The modern pollen-vegetation relationship of a tropical forest-savannah mosaic landscape, Ghana, West Africa

Transitions between forest and savannah vegetation types in fossil pollen records are often poorly understood due to over-production by taxa such as Poaceae and a lack of modern pollen-vegetation studies. Here, modern pollen assemblages from within a forest-savannah transition in West Africa are presented and compared, their characteristic taxa discussed, and implications for the fossil record considered. Fifteen artificial pollen traps were deployed for 1 year, to collect pollen rain from three vegetation plots within the forest-savannah transition in Ghana. High percentages of Poaceae and Melastomataceae/Combretaceae were recorded in all three plots. Erythrophleum suaveolens characterised the forest plot, Manilkara obovata the transition plot and Terminalia the savannah plot. The results indicate that Poaceae pollen influx rates provide the best representation of the forest-savannah gradient, and that a Poaceae abundance of >40% should be considered as indicative of savannah-type vegetation in the fossil record

EFFECTS OF SELECTIVE LOGGING ON CARBON DYNAMICS: VARIATION IN ABOVEGROUND BIOMASS AND SOIL RESPIRATION IN PRE- AND POST-LOGGING FOREST STANDS OF A MOIST TROPICAL FOREST IN GHANA

Tropical forests play an important role in the global carbon cycle, but are threatened by human activities, particularly selective logging, which is projected to increase in extent and intensity due to the demands of a rapidly growing human population. Yet, the impacts of selective harvest on carbon dynamics of residual forests is poorly understood. This dissertation examines the effects of selective harvest involving twice the standard logging intensity in Ghana (6.5 vs. 2 to 3 trees ha-1) on aboveground biomass (AGB) and soil respiration in pre- and post-logging forest stands of a moist semi-deciduous forest in Ghana. Using standardized protocols, data were collected in one-hectare plots to observe variation in AGB and soil respiration before and after selective harvest. Prior to logging, AGB was 318.6 Mg ha-1. However, one year after the removal of 121.6 m3 ha-1 of timber trees, AGB declined by 16.9%. Variation in AGB both before and after logging was better explained by species dominance and functional diversity than by species richness. In particular, the dominance of certain species influenced carbon storage before and after logging, due, in part, to environmental filtering of species based on plant functional types and/or life form. While C storage in trees was associated with LAI before logging, LAI was most important for liana C storage after logging. There were significant differences (P ≤ 0.05) in seasonal variation of soil respiration before and after logging, and between a 10- and 20-year post-logging stands with soil respiration higher in the wet season. Similarly, there were significant differences (P ≤ 0.05) in seasonal variation among components of soil respiration in the 10- and 20-year post-logging stands. Autotrophic soil respiration was 33% higher in the 20-year post-logging stand while heterotrophic soil respiration remained similar between the two stands. In general, soil moisture was the most important factor influencing soil respiration across the post-logging stands and for components of soil respiration, particularly root and mycorrhizal respiration. This information about patterns and underlying controls on soil respiration from different soil components should aid attempts to accurately model soil respiration over space and time

Assessment of aboveground, belowground, and total biomass carbon storage potential of

This article reports on a study conducted to assess the carbon storage potential of Bambusa vulgaris, the predominant bamboo species in Ghana. The study aimed to fill a knowledge gap on the potential of bamboo to sequester carbon for climate change mitigation in Ghana. Unlike previous studies that only focused on aboveground biomass, this study assessed belowground, litter, and coarse wood carbon pools. Allometric parameters and models were used to measure the aboveground biomass, while other carbon pools were directly measured. The results showed that the aboveground biomass of B. vulgaris had a carbon stock of 42.85 ± 9.32 Mg C ha−1, which was 73% of the total biomass carbon stock. The carbon stocks of belowground, coarse wood and litter were 8.57, 3.02, and 4.25 Mg C ha−1, respectively. The study also found that B. vulgaris had a high carbon dioxide sequestration potential of 215.39 Mg CO2e ha−1 compared to 147–275 Mg CO2e ha−1 for trees in general. The findings suggest that B. vulgaris could contribute to Ghana's transition to a low-carbon economy through carbon stock monitoring, reporting, and policy development to minimise the impact of climate change. Moreover, the inclusion of relevant carbon pools, including coarse wood and litter, in forest carbon estimates should be encouraged to provide a comprehensive understanding of the plant carbon cycle

Data from: Fine-root exploitation strategies differ in tropical old-growth and logged-over forests in Ghana

Understanding the changes in root exploitation strategies during post-logging recovery is important for predicting forest productivity and carbon dynamics in tropical forests. We sampled fine (diameter < 2 mm) roots using the soil-core method to quantify fine-root biomass, and architectural and morphological traits to determine root exploitation strategies in an old-growth forest and in a 54-year-old logged-over forest influenced by similar parent material and climate. Seven root traits were considered: four associated with resource exploitation potential or an ‘extensive’ strategy (fine-root biomass, length, surface area and volume); and three traits which reflect exploitation efficiency or an ‘intensive’ strategy (specific root area, specific root length and root tissue density). We found that total fine-root biomass, length, surface area, volume, and fine-root tissue density were higher in the logged-over forest, whereas the old-growth forest had higher total specific root length and specific root surface area than the logged-over forest. The results suggest different root exploitation strategies between the forests. Plants in the old-growth forest invest root biomass more efficiently to maximize soil volume explored, whereas plants in the logged-over forest increase the spatial distribution of roots resulting in the expansion of the rhizosphere

Fine-root traits in tropical old-growth and logged-over forests

This data file contains mean fine-root (< 2 mm in diameter) biomass, architectural and morphological traits measured in a tropical old-growth forest, and in a 54-year-old logged-over forest in Ghana

Forest biomass, productivity and carbon cycling along a rainfall gradient in West Africa

© 2017 John Wiley & Sons Ltd Net Primary Productivity (NPP) is one of the most important parameters in describing the functioning of any ecosystem and yet it arguably remains a poorly quantified and understood component of carbon cycling in tropical forests, especially outside of the Americas. We provide the first comprehensive analysis of NPP and its carbon allocation to woody, canopy and root growth components at contrasting lowland West African forests spanning a rainfall gradient. Using a standardized methodology to study evergreen (EF), semi-deciduous (SDF), dry forests (DF) and woody savanna (WS), we find that (i) climate is more closely related with above and belowground C stocks than with NPP (ii) total NPP is highest in the SDF site, then the EF followed by the DF and WS and that (iii) different forest types have distinct carbon allocation patterns whereby SDF allocate in excess of 50% to canopy production and the DF and WS sites allocate 40%–50% to woody production. Furthermore, we find that (iv) compared with canopy and root growth rates the woody growth rate of these forests is a poor proxy for their overall productivity and that (v) residence time is the primary driver in the productivity-allocation-turnover chain for the observed spatial differences in woody, leaf and root biomass across the rainfall gradient. Through a systematic assessment of forest productivity we demonstrate the importance of directly measuring the main components of above and belowground NPP and encourage the establishment of more permanent carbon intensive monitoring plots across the tropics

Forest biomass, productivity and carbon cycling along a rainfall gradient in West Africa

© 2017 John Wiley & Sons Ltd Net Primary Productivity (NPP) is one of the most important parameters in describing the functioning of any ecosystem and yet it arguably remains a poorly quantified and understood component of carbon cycling in tropical forests, especially outside of the Americas. We provide the first comprehensive analysis of NPP and its carbon allocation to woody, canopy and root growth components at contrasting lowland West African forests spanning a rainfall gradient. Using a standardized methodology to study evergreen (EF), semi-deciduous (SDF), dry forests (DF) and woody savanna (WS), we find that (i) climate is more closely related with above and belowground C stocks than with NPP (ii) total NPP is highest in the SDF site, then the EF followed by the DF and WS and that (iii) different forest types have distinct carbon allocation patterns whereby SDF allocate in excess of 50% to canopy production and the DF and WS sites allocate 40%–50% to woody production. Furthermore, we find that (iv) compared with canopy and root growth rates the woody growth rate of these forests is a poor proxy for their overall productivity and that (v) residence time is the primary driver in the productivity-allocation-turnover chain for the observed spatial differences in woody, leaf and root biomass across the rainfall gradient. Through a systematic assessment of forest productivity we demonstrate the importance of directly measuring the main components of above and belowground NPP and encourage the establishment of more permanent carbon intensive monitoring plots across the tropics