Sample Size Affect Ethnobotanical Index Values: Bootstrap as a Remedial Approach

Ethnobotanical indices are widely used to quantify cultural importance of plants in social studies. This study aims to show users of ethnobotanical indices the effect of sample variation and what methodological approach can be used to circumvent the problems related to sample variation. The methods used are to write an algorithm and used to simulate different sample sizes from which four ethnobotanic indices selected for the present study were estimated. Results showed the instability of the ethnobotanical indices under variations in the size of informants. It proposes bootstrapping as a statistical aid tool to remove the sample size effect in quantitative ethnobotany. For the indices used in the present study 1000 re-samplings eliminated the effect of sample size on the value of the indices. Researchers will have to take this new approach into account in order to calculate more precise ethnobotanical indices in order to better appreciate the cultural importance of plants.

Mineral Fertilization Influences the Acceptability of Fresh Pulp and Juice Made from Sugarloaf Pineapple

Fertilization practices can influence the quality of pineapple fruit and consequently its acceptability by consumers who are increasingly oriented towards high quality agri-food products. This study aimed at evaluating the influence of N, P and K on some physico-chemical and organoleptic characteristics of pineapple (Ananas comosus L. Merr) for fresh consumption and juice processing. A complete NPK factorial design was installed in the south Benin. The treatments NPK in g plant-1 were randomized into four blocks: T1;T2;T3;T4;T5;T6;T7;T8;T9. Brix juice was determined using a refractometer and pH with a pH meter. An evaluation of sensory characteristics such as sweetness, acid taste and aroma of fresh pineapple pulp and processed juice was made by a panel of tasters selected and trained. A principal components analysis, followed by a numerical classification was performed on fruits’ sensory and physicochemical characteristics. Results showed that juice pH was significantly influenced by the phosphorus and potassium. Potassium influenced significantly juice yield. Some physico-chemical characteristics and sensory attributes were correlated between them and groups of treatments are formed for both the juice and the fresh fruit.

Grazing effects on vegetation dynamics in the savannah ecosystems of the Sahel

Background The savannah ecosystems of Sahel have experienced continuous and heavy grazing of livestock for centuries but still,their vegetation response to grazing pressure remains poorly understood.In this study,we analysed the herbaceous plant dynamics,measured by species diversity,composition,cover,and biomass in response to grazing pressure in the savannah ecosystems of Sahel.In Senegal,we selected four savannah sites represented with high,moderate,light and no grazing intensity levels.Transect survey methods were used for sampling the vegetation data within each of the sites.Species richness and composition were analysed using species accumulation curve and multivariate analyses.Furthermore,we used General Linear Models and a piecewise Structural Equation Model(pSEM)to examine the relationships between grazing intensity,vegetation cover,diversity and biomass.Results The herbaceous species diversity and composition varied significantly among the different grazing intensity levels(p<0.001).The plant species composition shifted from the dominance of grass cover to the dominance of forb cover with increasing grazing pressure.Moreover,the attributes of species diversity,herbaceous biomass,and ground cover were higher on sites with low grazing than sites with high and moderate grazing intensity.Across all sites,species diversity was positively related to total biomass.The pSEM explained 37%of the variance in total biomass and revealed that grazing intensity negatively influenced total biomass both directly and indirectly through its negative influence on species diversity.Conclusions Managing grazing intensity may lead to higher plant production and higher mixed forage establishment in the dryland savannah ecosystems.This information can be used to support land management strategies and promote sustainable grazing practices that balance the needs of livestock with the conservation of ecosystem health and biodiversity.

On the reliability of predictions on Covid-19 dynamics: A systematic and critical review of modelling techniques

Since the emergence of the novel 2019 coronavirus pandemic in December 2019(COVID-19),numerous modellers have used diverse techniques to assess the dynamics of transmission of the disease,predict its future course and determine the impact of different control measures.In this study,we conducted a global systematic literature review to summarize trends in the modelling techniques used for Covid-19 from January 1st,2020 to November 30th,2020.We further examined the accuracy and precision of predictions by comparing predicted and observed values for cumulative cases and deaths as well as uncertainties of these predictions.From an initial 4311 peer-reviewed articles and preprints found with our defined keywords,242 were fully analysed.Most studies were done on Asian(78.93%)and European(59.09%)countries.Most of them used compartmental models(namely SIR and SEIR)(46.1%)and statistical models(growth models and time series)(31.8%)while few used artificial intelligence(6.7%),Bayesian approach(4.7%),Network models(2.3%)and Agent-based models(1.3%).For the number of cumulative cases,the ratio of the predicted over the observed values and the ratio of the amplitude of confidence interval(CI)or credibility interval(CrI)of predictions and the central value were on average larger than 1 indicating cases of inaccurate and imprecise predictions,and large variation across predictions.There was no clear difference among models used for these two ratios.In 75%of predictions that provided CI or CrI,observed values fall within the 95%CI or CrI of the cumulative cases predicted.Only 3.7%of the studies predicted the cumulative number of deaths.For 70%of the predictions,the ratio of predicted over observed cumulative deaths was less or close to 1.Also,the Bayesian model made predictions closer to reality than classical statistical models,although these differences are only suggestive due to the small number of predictions within our dataset(9 in total).In addition,we found a significant negative correlation(rho=-0.56,p=0.021)between this ratio and the length(in days)of the period covered by the modelling,suggesting that the longer the period covered by the model the likely more accurate the estimates tend to be.Our findings suggest that while predictions made by the different models are useful to understand the pandemic course and guide policy-making,some were relatively accurate and precise while other not.