharge and
behind this had stilling bonds that reduced the flow velocity and therefore had an accumulation of
sediment which had to be removed. It should be noted that every 8 years a different catchment was
afforested in order to see if the age of the catchment affected the stream flow. IN this it was seen that
the peak stream flow reduction was at 15 years but a reduction in the stream flow could be seen after
five years. There are negatives to having afforestation of pinus specifies of conifers that are not
indigenous. This would be due to the fact that they overtake the natural vegetation and this relates to
the endangerment of various natural specifics and organisms due to the fact that their biomes are
being destroyed. Alongside this is the fact that the conifers have large amount of water consumption
and therefore result in reduced stream flow and there is less water soil infiltration due to the presence
of interception. A conifer forest has a larger biomass than a fynbos biome and therefore has a larger
intensity of burning heat when a fire takes place. This results in the organic matter in the soil being
burnt out as well as the burning of chemicals and therefore the soil particles become hydrophobic and
do not allow for the absorption of water and thus there is a greater amount of erosion taking place.
Although there are many negatives of having a conifer forest, the benefits of it is that it generates
income for the country through the sales of timber within the country and internationally, this also
allows for job creation to take place. It allows for recreational activities and is aesthetic for many of
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