## 5 Conclusions  
Our study in North Angola identified three Al accumulators growing on extremely acidic sandy soils (_A. quangensis_, _E. malangensis_, and _L. lancolata_). Moreover, leaves of _T. mauritianum_ growing on sandy clay loam exhibit an Al-content exceeding 1000 mg/kg. As high soluble Al contents are the major difficulty for crop production in Sub-Saharan Africa, those species seem to be suitable crops for the unfavorable soils. Common among the identified Al accumulators are high foliar Mn contents, which reflect the increased mobility of both elements in the soil. The high C:N ratio is an indication for elevated contents of lignin and cellulose. The decomposition of plant parts from specimens with a high C:N ratio is slow. A co-cultivation of the low C:N ratio covers the crops from the family of Fabaceae. In addition, Brassicaceae seem to have positive effects on the C:N ratio in the soil. The identified Al accumulators have a restricted distribution area, only _T. mauritianum_ inhabits regions outside of Central Africa. These rare species have to be considered particularly in future protection actions as they are adapted to the poor soil conditions (Al and Mn toxicity, acid pH) [35]. Furthermore, the systematic screening for metal accumulation properties of the genera of interest have to be conducted, especially for _Landolphia_ spp. where fruits are already known to contain >1000 mg/kg Al in fresh fruit pulp [18]. Although _Vitex madiensis_ subsp. _madiensis_ shows no metal accumulation properties, the plant also grows on sandy soil and seems to be a suitable crop for barren, open vegetation sites, bearing tasty \"chocolate berries\". At the moment, fruits of _A. quangensis_, _C. schweinfurthii_, _L. lancolata_, and _V. madiensis_ subsp. _madiensis_ are found on local markets. Therefore, they are of special interest in the contribution of rural household income. Global trading analyses of the studied species were still not conducted. As a result, data regarding prices and profit margins are lacking. However, the sale of natural products is often even lucrative on a regional level, as high demand and convenient sales increase exist in the capital Luanda [49]. Cultivating the studied species of interest on barren, open vegetation sites can help in improving the nutritional situtation on-site, generating an alternative income, and utilizing the exisiting soil conditions without expensive ameliorating techniques.  
Conceptualization, investigation, data curation, writing--original draft, C.B.; project administration, writing--review and editing, T.L.; investigation, M.H.G.P.; investigation, F.A.; supervision, writing--review and editing, C.N.; methodology, supervision, writing--review and editing, K.-H.F. All authors have read and agreed to the published version of the manuscript.  
Travel of first author [PERSON] was financially supported by the Erasmus+ program. Special thanks go to the Graduate Academy of the Technische Universitat Dresden, which granted a scholarship for the expenses of the first author as a PhD student.  
Not applicable.  
Informed Consent Statement: Informed consent was obtained from all subjects involved in the study.  
We would like to thank all of the participants and informants in Angola, who guided us to the points of interest and gave us the permission to work in the surrounding areas. The published results were obtained in collaboration with the Instituto Nacional de Biodiversidade e Conservacao (INBC) of the Ministerio da Cultura, Turismo e Ambiente da Republica de Angola. The authors are greatly indebted to [PERSON], [PERSON], and [PERSON] for supporting the analytical work in the laboratory of the Institute of Soil Science and Site Ecology, Department of Forest Sciences, Technische Universitat Dresden, Germany. For assistance in the identification of _Raptionacme maliensis_ we thank [PERSON].  
The authors declare no conflict of interest.