Plant Diversity, Regeneration Dynamics, and Socio-Ecological Impacts at the Forest-Savanna Transition Zone, Cameroon

Study Area and Periods

This study was carried out in Lom Pangar in Deng Deng village, Belabo Subdivision, Lom and Djerem Division, East Region of Cameroon. It is a watershed located in Cameroon in major part precisely within the East and Adamaoua regions with a small part in the Central African Republic, a country that borders Cameroon in its eastern part. That geographical location gives Lom Pangar the characteristic of transboundary river basin of surface area 19700 km2. The Lom River runs throughout Central Africa Republic for about 5 km around before reaching the Cameroonian territory. The study area is located between latitudes 4o10′′00N and 7o11′′00N and longitudes 13°30′′00E and 15o02′′00E Figure 1.

In the tropical region like Deng characterized by a sub- equatorial climate with four seasons, semi-deciduous forest, and Savanna vegetation, temperature range from 20oC to 30oC throughout the year, while the average annual rainfall amounts to about 2,921, with the wettest month typically seeing around 212mm of rainfall. The geology consists of deeply weathered ferritic soils, and the relief is characterized by gentle rolling terrain.

Since 2016, a hydropower reservoir has been constructed at the outlet of Lom Pangar River basin in the forestry part of East Cameroon. The population and the environment are trapped in a brutally changing lifestyle with this construction, together with the Deng Deng National Park. The Lom Pangar hydropower dam for instance is located at about 350 km to the Northeast of Yaoundé, the capital city of the country and precisely at around 120 km from the capital city of the East region, Bertoua. The site of the Dam in the Lom River is 5 km downstream from the confluence of Lom and Pangar rivers, and around 13 km to the East of the confluence of the rivers Lom and Djerem. The geographical location of the Dam is: latitude N 05o 25′′, longitude E 13o 30′′ and has for main purposes, the regulation of the Sanaga river to increase the power generation of two hydropower plants located downstream during the dry season and the generation of 30

MW of power onsite, for the eastern grid of Cameroon. It has a 50-meters height and a 610 km2 size with a storage capacity of six billion m3. Unfortunately, these dynamic changes have significantly altered the local ecosystem, displacing communities, affecting traditional hunting and fishing practices, distortion of the agricultural calendar forcing farmers to adapt to new climatic conditions, a reduction in territory, overhunting and illegal exploitation, flooding of the surrounding rivers which affects flora and fauna across different zones. The study was conducted within the Forest- Savanna Transition Zone of Cameroon, focusing specifically on the zone of influence (Right-of-Way) of the Chad-Cameroon pipeline project corridor which was constructed in 2003 and sections adapted in 2016 to accommodate the dam project. This area is characterized by a mosaic of semi-deciduous forest patches, wooded savannas, and ecotonal landscapes, representing a biologically sensitive interface subject to significant development pressure. Field data collection was carried out in February 2020. The selection of specific communities and sites within the corridor were determined by their proximity and accessibility to the pipeline route and their known reliance on forest resources and NTFPs.

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Research Design

This study adopted a convergent parallel mixed-methods research design. This approach was necessary to achieve a holistic understanding of the complex socio-ecological system by concurrently collecting and analyzing: (1) Quantitative Ecological Data (on plant diversity and regeneration); (2) Quantitative Socio-Economic Data (on resource reliance patterns); and (3) Qualitative Ethnobotanical Data (on community knowledge and perceptions). The findings from all three data streams were integrated during the interpretation phase to provide a robust, triangulated analysis of ecological sensitivity, human-environment interactions, and the effectiveness of conservation measures. Quantitative Field Sampling and Data Collection Ecological and Floristic Survey (Objectives 1 and 2): To fulfill the primary ecological objectives of assessing diversity and regeneration, multiple lines transect were established perpendicular to the pipeline corridor to capture the transition gradients across forest, ecotone, and savanna plant communities. Along these transects, all woody individuals (diameter at breast height, DBH ≥10  cm) were identified, measured, and recorded to quantify floristic diversity, density, and vegetation structure. Within each transect, multiple quadrats (10 m×10 m or smaller nested plots) were systematically established. These plots were used for the detailed census of natural regeneration, including seedlings (height <1  m) and saplings (DBH <10  cm), to assess the recruitment success and regeneration potential of dominant and sensitive species.

Socio-Economic and Ethnobotanical Survey (Objective 3): A structured questionnaire was administered to a total of 300 community members (aged 18 years and above) who were permanent residents in selected communities along the pipeline’s zone of influence. A stratified random sampling method was used to ensure representativeness, with strata defined by distinct communities or geographical segments along the pipeline corridor. This ensured the capture of variations in resource availability, reliance patterns, and exposure to challenges. Within each stratum, households were selected using a simple random sampling technique. The sample size for the socio-economic survey was calculated using Cochran’s sample size formula (Barlett et al. 2001) for the required sampled size (n0​):

n0​=d2t2s2​ Where: t = z-value for selected alpha level (0.10, or 90% confidence level) s = estimate of standard deviation (1.65) d = acceptable margin of error (0.03) The finite sample population size (n) was then calculated from the total population (N) using the formula: n=n0​/(1+(n0​ /N)). This calculation guided the proportional allocation of questionnaires based on the population size of each sampled community. For instance, in a community with a population of 2,000, 156 questionnaires were administered.

Qualitative Data Collection and Triangulation

Qualitative data was collected to complement and triangulate the quantitative findings, particularly concerning the socio-economic reliance on NTFPs and the mechanisms of local resource governance. A total of 8-10 in-depth interviews were conducted with a diverse range of stakeholders whose expertise was critical to the study’s objectives. These included local chiefs, elderly community members knowledgeable in ethnobotany and local history, environmental agency representatives, agricultural extension workers, and local NTFP collectors.

A total of six FGDs were organized across the sampled communities, designed to complement information on knowledge, beliefs, attitudes, and perceptions. Participants were grouped considering factors such as gender, age group, and occupation (farming, fishing, NTFP collection).

A trained facilitator guided the discussions, supported by a note-taker and non-verbal behavioral observer.

Field observations were systematically conducted to record visual evidence related to land use, signs of ecological disturbance (erosion, invasive species along the pipeline ROW), and resource extraction activities. A GPS camera was used to collect geographic data on major sampling points and culturally valued sites (NTFP harvest zones) for mapping purposes. A comprehensive desktop review synthesized existing information from peer-reviewed literature, government reports, and national statistics were explored to provide contextual and baseline data.

Data Analysis and Presentations

Both quantitative and qualitative analysis methods were employed. For quantitative data analysis, data from the ecological surveys and structured questionnaires were coded and entered into the Statistical Package for the Social Sciences (SPSS) software (Version 23.0). Descriptive Statistics (frequencies, percentages, means and standard deviations) were generated using Microsoft Excel (Version 23.0) and SPSS to profile respondents, describe floristic composition, and quantify reliance patterns. Inferential Statistics, including Chi-square tests and Pearson correlation, were employed to formally test hypotheses and examine relationships between variables (correlation between distance from the pipeline and NTFP diversity; relationship between land use type and regeneration success).

For qualitative data analysis, audio recordings from interviews and FGDs were transcribed verbatim. The qualitative data was analyzed using a thematic analysis approach, involving familiarization, initial coding, searching for themes, reviewing themes, defining and naming themes, and producing the report. This identified recurring patterns, perceptions, challenges, and nuanced perspectives on resource use and mitigation efforts. Results were presented using a combination of tables, figures, maps, and narrative descriptions, supported by direct quotes from interviews and FGDs to illustrate key themes.

Ethical Considerations

Prior to commencing data collection, ethical approval was obtained from the University of Yaoundé 1 Ethic Committee for Research within the Plant Biology Department. All participants were provided with comprehensive information about the study’s purpose, objectives, and methods, and informed consent was obtained either verbally or in writing before any data collection began. Participants were assured of their voluntary participation and their right to withdraw at any time.

Floristic Diversity and Vegetation Structure

Overall Diversity and Composition: The ecological survey along the pipeline corridor identified a total of 215 plant species belonging to 58 families and 149 genera. The most dominant families, both in terms of species richness and abundance, were Fabaceae (35 species, 16.3% of total flora), Euphorbiaceae (18 species), and Malvaceae (12 species). The overall Shannon-Weiner Diversity Index (H′) was 3.58, indicating moderately high species heterogeneity across the sampled communities Table 1.

As seen on Table 2, the Ecotone/Transition zone exhibited the highest species richness (H′=3.71) compared to the core Forest Patches (H′=3.89), primarily due to the co- occurrence and overlap of fire-tolerant savanna species and shade-tolerant forest species, corroborating the expected “crossroads” phenomenon. Conversely, the Savanna patches displayed the lowest diversity (H′=3.15) but contained a unique suite of pyrophytic and drought-resistant flora. The Ecotone/Transition zone acts as a mixing bowl, or an evolutionary and dispersal overlap zone, where the floras of two major biomes intermingle. Shade-tolerant, zoochorous (animal-dispersed) species that depend on higher humidity and canopy closure for establishment (Terminalia superba juveniles) persist as remnants or successful recruits in the more sheltered niches. Fire-tolerant, pyrophytic, and drought- resistant species that thrive in open conditions (Vitellaria paradoxa, Crossopteryx febrifuga). Furthermore, the fragile balance maintaining this co-occurrence is highly susceptible to change; clearing the ROW can instantly eliminate the shade necessary for forest species to survive in the ecotone, leading to localized extinction of the forest guild and a shift toward savanna dominance. The Savanna environment is inherently harsher, characterized by intense dry seasons, nutrient-poor soils, and high-frequency disturbances (fire and draught). This severe environmental filter excludes most forest species, limiting the overall richness to a highly specialized set of flora. The NTFPs found here (Shea butter from Vitellaria paradoxa) are often resilient, providing a more stable, albeit limited, resource base for communities during periods of ecological stress.

Natural Regeneration Dynamics

Regeneration Density and Success: The analysis of regeneration density shows that plant recruitment follows a distinct ecological gradient across the study area. Specifically, the high mean density of 1,520±180 individuals per hectare observed in the core Forest Patches indicates a healthy, multi-storied ecosystem where conditions like shade, moisture, and rich leaf litter are optimal for continuous seed germination and seedling survival, thus signifying a stable, late-successional community Table 3. In contrast, the much lower density of 580±95 individuals per hectare in the open Savanna Patches is attributed to a severe environmental filter, where intense drought, high light, and frequent fires impose a significant bottleneck on seedling establishment, limiting the population to only the most specialized, fire- tolerant individuals. The most crucial finding, however, lies in the regeneration success ratio—,the density of recruits relative to the parent population—,which quantifies the localized impact of the pipeline corridor. In the relatively undisturbed Forest Patches, the success ratio for key timber species like Piptadeniastrum africanum stands at a robust 0.45, indicating a healthy capacity for long-term population stability and self-replacement.

Table 3: Mean Regeneration Density across Vegetation Zones. Source: Fieldwork, 2020 This stability is fundamentally compromised in the Ecotone Right-of-Way (ROW), where the success ratio plummets to a mere 0.12. This dramatic 73% reduction in successful recruitment signifies a profound ecological recruitment failure that the system is currently unable to reverse through natural means. This failure is driven by several compounding mechanisms: physical obstruction and soil compaction resulting from construction mechanically destroy existing regeneration and severely inhibit new root penetration; the loss of canopy creates a sudden microclimate shock—,characterized by increased temperature and decreased humidity—,which is lethal to shade-dependent forest seedlings; , and the newly exposed ground facilitates rapid competition from opportunistic pioneer species, which ultimately stalls the natural successional process toward the original community structure. Consequently, for a slow-growing, high-value species like P. africanum, a ratio of 0.12 implies that the current mature population has an insufficient juvenile base established. Without immediate, active restoration, this failure translates directly into a time- delayed local extirpation as the existing adult trees senesce and dies off, demonstrating a clear and concerning break in the species’ life cycle within the infrastructure corridor.

Species Composition of Regeneration: The analysis of the regenerating plant community reveals a profound imbalance in species representation, which underscores the disruptive nature of the pipeline construction and portends long- term negative consequences for ecosystem function and economic value. The regeneration cohort in disturbed areas, specifically the Ecotone Right-of-Way (ROW), is numerically dominated by fast-growing, pioneer species such as Musanga cecropioides (Umbrella tree) and Macaranga spp. These species constituted up to 45% of all recorded seedlings in these disturbed plots. This pattern suggests that the ecosystem has been reset to an early stage of secondary succession, where the priority is to quickly cover the exposed soil. Pioneer species are characterized by high growth rates, light-demanding nature, wind-dispersal, and short lifespans. Their dominance indicates that the environmental conditions in the ROW—namely, high light exposure, bare soil, and rapid nutrient turnover—have filtered out the original, slow-growing forest species. This is a typical post- disturbance signal, where the system’s initial recovery phase prioritizes biomass accumulation and structural recovery over the restoration of original species diversity.

While the rapid growth of pioneers provides essential ecosystem services (stabilizing soil, shading the ground, and creating microhabitats), their short-term dominance shows that natural succession is currently arrested at a ruderal stage by recurrent disturbance. These pioneers are acting as a temporary “nursing canopy” rather than being the final, desired component of the forest structure. The most critical ecological and economic implication is the critically low regeneration of climax and high-value timber species, alongside a significant reduction in economically important NTFP species. This finding demonstrates that natural recovery is failing to restore the fundamental economic and ecological value of the stand structure attributable to the sustained disturbance of the pipeline corridor initially in 2003 and then in 2016 during the adaptation and dam project and followed by regular clearance of a reduced maintenance footprint.

The statistically significant lower regeneration of NTFP species in the ROW compared to intact areas (Chi-square test, χ2=18.3,p<0.001) confirms that the infrastructure project has not only reduced current harvests but has also compromised the future supply of vital community resources. This loss represents a long-term economic burden on local communities, as the absence of NTFP seedlings today translates to a lack of harvestable resources for the next generation. The original climax species (those that define the mature forest’s ecological status, such as deep-rooted trees providing long-term carbon storage and complex habitat structure) are being outcompeted or are failing to establish due to the changed microclimate. This implies that the recovered ecosystem will be floristically impoverished and functionally simplified for decades. The structure of the recovered forest will be less dense, less diverse, and provide fewer ecosystem services associated with a mature forest.

Ecological Sensitivity and Socio-Economic Reliance (Objective 3)

NTFP Abundance and Distribution: The survey revealed no permanent settlements in the study area, but temporary settlements of pastoralists and camps of hunters and fishermen were identified. The ethnobotanical survey, supported by field inventory, identified diverse plant species actively harvested as NTFPs. The most frequently cited and economically important NTFPs were: Irvingia gabonensis (Bush Mango), Ricinodendron heudelotii (Njansang) and Gnetum africanum (Eru/Okok). Others include Xylopia aethiopica, Canarium schweimfurthii Tetrapleura tetraptera, Erythrophleum suaveolens and Voacanga africana, were frequently observed. Hunting and subsistence fishing were also practiced in the area. The botanical survey identified three main habitat types: typical forest, swamp/seasonally inundated forests, and savanna. A total of 101 tree species were recorded, with no species listed as threatened by the IUCN Table 4. The natural regeneration quadrats revealed high diversity indices in the forest areas, but poorer diversity in the forest-savanna transition areas.

Table 4: Floristic Composition and Conservation Status of Recorded Plant Species. Source: Fieldwork, 2020 Table 3 presents the list of all woody plant species identified during the field survey, categorized by their primary habitat affiliation to illustrate the floristic makeup of the forest-savanna transition zone The universal Least Concern (LC) status also indicates that while these species are not globally threatened with extinction, their local abundance, distribution, and functional role within the pipeline corridor are highly threatened.

Key Fauna Species Encountered and Associated Risks The fauna survey identified various species of ecological importance, including mammals, birds, reptiles, and invertebrates categorized by their conservation risk level and the primary threats they face, demonstrating the pipeline corridor’s role as a major source of ecological pressure on animal populations Table 4a.

Table 4(a): Key Fauna Species Encountered and Associated Risks. Source: Fieldwork, 2025 As seen on Table 4, the presence of “High Risk” species— particularly the African Elephant (Loxodonta africana), Western Lowland Gorilla (Gorilla gorilla gorilla), and Giant Ground Pangolin (Manis gigantea)—confirms the high conservation value of the area. The corridor, therefore, cuts across critical habitats used by globally significant and protected megafauna. The inclusion of multiple species of Duikers and Monkeys highlights the high biomass and diversity of both arboreal and terrestrial mammal’s characteristic of the forest-savanna ecotone. The identified threats directly relate to the presence of the pipeline and associated infrastructure, and the associated fragmentation of the landscape is linked to increased accessibility. The pipeline’s maintenance ROW acts as an easy access route for hunters, particularly for target species such as duikers, Red River Hogs, the valuable Pangolin and Gorilla. The high number of species listed under this threat underscores the need for enhanced anti-poaching patrols along the corridor. This threat is directly related to habitat fragmentation and increased traffic. The pipeline maintenance roads and the linear clearing forces animals to cross an open area, exposing them to vehicle collision, particularly medium-to-low risk species like rats and squirrels, which have shorter flight distances. The high frequency of this threat indicates that the ROW is functioning as an ecological trap for moving fauna.

The inclusion of the Crested Turaco (Corytheola cristata) highlights the diversity of threats, where even a bird species is targeted for specific human uses (“poaching for feeders”), demonstrating the broad impact of human activities on wildlife resources in the area. The distribution of mature, harvestable NTFP species was significantly lower (Pearson r=−0.68,p<0.01) in communities that were in direct proximity to the permanent pipeline ROW than in communities further away. Qualitative interviews confirmed that the pipeline construction and other infrastructure development like the dam led to the direct loss of key NTFP source trees and increased pressure on remaining, accessible patches.

Tables 5 and 6 provide crucial quantitative metrics for assessing the ecological impact of the disturbance, specifically by comparing the post-disturbance Regeneration plots (within the Ecotone Right-of-Way, ROW) to the Control plots (adjacent, intact forest/ecotone).

As seen in Table 5, based on the Shannon Diversity Index (H′), the Control plots exhibit a higher diversity index (H′=3.2) than the Regeneration plots (H′=2.8). The Shannon index measures both species richness (the number of different species) and species evenness (how equally abundant each species is). The lower value in the Regeneration plots confirms that the disturbance—the pipeline corridor clearing—has negatively impacted the overall complexity of the plant community. However, based on Pielou’s Equitability Index (J′), The Control plots have a higher equitability index (J′=0.75) compared to the Regeneration plots (J′=0.7). Hence, Equitability (or Evenness) measures how uniform the abundance of species is. A value closer to 1.0 indicates that all species are present in roughly equal numbers. The lower J′ in the Regeneration plots further supports the observation that the community structure is unbalanced. The disturbance has favored the rapid proliferation of a few pioneer species at the expense of others, leading to a less equitable distribution of individuals among species. This confirms that the ecosystem is in a state of stress and early secondary succession.

Table 6: Jaccard and Sorensen similarity indices for regeneration and control plots. Source: Fieldwork, 2020 Based on the Jaccard Similarity Index (Cj​), result noted that the Jaccard index value is 0.65 (or 65%). This index only considers the presence or absence of species. A value of 0.65 suggests a relatively high degree of shared species identity between the disturbed (Regeneration) and intact (Control) plots. This high value indicates that the Regeneration plots still contain a large proportion of the same species found in the original forest/ecotone community, meaning the disturbance has not yet caused massive, widespread local extinction of species identity.

Based in the Sorensen Similarity Index (Cs​) on Table 6, the Sorensen index value is 0.79 (or 79%). This is often considered more sensitive than Jaccard because it gives more weight to shared species. The slightly higher Cs​value suggests that the most abundant species in the two plots are largely the same. While the similarity indices are relatively high (65−79%), indicating that the species pool is intact, the diversity indices (H′ and J′) clearly show that the relative abundance (or quantity) of individuals within those species has changed dramatically.

Community Reliance and Socio-Economic Implications: The socio-economic survey on the respondents provided statistical evidence of the communities’ reliance patterns as presented in Table 7.

Table 7: Community Reliance and Socio-Economic Implications. Source: Fieldwork 2020 Table 7 provides compelling statistical evidence of the high and multifaceted dependence of the communities on NTFPs, demonstrating their critical role in both daily subsistence and economic stability. Fuelwood/Charcoal is the single most essential resource, with 98.10% of households relying on it. This percentage underscores the absolute dependence on forest resources for basic energy needs (cooking, heating), confirming that the forest is the primary energy source in the study area. This category provides the second largest financial contribution at 12%. Although fuelwood is slightly more relied upon, the Food (Fruits, Vegetables) category contributes the largest share to household income, accounting for 25% of the average household’s total earnings. These points to the importance of selling surplus wild fruits and vegetables (bush mango, leafy greens) as key income-generating activities and a safety net for local economies. Reliance on Food (Fruits, Vegetables) is also near-universal at 91.30%, highlighting the fundamental importance of wild harvests for dietary diversity and direct food security. Medicinal Plants show a very high reliance of 85.70%, indicating that traditional knowledge and remedies derived from the forest are a vital, primary source of healthcare for the vast majority of the population. Despite 85.70% reliance, medicinal plants show a 0% mean contribution to household income. This result confirms that these resources are overwhelmingly utilized for non-market, direct subsistence purposes (healing and cultural practices). Inferential statistics (Chi- square test) demonstrated a strong positive relationship (χ2=35.1,p<0.001) between the perceived degradation of the forest-savanna ecosystem and a reported increase in travel time (mean: from 35 min to 95 min) to collect essential NTFPs Table 8. This statistical evidence validates the qualitative finding that ecosystem degradation has directly resulted in livelihood disruption. This tripling of time represents a significant increase in labor cost and a decrease in household efficiency. The additional hour spent collecting resources is time that cannot be dedicated to other essential activities like farming, education, or earning cash income.

This result provided on Table 8 presents a crucial bridge between the ecological metrics (like reduced regeneration success) and the socio-economic impacts Table 7, establishing a clear causal chain where environmental harm directly impairs human well-being.

Stakeholder Perceptions and Management Gaps: Thematic analysis of the FGDs and Key Informant Interviews revealed three core themes concerning the human- environment interaction along the corridor with mitigation measures, ranging from avoidance and minor re-routing to in-situ preservation and monitoring. For example, the study recommended avoiding the felling of significant trees and implementing speed limits on project roads to reduce vehicle collisions with wildlife as seen on Table 9.

Results in Table 9 highlighted that while the pipeline construction damage was inevitable, the failure to integrate NTFP management and leverage local regeneration knowledge represents a persistent policy and implementation gap that continues to compromise the long-term ecological and social sustainability of the forest-savanna transition zone.