**3.5. Human influence on distribution of small mammals and plant species in West Usambara Mountains**

**Table 3** and **Figure 7** present results of the influence of human being on small mammals and plant species. History shows that once the Usambara was covered by natural forests where diverse plants and myriads of small mammals were living in none-disturbed habitats. In 1980, most of the land has been cleared, and **Table 3** shows a strong statistical significance influence of cultivation on plant species. Other studies [58], compared biological diversity, Ecological Biogeography of West Usambara Mountains: A Study on the Influence of Abiotic... http://dx.doi.org/10.5772/intechopen.72068 159


Significant codes: 0 '\*\*\*' 0.001 '\*\*' 0.01 '\*' 0.05 '.' 0.1 ' ' 1.

Null deviance: 360945 on 481 degrees of freedom.

Residual deviance: 233953 on 460 degrees of freedom.

AIC: 4395.

and rock outcrops offer small mammal both safe havens and breeding places. This implies that surface stones and rock outcrops create microhabitats that are hardly accessible to disturbances due to other organisms mostly humans. All predictors had positive coefficients, which show positive correlation of the independent variables to dependent ones. Surface stones and rock outcrops are microhabitats with unique characteristics, which influence spatial distribution of the small mammals particularly in the plateau [51]. The results also show that surfaces stones make microhabitat which influence abundance and hence distribution small mammals along the landscape, and the high population of small species at the plateau may be attributed to microhabitat as well as stable food supply associated to food crop cultivation. The results also agreed well with field data which show that few species were captured per trap station in the plain than the plateau, and also the plant species richness and diversity are greater in the plateau than the plain. Similar results were reported by Meliyo et al. [51] and Njaka et al. [6]. The results are also in agreement with those presented by Hastie et al. [55] who indicated that microhabitat influences local density of species and their spatial distribution, however, our results could not show that temperature and moisture to be important drivers of spatial

**Table 3** and **Figure 6** present results depicting abiotic factors influencing spatial distribution of plant species along the landscape of West Usambara Mountains. The results show that elevation (metres above sea level), top soil depth and cultivation practices are major determinants of spatial distribution of plant species and they are statistically significant (*p* < 0.001) predictors, although cultivation practices are negatively influencing plant distribution i.e.

Other negatively influencing factors of statistical significance are hillshade (*p* < 0.01) and surface stones (*p* < 0.05) and atmospheric temperature in degrees Celsius (p < 0.05) (**Table 3** and **Figure 6**). Our results are in agreement with findings by Chen et al. [56] who studied factors affecting the distribution of pant species in Hainan Island, China, and reported many factors

Similarly, our results on spatial distribution of plant species in the west Usambara Mountains are supported finding by Trigas et al. [57] who reported an increase in proportion of plant species endemism with increasing elevation of Cretan Mountain that could only be explained by elevation-driven ecological factors. Ecologically, there are many factors coming into play, including temperature, rainfall, soils, and where human disturbances occur particularly

deforestation, these leading to plant species extinctions in some area in the world [56].

**3.5. Human influence on distribution of small mammals and plant species in West** 

**Table 3** and **Figure 7** present results of the influence of human being on small mammals and plant species. History shows that once the Usambara was covered by natural forests where diverse plants and myriads of small mammals were living in none-disturbed habitats. In 1980, most of the land has been cleared, and **Table 3** shows a strong statistical significance influence of cultivation on plant species. Other studies [58], compared biological diversity,

including elevation, soils, rainfall and human disturbances.

distribution in the study area.

vegetation clearing.

158 Pure and Applied Biogeography

**Usambara Mountains**

**Table 3.** Factors influencing distribution of plant species along the landscape of West Usambara Mountains, Tanzania.

indicated that human population growth has negatively affected natural resources, and hence biodiversity (**Figure 7**). Some hotspots such as eroded lands, deforested areas, dried water sources and undesirable tree species have been identified as creation of mankind, which are inversely related with rich biological diversity. Many animals (small and large) have been killed for food or because they destroy food crops planted. The consequences have been decline over time in per capita food production and increasing food insecurity and poverty, which are accelerating degradation of biodiversity of both plant and animal [58], particularly in the western facing drier West Usambara Mountains.

**Figure 6.** Plot of deviance residuals from GLM fitted to establish factors influencing plant species distribution along the landscape of West Usambara Mountain, Tanzania.

**Figure 7.** Historical account of human population pressure influence to the natural resources degradation West Usambara Mountains of Tanzania (Source: Meliyo et al. [58]).
