**3. Results and discussion**

The wetland in Butha-Buthe is a palustrine wetland [13] and it is situated in the Mountain AEZ. It is located at an altitude/elevation of between 3181 and 3202 m above sea level (asl) and at points Latitude 28° 53.821/Longitude 28° 47.993 E. The site falls within the Afroalpine Grassland zone characterized by grasses-*Festuca caprina, Merxmuellera disticha* and *Pentaschistis oreodoxa;* shrubs and woody plants—*Chrysocoma ciliate, Erica dominans* and *Euryops evansii;* and other flowering plants—*Kniphofia caulescens, Helichrysum trilineatum, Dierama robustum, Zaluzianskaya ovate* and *Dianthus basuticus var. grandiflorus* [13]. Ha Matela: Ha Matela wetland is a Riverine wetland situated in the Foothills AEZ at an elevation of 1820 m above sea level, at points; Latitude: −29°38.3333/Longitude: 27°76.6667. It is characterized as the Afromontane Grassland zone. Dominant grasses includes: *Themeda triandra, Festuca caprina, Merxmuellera macowanii* and *Eragrostis curvula;* trees and shrubs: *Salix mucronata, Rhus erosa, Rhus pyroides, Leucosidea sericea, Myrsine Africana, Rhoicissus tridentate, Buddleja loricata* and *Chrysocoma ciliate* and flowering plants: *Gladiolus (several species), Kniphofia (several species), Helichrysum (many species), Agapanthus campanulatus subsp. Patens, Dierama robustum, Euphorbia clavarioides* and *Aloe polyphyll*. The geology of Lesotho is called formation [37] with sedimentary and volcanic clastics. Wetlands in these two agro-ecological zones: the Mountains and Lowlands (**Table 1**) were characterized as low, medium or high impacted wetlands based on local (i) land-use characteristics and (ii) intensity of anthropogenic pressures such as mining, smelting and discharge of industrial pollutant into the wetlands [38]. According to [38], the low impacted wetlands has little (i.e. <5%) or no agricultural activity within 150 m of the wetland boundary. Secondly, wetlands that were classified as highly impacted had agricultural activities; within 10 m of wetland boundary (i.e. < 33% of the wetland area is impacted). The medium impacted wetlands had agricultural activities between 5 and 32% of the wetland boundary. Wetlands in the Lowlands AEZ (i.e. Ha-Matela) were classified as being highly impacted, while that in the Mountains (i.e. Butha Buthe) had little impacts after [38]. About 2000 m transects were chosen and divided into upper (US), middle (MS) and toe slope (TS). Profile pits (1.20 m) were dug

16 Wetlands Management - Assessing Risk and Sustainable Solutions

**Figure 2.** The location of Lesotho within South Africa and its four agro-ecological zones.

Generally, most of the wetlands across all agro-ecological zones of Lesotho are either used for livestock watering, grazing and agriculture and drinking water. In a related study on comparative assessments of wetlands in West and Southern Africa, it was found that most of the rural population used the wetlands largely for grazing and watering (**Figure 3**). It is evident from this result that approximately, 21% respectively of the population considered wetlands being important for irrigation and livestock grazing and watering. Similar observations were made by researchers from Southern Africa [45, 46], Taznania [47] and Kenya [45]. These authors found that wetlands constituted an important area of the livelihoods of the rural people. Hence, one of the major constraints to the sustainable use of wetlands in Lesotho and Africa in general is the lack of information on the diverse benefits that can be obtained from wetlands if properly managed. Hence, this information is needed by the government planners, natural resource managers and local communities.

A close observation of the soil physico-chemical properties of these wetlands is shown in **Table 2**. Results showed that the particle size distribution (i.e. texture) of the wetland soils at Butha Buthe was dominated by sand size texture compared to that at Ha-Matela. At the latter site, the particle size distribution had almost equal proportions of sand, silt and clay sized particles (**Table 2**). Both wetland soils generally had acidic soil pH (i.e. 4.69–5.44),


**Table 2.** Physical and chemical properties of wetlands in Butha Buthe and Ha-Matela, Lesotho. low available P ranging between 1.40 and 3.29 mg kg−<sup>1</sup>

contents observed in the Ha-Matela soils (i.e. 0.28 cmol kg−<sup>1</sup>

had higher bulk density (BD) (i.e. 1.24–1.55 g cm3

**Figure 3.** Utilization of wetlands in the Lowlands AEZ of Lesotho.

**Figure 4.** Bulk density, Butha Buthe (BB) and Ha-Matela (HM).

4.54 mg kg−<sup>1</sup>

1.32–1.38 g cm3

able Ca (10.44–17.51 cmol kg−<sup>1</sup>

(Butha Buthe) and between 2.94 and

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19

). Wetland soils in Butha Buthe

) compared to Ha-Matela wetlands (i.e.

(Ha-Matela). Some researchers had associated phosphorus mineralization in

Isotopic Signatures (δ<sup>13</sup>C and δ15N) and Characteristics of Two Wetland Soils in Lesotho…

). The higher BD in the former compared to the latter might be attributed to

) was noted in Butha Buthe wetlands as opposed to very low

wetland soils was associated negatively with acidic soil pH and coarser soil texture [49–51]. The soil organic matter across both wetland types was relatively high. Higher exchange-

higher sand contents (**Figure 4**). The ratio of silt and clay—called silt:clay ratio—is an index of soil age and the ease of erodibility [52]. Lower ratio of between 0.43 and 1.99 (Ha-Matela) compared to 1.10 and 9.89 (Butha Buthe) is an indication that wetland soils in the former site are older and would be easily eroded compared to the latter (**Figure 5**). This was in agreement with the findings of some researchers that lower silt/clay ratio is an indication of high degree of erosion [52, 53]. Higher SOC contents were observed in the Butha Buthe wetlands

**)**

1 1 1 2 2 2 1 1 1 2 2 2 low available P ranging between 1.40 and 3.29 mg kg−<sup>1</sup> (Butha Buthe) and between 2.94 and 4.54 mg kg−<sup>1</sup> (Ha-Matela). Some researchers had associated phosphorus mineralization in wetland soils was associated negatively with acidic soil pH and coarser soil texture [49–51]. The soil organic matter across both wetland types was relatively high. Higher exchangeable Ca (10.44–17.51 cmol kg−<sup>1</sup> ) was noted in Butha Buthe wetlands as opposed to very low contents observed in the Ha-Matela soils (i.e. 0.28 cmol kg−<sup>1</sup> ). Wetland soils in Butha Buthe had higher bulk density (BD) (i.e. 1.24–1.55 g cm3 ) compared to Ha-Matela wetlands (i.e. 1.32–1.38 g cm3 ). The higher BD in the former compared to the latter might be attributed to higher sand contents (**Figure 4**). The ratio of silt and clay—called silt:clay ratio—is an index of soil age and the ease of erodibility [52]. Lower ratio of between 0.43 and 1.99 (Ha-Matela) compared to 1.10 and 9.89 (Butha Buthe) is an indication that wetland soils in the former site are older and would be easily eroded compared to the latter (**Figure 5**). This was in agreement with the findings of some researchers that lower silt/clay ratio is an indication of high degree of erosion [52, 53]. Higher SOC contents were observed in the Butha Buthe wetlands

**Figure 4.** Bulk density, Butha Buthe (BB) and Ha-Matela (HM).

**Transects**

**Position**

**Sand (%)** Butha Buthe (Mountains AEZ)

1 1 1 2 2 2 1 1 1 2 2 2 **Table 2.**

Physical and chemical properties of wetlands in Butha Buthe and Ha-Matela, Lesotho.

TS

44.97

29.30

26.56

5.25

4.64

3.13 US, upper slope; MS, mid-slope; TS, toe slope; AVP, available P; SOM, soil organic matter; CEC, cation exchange capacity; pHw, pH in water.

3.90

1.06

0.38

0.25

0.17

MS

39.23

33.91

27.08

5.06

4.56

2.56

4.32

1.03

0.41

0.53

0.17

US

38.37

36.97

25.33

5.69

4.72

3.30

2.94

1.28

0.37

1.15

0.17

TS

34.12

36.81

30.58

5.12

4.37

2.83

3.35

0.38

0.47

0.10

0.17

MS

40.78

23.28

36.00

5.02

4.39

3.21

3.74

0.28

0.34

0.09

0.17

US

24.66

33.33

42.83

5.42

4.46

4.11

4.54

0.63

0.49

0.09

0.18

TS

70.84 Ha-Matela (Lowlands AEZ)

7.40

21.72

4.95

4.49

3.04

7.74

17.06

0.05

4.69

4.92

MS

78.21

5.08

16.71

4.69

4.31

2.42

8.00

11.28

0.04

2.35

5.97

18 Wetlands Management - Assessing Risk and Sustainable Solutions

US

66.65

5.42

27.93

5.00

4.47

3.29

8.38

10.44

0.04

4.57

4.82

TS

62.95

7.32

29.53

5.33

4.66

2.23

4.58

15.31

0.05

2.89

0.05

MS

63.99

10.17

25.81

5.26

4.60

2.71

5.25

15.00

1.49

5.38

2.07

US

67.16

12.04

20.81

5.44

4.69

1.40

4.49

17.51

0.05

3.17

5.23

**Clay (%)**

**Silt (%) pHw**

**pHKCl**

**AVP (mg kg−1**

**)**

**SOM (%)**

**Ca (cmol kg−1**

**)**

**K (cmol kg−1**

**)**

**Na (cmol kg−1**

**)**

**CEC (cmol kg−1**

**)**

compared to the Ha-Matela wetlands (**Figure 6**). The high SOC is related to the balance of input from net primary production and microbial decomposition and the decomposition rates in wetlands are generally low due to low availability of oxygen and low temperatures [54].

Thus, one of the reasons for higher SOC in Butha Buthe wetlands is due to high altitude (i.e. 2000–3483 m) and low temperature (i.e. ≤8°C) in winter periods. Furthermore, the SOC

in the former site are much more stable and would not be easily eroded. Serval authors had attributed higher soil organic carbon density to several factors and these includes type of land use and soil management practices and these can significantly influence soil organic SOC dynamics and C flux from the soil [22, 55–59]. The vegetation isotopic δ13C and δ15N across the

) compared to that

21

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) (**Figure 7**). These results showed that wetland soils

Isotopic Signatures (δ<sup>13</sup>C and δ15N) and Characteristics of Two Wetland Soils in Lesotho…

density was observed in the Butha-Buthe wetlands (6.69–16.51 kgC m−<sup>2</sup>

in the Ha-Matela (6.46–13.91 kgC m−<sup>2</sup>

**Figure 8.** Isotopic δ<sup>13</sup>C, %C, δ<sup>15</sup>N and % N of vegetation, Butha Buthe.

**Figure 5.** Silt clay ratio, Butha Buthe (BB) and Ha-Matela (HM).

**Figure 6.** Soil organic carbon, Butha Buthe (BB) and Ha-Matela (HM).

**Figure 7.** Soil organic carbon density, Butha Buthe (BB) and Ha-Matela (HM).

Thus, one of the reasons for higher SOC in Butha Buthe wetlands is due to high altitude (i.e. 2000–3483 m) and low temperature (i.e. ≤8°C) in winter periods. Furthermore, the SOC density was observed in the Butha-Buthe wetlands (6.69–16.51 kgC m−<sup>2</sup> ) compared to that in the Ha-Matela (6.46–13.91 kgC m−<sup>2</sup> ) (**Figure 7**). These results showed that wetland soils in the former site are much more stable and would not be easily eroded. Serval authors had attributed higher soil organic carbon density to several factors and these includes type of land use and soil management practices and these can significantly influence soil organic SOC dynamics and C flux from the soil [22, 55–59]. The vegetation isotopic δ13C and δ15N across the

**Figure 8.** Isotopic δ<sup>13</sup>C, %C, δ<sup>15</sup>N and % N of vegetation, Butha Buthe.

**Figure 6.** Soil organic carbon, Butha Buthe (BB) and Ha-Matela (HM).

**Figure 5.** Silt clay ratio, Butha Buthe (BB) and Ha-Matela (HM).

20 Wetlands Management - Assessing Risk and Sustainable Solutions

compared to the Ha-Matela wetlands (**Figure 6**). The high SOC is related to the balance of input from net primary production and microbial decomposition and the decomposition rates in wetlands are generally low due to low availability of oxygen and low temperatures [54].

**Figure 7.** Soil organic carbon density, Butha Buthe (BB) and Ha-Matela (HM).

cations (K, Ca, Mg and Na), lower silt/clay ratios as well as lower SOC contents and SOC density, higher bulk density and less negative δ13C compared to that of Mountains AEZ (Butha Buthe). However, the severity of degradation, can be shown by the δ13C values as these values are sensitive indicators of nutrient stress and δ13N served as a robust indicator of wetland eutrophication. These results showed that soil indicators used as well as stable isotopes signatures used (i.e. δ13C and δ13N) may be used as monitoring tools for wetland management and

Isotopic Signatures (δ<sup>13</sup>C and δ15N) and Characteristics of Two Wetland Soils in Lesotho…

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23

The work was funded by Regional Universities Forum (RUFORUM), Uganda for Capacity Building in Agriculture under grant RU 2009/GRG 15. The Isotopic study was funded by the International Atomic Energy Agency (IAEA), grant number CRP 15399 for A.O Olaleye. The cooperation of the staff and students of the National University of Lesotho, Roma, Lesotho is

Natural Resources and Environmental Management, Department of Crop Production,

[1] Population C, ICF M. Lesotho 2009: Results from the Demographic and Health Survey.

[2] Moyo S, Sill M. The Southern African Environment: Profles of the SADC Countries.

[3] Nkheloane T, Olaleye AO, Mating R. Spatial heterogeneity of soil physico-chemical properties in contrasting wetland soils in two agro-ecological zones of Lesotho. Soil

[4] Kansiime F, Saunders MJ, Loiselle SA. Functioning and dynamics of wetland vegetation of Lake Victoria: An overview. Wetlands Ecology and Management. 2007;**15**(6):443-451

Faculty of Agriculture, University of Swaziland, Luyengo, Swaziland

restoration.

**Acknowledgements**

also acknowledged.

**Conflict of interest**

No conflict of interests.

Olaleye Adesola Olutayo

Address all correspondence to: olaleye@uniswa.sz

Studies in Family Planning. 2011;**42**(4):305

London: Routledge; 2014

Research. 2012;**50**(7):579-587

**Author details**

**References**

**Figure 9.** Isotopic δ<sup>13</sup>C, %C, δ<sup>15</sup>N and % N of vegetation, Ha-Matela.

two wetlands and years (2008–2010) are shown in **Figures 8** and **9**. The less negative values of Isotopic δ13C (Ha-Matela), compared to Butha Buthe is an indication of degradation [29, 36, 60]. High δ15N in Butha Buthe is ascribed to nutrient enrichment as a result of anthropogenic activity (i.e. livestock grazing [61].

### **4. Conclusions**

Human influences have led to disturbances in the wetland ecosystems in Lesotho. The study showed that despite the fact that soil characteristics can be used to assess changes in the ecosystems, environmental isotopes of C and N in aquatic plants responded positively to nutrient increase due to δ13C values in plants. Results showed wetlands located in the Lowlands (Ha-Matela) AEZ are much more degraded and heavily impacted as indicated by low base cations (K, Ca, Mg and Na), lower silt/clay ratios as well as lower SOC contents and SOC density, higher bulk density and less negative δ13C compared to that of Mountains AEZ (Butha Buthe). However, the severity of degradation, can be shown by the δ13C values as these values are sensitive indicators of nutrient stress and δ13N served as a robust indicator of wetland eutrophication. These results showed that soil indicators used as well as stable isotopes signatures used (i.e. δ13C and δ13N) may be used as monitoring tools for wetland management and restoration.
