Search

Summary(1)The research conducted, including the rationaleThe direct effect of aridity on photosynthetic and water-transport strategies is not easy to discern in global analyses because of large-scale correlations between precipitation and temperature. We analyze tree traits collected along an aridity gradient in Ghana, West Africa, that shows little temperature variation, in an attempt to disentangle thermal and hydraulic influences on plant traits.(2)MethodsPredictions derived from optimality theory of the variation of key plant traits along the gradient are tested with field measurements.(3)ResultsMost photosynthetic traits show trends consistent with optimality-theory predictions, including higher photosynthetic rates in the drier sites, and an association of higher photosynthetic rates with greater respiration rates and greater water transport. Leaf economic and hydraulic traits show less consistency with theory or global-scale pattern, especially predictions based on xylem efficiency-sfatety trafeoff. Nonetheless, the link between photosynthesis and water transport still holds: species (predominantly deciduous species found in drier sites) with both higher sapwood-to-leaf area ratio (AS/AL) and potential hydraulic conductivity (Kp), implying higher transpiration, tend to have both higher photosynthetic capacity, and lower leaf-internal CO2.(4)ConclusionsThese results indicate that aridity is an independent driver of spatial patterns of photosynthetic traits, while plants show a diversity of water-transport strategies along the aridity gradient.Plain language summaryAlong an aridity gradient in Ghana, West-Africa, we used optimality theory to explain why higher photosynthetic rates should be found at drier places and how plants arrange water transportation to support quicker photosynthesis at the drier site. We also reported surprising data-theory inconsistency for some hydraulic traits along the aridity gradient where further research is needed.

Forest-savanna boundaries extend across large parts of the tropics but the variability of photosynthetic capacity in relation to soil and foliar nutrients across these transition zones is poorly understood. For this reason, we compared photosynthetic capacity (maximum rate of carboxylation of Rubisco at 25 C° (Vcmax25), leaf mass, nitrogen (N), phosphorus (P) and potassium (K) per unit leaf area (LMA, Narea, Parea and Karea, respectively), in relation to respective soil nutrients from 89 species at seven sites along forest-savanna ecotones in Ghana and Brazil. Contrary to our expectations, edaphic conditions were not reflected in foliar nutrient concentrations but LMA was slightly higher in lower fertility soils. Overall, each vegetation type within the ecotones demonstrated idiosyncratic and generally weak relationships between Vcmax25 and Narea, Parea and Karea. Species varied significantly in their Vcmax25 ↔ Narea relationship due to reduced investment of total Narea in photosynthetic machinery with increasing LMA. We suggest that studied species in the forest-savanna ecotones do not maximize Vcmax25 per given total Narea due to adaptation to intermittent water availability. Our findings have implications for global modeling of Vcmax25 and forest-savanna ecotone productivity.

Although herbicides have extensively been used in forest landscape restoration, its effects and opportunity costs have rarely been studied in Ghana. This study evaluated types of herbicides used, assessed the perceptions of the effects of herbicide usage among farmers enrolled in a taungya (i.e. farm forestry programs) in the dry semi-deciduous ecological zone of Ghana. The study also analyzed the challenges associated with the application of herbicides and determined the impact of socio-economic factors that influence farmers decision to use herbicides on farms. Data were collected from 300 taungya farmers and 20 herbicide traders in Offinso North, Offinso South, and Techiman South Municipal. Data collection was completed in December 2016. Data were analyzed descriptively and quantitatively. Results indicate that 100% of farmers perceived herbicides as having deleterious effects on flora (seedlings, under-storey wild foods, medicines) and fauna (soil micro-organisms, fish in rivers) as well as water quality, soil structure and human health. Nevertheless, 93% of them use herbicides to reduce labour costs and to establish larger acreages. Based on their functional properties, 85% of herbicides traded are non-selective for bush clearing and 15% are selective for weeding. Farmers use them indiscriminately due to poor knowledge on recommended practices and intensity of invasiveness of weed species. Education, residential status and age of respondents significantly predicted usage. The study recommends a review of Ghana's pesticide deployment strategies and herbicides guide book for use in farm forestry. Capacity of frontline forestry professionals, traders and farmer-based organizations must be enhanced to effectively advice and monitor safe application. Plant based herbicides must be promoted for safety and enhancement of biodiversity.

The sizes and shapes of tree crowns are of fundamental importance in ecology, yet understanding the forces that determine them remains elusive. A cardinal question facing ecologists is the degree to which general and non-specific versus ecological and context-dependent processes are responsible for shaping tree crowns. Here, we test this question for the first time across diverse tropical ecosystems. Using trees from 20 plots varying in elevation, precipitation, and ecosystem type (savanna-forest transitions) across the paleo- and neo-tropics, we test the relationship between crown dimensions and tree size. By analyzing these scaling relationships across environmental gradients, biogeographic regions, and phylogenetic distance, we extend Metabolic Scaling Theory (MST) predictions to include how local selective pressures shape variation in crown dimensions. Across all sites, we find strong agreement between mean trends and MST predictions for the scaling of crown size and shape, but large variation around the mean. While MST explained approximately half of the observed variation in tree crown dimensions, we find that local, ecosystem, and phylogenetic predictors account for the half of the residual variation. Crown scaling does not change significantly across regions, but does change across ecosystem types, where savanna tree crowns grow more quickly with tree girth than forest tree crowns. Crowns of legumes were wider and more voluminous than those of other taxa. Thus, while MST can accurately describe the central tendency of tree crown size, local ecological conditions and evolutionary history appear to modify the scaling of crown shape. Importantly, our extension of MST incorporating these differences accounts for the mechanisms driving variation in the scaling of crown dimensions across the tropics. We present allometric equations for the prediction of crown dimensions across tropical ecosystems. These results are critical when scaling the function of individual trees to larger spatial scales or incorporating the size and shape of tree crowns in global biogeochemical models.

Tropical ecosystems adapted to high water availability may be highly impacted by climatic changes that increase soil and atmospheric moisture deficits. Many tropical regions are experiencing significant changes in climatic conditions, which may induce strong shifts in taxonomic, functional and phylogenetic diversity of forest communities. However, it remains unclear if and to what extent tropical forests are shifting in these facets of diversity along climatic gradients in response to climate change. Here, we show that changes in climate affected all three facets of diversity in West Africa in recent decades. Taxonomic and functional diversity increased in wetter forests but tended to decrease in forests with drier climate. Phylogenetic diversity showed a large decrease along a wet-dry climatic gradient. Notably, we find that all three facets of diversity tended to be higher in wetter forests. Drier forests showed functional, taxonomic and phylogenetic homogenization. Understanding how different facets of diversity respond to a changing environment across climatic gradients is essential for effective long-term conservation of tropical forest ecosystems., Different aspects of biodiversity may not necessarily converge in their response to climate change. Here, the authors investigate 25-year shifts in taxonomic, functional and phylogenetic diversity of tropical forests along a spatial climate gradient in West Africa, showing that drier forests are less stable than wetter forests.

Deconstructing functional trait variation and co-variation across a wide range of environmental conditions is necessary to increase the mechanistic understanding of community assembly processes and improve current parameterization of dynamic vegetation models. Here, we present a study that deconstructs leaf trait variation and co-variation into within-species, taxonomic-, and plot-environment components along three tropical environmental gradients in Peru, Brazil, and Ghana. To do so, we measured photosynthetic, chemical, and structural leaf traits using a standardized sampling protocol for more than 1,000 individuals belonging to 367 species. Variation associated with the taxonomic component (species + genus + family) for most traits was relatively consistent across environmental gradients, but within-species variation and plot-environment variation was strongly dependent on the environmental gradient. Trait-trait co-variation was strongly linked to the environmental gradient where traits were measured, although some traits had consistent co-variation components irrespective of gradient. Our results demonstrate that filtering along these tropical gradients is mostly expressed through trait taxonomic variation, but that trait co-variation is strongly dependent on the local environment, and thus global trait co-variation relationships might not always apply at smaller scales and may quickly change under future climate scenarios. Fil: Oliveras, Imma. University of Oxford; Reino Unido Fil: Bentley, Lisa. Sonoma State University; Estados Unidos Fil: Fyllas, Nikolaos M.. University Of The Aegean; Grecia Fil: Gvozdevaite, Agne. University of Oxford; Reino Unido Fil: Shenkin, Alexander Frederick. University of Oxford; Reino Unido Fil: Peprah, Theresa. Forestry Research Institute Of Ghana; Ghana Fil: Morandi, Paulo. Universidade Federal do Mato Grosso do Sul; Brasil Fil: Peixoto, Karine Silva. Universidade Federal do Mato Grosso do Sul; Brasil Fil: Boakye, Mickey. Forestry Research Institute Of Ghana; Ghana Fil: Adu-Bredu, Stephen. Csir - Forestry Research Institute Of Ghana; Ghana Fil: Schwantes Marimon, Beatriz. Universidade Do Estado de Mato Grosso; Brasil Fil: Marimon Junior, Ben Hur. Universidade Do Estado de Mato Grosso; Brasil Fil: Salinas, Norma. Pontificia Universidad Católica de Perú; Perú Fil: Martin, Roberta. Arizona State University; Estados Unidos Fil: Asner, Gregory. Arizona State University; Estados Unidos Fil: Díaz, Sandra Myrna. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentina Fil: Enquist, Brian J.. University of Arizona; Estados Unidos Fil: Malhi, Yadvinder. University of Oxford; Reino Unido

Climatic changes have profound effects on the distribution of biodiversity, but untangling the links between climatic change and ecosystem functioning is challenging, particularly in high diversity systems such as tropical forests. Tropical forests may also show different responses to a changing climate, with baseline climatic conditions potentially inducing differences in the strength and timing of responses to droughts. Trait-based approaches provide an opportunity to link functional composition, ecosystem function and environmental changes. We demonstrate the power of such approaches by presenting a novel analysis of long-term responses of different tropical forest to climatic changes along a rainfall gradient. We explore how key ecosystem's biogeochemical properties have shifted over time as a consequence of multi-decadal drying. Notably, we find that drier tropical forests have increased their deciduous species abundance and generally changed more functionally than forests growing in wetter conditions, suggesting an enhanced ability to adapt ecologically to a drying environment.

Allanblackia parviflora A. Chev. also called vegetable tallow tree provides a variety of non-timber forest products of great importance to rural households including shade, timber, medicine and seed oil but attempts have not been made to improve the tree species and increase its production. Consequently, the species is being threatened due to unsustainable exploitation and poor regeneration and cultivation appears as the only viable option. In order to cultivate the species at meaningful scale, it is necessary to establish the optimum range of environmental factors that influence its propagation and growth. This study was therefore designed to investigate Allanblackia growth parameters and bio-accumulation under different growth media in a greenhouse study. The media were: 1) TS = top soil alone, 2) AB soil = Allanblackia soil alone, 3) TS + H = Top soil alone + humus, 4) AB + TS = Allanblackia soil alone + Top soil alone and 5) SAB = Sterilized Allanblackia soil alone. Each treatment was replicated three times in a complete randomized design. The experiment lasted for 18 months. Results showed that Fe was the micronutrient that accumulated greatest in the plant tissue. Among the treatments, Allanblackia soil showed the highest accumulation of Zn in the plant tissue with the top soil showing the least (7.67 mg&#183kg-l). Humus contributed largely to the bio-accumulation of Cu in the plant tissue. Bio-accumulation of manganese in the plant tissue ranged from 13.30 mg&#183kg-l to 207 mg&#183kg-l suggesting difference in manganese absorption by Allanblackia as influenced by the treatments. The growth parameters of Allanblackia parviflory were impacted differently by the growth media. The result was however controversial since no differences were found between growth of seedlings in sterilized Allanblackia soil and Allanblackia soil.

The leaf economic spectrum (LES) describes a set of universal trade-offs between leaf mass per area (LMA), leaf nitrogen (N), leaf phosphorus (P) and leaf photosynthesis that influence patterns of primary productivity and nutrient cycling. Many questions regarding vegetation-climate feedbacks can be addressed with a better understanding of LES traits and their controls. Remote sensing offers enormous potential for generating large-scale LES trait data. Yet so far, canopy studies have been limited to imaging spectrometers onboard aircraft, which are rare, expensive to deploy and lack fine-scale resolution. In this study, we measured VNIR (visible-near infrared (400–1050 nm)) reflectance of individual sun and shade leaves in 7 one-ha tropical forest plots located along a 1200–2000 mm precipitation gradient in West Africa. We collected hyperspectral imaging data from 3 of the 7 plots, using an octocopter-based unmanned aerial vehicle (UAV), mounted with a hyperspectral mapping system (450–950 nm, 9 nm FWHM). Using partial least squares regression (PLSR), we found that the spectra of individual sun leaves demonstrated significant (p < 0.01) correlations with LMA and leaf chemical traits: r2 = 0.42 (LMA), r2 = 0.43 (N), r2 = 0.21 (P), r2 = 0.20 (leaf potassium (K)), r2 = 0.23 (leaf calcium (Ca)) and r2 = 0.14 (leaf magnesium (Mg)). Shade leaf spectra displayed stronger relationships with all leaf traits. At the airborne level, four of the six leaf traits demonstrated weak (p < 0.10) correlations with the UAV-collected spectra of 58 tree crowns: r2 = 0.25 (LMA), r2 = 0.22 (N), r2 = 0.22 (P), and r2 = 0.25 (Ca). From the airborne imaging data, we used LMA, N and P values to map the LES across the three plots, revealing precipitation and substrate as co-dominant drivers of trait distributions and relationships. Positive N-P correlations and LMA-P anticorrelations followed typical LES theory, but we found no classic trade-offs between LMA and N. Overall, this study demonstrates the application of UAVs to generating LES information and advancing the study and monitoring tropical forest functional diversity.

The genus Allanblackia consists of multipurpose, valuable non-timber forest tree species found in the rain forest zones of Africa. The seed oil of Allanblackia spp. has a high commercial value and demand for industrial purpose amounting to >100,000 kg oil per year. Wild harvesting from Ghana, Nigeria and Tanzania cannot meet the market demand for Allanblackia oil, hence the need for domestication. A genebank of A. parviflora A. Chev. was established in Ghana in July 2007 for conservation of the genetic resources of the species and for future use in its domestication programme, using 406 seedlings derived from collections made from eight different populations in three different provenances in Ghana. Six years after establishment, the survival rate, growth parameters (height and diameter), reproductive biology (flowering and fruiting behaviour, flower colours and sex ratio of the trees) were assessed. The mean survival rate was 73.65 %. There was no significant difference in mean tree height (cm) (F = 1.017, df = 7, P > 0.05) and mean diameter at breast height (F = 1.683, df = 7, P > 0.05) among the populations. Mean tree height (F = 0.309, df = 2, P > 0.05) and mean diameter at breast height (F = 0.686, df = 2, P > 0.05) were also not significantly different among the provenances. There was a highly significant positive correlation between the volume of the tree and the number of fruits per tree (R = 0.483, P

Allanblackia parviflora A. Chev., an underutilized fruit tree species commonly found in tropical rainforest of West Africa, has potential for integration into agroforestry systems for economic and environmental benefits. The seed oil of A. parviflora is considered economically important but wild fruits collection produces an average of 40 tons of oil annually. However, over 100,000 tons of Allanblackia seed oil is needed annually by food and cosmetics industries. The need to domesticate and conserve A. parviflora to ensure adequate sustainable supply of seed oil and to sustainably manage the genetic resources is therefore critical. This paper reviews the current state-of-the art on domestication and sustainable use efforts of Allanblackia. Propagation methods have been developed to encourage large scale commercial cultivation, include grafting, rooting of stem cuttings and research into improved seed germination. Range-wide germplasm collection has been undertaken leading to establishment of 140 accessions in a gene bank for future source of germplasm. Mother blocks, i.e. established plots consisting of grafts, seedlings and cuttings, have been established at Rural Resource Centres with 58 elite clones, which have been recommended for distribution to farmers. The diversification of cropping systems to include A. parviflora trees is projected to contribute to community livelihoods development and poverty reduction through large-scale production and supply chain development of the species. Furthermore, the integration of A. parviflora into agroforestry systems is important for the conservation of the genetic resources of the species.

Allanblackia parviflora A. Chev, is an indigenous fruit tree species that could be used in agroforestry systems with both environmental and economic benefits. The seed oil is of prime importance as a foreign exchange earner and is being developed as a rural based enterprise in many African countries notably Ghana, Nigeria, Cameroon and Tanzania. Methods for propagation and conservation of the species are therefore of prime importance. The seeds of the species are however difficult to germinate hindering its domestication process. Allanblackia parviflora seeds were collected from seven different populations in Ghana and were subjected to four different seed germination trials at the nursery of CSIR-Forestry Research Institute of Ghana at Fumesua, Kumasi. This was followed by studying the effect of stage of seed germination on establishment after potting. Intact seeds began germination at 7 months after sowing and at 24 months, significant (P

The seeds of Allanblackia trees produce edible oil with significant global market potential. Consequently, a private-public partnership involving Unilever and known as ‘Novella Africa’ is engaged in the development of Allanblackia as a new crop in a number of African countries. The purpose of this partnership is to build a profitable and sustainable initiative for harvest, marketing and cultivation. Rural communities are directly involved and a participatory approach to domestication is being followed to maximise farmers' livelihood benefits. This is the first time a multinational company has partnered in such an approach, and the initiative represents an example for the domestication of other new tree crops. Investing in good communication between partners is considered to be essential to success by ensuring trust and a common understanding of priorities. Progress to date has involved the establishment of market supply chains for oil, based firstly on wild harvest, and the initiation of cultivat...

Allanblackia parviflora A. Chev. (Clusiaceae Lindley) is an indigenous tree species which is found in the rain forest regions of Ghana. It is a potential candidate fruit tree species being introduced in agroforestry systems. Information on genetic diversity, reproductive biology and fruit yield are not known. Field expeditions to seven populations of Allanblackia parviflora in Ghana were undertaken in 2003–2006 during which fruits were collected from 109 trees for characterization. The species was found to be dioecious. The colour of flowers varied from whitish to reddish. No ecological differences in number of fruits per tree, fruit shape and seed health were observed. However, large variations in fruit size and shape were observed among individual trees sampled. A high heritability (h 2 = 0.822) in fruit size and genetic gain (G = 20.1%) in fruit size for selection of trees with above average fruit size were observed. A positive significant correlation was observed between fruit size and seed weight (R = 0.54, P

Triplochiton scleroxylon K. Schum is an economic timber tree species native to West Africa. As viable seeds of this species are rarely available, vegetative propagation techniques have been developed for the species to overcome this difficulty of seed supply, and to encourage reforestation efforts. Two studies have been carried out to develop vegetative propagation techniques as basis for future genetic improvement of Triplochiton scleroxylon K. Schum. The studies sought to assess the rooting ability of leafy stem cuttings from coppice shoots from different stump heights and coppice shoots from budded/grafted, mature trees and saplings. Rooting percentage was significantly (P JOURNAL OF THE GHANA SCIENCE ASSOCIATION Volume 1 Number 1, July (1998) pp. 151-157