**3. Research methods**

### **3.1 Sample collection**

234 International Perspectives on Global Environmental Change

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

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

this study were to investigate the following in a lunette dune-pan environment:

The correlations amongst soil, vegetation and land use characteristics.

Soil physical and chemical characteristics;

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

(Sekoma) locations of the village (Figure 2).

**2. The study site** 

 Woody vegetation properties; Land use attributes; 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 (Goldsmith & Harrison, 1976).

> 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.

Investigating Soils, Vegetation and Land Use in

**3.2 Mini-social survey** 

the respondents.

at = 0.01 and 0.05.

**4. Results** 

a Lunette Dune-Pan Environment: The Case of Sekoma Lunette Dune-Pan Complex, Botswana 237

A non-probability sampling procedure known as purposive sampling (Rea & Parker, 2005) was employed in a mini-social survey to gather data on the perceptions of the communities about the spatial and temporal environmental changes that they had witnessed in the lunette-dune pan environment over the years. The method facilitated the use of professional assessment, instead of randomness, in choosing the respondents (Rea & Parker, 2005). The survey was therefore, restricted only to key informants who were considered to be endowed with indigenous knowledge within the Sekoma community. Consequently, two focused group discussions, one constituted by the chief and village elders and the other by the Village Development Committee (VDC) members were conducted in the village. Openended questions were posed to the groups to facilitate freedom of expression. In the questionnaire, the most predictable answers had been pre-stated for data capturing convenience, but were not read out to respondents to minimize the researcher's influence on the respondent's view. Recording of the responses was conducted during the interview process. In addition, notes were made on the relevant additional information provided by

To explore the distribution pattern of selected soil resources in the lunette dune-pan environment, correlation analysis (Table 3) was used to establish the relationships between soil variables at different sampling depths (SD) and the distance from the pan fringes. It was observed that only sodium indicated a significant negative correlation (*r =0.991, P =0.009*) at SD 0–20 cm in the Tshube lunette dune at = 0.01. Aluminium and organic carbon also exhibited negative correlations (*r* = -*0.980, P = 0.020* and *r = -0.958, P = 0.042* respectively) with distance at = 0.05. At SD 40-60 cm, sodium (*r = -0.958, P = 0.042*) and EC (*r = - 0.985, P = 0.015*) showed negative significant relationships with distance at = 0.05. It was observed that at SD 80-100 cm all soil variables indicated negative relationships with distance except sand fraction, but the relationships were not significant at both = 0.01 and 0.05. ECEC was the only soil variable that showed significant and negative relation with distance (*r = -0.998, P = 0.002*) at SD 130-150 cm and = 0.01. Furthermore, all other soil variables indicated negative relationships with distance except sand fraction, phosphorus and pH. Magnesium (*r = -1, P = 0.011*), manganese (*r = -0.999, P = 0.033*) and phosphorus (*r = 0.999, P = 0.029*) were the only soil variables that exhibited significant relationships with distance at = 0.05

In Leremela lunette dune, none of the selected soil variables showed a significant relationship with distance from the pan fringes (SP1) to the slip face slope (SP 4) at SD 0-20 cm and = 0.01 and 0.05 (Table 3). However, all variables displayed negative relationships with distance except sand fraction, aluminium and manganese. Magnesium (*r = 0.984, P = 0.016*) was the only soil variable that indicated positive significant relationship with distance at = 0.05 in relation to the SD 40-60 cm. With the exception of sand fraction, manganese and phosphorus, all other soil variables were negatively related to distance at SD 40-60 cm. From SD 60-200 cm, soil variables and distance were not significantly related

**4.1 Pedo-geomorphological characteristics of the lunette dunes** 

in relation to SD 180-200 cm (Table 3) in the Tshube lunette dune.

Fig. 3. Detailed layout of quadrats for sampling.


Table 1. Methods of vegetation study.


Table 2. Summary of methods of soil study.

#### **3.2 Mini-social survey**

236 International Perspectives on Global Environmental Change

Fig. 3. Detailed layout of quadrats for sampling.

Table 1. Methods of vegetation study.

*Parameter Method of*

Soil Organic Carbon Walkley-Black

Table 2. Summary of methods of soil study.

Available Phosphorus

Electrical conductivity&

pH

Particle size (sand, silt-clay)

Effective Cation Exchange Capacity (ECEC) and Exchangeable cations (Ca, Mg, Na, K), Al, Fe &Mn

*Parameter Method of Analysis References*

Species density Simple counts Krebs (1989)

particular quadrat

Species composition list of plant species within a

*Analysis* 

1:2 (soil:water)

wet oxidation

(BaCl2)

Barium Chloride

ratio

Species Cover Crown-Diameter method Muller-Dombois &Ellenberg,

Species distribution Spatial range of species Bonham(1989);Krebs (1989)

Olsen's UV- Visible

1974; Krebs (1989)

*Analytical Instrument References* 

Various apparatus Van Reeuwijk

Spectrophotometer

Sieve Retsch shaker and sieve Buurmanet al.

InoLabcond 730 WTW series electrical conductivity meter & HANNA pH 210 pH meter

Atomic Absorption Spectrophotometer (AAS)

Bonham(1989);Krebs (1989)

ISRIC, 1993

Sonnevelt & van den Ende (1971); Janzen (1993) Soon & Warren (1993).

(1996)

(1993)

Hendershot & Duquette (1986)

A non-probability sampling procedure known as purposive sampling (Rea & Parker, 2005) was employed in a mini-social survey to gather data on the perceptions of the communities about the spatial and temporal environmental changes that they had witnessed in the lunette-dune pan environment over the years. The method facilitated the use of professional assessment, instead of randomness, in choosing the respondents (Rea & Parker, 2005). The survey was therefore, restricted only to key informants who were considered to be endowed with indigenous knowledge within the Sekoma community. Consequently, two focused group discussions, one constituted by the chief and village elders and the other by the Village Development Committee (VDC) members were conducted in the village. Openended questions were posed to the groups to facilitate freedom of expression. In the questionnaire, the most predictable answers had been pre-stated for data capturing convenience, but were not read out to respondents to minimize the researcher's influence on the respondent's view. Recording of the responses was conducted during the interview process. In addition, notes were made on the relevant additional information provided by the respondents.
