**Investigating Soils, Vegetation and Land Use in a Lunette Dune-Pan Environment: The Case of Sekoma Lunette Dune-Pan Complex, Botswana**

S. Mosweu1, J.R. Atlhopheng1 and M.P. Setshogo2 *1Department of Environmental Sciences 2Department of Biological Sciences University of Botswana, Gaborone, Botswana* 

#### **1. Introduction**

The association between vegetation and environmental factors has been a subject of ecological studies over time (e.g. Monier & Amer, 2003; McDonald et al., 1996). Some of these studies have addressed facilitative and competitive interactions between woody and herbaceous plants (Maestre et al., 2003), whilst others focused on the feedbacks in the dynamics of plant communities (Schwinning et al., 2005). On the other hand, there is considerable empirical research work on pans and their associated landforms (e.g. Lancaster, 1986; Goudie & Thomas, 1986; Cooke et al., 1993). Common land forms associated with pans like lunette dunes have particularly received significant attention from researchers (e.g. Lancaster, 1978; Goudie & Thomas, 1986; Holmgren & Shaw, 1996). Most of the afore-mentioned studies have mainly focused on the morphology, sedimentology and the origin of lunette dunes and pans. In addition, they have considered the significance of lunette dunes in palaeo-environmental reconstruction (Holmgren & Shaw, 1996; Lancaster, 1989; Marker & Holmes, 1995).

Livestock production dominated by cattle rearing plays a pivotal economic role in the Kalahari area (van de Maas et al., 1994; Chanda et al., 2003; Mosweu et al., 2010). The most limiting factor in livestock production in Kalahari over the years has been the availability of surface water and fodder resources. Consequently, lunette dune-pan environments continue to play a central role as sources of both water (Figure 1) and fodder resources for livestock in the area. As a result, lunette dune-pan environments exist in the Kalahari as unique interspersed micro-ecosystems that are significantly intertwined with the livelihoods of rural communities of the area (Chanda et al., 2003; Mosweu & Areola, 2008).

Although some research work has been conducted on the lunette dunes, pans, vegetationenvironment relationships, and land use in the Kalahari environment (e.g. Chanda et al., 2003; Privette et al., 2004; Shugart et al., 2004; Wang et al., 2007; Mosweu, 2008), paucity still exists in researches that consider lunette dunes, pans and their environs as unique microecosystems of significance to rural communities inhabiting semi-arid and arid regions. This scenario prevails in spite of the fact that the state of lunette dune-pans as micro-ecosystems remains vital in the sustainability of the livelihoods of the Kalahari rural communities and

Investigating Soils, Vegetation and Land Use in

Mapping, Gaborone, Botswana).

**3. Research methods 3.1 Sample collection** 

(Goldsmith & Harrison, 1976).

a Lunette Dune-Pan Environment: The Case of Sekoma Lunette Dune-Pan Complex, Botswana 235

Fig. 2. Study site location (Author using base maps from Department of Surveys and

Stratified transect sampling was used in this study. This is a systematic sampling method in which sampling points were arranged linearly and continuously. Transects were established from the pan fringes across selected lunette dunes (Tshube, Leremela and Kebuang) to the end of the slip face slope of each dune (Figure 3). Sampling was carried out at the pan fringes, wind ward slope, dune crest and slip face slope which were referred to as sampling points 1, 2, 3, and 4 respectively (Figure 3). At the slopes, sampling was carried out at the approximate mid-point of the slopes. A similar method was used with success in other studies including salt-marshes, inter-tidal zones, study of pattern and succession on dunes, altitudinal gradients, from dry to wet heath and across gradients of trampling intensity

Three quadrats of 20 m2 separated by 10 m were located at sampling points marked 1, 2, 3 and 4 (Figure 3) along the transects. The quadrats were identified as indicated in Figure 3 (Tshube 1-12; Leremela 13-24; Kebuang 25-36; 'S' denotes site). Vegetation and soil sampling was conducted in each of the quadrats. Soil samples were collected in the center of each quadrat using an auger that had a sample collection chamber length of 20 cm and a volume of ca. 23.75 mL. Therefore, about 23.75 mL per sample volume were collected. It was observed in the preliminary study that a soil profile established in the dunes did not show soil horizons. Therefore, soil samples were collected at predetermined sampling depths (SDs) of 0-20 cm, 40-60 cm, 80-100 cm, 130-150 cm and 180-200 cm. Methods used in this

study to investigate vegetation and soil are summarized in Tables 1 and 2.

other communities residing in semi-arid and arid regions elsewhere. It is on this basis that the main aim of this chapter was to examine the interrelationships among the soil, vegetation, topography and land use in a lunette dune-pan environment with a view to elucidate their interactions and the consequent environmental changes thereof. Thus, the specific objectives of this study were to investigate the following in a lunette dune-pan environment:


Fig. 1. Hand-dug well located in Sekoma pan.

### **2. The study site**

A lunette dune-pan complex located in the Sekoma village (Figure 2) in the Kalahari region of Botswana was chosen as a case study area. The state of the environment, current land use practices and geographical position of the Sekoma lunette dune-pan system present an ideal environment for the investigation of environmental changes and ecosystem dynamics particularly in lunette dune-pan micro-ecosystems. The geographical location of the study site along the Kalahari Transect (KT) 'megatransect' which has been established by the International Geosphere-Biosphere Programme (IGBP) for the study of both regional and universal environmental changes (e.g. Shugart et al., 2004; Wang et al., 2007) positions this study within an international context of studies focusing on environmental changes.

The lithology of the area is characterized by the dolomite Precambrian aquifer system (Geological Survey Department, 1995). The general structure of vegetation in the area is shrub savanna and the vegetation is classified as southern Kalahari bush savanna (Department of Surveys and Mapping, 2001). The mean annual rainfall in the area is about 400 mm (Bhalotra, 1985) and the rainfall season is characterized by erratic rainfall patterns. The lunette dune-pan complex is situated between the former (Sekoma West) and current (Sekoma) locations of the village (Figure 2).

Investigating Soils, Vegetation and Land Use in a Lunette Dune-Pan Environment: The Case of Sekoma Lunette Dune-Pan Complex, Botswana 235

Fig. 2. Study site location (Author using base maps from Department of Surveys and Mapping, Gaborone, Botswana).
