Factors Affecting the Impact of Off-Road Driving on Soils in an Area in the Kruger National Park, South Africa

Abstract

Studies on the effects of off-road driving on soils were conducted in the Makuleke Contractual Park of the Kruger National Park. The studies were conducted on three different soils with different textures and soil compactibilities. Traffic pressure was applied with a game drive vehicle loaded with 11 sand bags, each weighing 70 kg. This gave a total vehicle mass of 3,795 kg, simulating a vehicle fully laden with tourists. The study included: (i) comparing of the effects of four different tyre pressures; (ii) comparing the effects of 1–3 vehicle passes over the same tyre tracks; (iii) comparison of traffic effects under dry and wet soil moisture conditions, on soil compaction, respectively. After each pass penetration resistances were measured (a) on the tyre tracks, (b) between the tyre tracks and (c) at different distances outside the tyre tracks. As expected, vehicular traffic caused soil compaction below the wheel tracks. Lower tyre pressures caused less compaction than higher tyre pressures. Fewer vehicle passes also caused less compaction than more passes on the same tracks, but most compaction occurred during the first pass. Thus, driving on the same tracks more than once is less damaging than driving once on different tracks. Controlled traffic should be considered when developing management strategies for off-road driving in wildlife protected areas.

Quantifying the Impact of Off-Road Driving on Root-Area Distribution in Soils

“…All soils in this study have low organic matter contents (Table 5), which would increase their vulnerability to disaggregation and compaction (Nortjé et al, 2012). Relatively high exchangeable sodium contents or lopsided Mg:Ca ratios would also increase the vulnerability of soils to disaggregation (Bloem & Laker, 1994), but these are not problems in the soils of the present study (Table 5).…”

“…Soil crusting and sub-soil compaction was much more severe at site 2, than at sites 1 and 3 (Nortjé et al, 2012), and these impact differences are also reflected in the root density distributions (Figs 6,8 and 10). A shallower root system will make plants more vulnerable to drought, because utilization of water stored in the subsoil is very important to plants.…”

“…The Oakleaf soils are classified as Cambisols according to (Nortjé et al, 2012). There is a clay increase from the topsoil to the weakly structured subsoil.…”

“…The soil of Site 2 with alluvial stratifications is on the lowest terrace next to the river, presently being affected by sediment deposition. There were important differences between the three soils regarding their chemical and physical characteristics (Nortjé et al, 2012). Particle size distribution (soil texture) was determined with a combination of sieve and pipette methods (AgriLASA, 1990;Jackson, 1958).…”

“…The term 'Big Five' comes from hunting traditions and refers to five of Africa's greatest wild animals: lion (Panthera leo), leopard (Panthera pardus), elephant (Loxodonta africana), buffalo (Syncerus caffer ) and the two species of African rhinoceros, the black (Diceros bicornis) and the white rhinoceros (Ceratotherium simum). But such activities are often implemented without knowledge regarding the impacts of the activities on the environment or the soils (Nortjé et al, 2012;Nortjé, 2014). Certain principles and guidelines were set for practising ORD in the concession areas, but some of these guidelines and principles have not been tested.…”