Different species occupy different niches in the web cycle of life. Knowing what species inhabit an ecosystem, and how many of each kind there are, is critical to understanding that ecosystem's structure and function, and predicting future changes.
Tropical forest ecosystems are known for sheltering the greatest biodiversity by comparison with many other ecosystems located in the same climatic zone. The tropical Forests are essential for life on earth and about 1.6 billion people depend on them for their livelihood.
The Kasyoha-Kitomi Central Forest Reserve (KKCFR) is part of a network of protected areas (PAs) located in the Albertine Rift region. This region is known for its rare and endemic flora and fauna.
The Albertine Rift Forest system is a chain of forest patches (with interconnected forest corridors) that are a major global centre of diversity and endemism and are a focus of most conservation and development agencies. Unfortunately, these unique and rare species (in KKCFR) are under serious threat from anthropogenic activities.
Indeed, as Plumptre et al., (2007) noted, they identified the major threats to the KKCFR forest as; hunting, illegal harvesting of timber and other plant products, charcoal burning, forest encroachment and mining. Recently (in 2021), the NFA granted permission to Jena Herbals U (Ltd) to harvest bark from tree species of Warbugia ugandensis and Zanthoxhylum gilletii for the manufacture of Covid-19 therapeutic drug (Covidex). The Covidex drug is now widely available in all Ugandan pharmacies. The commercialization of the bark harvest from the two trees is a precursor to negative harvest impacts on the two tree species as discussed below.
Three taxa; vegetation (trees, shrubs, lianas, vines, and herbs), terrestrial vertebrates (small mammals) and birds were used as surrogate indicator species for the assessment of the status of total biodiversity in KKCFR. Furthermore, the study used the biodiversity assessment done in 2016 as a baseline to compare the changes in biodiversity currently (2022).
Human activities in KKCFR of 2022 were also recorded and compared with those previously done in 2016 (baseline). After analyzing the field data collected in 2016 and 2022 using R open-source statistical software version 3.2.2, the study came out with the following results.
A total of 110 tree species were recorded in KKCFR between the 2016 and 2022 study period. In 2016, Ninety-four tree species were recorded while in 2022 forty-nine tree species were recorded . Of these tree species, Strombosia schefflera, Funtimia africana, Warbugia ugandensis, Xymalos monospora, Macaranga kilimadscherica and Shirakiopsis elliptica were the most dominant in descending order.
There was no significant difference in the abundance of the tree stems (expressed per unit hectare) recorded in 2016 and 2022. However, tree species' evenness (abundance) and richness (diversity) were higher in the year 2016 than in 2022.
A total of 92 shrub and liana species were recorded in KKCFR between 2016 and 2022 study period. In 2016, forty seven shrub and liana species were recorded in while in 2022 forty six species of shrubs and lianas were recorded. Of these, the most dominant shrub and liana species in descending order were Piper capense, Triumfetta brachyceros, Piper guineense, Brillantaisa citricosa, Dracaena laxissima and Alchornea hirtella.
The total stem abundance of the shrubs and lianas (expressed per unit hectare) was significantly different between 2016 and 2022. In terms of species evenness and richness (diversity), the year 2016 recorded higher values than 2022, with the implication that since 2016, KKCFR could have lost some shrub and liana species perhaps due to human activities.
A total of 57 vines and herbs species were recorded in KKCFR between 2016 and 2022 study periods. Forty-seven vine and herb species were recorded in 2016 while forty-six vine and herb species were recorded in 2022. Of these, the most dominant vine and herb species in descending order Oplismenus hirtelleus, Panicum adenophorum, Panicum adenophorum, Pteendium aquilium, Palisota mannii, Panicium sp., and Asplenium sp.
The relative abundance of the vines and herbs (expressed per unit hectare) were significantly different between 2016 and 2022. Species evenness and richness of the vines and herbs was higher in 2016 than in 2022 perhaps a result of human activities in KKCFR.
A total of 9 rodent species were recorded in KKCR between 2016 and 2022 study period. In 2016, nine species of rodents were recorded while in 2022, only five species of rodents were recorded. Of these, the most dominant rodent species in descending order were Malacomys longipes, Praomys jacksonii, Praomys jacksonii, Laphuromys sp and Syvisorex grantii.
The relative abundance of the rodents (expressed per unit hectare) was not significantly different between 2016 and 2022. Furthermore, the rodents’ species evenness and richness were slightly higher in 2016 than in 2021 perhaps caused by human activity impacts.
A total of 135 bird species were recorded in KKCFR in both 2016 and 2022 study time periods. In 2016, 81 bird species were recorded, while in 2022 110 bird species were detected. Three species are endemic to the mountains along the Albertine Rift - Blue-headed Sunbird Cyanomitra alinae, Red-faced Woodland Warbler Phylloscopus laetus, and the Yellow-eyed Black Flycatcher Melaenornis ardesiacus.
The most common bird species encountered were the Tambourine Dove Turtur tympanistria, Yellow-whiskered Greenbul Eurillas latirostris, Yellow-rumped Tinkerbird Pogoniulus bilineatus, African Paradise- flycatcher Terpsiphone viridis, Common Bulbul Pycnonotus barbatus, Montane Oriole Oriolus larvatus, and Narina Trogon Apaloderma narina.
Due to the heterogeneous habitat created by disturbance being taken up by large numbers of successional or opportunistic species, while precluding some primary forest specialists, the species richness and density were higher in 2022 than 2016. However, the species diversity, evenness and dominance were lower in 2022 than in 2016.
This could be attributed to the ongoing severe but localized human disturbances in our study area that made the birds to frequently move between different sites while feeding or breeding so that their populations were unstable and transient with a few residents. Increased forest disturbance created more forest edge, tree fall gaps and secondary forest that favour the forest generalists (F-species).
Therefore, the F-species increased in number of species and density. However, the F-species are of low conservation value since they are widely distributed. The forest interior specialists (FF-species) were found to be declining.
Increased forest canopy openings and vegetation density at ground level because of disturbance favour the frugivores and mixed feeders. However, the flycatchers, forage gleaners and ground feeders were adversely affected by changes in the microclimate caused by forest disturbance.
The understory insectivores – flycatchers, forage gleaners and ground feeders - that are highly susceptible to forest disturbance can be useful as indicators of forest disturbance impacts. KK has not been colonized by forest visitors (f-species) of non-forest and edge habitats. This probably implies that the vegetation structure and composition of the CFR has only been moderately modified.
The two harvested tree species of Warbugia ugandensis and Zanthoxylum gilleti for bark showed a population distribution with very many seedlings and juveniles but fewer harvestable mature or adult individuals (those >11.5cm). Of the 196 tree species of Warbugia ugandensis sampled, only 36% had not been harvested for bark while 45% had been totally ringbarked.
Furthermore, of the 67 Zanthoxylum gilleti trees sampled, 41% had not been harvested for bark and 33% had been ringbarked. This study shows that there is an unsustainable/uncontrolled harvest of bark from the two trees in KKCFR and this is detrimental to the survival of those trees.
The most prevalent human activities recorded in KKCFR for both 2016 and 2022 in descending order were fresh human trails, firewood collection, tree bark harvest and charcoal burning. The number of human activity signs recorded in KKCFR increased from 29 in 2016 to 102 in 2022 and was statistically significant.
This study also observed the active replacement of natural forest patches with eucalyptus plantation by NFA. The human activities in KKCFR have been increasing with increased demand of forest resources exacerbated by the human population growth of the surrounding local communities.
Without a doubt, the human activities within the KKCFR have more than tripled and are likely to increase further as the human population increases and with the increased commercialization of forest resources (bark harvests and charcoal burning). This is a precursor to the increased loss of biodiversity in the KKCFR.
Although the biodiversity loss is not yet at an alarming wide scale, the loss of some flora and fauna species since 2016 is of particular concern to conservationists. Several recommendations have been suggested by this study that includes enhanced strict law enforcement in KKCFR and proactively encouraging agroforestry activities in the local communities around KKCFR by development organizations.
Bark harvest from the trees of Warbugia ugandensis and Zanthoxylum gilleti should be strictly by NFA with guidelines of dos and don’ts to help sustain the bark harvest and the two tree species.