Potential toxic elements accumulation in soils and parts of palm (Elaeis guineensis) growing on reclaimed tailings and mined spoils in southwestern Ghana.

This study examined the accumulation of potentially toxic elements (PTE) in oil palm (Elaeis guineensis) biomass, fruits, and soils. About 40 soil samples to a depth of 40 cm and 90 palm biomass samples from roots, leaves/stems, and fruits were collected from reclaimed tailings dam and control sites at two mining areas in southwestern Ghana. PTE concentrations and pollution indices were analyzed via various inferential statistics. The PTE (As, Fe, Zn, Mn, and Cu) concentrations in the palm roots were significantly higher (p < 0.001) than in the soil at Ghana Manganese Company (GMC) Ltd, Nsuta except for As which was significantly higher (p < 0.0001) in the fruits than the soil. Soil PTE concentration was however significantly higher (p < 0.0001) than that of the roots, leaves, and fruits at the Bogoso tailings dam. The contamination factors, enrichment factors, geoaccumulation indices, and pollution load index (PLI) of soils at the tailings dam and reclaimed sites were significantly higher than the control sites. The PLI of the reclaimed tailings and control sites at Bogoso were 17.98 ± 0.56 and 6.06 ± 0.58, respectively, implying the soils at Bogoso are severely polluted with As, Fe, Zn, and Mn while those of the GMC are unpolluted. Bioaccumulation factors were significantly higher in roots than in the leaves and fruits (p < 0.0001) and were greater than 2 at GMC. The translocation of Cu and As to the fruits was significantly high on both study locations with TF of As = 9 at GMC. PTE accumulation in the palm biomass reduced soil PTE concentrations, but the soils on these mined spoils were severely polluted. These high As contents, in the fruits, may contaminate the food chain and increase PTE-related health risks among human populations. Therefore, phytoremediation of mine spoils with oil palm should be done with caution. Experimental studies to examine soil amendment effects on PTE accumulation capacity or removal efficacy by the palm plants at various ages are recommended.

Temperature and aridity regulate spatial variability of soil multifunctionality in drylands across the globe.

The relationship between the spatial variability of soil multifunctionality (i.e., the capacity of soils to conduct multiple functions; SVM) and major climatic drivers, such as temperature and aridity, has never been assessed globally in terrestrial ecosystems. We surveyed 236 dryland ecosystems from six continents to evaluate the relative importance of aridity and mean annual temperature, and of other abiotic (e.g., texture) and biotic (e.g., plant cover) variables as drivers of SVM, calculated as the averaged coefficient of variation for multiple soil variables linked to nutrient stocks and cycling. We found that increases in temperature and aridity were globally correlated to increases in SVM. Some of these climatic effects on SVM were direct, but others were indirectly driven through reductions in the number of vegetation patches and increases in soil sand content. The predictive capacity of our structural equation modelling was clearly higher for the spatial variability of N- than for C- and P-related soil variables. In the case of N cycling, the effects of temperature and aridity were both direct and indirect via changes in soil properties. For C and P, the effect of climate was mainly indirect via changes in plant attributes. These results suggest that future changes in climate may decouple the spatial availability of these elements for plants and microbes in dryland soils. Our findings significantly advance our understanding of the patterns and mechanisms driving SVM in drylands across the globe, which is critical for predicting changes in ecosystem functioning in response to climate change.

Factors influencing local ecological knowledge of forage resources: Ethnobotanical evidence from West Africa's savannas.

Recording local ecological knowledge (LEK) is a useful approach to understanding interactions of the complex social-ecological systems. In spite of the recent growing interest in LEK studies on the effects of climate and land use changes, livestock mobility decisions and other aspects of agro-pastoral systems, LEK on forage plants has still been vastly under-documented in the West African savannas. Using a study area ranging from northern Ghana to central Burkina Faso, we thus aimed at exploring how aridity and socio-demographic factors drive the distributional patterns of forage-related LEK among its holders. With stratified random sampling, we elicited LEK among 450 informants in 15 villages (seven in Ghana and eight in Burkina Faso) via free list tasks coupled with ethnobotanical walks and direct field observations. We performed generalized linear mixed-effects models (aridity- and ethnicity-based models) and robust model selection procedures. Our findings revealed that LEK for woody and herbaceous forage plants was strongly influenced by the ethnicity-based model, while aridity-based model performed better for LEK on overall forage resources and crop-related forage plants. We also found that climatic aridity had negative effect on the forage-related LEK across gender and age groups, while agro- and floristic diversity had positive effect on the body of LEK. About 135 species belonging to 95 genera and 52 families were cited. Our findings shed more light on how ethnicity and environmental harshness can markedly shape the body of LEK in the face of global climate change. Better understanding of such a place-based knowledge system is relevant for sustainable forage plants utilization and livestock production.