# Functional Traits of Plant Species Suitable for Revegetation of Landfill Waste from Nickel Smelter
## 4 Discussion  
### Functional Traits and Ecological Plasticity  
Low SLA values are typical for species inhabiting environments with low nutrient content, lack of water and light [27]. Our results confirmed low SLA values, mainly for the type of _Populus alba_. However, it should be noted that all selected species occurred in the area outside the shade with enough light, which is an essential factor for SLA, because its values are mainly related to the photosynthetic activity of the leaves. Despite the lowest achieved SLA values, we can agree with the findings of [PERSON] et al. [33] that the _Populus alba_ species is able to colonize contaminated substrates and grow even in extreme conditions. In terms of its ecological plasticity, _Populus alba_ showed rapid growth, high biomass production, easy seed dispersal, fast attachment and root system development. We can classify _Calamagrostis epigejos_ among C-strategists at our site. In addition, according to [PERSON] et al. [32], _Calamagrostis epigejos_ has a high growth potential, which could be used especially in disturbed habitats for shortening succession series and faster reclamation. The resulting SLA values for _Diplotaxis muralis_ indicate that this species is the best of the selected species adapted to the conditions of the habitat. This is probably due to the fact that this species can be included among the R-strategists which enter the habitats in the early stages of succession, have the high reproductive capacity and rapid germination as well as rapid population growth with short life cycle and short vegetation phase. Higher water content in the leaves and a narrower leaf blade contribute to a higher SLA [34; 35]. Plants with higher SLA flexibly respond to changes in resource availability in the soil [36], are more productive [37] but more prone to damage herbivores [38]. Cin  
Figure 10: Correlations between a specific leaf area (SLA) and leaf water content (LWC) of the selected species (PA—_Populus alba_, DM—_Diplotaxis muralis_, CE—_Calamagrostis epigejos_) (values for SLA are given in cm\({}^{2}\cdot\)g\({}^{-1}\) and for LWC in g\(\cdot\)g\({}^{-1}\)). [PERSON] et al. [39] showed that productivity-related traits (SLA, LDMC) strongly reflect the soil moisture gradient. The LDMC reflects the availability of nutrients and water in the soil. Based on the obtained results, we can state that the _Dipidotaxis muralis_ species is well adapted to adverse conditions, as selected species were investigated in habitats with low soil moisture and nutrient content but with a high content of heavy metals. Its leaves are stiff, which is also a manifestation of its resistance to adverse external influences and its ability to use nutrients efficiently. Thus, it can survive long periods without water supply. For _Populus alba_ and _Calamagrostis epigejos_ species, regardless of their higher LDMC values, we assume that they are also resistant to adverse habitat conditions. In the case of the _Populus alba_, even though it requires higher humidity, it can also occur in water-deficient habitats. _Calamagrostis epigejos_ is an ecologically plastic species which can occur in adverse habitats. We believe that this species was able to adapt well to extreme conditions in the habitat. The LDMC and SLA are highly correlated characteristics that reflect different plant adaptations. Each of these properties may indicate different functional strategies, where the SLA is mainly related to the light availability and photosynthetic activity, and the LDMC indicates the water and nutrient availability in soil. In terms of different adaptations and life strategies, we can divide selected species into two functional groups. _Dipidotaxis muralis_ belongs to the first functional group with lower LDMC values. We assume that it is well adapted to the given habitat and can effectively use available nutrients and water.