Climate and soil effects on tree species diversity and aboveground carbon patterns in semi-arid tree savannas

Climatic and edaphic effects are increasingly being discussed in the context of biodiversity-ecosystem functioning. Here we use data from West African semi-arid tree savannas and contrasting climatic conditions (lower vs. higher mean annual precipitation-MAP and mean annual temperature-MAT) to (1) determine how climate modulates the effects of species richness on aboveground carbon (AGC); (2) explore how species richness and AGC relate with soil variables in these contrasting climatic conditions; and (3) assess how climate and soil influence directly, and/or indirectly AGC through species richness and stand structural attributes such as tree density and size variation. We find that greater species richness is generally associated with higher AGC, but more strongly in areas with higher MAP, which also have greater stem density. There is a climate-related influence of soils on AGC, which decreases from lower to higher MAP conditions. Variance partitioning analyses and structural equation modelling show that, across all sites, MAP, relative to soils, has smaller effect on AGC, mediated by stand structural attributes whereas soil texture and fertility explain 14% of variations in AGC and influence AGC directly and indirectly via species richness and stand structural attributes. Our results highlight coordinated effects of climate and soils on AGC, which operated primarily via the mediation role of species diversity and stand structures.

Mycelial nutrient transfer promotes bacterial co-metabolic organochlorine pesticide degradation in nutrient-deprived environments

Biotransformation of soil organochlorine pesticides (OCP) is often impeded by a lack of nutrients relevant for bacterial growth and/or co-metabolic OCP biotransformation. By providing space-filling mycelia, fungi promote contaminant biodegradation by facilitating bacterial dispersal and the mobilization and release of nutrients in the mycosphere. We here tested whether mycelial nutrient transfer from nutrient-rich to nutrient-deprived areas facilitates bacterial OCP degradation in a nutrient-deficient habitat. The legacy pesticide hexachlorocyclohexane (HCH), a non-HCH-degrading fungus (Fusarium equiseti K3), and a co-metabolically HCH-degrading bacterium (Sphingobium sp. S8) isolated from the same HCH-contaminated soil were used in spatially structured model ecosystems. Using ¹³C-labeled fungal biomass and protein-based stable isotope probing (protein-SIP), we traced the incorporation of ¹³C fungal metabolites into bacterial proteins while simultaneously determining the biotransformation of the HCH isomers. The relative isotope abundance (RIA, 7.1-14.2%), labeling ratio (LR, 0.13-0.35), and the shape of isotopic mass distribution profiles of bacterial peptides indicated the transfer of ¹³C-labeled fungal metabolites into bacterial proteins. Distinct ¹³C incorporation into the haloalkane dehalogenase (linB) and 2,5-dichloro-2,5-cyclohexadiene-1,4-diol dehydrogenase (LinC), as key enzymes in metabolic HCH degradation, underpin the role of mycelial nutrient transport and fungal-bacterial interactions for co-metabolic bacterial HCH degradation in heterogeneous habitats. Nutrient uptake from mycelia increased HCH removal by twofold as compared to bacterial monocultures. Fungal-bacterial interactions hence may play an important role in the co-metabolic biotransformation of OCP or recalcitrant micropollutants (MPs).

Genetic diversity and population structure of cowpea [Vigna unguiculata (L.) Walp.] accessions from Togo using SSR markers

Cowpea [Vigna unguiculata (L.) Walp.] is a crop with significant agronomic and nutritional value. In Togo, the crop is very appreciated by local people. It is the third food habit in Togo after maize and rice. However, several accessions of cowpea cultivated in Togo are now prone to extinction, creating a risk of genetic erosion. It is therefore urgent to assess the genetic diversity of accessions in order to set up a good conservation program. To achieve this, genetic diversity and phylogenetic relationships among 70 accessions of cowpea collected in the five (5) administrative regions of Togo were assessed using Simple Sequence Repeat (SSR) molecular markers. The twenty-eight SSR primers used in this study generated a total of 164 alleles with an average of 5.82 alleles per locus. Polymorphic Information Content (PIC) values ranged from 0.20 to 0.89 with an average value of 0.58. Population structure analysis using model-based revealed that the cowpea germplasm was grouped into two subpopulations. The analysis of molecular variance (AMOVA) revealed that 98% of genetic variation existed among accessions within regions. The fixation index (Fst) value, which was 0.069 was low, indicating relatively low population differentiation. The phylogenetic analysis grouped the 70 accessions into two main groups that can be further divided into four groups independent of their origins. This study provides a foundation for a Togolese cowpea germplasm conservation program and can serve for the selection of parental material for further studies aimed at the genetic improvement of local germplasm.

Soil fungal community structure and seasonal diversity following application of organic amendments of different quality under maize cropping in Zimbabwe

Recent advocacy for Integrated Soil Fertility Management (ISFM) in smallholder farming systems in east and southern Africa show substantial evidence of increased and sustained crop yields associated with enhanced soil productivity. However, the impact ISFM on soil fungi has received limited attention, yet fungi play key roles in crop growth. Following total soil DNA extraction with ZR soil microbe miniprep kit, illumina sequencing was used to, examine the fungal communities (ITS1F) under a maize crop following co-application of organic nutrient resources including Crotalaria juncea, cattle manure and maize stover with inorganic fertilizers at three-time periods (T1-December, T2-January, and T3-February) in Zimbabwe. Ninety-five fungal species were identified that were assigned to Ascomycota (>90%), Basidiomycota (7%) and Zygomycota (1%). At T1, Ascomycota and Basidiomycota were identified across treatments, with Ascomycota attaining > 93% frequency. Fungal succession was noted and involved reduction of Ascomycota coupled by increase in Basidiomycota under the different treatments. For example at T3, Basidiomycota increased to 34% while Ascomycota declined to 66% under manure but remained unchanged in other two organics. Pre-season mineral nitrogen (N) associated with the 'Birch effect' apparently influenced the fungal community structure at T1 while readily available fertilizer N was critical at T2 and T3. The low-quality maize stover promoted the presence of Exophiala sp SST 2011 and this was linked to N immobilization. The impact of N addition was more pronounced under medium (manure) to low-quality (maize stover) resources. Fungi required phosphorus (P) and N for survival while their proliferation was dependent on substrate availability linked to resource quality. Interactive-forward test indicated that soil available P and N were most influential (P < 0.05) factors shaping fungal communities. Co-application of medium to high quality organic and inorganic resources show promise as a sustainable entry point towards enhancing belowground fungal diversity critical in driving nutrient supply.

Biomass, carbon stock and sequestration potential of Oxytenanthera abyssinica forests in Lower Beles River Basin, Northwestern Ethiopia

BACKGROUND

Given the large bamboo resource base with considerable potential to act as an important carbon sink, Ethiopia has included bamboo in the national Reducing Emissions from Deforestation and Forest Degradation and enhancing forest carbon stocks (REDD+) and Clean Development Mechanisms (CDM) programs. However, little is known about the carbon stock and sequestration potential of bamboo forests. As a result, this research was conducted to quantify the carbon sequestration and storage capacity of Oxytenanthera abyssinica forests in the Lower Beles River Basin, northwestern Ethiopia. To this end, a total of 54 circular plots, each measuring 100 m² with a radius of 5.64 m, were established to conduct the inventory in Assitsa and Eddida bamboo forests, the typical bamboo sites in Lower Beles River Basin. Biomass accumulation of bamboo was estimated using an allometric equation based on diameter at breast height (DBH) and age. Soil samples were taken from two different soil depths (0-15 and 15-30 cm) to determine soil organic carbon.

RESULTS

Results indicate that the mean biomass of the bamboo forests in the study area accounted for about 177.1 [Formula: see text] 3.1 Mg ha^-1. The mean biomass carbon and soil organic carbon stock of the bamboo forests were 83.2 [Formula: see text] 1.5 Mg C ha^-1 and 70 [Formula: see text] 1.7 Mg C ha^-1, respectively. Therefore, the mean carbon stock of the O. abyssinica bamboo forests was 152.5 [Formula: see text] 2.5 Mg C ha^-1 to 559.8 [Formula: see text] 9.0 ton CO₂ ha^-1.

CONCLUSION

This study highlights the importance of assessing bamboo's carbon stock and sequestration potential for enhancing its role in climate change mitigation and sustainable resource management. The O. abyssinica bamboo forests of the study area have significant carbon stock and sequestration potential. Therefore, sustainable management of these crucial vegetation resources will enhance their role in providing ecosystem services, including climate change mitigation.

Root exudate chemical cues of an invasive plant modulate oviposition behavior and survivorship of a malaria mosquito vector

Gravid female Anopheles gambiae mosquitoes identify suitable oviposition sites through a repertoire of cues, but the influence of allelochemicals, especially root phytochemicals in modulating this behavior and impacting subsequent progeny bionomics remains unexplored. We addressed these questions in the malaria vector Anopheles gambiae and its invasive host plant Parthenium hysterophorus. Using chemical analysis combined with laboratory behavioral assays, we demonstrate that a blend of terpenes, namely α-pinene, α-phellandrene, β-phellandrene, 3-carene and (E)-caryophyllene emitted from P. hysterophorus root exudate treated-water attracted gravid females. However, fewer eggs (55%) hatched in this treatment than in control water (66%). The sesquiterpene lactone parthenin, identified in both the natural aquatic habitat harboring P. hysterophorus and root exudate-treated water was found to be responsible for the ovicidal effect. Moreover, larvae exposed to parthenin developed 2 to 3 days earlier but survived 4 to 5 days longer as adults (median larval survival time = 9 days (all replicates);11 to 12 days as adults) than the non-exposed control (median larval survival time = 11 days (reps 1 & 2), 12 days (rep 3); 6 to 7 days as adults). These results improve our understanding of the risk and benefits of oviposition site selection by gravid An. gambiae females and the role root exudate allelochemicals could play on anopheline bionomics, with potential implications in malaria transmission.

Wild edible ectomycorrhizal fungi: an underutilized food resource from the rainforests of Tshopo province (Democratic Republic of the Congo)

BACKGROUND

Ectomycorrhizal (EcM) fungi constitute a source of income as well as proper food with considerable nutritional value. Although edible EcM fungi are highly diverse and expected to host considerable nutritional attributes, only few studies focus on their use and promotion in the province of Tshopo (DR Congo). This study provides original ethnomycological and diversity data on edible ectomycorrhizal rainforest fungi from the Man-and-Biosphere reserve of Yangambi and the reserve of Yoko.

METHODS

The list of edible fungi follows the current taxonomy. Taxa were collected in plots situated in different types of rainforests. Each taxon is supported by herbarium reference specimens. Ethnomycological data on locally consumed EcM fungi were collected from randomly selected people living near the Man-and-Biosphere reserve of Yangambi and the Yoko reserve. People were interviewed using a semi-structured questionnaire. The interview campaign involved 160 informants, all randomly selected from 6 different ethnic communities.

RESULTS

The results reveal that rainforests from the Yangambi Biosphere reserve and Yoko forest reserve provide a relatively high number of edible fungi, more than local people actually use. Mixed forest stands hold the highest diversity in saprotrophic edible fungi (p value < 0.001) while no significant difference (p value > 0.05) was observed in the number of saprotrophic and EcM fungi within monodominant forests. In spite of being accessible, this renewable natural resource is underexploited. Although a wide array of EcM fungi is available in primary forests dominated by ectomycorrhizal trees, local people's major interest goes to the saprotrophic fungi from areas with degraded mixed forests.

CONCLUSION

The lack of local interest for EcM fungi is probably related to the considerable distance people have to cover to collect them. As a result, the edible EcM fungi from the Tshopo area represent a potentially interesting but underutilized resource.

Efficient [Formula: see text] adsorption using peach stone-derived granular activated carbon

Agricultural wastes have attracted attention as alternative precursors for the production of granular activated carbon. Using batch sorption studies, we demonstrated that granular activated carbon prepared through chemical activation using zinc chloride followed by physical activation in nitrogen environment at high temperatures can effectively adsorb aurocyanide from solution. Furthermore, gold recovery process using the granular activated carbon was amenable to optimization of adsorption parameters such as carbon dosage, initial aurocyanide concentration and contact time. These results may open new fronts on the application of low-cost granular activated carbon, particularly in the carbon-in-pulp metallurgical process.

Molecular, Biochemical, and Dietary Regulation Features of α-Amylase in a Carnivorous Crustacean, the Spiny Lobster Panulirus argus

Alpha-amylases are ubiquitously distributed throughout microbials, plants and animals. It is widely accepted that omnivorous crustaceans have higher α-amylase activity and number of isoforms than carnivorous, but contradictory results have been obtained in some species, and carnivorous crustaceans have been less studied. In addition, the physiological meaning of α-amylase polymorphism in crustaceans is not well understood. In this work we studied α-amylase in a carnivorous lobster at the gene, transcript, and protein levels. It was showed that α-amylase isoenzyme composition (i.e., phenotype) in lobster determines carbohydrate digestion efficiency. Most frequent α-amylase phenotype has the lowest digestion efficiency, suggesting this is a favoured trait. We revealed that gene and intron loss have occurred in lobster α-amylase, thus lobsters express a single 1830 bp cDNA encoding a highly conserved protein with 513 amino acids. This protein gives rise to two isoenzymes in some individuals by glycosylation but not by limited proteolysis. Only the glycosylated isoenzyme could be purified by chromatography, with biochemical features similar to other animal amylases. High carbohydrate content in diet down-regulates α-amylase gene expression in lobster. However, high α-amylase activity occurs in lobster gastric juice irrespective of diet and was proposed to function as an early sensor of the carbohydrate content of diet to regulate further gene expression. We concluded that gene/isoenzyme simplicity, post-translational modifications and low Km, coupled with a tight regulation of gene expression, have arose during evolution of α-amylase in the carnivorous lobster to control excessive carbohydrate digestion in the presence of an active α-amylase.