**3.1 General structure of exotic and native forests**

A description of the existing trees, seedlings and saplings in all the three exotic and native forests studied in the Mountain cloud forests of Taita Hills is shown in Table 1. Significantly higher tree stem densities were found in the native forests than in the exotic forests. Similarly, the native forests had higher numbers of seedlings and saplings although not significantly different from those in Eucalyptus forests. The numbers of seedlings were not different between the pine and eucalyptus forests.


The p-value shows significance levels of a one way ANOVA test for differences between forest types. Values followed by the different letter superscripts are significantly different. Seedlings refer to young trees of < 1.3m height; Saplings ≥1.3.m high and ≤ 5cm dbh.

Table 1. Characteristics of the native tree species regenerated among the four forest types in the Taita Hills

#### **3.2 A typical regeneration and diversity of native species within the exotic and native forests in the three forest fragments in the Taita Hills**

In general, the diversity and densities of regenerated native species were higher in the native forests than in the exotic plots forests. The typical native species in cypress plantations were *Macaranga conglomerata, Rapanea melanophloesos, Rytigynia uhligii Tabernaemontana stapfiana* and *Syszygium guineese*; in the eucalyptus plantations were:

Native Tree Species Regeneration and Diversity in the Mountain Cloud Forests of East Africa 247

**Nga Cha Mbo Nga Cha Mbo Nga Cha Mbo Nga Cha Mbo** 

*Macarnaga conglomerata* Brenan 10 103 15 147 29 15 153 47

*Oxyanthus speciosus* DC 118 29 82 6 *Polyscias fulva* Harms 10 29 15 24 18

*Pleiocarpa pycnatha* K Schum 29 147 15 44 676

*Rapanea melanophloeos* L. Mez 88 74 10 59 24

*Sysygium guineense* Willd 108 118 103 88 74 71 15 671

Table 2. Densities all native woody (#/ha) species occurring in at least three plots at each of

*Albizia gummifera, Oxyanthus speciosus, T. stapfiana* and *S. guineese;* and the pine plantations were A*. gummifera, M. conglomerate, Newtonia buchananii, Pleiocarpa pycnatha, R. uhligii T. stapfiana, Vangueria volkensii* and *S. guineese.* The exotic plantations of Chawia hosted the highest number of native species among all the exotic forests, while cypress and pine forests

\*Denotes exotic species and the woody species include tree, saplings and seedlings regenerated

the three forests fragments of Ngangao (Nga), Chawia (Cha) and Mbololo (Mbo).

had more native species than eucalyptus forest.

29 843 235 485

*Phoenix reclinata* Jacq 44 15 15 221

*Maesa lanceolata* Engl. 10 7 29 24

*Albizia gummifera* J.F.Gmel 44 81 0 74 69 88 132

*Eucalyptus saligna* 

*Pinus patula* 

29 294 35 512

39 29 15 12 47

78 235 353 265 82

309 338 1088 118 176 76

44 29 29 41

10 15 137 59 24

Native Stands

**Species** *Cupressus* 

*Newtonia buchananii*  G.C.C.Gilbert & Boutique

*\*Phoenix patula* Schiede ex

*Podocarpus latifolius* R.Br. ex

*Rytigynia uhligii* K.schum.&

*T.abernamontana stapfiana* 

*Vangueria volkensii* 

*Xymalos monospora*  (Harv.)Baill.

Schlecht.& Cham

Mirb

K.Krause

Britten

K:Schum

combined

*lusitanica* 

*\*Acacia mearnsii* De wild 1304 15 7 1529 309 29

*\*Cupressus lusitanica* Miller 637 956 684 574 44 *\*Eucalyptus saligna* R. Baker 7 2000 706 1103


Native Tree Species Regeneration and Diversity in the Mountain Cloud Forests of East Africa 247

246 Biodiversity Loss in a Changing Planet

where a, is the number of species present in both forest types or locations compared, b is the number of species in only one forest type or location; and c is the number of species

When establishing diversities and studying the regeneration dynamics, densities of native tree species in the study sites and forest stands (e.g., in exotic and native forests) have to be calculated on per area basis as well. In order to show the differences both in diversity and regeneration levels, further statistical analyses have to be done for the indices and densities derived. There are several statistical methods (SAS, STATA, SPSS) which can be used to assess such data sets. In the case of Taita hills, a one way ANOVA was used and SPSS 15 for windows software method adopted for the statistical analyses. The means were separated by applying Tukey's test to test the differences in the diversities and densities between the

A description of the existing trees, seedlings and saplings in all the three exotic and native forests studied in the Mountain cloud forests of Taita Hills is shown in Table 1. Significantly higher tree stem densities were found in the native forests than in the exotic forests. Similarly, the native forests had higher numbers of seedlings and saplings although not significantly different from those in Eucalyptus forests. The numbers of seedlings were not

> Sapling species (#/ha)

Cypress 765b 1.2b 412b 1.5b 0.85b 0.56b 4.17b 3852 Eucalyptus 897b 2.2ab 962ab 1.7b 0.99b 0.64ab 4.00b 3911 Pine 829b 1.7a 312b 2.8ab 1.14b 0.75abc 5.75b 1667 Native 1016a 6.9a 2575a 4.3a 1.82a 0.78a 11.42a 11015 p-value ≤0.05 ≤0.05 ≤0.05 ≤0.05 ≤0.05 0.031 ≤0.05 NS The p-value shows significance levels of a one way ANOVA test for differences between forest types. Values followed by the different letter superscripts are significantly different. Seedlings refer to young

Table 1. Characteristics of the native tree species regenerated among the four forest types in

**3.2 A typical regeneration and diversity of native species within the exotic and native** 

In general, the diversity and densities of regenerated native species were higher in the native forests than in the exotic plots forests. The typical native species in cypress plantations were *Macaranga conglomerata, Rapanea melanophloesos, Rytigynia uhligii Tabernaemontana stapfiana* and *Syszygium guineese*; in the eucalyptus plantations were:

Species richness (S)

Species diversity (H')

Species Evenness (H'E)

Abundance (N)

present in the other forest type or location.

**3. Regeneration and species diversities** 

**3.1 General structure of exotic and native forests** 

different between the pine and eucalyptus forests.

Seedling species (#/ha)

trees of < 1.3m height; Saplings ≥1.3.m high and ≤ 5cm dbh.

**forests in the three forest fragments in the Taita Hills** 

Seedling density (#/ha)

forest sites and types.

Forest type Stand

the Taita Hills

density (tree/ha) Cj = a/a+b+c (5)

\*Denotes exotic species and the woody species include tree, saplings and seedlings regenerated combined

Table 2. Densities all native woody (#/ha) species occurring in at least three plots at each of the three forests fragments of Ngangao (Nga), Chawia (Cha) and Mbololo (Mbo).

*Albizia gummifera, Oxyanthus speciosus, T. stapfiana* and *S. guineese;* and the pine plantations were A*. gummifera, M. conglomerate, Newtonia buchananii, Pleiocarpa pycnatha, R. uhligii T. stapfiana, Vangueria volkensii* and *S. guineese.* The exotic plantations of Chawia hosted the highest number of native species among all the exotic forests, while cypress and pine forests had more native species than eucalyptus forest.

Native Tree Species Regeneration and Diversity in the Mountain Cloud Forests of East Africa 249

either the intermediately disturbed fragment (Ngangao) or the highly disturbed one (Chawia). Among the exotic forests, pine plantations in Chawia had higher species richness than the rest of the exotic forests. A comparison within each fragment showed that in Ngangao the regeneration of trees within the native forest was higher than within the exotic forests (Shannon-Weaver's index 7 and Effective number 7). In contrast, Shannon-Weaver's indices and Effective numbers in the three forest fragments were almost similar. In Chawia, the Shannon-Weaver's indices were higher for the exotic forests than for the native forest. The highest one was that for the pine forest; with a Shannon-Weaver's index of 1.73 and Effective number 6, followed by cypress and eucalyptus forests respectively. Similarly, the pine forest had the highest number of species as well as total density of species regenerated. In Mbololo, the Shannon-Weaver's indices for the regenerated native species were rather similar for all forest types except in the native forest which indicated somewhat higher values. Comparatively, the native species that regenerated in the different forest types in both Ngangao and Mbololo appeared similar again with the exception of those in the native forests where the values were higher. As mentioned above, in Chawia, the regeneration was more

The Shannon-Weaver's diversity indices (H') were higher in the native forests than in the exotic plantations in Ngangao and Mbololo whereas in Chawia this index was lowest in the native forests. A one-way analysis of variance using Tukey's test indicated differences in diversity indices between the native forests and all types of exotic forests. In particular, these were highly significant between the native forests and the cypress or eucalyptus forests (p=000) and between the native forests and pine forests (p=0.001). No significant differences were found between exotic forests. All the exotic forests in Ngangao had almost similar diversities with very slight differences in the regeneration pattern, possibly because the exotic plantations here were established in barren areas22 which provided fewer opportunities for the regeneration of native species. The differences in regenerations patterns observed between the exotics forests in Mbololo on the other hand and the more at the Chawia and Ngangao fragments were most likely due to a lower level of disturbance Mbololo fragment experienced. This observation is corroborated by the high Shannon-Weaver's indices and effective numbers in the native forests and the presence of few secondary species that are indicators of disturbance (e.g. *P. reclinata M. lanceolata* and *T. stapfiana*). Ngangao, on the other hand, had more species associated with disturbance such as *M. conglomerata, R. uhlighii* and *M. lanceolata* 

The application of effective numbers facilitated distinction of differences in diversity among the exotic forest types. The effective numbers were also consistent with the Shannon-Weaver's indices. The effective numbers were higher in exotic forests in Chawia than in native forests and in all the exotic forests both in Ngangao and Mbololo. The effective numbers were also high in the native forests at Mbololo and Ngangao fragments. The Shannon-Weaver's evenness index (H'E) reached its highest value in the native forests of Ngangao site (0.89) and in pine plantation at Mbololo fragment (0.81). The most uneven forest in terms of diversity was the cypress plantation at Mbololo fragment (0.39). A one way ANOVA for Shannon-Weaver's evenness showed that there was a significant difference between the exotic forests and the native forests in general and also a significant difference in the species evenness between the cypress forest and the native forest (0.031). With respect to the abundance of regenerated individuals at each fragment, the native forest plots in Chawia had the lowest number (794) compared to the other native plots of Ngangao (1365)

pronounced in the exotic forests than in the native forest.

also confirming the earlier observations by Bytebier48.

or Mbololo (19928).

#### **3.3 Variation in species regenerations and diversity among forest types**

The species found naturally regenerated and their diversities are shown in Table 3. With regard to species diversity (H'), richness (S), Evenness (H'E) and abundance (N) of the native species regenerated in the different forests, the native forest had higher average totals than the exotic forests. However, some of the values in native forests were not significantly different from those found in some of the exotic plantations (e.g. H' in native, pine or eucalyptus forests).


Standard error is shown in the parenthesis for Shannon's index (H') and Shannon's evenness index (H'E); while for ths individual species (N) and species richness (S), the value in parenthesis denotes standard deviation.

Table 3. Number of individual species (N), species richness (S), Shannon's index (H'), Shannon's evenness index (H'E) and effective numbers (EF) observed in four forest types in three forest fragments of the Taita Hills (n=65 plots)

The native forests had a higher species diversity than the exotic plantations. Other studies in East Africa7 have shown the same trend. The study under discussion however, showed that, the highly disturbed forest site of Chawia had higher tree species diversity in the exotic forests than in the native forests. The reason for this is probably attributed to the fact that native forest land had been cleared for the establishment of the exotic forests instead of bare land. Moreover, some of these exotic plantations were established around the native forests as buffers. Therefore, the high levels of anthropogenic activities at this site45,46 and a possible presence of soil seed bank47 associated with the initial clearance of the native forests may explain the high levels of regenerated native species. These results also compare well with those established by Yirdaw and Luukkanen47 in eucalyptus plantations surrounding a native forest in Ethiopia; in their study, higher species diversity was found close to the native forests as compared to stands that were planted further away.

An analysis of variance showed a significantly higher species richness in the native forests than the exotic plantations (p=0.000). A comparison between the three forest fragments, showed a significant difference in species richness only between the least and intermediately disturbed sites of Mbololo and Ngangao respectively (p=0.002). In general no statistical differences were detected in species abundance (N) between the native and exotic forests types; and between the three fragments. Nevertheless, the native forests in the least disturbed site (Mbololo) had a higher abundance (N) and number of species (S) than the exotic forests at the same fragment. The regenerated species showed higher abundance at this fragment than in

The species found naturally regenerated and their diversities are shown in Table 3. With regard to species diversity (H'), richness (S), Evenness (H'E) and abundance (N) of the native species regenerated in the different forests, the native forest had higher average totals than the exotic forests. However, some of the values in native forests were not significantly different from those found in some of the exotic plantations (e.g. H' in native, pine or

**Forest Area Forest type S N H' H'E EF Ngangao** Cypress 4 (2) 2088 (2108) 0.88 (0.22) 0.64 (0.07) 2

**Chawia** Cypress 7 (3) 1485 (457) 1.53(0.26) 0.78 (0.216) 5

**Mbololo** Cypress 3 (1) 6358 (15609) 0.48 (0.13) 0.39 (0.062) 2

Standard error is shown in the parenthesis for Shannon's index (H') and Shannon's evenness index (H'E); while for ths individual species (N) and species richness (S), the value in parenthesis denotes

Table 3. Number of individual species (N), species richness (S), Shannon's index (H'), Shannon's evenness index (H'E) and effective numbers (EF) observed in four forest types in

The native forests had a higher species diversity than the exotic plantations. Other studies in East Africa7 have shown the same trend. The study under discussion however, showed that, the highly disturbed forest site of Chawia had higher tree species diversity in the exotic forests than in the native forests. The reason for this is probably attributed to the fact that native forest land had been cleared for the establishment of the exotic forests instead of bare land. Moreover, some of these exotic plantations were established around the native forests as buffers. Therefore, the high levels of anthropogenic activities at this site45,46 and a possible presence of soil seed bank47 associated with the initial clearance of the native forests may explain the high levels of regenerated native species. These results also compare well with those established by Yirdaw and Luukkanen47 in eucalyptus plantations surrounding a native forest in Ethiopia; in their study, higher species diversity was found close to the

An analysis of variance showed a significantly higher species richness in the native forests than the exotic plantations (p=0.000). A comparison between the three forest fragments, showed a significant difference in species richness only between the least and intermediately disturbed sites of Mbololo and Ngangao respectively (p=0.002). In general no statistical differences were detected in species abundance (N) between the native and exotic forests types; and between the three fragments. Nevertheless, the native forests in the least disturbed site (Mbololo) had a higher abundance (N) and number of species (S) than the exotic forests at the same fragment. The regenerated species showed higher abundance at this fragment than in

three forest fragments of the Taita Hills (n=65 plots)

native forests as compared to stands that were planted further away.

Eucalyptus 3 (1) 9044 (7637) 0.82 (0.89) 0.80( 0.099) 2 Pine 5 (3) 1588 (733) 0.89 (0.26) 0.51 (0.136) 2 Native 9 (2) 1365 (147) 1.97 (0.16) 0.89 (0.02) 7

Eucalyptus 6 (1) 1176 (825) 1.31 (0.08) 0.78 (0.071) 4 Pine 11 (1) 2794 (1123) 1.73 (0.15) 0.72 (0.032) 6 Native 5 (3) 794 (573) 1.07 (0.36) 0.63 (0.056) 3

Eucalyptus 4 (1) 1515 (391) 0.83(0.12) 0.68 (0.041) 2 Pine 4 (1) 1221 (194) 1.22 (0.16) 0.81 (0.098) 3 Native 15 (3) 19928 (39748) 2.05 (0.13) 0.78 (0.035) 8

**3.3 Variation in species regenerations and diversity among forest types** 

eucalyptus forests).

standard deviation.

either the intermediately disturbed fragment (Ngangao) or the highly disturbed one (Chawia). Among the exotic forests, pine plantations in Chawia had higher species richness than the rest of the exotic forests. A comparison within each fragment showed that in Ngangao the regeneration of trees within the native forest was higher than within the exotic forests (Shannon-Weaver's index 7 and Effective number 7). In contrast, Shannon-Weaver's indices and Effective numbers in the three forest fragments were almost similar. In Chawia, the Shannon-Weaver's indices were higher for the exotic forests than for the native forest. The highest one was that for the pine forest; with a Shannon-Weaver's index of 1.73 and Effective number 6, followed by cypress and eucalyptus forests respectively. Similarly, the pine forest had the highest number of species as well as total density of species regenerated. In Mbololo, the Shannon-Weaver's indices for the regenerated native species were rather similar for all forest types except in the native forest which indicated somewhat higher values. Comparatively, the native species that regenerated in the different forest types in both Ngangao and Mbololo appeared similar again with the exception of those in the native forests where the values were higher. As mentioned above, in Chawia, the regeneration was more pronounced in the exotic forests than in the native forest.

The Shannon-Weaver's diversity indices (H') were higher in the native forests than in the exotic plantations in Ngangao and Mbololo whereas in Chawia this index was lowest in the native forests. A one-way analysis of variance using Tukey's test indicated differences in diversity indices between the native forests and all types of exotic forests. In particular, these were highly significant between the native forests and the cypress or eucalyptus forests (p=000) and between the native forests and pine forests (p=0.001). No significant differences were found between exotic forests. All the exotic forests in Ngangao had almost similar diversities with very slight differences in the regeneration pattern, possibly because the exotic plantations here were established in barren areas22 which provided fewer opportunities for the regeneration of native species. The differences in regenerations patterns observed between the exotics forests in Mbololo on the other hand and the more at the Chawia and Ngangao fragments were most likely due to a lower level of disturbance Mbololo fragment experienced. This observation is corroborated by the high Shannon-Weaver's indices and effective numbers in the native forests and the presence of few secondary species that are indicators of disturbance (e.g. *P. reclinata M. lanceolata* and *T. stapfiana*). Ngangao, on the other hand, had more species associated with disturbance such as *M. conglomerata, R. uhlighii* and *M. lanceolata*  also confirming the earlier observations by Bytebier48.

The application of effective numbers facilitated distinction of differences in diversity among the exotic forest types. The effective numbers were also consistent with the Shannon-Weaver's indices. The effective numbers were higher in exotic forests in Chawia than in native forests and in all the exotic forests both in Ngangao and Mbololo. The effective numbers were also high in the native forests at Mbololo and Ngangao fragments. The Shannon-Weaver's evenness index (H'E) reached its highest value in the native forests of Ngangao site (0.89) and in pine plantation at Mbololo fragment (0.81). The most uneven forest in terms of diversity was the cypress plantation at Mbololo fragment (0.39). A one way ANOVA for Shannon-Weaver's evenness showed that there was a significant difference between the exotic forests and the native forests in general and also a significant difference in the species evenness between the cypress forest and the native forest (0.031). With respect to the abundance of regenerated individuals at each fragment, the native forest plots in Chawia had the lowest number (794) compared to the other native plots of Ngangao (1365) or Mbololo (19928).

Native Tree Species Regeneration and Diversity in the Mountain Cloud Forests of East Africa 251

Since the advent of the biological diversity convention of 1992, many countries have, as part of their global commitment to sustainable development, paid great attention to ecosystem conservation. Moreover, the realization that some vital biological resources are on the brink of extinction and yet they are vital for social and economic development reinforces the urgency for conservation. Similarly, due to the apparent loss of biodiversity and ecological functions in the forests of the Taita Hills and in many other forests in Kenya, a newly promulgated Forest Act51 provides several options for managing the forests, including those under threat such as the Taita Hills forests. These options include opportunities for stakeholders, particularly the local communities residing around these forests to participate in their management. As a result, Community Forest Associations have been formed for the different forest fragments in Taita Hills in preparation for their participatory management. Community involvement in management has already entailed participation in forest reforestation activities such as replanting with seedlings of native tree species in order to enhance the replacement of the exotic species. In areas outside the forests and on farms tree planting is being carried out so as to ease pressure off the forest. Scientific approach has been applied to facilitate the restoration by identifying suitable sites for planting. In particular, a GIS-based, least-cost modelling technique has been used to identify such sites52 and after integrating biological and socioeconomic data within the forest corridors46, a set of exotic plantations with highest priority for restoration activities have been identified by both the government and Non Governmental organizations that are active in the area. The choice of species planted is based on their potential to increase landscape connectivity or on their importance for conservation of critically endangered taxa, although with regard to soil characteristics of the forest fragments,

any of the native species is suitable and can be used for restoration exercise53.

**4.2 Forest restoration and management for biodiversity enhancement** 

farmer-friendly exotic trees (e.g. *Grevillea robusta*).

**Box 2. Community activities for restoration of forest biodiversity between two** 

Ngangao and Chawia forest fragments are being linked through a three-step reforestation plan. This includes forest enrichment, agricultural matrix enrichment through on-farm tree planting and conversion of exotic plantations to native forest. As native forest enrichment is being done, it is accompanied by gradual removal of exotic species from the canopy level to increase the light availability for the planted native tree seedlings and to allow faster recruitment of seedlings from the soil seed bank. Local initiatives to enhance these restorations activities include the establishment of tree nurseries to supply seedlings necessary for planting with native tree species (e.g. *Prunus africana*.) and

Forest restoration can be enhanced by the presence of appropriate conditions, some of which include the following: placement of the plantations, edge effect, presence of gaps, seed dispersal mechanisms with mammals as dispersing agents and an existing soil seed bank. In most cases these factors work in tandem. In the study discussed here, fragments which showed some degree of disturbance (Chawia and Ngangao) had stronger edge effects since they were located in the middle of agricultural lands due to their fragmentation, this

**4. Strategies for diversity restoration** 

**4.1 Stakeholder involvement** 

**fragments** 

#### **3.4 Similarities of species regenerated at the three sites**

Table 4 shows the similarities in species composition between the different forest types and fragments. The highest similarity (77 %) was found between the cypress and pine forests in Chawia; the pine and cypress forests in Ngangao also showed a high species similarity (64%), which almost corresponded with the species diversity values found (11 and 13 species respectively). In Mbololo, the highest species similarity was 59% between the exotic forests of pine and cypress. The cypress forests in Mbololo were twice as diverse with 13 species as the eucalyptus forest and yet they shared a similarity of 50% species, the same as for these exotic forests in Chawia. The majority of the forests studied however, shared less than 30% of the species, while the forests which did not share any species were the eucalyptus forests in Mbololo and the native forests in Ngangao, as well as the eucalyptus and native forests in Mbololo.


Table 4. Similarities(%) of species regenerated in four forest types (C=Cypress,

E=Eucalyptus, P-Pine and N= Native) from the three forest fragments. Values in bold similarities from 50%

Highest species similarities in the undergrowth of pine and cypress forests in Chawia and Ngangao observed were possibly because these forests were located close to each other. Thus, there were either similar seed dispersal mechanisms or the forests could have had similar soil seed banks. The complete absence of similar species in eucalyptus and native forests in Mbololo and Ngangao implies that the eucalyptus plantations cannot support similar regeneration of species as the native forests, especially if the stem density is high as indeed was the case in these eucalyptus forests. In general, the native forests in Mbololo shared a low species similarity with other forests. A possible explanation is the low level of disturbances in this forest which provided few opportunities for seedling recruitment except through dispersal and gap dynamics. *Ocotea usambarensis* which is extinct in some regions in East Africa49 and under threat in Tanzania50, was observed in the native forests of Mbololo with 94 stems, although it is also known to be present in Ngangao. *Coffea fadenii, a*  wild coffee species, was only found in Ngangao, indicating the relatively low levels of disturbances experienced by these two sites. In Mbololo, the pine forest had a higher effective number and Shannon-Weaver's index than the eucalyptus and cypress forests plots possibly because the pine forest was located in the middle of the native forest, while cypress and eucalyptus had been planted at the edges.
