Livestock grazing is considered to be of great ecological importance in terrestrial ecosystems if sustained at acceptable levels. Overgrazing has ecological ramifications which lead to degradation of the ecosystem. This has become a problem in many parts of Tanzania. A study was conducted in Northen Slopes of Mount Kilimajaro in order to examine the impact of grazing on natural regeneration of the grazed vegetation. This paper is guided by the hypothesis that the species richness, species diversity and density of regenerants vary across grazing intensities. The study area was divided into four zones as per grazing intensity namely heavily grazed areas, moderately grazed, least grazed and ungrazed areas. Ten rectangular quadrats of 20 m × 25 m were established in each zone, making a total of 40 quadrats in the entire study area. A stratified random sampling procedure was used in locating quadrats in each zone of grazing intensity whereby two subquadrats of 2 m × 5 m were nested in bigger quadrats. Natural regeneration was assessed in terms of species diversity and density of seedlings, saplings and poles. Results indicate that species regeneration varied among areas with different grazing intensity. The variations of seedlings and saplings density among areas with different grazing intensity were statistically significant. The species diversity of regenerants differed significantly among areas with different grazing intensity. Keeping the grazing intensity at low and moderate levels will stimulate more plant growth and diversity as opposed to heavy grazing which will lead to vegetation retrogression.
The northern slopes of Mount Kilimanjaro have been facing grazing pressure resulting from increased livestock population in the area [
Mount Kilimanjaro is found on the Northern Tanzania, adjacent to Tanzania-Kenya international boundary (
The conservation history of Mount Kilimanjaro dates back in early 1900s when it was gazetted as Game Reserve and as a forest reserve in 1921 [
montane forest was under Forest and Beekeeping Department (FBD). Mount Kilimanjaro was inscribed by UNESCO as World Heritage Site in 1987 based on high fauna and flora diversity. In September 2005, the Park’s boundaries were adjusted to include Kilimanjaro Forest Reserve (1078.28 km2), thus the total area increased to 1834 km2 [
The climate of Mount Kilimanjaro varies from one ecological zone to another based on altitude, gradient and aspect. The montane forest that surrounds the mountain at altitude of 1600 - 2400 m.a.s.l on northern slopes and 1600 - 2800 m.a.s.l. on the southern slopes is characterized by a typical equatorial climate [
Majority of local communities bordering Mount Kilimanjaro are crop cultivators. These are mostly in Moshi rural, Hai, Siha and Rombo districts located in the southern, western and eastern sides of the Mountain. The major dominant form of agriculture in these districts is Agroforestry popularly known as “Chaga home gardens”. Agro-pastoralists are only found in Longido District which is located on the leeward side of Mountain in the northern slopes.
Preliminary survey was first carried out in montane forest of the northern slopes of Mount Kilimanjaro to define vegetation segments based on its homogeneity and grazing intensity. This was followed by zoning the area based on grazing intensities into heavily grazed areas, moderately grazed, least grazed and ungrazed areas. These areas were used for detailed study on natural regeneration pattern.
The sampling strategy was based on the four grazing intensities (i.e. heavily grazed, moderately grazed, least grazed and ungrazed). Ten rectangular quadrats of 20 m × 25 m were established in each category, making a total of 40 quadrats in the entire study area. A stratified random sampling procedure was used in locating quadrats in each category of grazing intensity. Two subquadrats of 2 m × 5 m were nested in bigger quadrats as recommended by [
The degree of livestock trampling was assessed by measuring percentage (by area) of trail and bare ground in
each 20 m × 25 m quadrat. Qualitative estimation of grazing intensity in each quadrat based on assessment of percentage utilization of vegetation by livestock was also done in each quadrat. A total of 3 grazing intensity classes based on the modified [
Plant natural regeneration was assessed in terms of species richness, species diversity and density of seedlings, saplings and poles. Species richness was analyzed through counting the total number of species found in each quadrant under a given grazing intensity. The plant species diversity was determined from raw data by using the Shannon’s diversity index (H') [
where:
pi = ni/N, the number of individuals found in the ith species as a proportion of total number of individuals found in all the species.
In = Natural logarithms to base e
The plant species evenness (E) of each area was calculated using the sample formula below (Alatalo, 1981).
where H' Shannon-Wiener Diversity Index and S is the total number of species (from the selected study sites.
One-way ANOVA was used to test the statistical significance of the observed differences across grazing intensities. The significance level for all tests was based on 5% critical limit.
Natural tree species regeneration varied among areas with different grazing intensity, where the Least grazed
Grazing intensity class | Interpretation |
---|---|
0 | No grazing |
1 | 1% - 20%: Least grazed |
2 | 21% - 60%: Moderately grazed |
3 | 61% - 100%: Heavily grazed |
areas had the highest density of regenerants (seedlings, saplings and poles) with a total of 27,150 stems/ha (
The variations of seedlings and saplings density (stems/ha) among areas with different grazing intensities were statistically significant at p < 0.05 (
The species diversity of regenerants differed significantly among areas with different grazing intensity based on Analysis of Variance (ANOVA) (F = 11.8095, p = 0.000016). Multiple comparison test based on Tukey HSD test showed the statistical significant differences existed between least grazed vs heavily grazed, least vs ungrazed, moderately grazed vs heavily grazed and moderately grazed vs ungrazed areas (
The difference in species richness of regenerants among areas with different grazing intensity was significant based on Analysis of Variance (ANOVA) (F = 10.53775, p = 0.000041). Multiple comparison test based on Tukey HSD test showed that the least and moderately grazed areas had significantly higher number of species than heavily and ungrazed areas (
Seedlings | Saplings | Poles | ||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
Grazing intensity | A | B | C | d | a | b | c | d | A | b | c | D |
Heavily (a) | - | 0.0002ab | 0.9969 | 0.0008ad | - | 0.92 | 0.06 | 0.77 | - | 0.5 | 0.7 | 1.0 |
Least (b) | - | - | 0.0002bc | 0.3045 | - | - | 0.01bc | 0.39 | - | - | 1.0 | 0.3 |
Moderately (c) | - | - | - | 0.0013cd | - | - | - | 0.36 | - | - | - | 0.4 |
Ungrazed (d) | - | - | - | - | - | - | - | - | - | - | - | - |
Level of grazing | Heavilya M = 1.2 ± 0.07 | Leastb M = 1.69 ± 0.098 | Moderatelyc M = 1.78 ± .099 | Ungrazedd M = 1.1 ± 0.11 |
---|---|---|---|---|
Heavilya | - | 0.006353 | 0.001148 | 0.920141 |
Leastb | - | - | 0.916979 | 0.001175 |
Moderatelyc | - | - | - | 0.000301 |
Ungrazedd | - | - | - | - |
Level of grazing | Heavilya M = 3.9 ± 0.31 | Leastb M = 8.4 ± 0.78 | Moderatelyc M = 7.3 ± 0.86 | Ungrazedd M = 4.8 ± 0.49 |
---|---|---|---|---|
Heavilya | - | 0.000259a | 0.003805 | 0.760216 |
Leastb | - | - | 0.630283 | 0.002116b |
Moderatelyc | - | - | - | 0.046103c |
Ungrazedd | - | - | - | - |
There was significant difference in trees regeneration among areas with different grazing intensities (
In terms of diversity among natural regenerants, the least and moderately grazed areas had the higher diversity of regeneration potential than ungrazed and heavily grazed areas (
From this study various communities regenerated differently due to different levels of grazing intensities. In heavily grazed areas, Euclea spinarum and Carissa spinarum had high density of regenerants than other areas. There was also successful regeneration of E. divinorum in heavily grazed areas since it is unpalatable and hence it was one of the least affected species by livestock grazing. E. divinorum has high concentrations of condensed tannins, as well as total phenolic compounds in their leaves thus bearing lower acceptability of its foliage by most herbivores [
This study found significant difference in plant natural regeneration pattern among areas with different grazing intensity in the Northern slopes of Mount Kilimanjaro. Moderately grazed areas had the highest plant species diversity complying with intermediate disturbance hypothesis. However, low tree species richness and lack of old aged stands in heavily grazed areas indicated the impacts of livestock grazing which contributed to prevention of trees to attain large size classes. The lowest regeneration potential in heavily grazed areas is an indication of unhealthy ecosystem.