Semi-deciduous Forest In Ghana Research Articles

Selective and clear-cut logging have varied imprints on tree community structure in a moist semi-deciduous forest in Ghana

Logging-induced disturbance can be an important agent of change in tropical forests. Understanding the relative impacts of specific logging regimes on tree community structure is essential for forest management and biodiversity conservation. In this study, we assessed the response of tree community structure to selective and clear-cut logging in a moist semi-deciduous forest in Ghana. We quantified the diversity, composition, density and basal area of trees (diameter at breast height ≥5 cm) in 30 20 × 20 m plots in each of three forest management systems (selectively logged, clear-cut logged, old-growth). Our results showed that the two logged forests harboured significantly lower tree species diversity than the old-growth forest. Nevertheless, the selectively logged forest supported significantly higher tree species diversity than the clear-cut logged forest. Similarly, both logging regimes caused shifts in tree species composition, but the shift was higher in the clear-cut forest than the selectively logged forest, indicating a better recovery in the selective logging stands. Selective and clear-cut logged forests supported similar stem density of trees, but they were lower than that of the old-growth forest. Finally, the old-growth forest exhibited significantly higher basal area than the selectively logged forest, which in turn, had significantly higher basal area than the clear-cut logged forest. Overall, selective logging imprints on tree community structure were lower than clear-cut logging due to faster recovery by the former. Our findings suggest that logged tropical forests may require a long period to fully recover.

Sustainability of Mahogany Production in Plantations: Does Resource Availability Influence Susceptibility of Young Mahogany Plantation Stands to Hypsipyla robusta Infestation?

Hypsipyla robusta Moore (Lepidoptera: Pyralidae), like many other moth species, shows selectivity when choosing host plants for its eggs. Four Meliaceae species (Khaya grandifoliola, K. ivorensis, Swietenia macrophyla, and Entandrophragma cylindricum) were established in a moist semideciduous forest in Ghana to study this selectivity at 12 and 21 months after planting. The analysis of variance (ANOVA) at aP-value of 0.05 was used to test the significance of differences in infestation by H. robusta between the species. H. robusta attacks were recorded by month 12 after planting in the field, and only Khaya spp. was attacked, with attacks evident on 15.5% of K grandifoliola and 6.6% K. ivorensis. Saplings in blocks closer to an older H. robusta infested K. grandifoliola stand had more infestation compared to saplings further away. The mean percentage of K. grandifoliola attacked was 38.9%, 38.9%, 13.3%, and 7.4% in 4 different plots located increasingly further away from the older infested plantation. A similar trend was found in K. ivorensis with 28.4%, 7.1%, 0.0%, and 0.0% in the plots located increasingly further away from the infested stand. These results indicate a higher number of shoot borer attacks at the edge of the plantation and in proximity to other infested plantations. After 21 months, the fastest-growing species and the fastest-growing individuals within the species were the most infested. K. grandifoliola recorded the fastest growth and most attacks followed by K. ivorensis and S. macrophylla. E. cylindricum recorded the least growth and no H. robusta infestation. After 21 months, the mean percentages of trees attacked were 59.1%, 23.7%, 5.6%, and 0.0% for K. grandifoliola, K. ivorensis, S. macrophylla, and E. cylindricum, respectively. Within species, the fastest-growing saplings experienced the most attacks. A positive correlation was observed between the plant size and H. robusta attacks (R2 = 0.76). Attacks resulted in the death of the apical shoot and the proliferation of multiple shoots in only the Khaya spp., with K. ivorensis recording a lower number of shoots than K. grandifoliola. These proliferated shoots were also attacked, and a positive correlation was observed between the number of proliferated shoots and H. robusta attacks (R2 = 0.84). These findings will assist plantation developers, forest managers, and investors in mahogany plantations to devise integrated pest management strategies to reduce the impact of Hypsipyla attacks on their plantations.

Selective and Clear-Cut Logging Have Varied Imprints on Tree Community Structure in a Moist Semi-Deciduous Forest in Ghana

Selective and Clear-Cut Logging Have Varied Imprints on Tree Community Structure in a Moist Semi-Deciduous Forest in Ghana

Forest recovery on skid trails and felling gaps following post-decadal selective logging in a moist semi-deciduous forest in Ghana

While several studies have been conducted on the impacts of logging on forest recovery in tropical forests, most of these studies have largely focused on short term forest recovery and without perspectives on how different logging intensities could influence the nature and extent of forest recovery in the long term. This study therefore aims to explore how varying site conditions, resulting from the creation of different disturbance types (skid trails and felling gaps) following selective logging at two logging intensities influenced long-term floristic composition eighteen years after logging. The study was conducted in the permanent sample plots located in a 134-ha compartment in the Pra-Anum Forest Reserve. Data collection was conducted on 160 recording plots distributed on three disturbance sites and an unlogged area, within two blocks of logging intensity of 26.32 m3/ha and 52.63 m3/ha (representing the volume of trees harvested per hectare). Results showed that the main skid trail had significantly lower species abundance and richness than the other disturbance types and the unlogged area. There was also a significant difference in species spatial distribution across all the four sites. These distribution patterns revealed differences in plant dominance at disturbance gradients, which indicate their success at competing for available resources within their niche space. Furthermore, the number of species belonging to particular ecological guilds classified from the different skid trails and unlogged areas as well logging intensities showed no significant variation. However, most of the species sampled across the disturbance regimes and unlogged area were observed to be shade tolerant. Logging disturbance and logging intensity did not influence the distribution of trees of national conservation importance (based on tree distribution, ecology, local abundance, interaction with ecosystem parameters and economic importance which have been used as basis conservation prioritization). However, disturbance type and higher logging intensities favoured tree species of minimal timber and national conservation importance, relative to the unlogged area. Given the increasing demand for timber products for both domestic and international markets, which is driving higher harvesting intensities legally and illegally, this study will inform forest management decision making on the long term dynamics of tree species recovery following logging.

Logging effects on seedling regeneration and diversity in a tropical moist semi-deciduous forest in Ghana

ABSTRACT The effect of time lag after logging on seedling dynamics was assessed in logged and unlogged forest plots located in the Pra-Anum Forest Reserve. Remnant tree attributes were sampled in six plots with sizes of 25 × 25 m in each forest type. Within each forest type, ten subplots with sizes 1 × 1 m were established for sampling seedling regeneration dynamics. Enumerated seedlings were grouped as pioneer, non-pioneer light demander, and shade-tolerant species. Regenerating seedlings were more diverse in the recently logged forest area characterised by Broussonetia papyrifera and Musanga cecropioides, and least in the unlogged forest driven predominantly by Celtis mildbraedii and Baphia nitida. Pioneer species were primarily dominant in the recently logged forest, while shade-tolerant and non-pioneer light-demanding species characterised the logged-over forest. Species richness and canopy openness of remnant stands explained 32 percent of the variations in regeneration richness between the logged and unlogged areas. Twenty-seven percent of the variations in seedling abundance was also explained by remnant trees richness, their size diameter and the degree to which their canopy has been opened. Logging-induced disturbance favours the sporadic emergence of pioneer species in recently disturbed areas which are later replaced by non-pioneer light-demanding or shade-tolerant species as light becomes limiting in the understory.

Wildfires cause shifts in liana community structure and liana-soil relationships in a moist semi-deciduous forest in Ghana

Lianas play significant ecological roles in tropical forest ecosystems, so knowledge of the factors that affect them is key to forest management. Nonetheless, there is limited information on how wildfires influence liana communities. This study therefore sought to determine the effects of wildfires on liana community structure and liana–soil associations in the Asenanyo Forest Reserve, Ghana. Thirty plots (20 × 20 m) were established in each of three forest stands (9-month-old burnt, 15-year-old burnt, unburnt) and sampled for lianas (diameter at 1.3 m from the rooting base ≥ 1 cm). Liana diversity, abundance and basal area were significantly lower in the two burnt forest stands. The 15-year-old burnt forest supported significantly higher values for these liana community attributes than the 9-month-old forest. There was a shift in liana species composition towards a more homogenized composition in the burnt forest. Liana–soil associations differed between the unburnt forest on the one hand and the two burnt forests on the other. Thus, in all, fire caused shifts in liana community structure and liana–soil associations in the forests. The findings of the study have implications for liana, fire and forest management.

Influence of management practices on stand biomass, carbon stocks and soil nutrient variability of teak plantations in a dry semi-deciduous forest in Ghana

Many forest plantations in the tropics are not well managed due to lack of resources and sometimes expertise; but if plantations are to fulfill their expected usefulness especially for climate change solutions, then best practices should be used. However, more data is required to demonstrate the gains that can be made in the various end uses of plantation-grown timber and the soils on which they are grown to encourage good practices among growers. The current study compared biomass, carbon stock accumulation and soils nutrient levels in an intensively managed (IMP) and less intensively managed (LIMP) teak plantation in Ghana. The data were collected from 10 sampled plots from each plantation type. The IMP significantly accumulated biomass and carbon stocks than the LIMP; however, LIMP had a higher number of forked trees than the IMP. Mean percentage of nitrogen, cation exchange capacity and concentrations of Mg, Ca, K, Na and Al were also higher under the IMP than the LIMP. Our results show that management practices have a significant effect on stand characteristics as well as the soils on which stands grow and therefore forest managers must endeavor to apply intensive management practices to optimize plantation benefits.

Changes in liana community structure and functional traits along a chronosequence of selective logging in a moist semi-deciduous forest in Ghana

ABSTRACTBackground: Lianas are an important component of tropical forests that respond to logging disturbance. Determining liana response to selective logging chronosequence is important for understanding long-term logging effects on lianas and tropical forests.Aims: Our objective was to quantify the response of liana communities to selective logging chronosequence in a moist semi-deciduous forest in Ghana.Methods: Liana community characteristics were determined in ten 40 m × 40 m plots randomly and homogenously distributed in each of four selectively logged forest stands that had been logged 2, 14, 40 and 68 years before the surveys and in an old-growth forest stand (ca. >200 years).Results: Liana species composition differed significantly among the forest stands, as a function of logging time span, while species richness fluctuated along the chronosequence. The abundance of liana communities and of reproductive and climbing guilds was lower in the logged forests than in the old-growth forest. The ratio of liana abundance and basal area to those of trees was similar in the logged forests, but significantly lower than those in the old-growth forest.Conclusions: Logging impacts on liana community structure and functional traits were largely evident, though no clear chronosequence trends were recorded, except for species composition.

Suitability of Chrysophyllum albidum from moist semi-deciduous forest in Ghana as a raw material for manufacturing paper-based products

ABSTRACTThe global demand for paper-based products continues to increase amidst challenges with raw material supply to the pulp industries. Considerable efforts to discover new wood resources from tropical forests to widen the material stock are ongoing. This study examined the suitability of the outer and inner wood fibres from different axial sections (i.e., butt, middle and top) of Chrysophyllum albidum from a moist semi-deciduous forest in Ghana for paper production. The fibre morphology and derived indices [i.e., Runkel Ratio, Slenderness Ratio, Flexibility Coefficient, Coefficient of Rigidity, Luce’s Shape Factor and Solids Factor] were determined using the methods by the International Association of Wood Anatomist. C. albidum inner and outer wood fibres were generally long and thin with wide lumen. The fibre-derived indices were similar to those of many popular paper-producing timbers such as Acacia mangium and Pinus sylvestris. The fibre morphology and derived indices of C. albidum meet the recommended thresholds for fibres for manufacturing writing and printing papers with good tearing and bursting strength properties. Thus, the wood’s fibres would be suitable for producing papers with good strength properties. Its utilization will contribute to expanding the raw material sources for the pulp and paper industry.

Variability in modern pollen rain from moist and wet tropical forest plots in Ghana, West Africa

How pollen moves within and between ecosystems affects factors such as the genetic structure of populations, how resilient they are to environmental change, and the amount and nature of pollen preserved in the sedimentary record. We set artificial pollen traps in two 100 m by 100 m vegetation plots, one in a wet evergreen forest, and one in a moist semi-deciduous forest in Ghana, West Africa. Five traps from each plot were counted annually from 2011 to 2014, to examine spatial and temporal variation in the pollen rain of the most abundant taxa shared between pollen and vegetation assemblages. Samples from the wet evergreen plot exhibited high variability within years, with the dominant pollen types changing between samples, and many pollen taxa being over-represented relative to their parent plant abundance in some traps whilst being entirely absent from others. The most abundant plant taxa of the wet evergreen plot (Drypetes and Cynometra) do, however, constitute major components of the pollen rain. There is less variation between samples from the moist semi-deciduous plot spatially, as it is dominated by Celtis, which typically comprises >70% of the pollen assemblages. We conclude that pollen rain in these tropical ecosystems is highly heterogeneous, and suggest that pollen assemblages obtained by trapping are susceptible to small-scale variations in forest structure. Conversely, this may mean that current recommendations of more than three years of trapping in tropical systems may be too high, and that space could substitute for time in modern tropical pollen trapping.

Effects of Broussonetia papyrifera invasion and land use on vegetation characteristics in a tropical forest of Ghana

The purpose of this study was to evaluate the effects of Broussonetia papyrifera (paper mulberry) invasion and land use on the floristic composition of a dry semi-deciduous forest in Ghana. Forty-five plots (25 m × 25 m each), distributed among three land uses—selectively logged (SL); abandoned farmlands (AF); and an undisturbed reference (RF)—were surveyed. Results showed lower tree species richness (S), diversity (H′), evenness (S) and basal area (BA) in the SL (46, 0.78, 0.32 and 269.12 m2 ha−1, respectively) and AF (40, 0.53, 0.45, and 131.16 m2 ha−1) sites compared to the RF site (79, 2.66, 0.87, 963.72 m2 ha−1). Similar patterns were found at the shrub layer, but no differences were observed at the herb layer. Non-metric multidimensional scaling ordination revealed distinct species composition among the land uses. The two disturbed habitats, SL and AF, were associated with increased B. papyrifera invasion particularly in the overstory, with importance value index and mean relative density of 45 and 65.03%, and 42 and 53.29%, correspondingly. However, the species was only sparsely represented in the RF site. Tree density of B. papyrifera correlated negatively with H′, S, E, BA, and native tree density and richness. These findings highlight the strong link between human land use (i.e., logging and slash-and-burn farming), invasion, and vegetation characteristics, and suggest the need to limit these disturbances to conserve biodiversity within tropical forest ecosystems.

Natural Regeneration Dynamics of Tree Seedlings on Skid Trails and Tree Gaps Following Selective Logging in a Tropical Moist Semi-Deciduous Forest in Ghana

One of the main threats to the sustainability of timber production in naturally managed forests in Ghana is insufficient regeneration of timber tree species. This study assessed regeneration success of a logged forest by comparing the species composition, diversity, density, recruitment, mortality, and growth of naturally established seedlings in 160 seedling plot samples of 50 m2 located randomly on main skid trails, secondary skid trails, felled tree gaps and unlogged parts of the same forest. The study was done within a 134-ha compartment in a selectively logged moist semi-deciduous forest in Ghana over a period of 33 months involving four enumerations. Seedlings population was initially dominated by pioneers, but after 33 months, population in all sites was dominated by non-pioneers. Seedling densities showed an increase initially in all the sites after logging, but declined after 10 months. The high seedling densities were driven by four (Albizia zygia, Ceiba pentandra, Celtis mildbraedii and Turreanthus africanus) out of the 37 species that regenerated. All four species exhibited a period of exceptionally high new seedling recruitment in the first 10 months. Diversity differed significantly among disturbance types initially, but after 33 months diversity was lower in the unlogged areas though not significant. Seedling mortality was initially greater in unlogged areas of the forest and growth rates higher in the logged areas. These results show that disturbed areas appear to be suitable sites for the regeneration of timber species following logging, although the long-term fate of trees growing on these areas remains uncertain as growth rates declined with time.

Carbon sequestration in iron-nodules in moist semi-deciduous tropical forest soil

Soil organic carbon (SOC) in tropical forest soils is typically characterized by fast turnover rates but mineralization might be inhibited resulting in long term organic matter protection. This study focuses on SOC trapped in iron oxides in a Paleudult (chromic Acrisol) located in the moist semi-deciduous forest in Ghana by determining the age of the SOC, quantifying the geochemical characteristics of the SOC, and estimating how much of the SOC that is bound so tightly to the oxides that it does not participate in the normal turnover of organic matter in the soil. The SOC has been characterized by using solid-state 13C nuclear magnetic resonance (NMR) spectroscopy and 14C dating. The turnover rate of the reactive SOC was determined by basal soil respiration (BSR) and a ratio between the SOC stock in the soil. The investigation shows that SOC associated with iron nodules has a 14C age of more than 21,000years and the absence of CO2 release during BSR measurements reveals that iron nodules have trapped and immobilized ~21% of SOC stored in the top 1m (~3.4kgCm−2). NMR results indicate that trapped SOC in the iron nodules is more decomposed than the organic matter in the topsoil.

Prevalence of Seed-dispersers in a Semi-deciduous Forest of Ghana

Seed dispersal is a necessary process for plant reproduction. The research seeks to give an overview of mammals and birds that exist and utilize a plantation in the semi-deciduous forest. The questions asked in this regard are: (1) which native mammalian fauna and or birds utilize the plantation area (2) what ecological roles do the mammals/bird play (3) Do different bird species inhabit the various vegetation types within the plantation. The study was carried out on a private plantation (7°3' N and 1°34' W) 42 km north of Kumasi, the Ashanti region, Ghana. An indirect questionnaire method was used to estimate the distribution of mammalian species that are good seed dispersers. Interviews were conducted with a total of 9 hunters in two near-by villages bordering the plantation area. The point count method was used for the bird survey, because it was easy to gather large amounts of data within a short period of time. A total of 45 counting stations were located in the plantation for the point count survey. Based on the evaluation of the questionnaire, eleven of the mammals were found in or around the plantation. A total of 32 bird species were sighted in the general bird survey and the point count sampling. The similarity of bird species in the remnant natural forest compared to the agro forestry area was 0.21, while that for the remnant natural forest compared to the actual plantation area was 0.18 using the Jaccards index. However the Shannon diversity index for birds calculated for the remnant natural forest was 1.682 while that of the actual plantation area and agro forestry areas are 1.693 and 2.074, respectively. It was concluded that seed-dispersal mammals and birds occurred on the plantation.

Dynamic of vegetation and palaeo-environments on middle and late Holocene in Benin

Interspecific variation in water-induced fluctuations in stem girth demonstrates the mechanisms promoting coexistence in seasonally dry tropical forest. In addition, these fluctuations are a potential, but unevaluated, source of bias in measurements of annual tree growth rates. To examine diurnal and seasonal patterns of stem diameter change, tree girth was measured over 2 years (1997–1999), using dendrometer bands, for three species (Celtis mildbraedii, C. zenkeri and Strombosia glaucescens) in semi-deciduous forest in Ghana. Soil matric potential was measured concurrently at 15 cm depth. In addition, measurements of all trees >20 cm dbh on three, 1 ha plots were made at the beginning and middle of the 1998/1999 dry season. During the severe 1997/1998 dry season, soil matric potential declined below −1.5 MPa and two species showed significant stem shrinkage. For the evergreen species, C. mildbraedii, there was a significant positive effect of tree diameter on stem shrinkage, and shrinkage was greater in the second, compared to the first, half of the dry season. For the deciduous species, C. zenkeri, shrinkage was reduced during the second half of the dry season, following leaf fall. During 1998/1999, soil matric potential, did not decline below −1.5 MPa, and rates of girth change remained positive for all species. There were no significant effects of size or phenology on the rate of girth change in the plot-based study. Deviations in annual increment calculated over successive monthly intervals indicate that a 10-fold difference in soil water availability between measurement occasions can lead to a 4% bias in estimates of annual growth. Measurements of forest plots should be made when inter-annual variation in soil water availability is low. In this forest, measurements should, therefore, be made during the wet season, contrary to published recommendations.

A post-logging assessment of some soil physical properties in a Ghanaian moist semi-deciduous forest

We assessed the impact of logging operations on some soil physical properties: penetration resistance, bulk density and matric potential in four logging gaps; loading bays, tree-fall gaps, primary skid trails, secondary skid trails and undisturbed site as control in a moist semi-deciduous forest in Ghana. Penetration resistance was significantly higher in loading bays and primary skid trails than in the other logging gaps with penetration resistance values of 64.84N/cm2, 116.56N/cm2 and 155.2N/cm2 for 0-2cm, 2-5cm and 5-7cm depths in the loading bays. Tree-fall gaps were the least compacted with corresponding penetration resistance values of 19.16N/cm2, 64.28.52N/cm2 and 91.38 N/cm2 for the various soil depths. Bulk density and soil matric potential however, did not significantly differ between gaps suggesting the impact of logging on soil compaction was quite low and could only be captured by penetration resistance. The low level of logging impacts on the forest soil may be accounted for by the time of logging which was the dry season and the small number of trees extracted (0.6 tree/ha) during logging. Keywords: Logging, moist semi-deciduous forest, soil physical properties, Ghana Ghana Journal of Forestry Vol. 19 & 20 2006: pp. 54-62

Water balance in a moist semi-deciduous forest in Ghana

Water balance in a moist semi-deciduous forest in Ghana

Characteristics and genesis of pisolitic soil layers in a tropical moist semi-deciduous forest of Ghana

In the tropical moist semi-deciduous forests of West Africa, gravelly soil horizons common on the summits and upper slopes in the landscape, are often covered by a thin layer of gravel-free soil. Previous investigations have shown that these top layers are formed by termites transporting gravel-free soil material from the subsoil to fallen logs and branches on the soil surface. The present study located at the upper part of a catena at Kade in Ghana shows that the gravel consists of iron nodules or pisolites of varying degree of cementation, quartz and a few remnants of unweathered metamorphic stones. According to chemical and mineralogical studies of pisolites from E, Bt and Bt/Cg horizons, pisolites in the three horizons consist of well crystallized goethite and hematite, and the pisolite content and hardness decrease with increasing soil depth. Furthermore, the very hard pisolites from the E horizon are richer in total iron oxides, especially hematite, than the pisolites in the horizons below but iron oxide crystallinity is similar in the three horizons indicating that pisolite hardening depends on the total content of iron oxides, in particular hematite. Based on the location of the gravel-rich soil horizon in the landscape, a general route for development of pisolite-rich soil horizons in West Africa is proposed including the following processes: (i) An upward transport of gravel-free material to the soil surface due to termite activity, (ii) ongoing removal of this material by water erosion, (iii) weathering of the rather soft metamorphic bedrock present at shallow depth and (iv) gley formation. These processes will over time lead to a lowering of the land surface and concentration of pisolites at the soil surface or in a layer near the soil surface.

Regeneration of timber species following selective logging in a moist semi-deciduous forest in Ghana

The natural regeneration and growth of timber tree species were studied in four logging gaps; loading bays, tree-fall gaps, primary skid trails and secondary skid trails with forest shade as control in a moist semi-deciduous forest in Ghana. There was prolific tree seedling emergence in all the sites in the first few months following logging but declined after 8 months. Species diversity as well as seedling numbers increased with reducing gap size from the loading bays to secondary skid trails. Weed biomass, however, increased with increasing gap size. Pioneer species were relatively abundant in loading bays than all the ecological species guilds while the non-pioneers showed preference for smaller gaps. Ceiba pentandra (pioneer), for example, was the only species that survived in the loading bays for the 27-month period of the study but could not survive in the forest shade. The limited regeneration of commercial tree species and increased colonization by competing weeds in larger gaps indicate the need for better control over harvest operations through gap size reduction and post-harvest competition control treatments to ensure sustainable production of economic tree species. Keywords: Ghana, moist semi-deciduous forest, logging, regeneration Ghana Journal of Forestry Vol. 17 & 18 2005: pp. 20-35

The Role of Termites in Soil Formation in the Tropical Semi-Deciduous Forest Zone, Ghana

Soil Macrofauna especially insects have been recognized as being an important factor in regulating soil processes and thereby the soil profde development. The influence of earthworms is well documented and it is the dominant member of the soil macrofauna influencing the soil formation processes in the temperate zone. In the tropics, termites and ants play the major role in the nutrient recycling and the movement and transportation of soil material. This paper describes the influence of termites on the soil formation in the tropical wet semi-deciduous forest in Ghana at the north coast of the Gulf of Guinea. The termites form distinct soil horizons especially at the summits of the landscapes where gravel free soil horizons are formed upon gravel rich horizons, and in some cases soil heaps are formed after the decomposition of huge trees.