**3.1 Impacts of soil degradation on phytodiversity**

#### *3.1.1 Floristic composition*

**Table 2** presents the pairwise comparison of soil degradation classes based on the index of similarity of Jaccard. On this basis, none of the soil degradation classes was similar to another. Given that the analysis was performed on the presence/ absence matrix, we were able to conclude that all soil degradation classes were dissimilar, according to the floristic list. However, we noticed that the floristic composition of the vegetation in slightly and moderately degraded soils, although dissimilar, was closest (index of similarity of Jaccard equals to 0.434). Considering the discriminant species of each degradation class, the greatest number of discriminant species were found on slightly and moderately degraded soils (5 plants species) while the lowest were found on highly degraded soils (2 plant species) (**Table 3**).

#### *3.1.2 Species richness, chorological types, life forms and dispersal types*

The first two canonical axes obtained from the discriminant analysis on indicators of biodiversity were significant because they explained 97.59% of the initial information. The correlation between the two axes and the indicators of biodiversity showed that all the indicators (species richness, chorological, life forms and dispersal types indexes) were well and positively correlated with the first axis (0.91, 0.99, 0.99, 0.98 respectively) (**Table 4**). Thus, the first axis described high values of species richness and high values of chorological, life forms and dispersal type indexes. None of the indicators of biodiversity were well correlated with the second axis (**Table 4**).

The **Figure 2** showed that slightly and moderately degraded soils were positively correlated with the first axis while high and extreme degraded soils were well negatively correlated with the same axis. Based on the information gathered on this axis we could conclude that slightly and moderately degraded soil showed the highest species richness and were characterized by the highest relative abundance of regional species, phanerophytes and sarcochory. On the other hand, highly and extremely degraded soils showed lower species richness and highest relative abundance of species with wide distribution, therophytes


**79**

phytes and sarcochory).

*Discriminant species of each soil degradation class.*

*Correlation between biodiversity indicators and the two canonical axes.*

**Table 3.**

**Table 4.**

*The Impacts of Soil Degradation Effects on Phytodiversity and Vegetation Structure on Atacora…*

*Cochlospermum planchonii* Hook.f. Light 0.0062 *Crossopteryx febrifuga* (G. Don)Benth. Light 0.0148 *Indigofera nigritana* Hook. f. Light 0.0202 *Strychnos spinosa* Lam. Light 0.0302 *Hexalobus monopetalus* (A.Rich.)Engl. & Diels Light 0.0374 *Basilicum polystachion* (L.) Moench. Moderate 0.0012 *Blumea crispata* Merxm. & Roessler var. cripata Moderate 0.0012 *Elephantopus mollis* Kunth Moderate 0.0032 *Andropogon pseudapricus* Stapf Moderate 0.0230 *Cissus corylifolia* (Baker) Planch. Moderate 0.0230 *Stylosanthes fruticosa* (Retz.)Alston High 0.0010 *Polygala multiflora* Poir. High 0.0084 *Spermacoce filifolia* (Schmach. & Thonn.) J.-P.Lebrun & Stork Extreme 0.0002 *Cochlospermum tinctorium* Perr. ex A.Rich Extreme 0.0134 *Chamaecrista mimosoides* (L.) Greene Extreme 0.0198

**classes**

**Probability**

**Species Soil** 

and sclerochory (or lower relative abundance of regional species, phanero-

distribution, therophytes and sclerochory followed a contrary trend.

Simple statistics and ANOVA were summarized in **Table 5** and demonstrated that the between soil degradation classes based on biodiversity indicators were significant. Weighted spectrums of chorological types, life forms and dispersal types of diaspores were illustrated in **Figure 3(a–c)**. The highest species richness was found on slightly and moderately degraded soils (30.5 ± 7.2; 31.33 ± 4.93) and the lower values of this variable were found on highly (11.33 ± 3.21) and extremely degraded soils (16.5 ± 12.08). The high values of chorological index, life forms index and dispersal types index characterized light degraded soils (respectively 5.83 ± 1.64; 6.21 ± 3.82; 2.20 ± 0.76) and these values decreased gradually on moderately degraded soils (3.45 ± 0.40; 2.73 ± 1.70; 1.70 ± 0.91) and highly degraded soils (2.44 ± 0.096; 0.89 ± 1.54; 1.08 ± 0.38) and reached the lowest values on extreme degraded soils (1.51 ± 0.62; 0.78 ± 0.38; 0.62 ± 0.79). In other words, regional species, phanerophytes and sarcochory presented a regressive trend from light to extreme degraded soils through moderate and high soil degradation classes while species with wide

**Variables Can 1 Can 2** Species richness (S) 0.91 −0.34 Chorological index of disturbance (*I*C) 0.99 0.02 Life forms index of disturbance (*I*L) 0.99 0.14 Dispersal types index of disturbance (*I*D) 0.98 0.13

*DOI: http://dx.doi.org/10.5772/intechopen.93899*

**Table 2.** *Index of similarity of Jaccard.* *The Impacts of Soil Degradation Effects on Phytodiversity and Vegetation Structure on Atacora… DOI: http://dx.doi.org/10.5772/intechopen.93899*


#### **Table 3.**

*Soil Erosion - Current Challenges and Future Perspectives in a Changing World*

*3.1.2 Species richness, chorological types, life forms and dispersal types*

computed with PC-ORD for Windows Version 5 [28].

**3.1 Impacts of soil degradation on phytodiversity**

**3. Results**

(**Table 3**).

axis (**Table 4**).

*3.1.1 Floristic composition*

degradation classes based on the cover data of their species lists. The analysis was

**Table 2** presents the pairwise comparison of soil degradation classes based on the index of similarity of Jaccard. On this basis, none of the soil degradation classes was similar to another. Given that the analysis was performed on the presence/ absence matrix, we were able to conclude that all soil degradation classes were dissimilar, according to the floristic list. However, we noticed that the floristic composition of the vegetation in slightly and moderately degraded soils, although dissimilar, was closest (index of similarity of Jaccard equals to 0.434). Considering the discriminant species of each degradation class, the greatest number of discriminant species were found on slightly and moderately degraded soils (5 plants species) while the lowest were found on highly degraded soils (2 plant species)

The first two canonical axes obtained from the discriminant analysis on indicators of biodiversity were significant because they explained 97.59% of the initial information. The correlation between the two axes and the indicators of biodiversity showed that all the indicators (species richness, chorological, life forms and dispersal types indexes) were well and positively correlated with the first axis (0.91, 0.99, 0.99, 0.98 respectively) (**Table 4**). Thus, the first axis described high values of species richness and high values of chorological, life forms and dispersal type indexes. None of the indicators of biodiversity were well correlated with the second

The **Figure 2** showed that slightly and moderately degraded soils were positively correlated with the first axis while high and extreme degraded soils were well negatively correlated with the same axis. Based on the information gathered on this axis we could conclude that slightly and moderately degraded soil showed the highest species richness and were characterized by the highest relative abundance of regional species, phanerophytes and sarcochory. On the other hand, highly and extremely degraded soils showed lower species richness and highest relative abundance of species with wide distribution, therophytes

**Soil classes Light Moderate High Extreme** Light — — — — Moderate 0.434 — — — High 0.149 0.19 — — Extreme 0.143 0.184 0.088 —

**78**

**Table 2.**

*Index of similarity of Jaccard.*

*Discriminant species of each soil degradation class.*


#### **Table 4.**

*Correlation between biodiversity indicators and the two canonical axes.*

and sclerochory (or lower relative abundance of regional species, phanerophytes and sarcochory).

Simple statistics and ANOVA were summarized in **Table 5** and demonstrated that the between soil degradation classes based on biodiversity indicators were significant. Weighted spectrums of chorological types, life forms and dispersal types of diaspores were illustrated in **Figure 3(a–c)**. The highest species richness was found on slightly and moderately degraded soils (30.5 ± 7.2; 31.33 ± 4.93) and the lower values of this variable were found on highly (11.33 ± 3.21) and extremely degraded soils (16.5 ± 12.08). The high values of chorological index, life forms index and dispersal types index characterized light degraded soils (respectively 5.83 ± 1.64; 6.21 ± 3.82; 2.20 ± 0.76) and these values decreased gradually on moderately degraded soils (3.45 ± 0.40; 2.73 ± 1.70; 1.70 ± 0.91) and highly degraded soils (2.44 ± 0.096; 0.89 ± 1.54; 1.08 ± 0.38) and reached the lowest values on extreme degraded soils (1.51 ± 0.62; 0.78 ± 0.38; 0.62 ± 0.79). In other words, regional species, phanerophytes and sarcochory presented a regressive trend from light to extreme degraded soils through moderate and high soil degradation classes while species with wide distribution, therophytes and sclerochory followed a contrary trend.

**Figure 2.** *Projection of soil degradation classes in the canonical system axis based on biodiversity indicators.*

### **3.2 Impacts of soil degradation on vegetation structure**

**Tables 6** and **7** summarize the results of MRPP computed on cover data of each plots. First, all the degradation soil classes were considered together (**Table 6**). Thereafter, the degradation soil classes were considered two by two (**Table 7**). Considering all soil degradation classes, the results showed that the vegetation cover data for the four soil degradation classes were significantly different (**Tables 5** and **6**). However, the pairwise comparison (**Table 7**) gave more details and showed that the vegetation cover data of moderately and highly degraded soils were broadly overlapping (p > 0.05). Moderate and high degraded soils presented a relative similar vegetation type i.e. shrub savannas.
