# Functional Traits of Plant Species Suitable for Revegetation of Landfill Waste from Nickel Smelter
## 5 Conclusions  
The landfill waste (SW Slovakia) and its surroundings represent, from the environmental point of view, a territory that is severely disturbed, ecologically unresolved and left to the self-cleaning ability of the natural landscape. The waste containing heavy metals has contaminated a wide area, and the landfill waste greening is considered the most suitable method of reclamation. For this reason, the site was selected for field research and more detailed study, which focused on its natural vegetation.  
The functional traits of three plant species that occur naturally at the site were evaluated, and the degree of adaptation of the plants to soil contaminated with heavy metals was determined. We focused on the species _Populus alba, Diplotaxis muralis_ and _Calamagrostis epigejos_, which formed more numerous populations in this habitat. We evaluated leaf characteristics on selected individuals (specific leaf area, dry matter content in leaves, water saturation deficit and leaf water content). The highest values of the specific leaf area were determined for _Dipidaxis muralis_ and the lowest in the case of _Populus alba_. On the contrary, _Dipidaxis muralis_ showed the lowest values of leaf dry matter content, while the other two species, _Populus alba_ and _Calamagrostis epigejos_, showed considerably higher values. The highest values of water saturation deficit were observed for _Populus alba_, _Dipidaxis muralis_ had slightly lower values, and _Calamagrostis epigejos_ showed the lowest values. Results of leaf water content revealed the best water management ability in the case of _Dipidaxis muralis_. This was confirmed by the significant correlation between specific leaf area and leaf water content of _Dipidaxis muralis_. We assume that this is related to the excellent plasticity of the species and its ability to adapt to adverse conditions.  
Based on the investigated functional traits, which are closely related to the ability of plants to adapt to the contaminated environment, we can conclude that if it is not possible to dispose of the landfill wastes conventionally, then natural greening is a suitable solution. The natural plant cover can be formed by plants that are able to plastically respond to the high contents of heavy metals in the soil and can create strong and viable populations. These plant species reduce water percolation due to interception and evapotranspiration, prevent water and wind erosion of the soil and therefore reduce the spread of contamination to the environment.  
Conceptualization, I.V., M.C. and T.O., methodology, I.V. and E.M.; formal analysis, T.O. and M.C.; investigation, I.V., M.C.; resources, E.M. and T.O.; data curation, M.C.; writing--original draft preparation, M.C.; writing--review and editing, M.C.; visualization, T.O.; supervision, I.V. and E.M.; project administration, M.C., I.V. and T.O.; funding acquisition, I.V. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Slovak Scientific Grant Agency VEGA projects 1/0712/20 and 2/0096/19.  
Data is contained within the article.  
The authors declare no conflict of interest.