## 4 Discussion
Ascomycota, Chytridiomycota, and Zygomycota were not affected by the presence of heavy metals, which could be related to the vast amount of extracellular polymeric substances (EPS) that exist on the surface of fungi. The EPS on the cytoderm of fungi contains a lot of extracellular sugar, protein, fat, and melanin, and active groups (such as sulfhydryl, carboxyl and hydroxyl) can provide the sites necessary for adsorption and the complexing of heavy metals. In this way, most heavy metals will precipitate on the microbial cell wall [30]. In addition, the EPS of fungi also contains a typical metal chelator in the form of oxal acid, which can immobilize heavy metal ions from forming insoluble oxalate precipitation and reduce the biological toxicity of heavy metals. The tolerance of fungi to heavy metals will therefore ultimately increase [31]. Microorganisms play an important role in maintaining the health of leaves and the balance of ecosystems [32; 33]. In this study, high-throughput sequencing was used to detect the diversity and richness of phyllosphere fungi residing in four native grass species. According to our study, _C. epigejos_ had greatest number of fungi but _I. cylindrical_ had the greatest fungal diversity (Table 1). We also found that the variation in diversity indices and the quantity in phyllosphere fungal communities were not identical. The main reason for this was that although the habitat of the native grass species was the same, the microenvironment of leaves was not suitable for the growth of all fungal groups and the uniformity of fungi ultimately declined. As a result, _C. epigejos_ had the greatest overall number of fungi but its diversity index was low, which was in accordance with the results reported by [PERSON] [34]. Ascomycota was the dominant phylum in the four native grass species as well as the soil, which suggested that this fungal phylum had stronger resistance and environmental adaptability. The main behavior of Ascomycota is saprophytic in both plants and soil. Thus, Ascomycota can decompose most plant and animal residue as well as decompose unusable substances into nutrients that can be directly used by other biota, which are necessary for the function of various substrates. Therefore, Ascomycota became the dominant species in the heavy metal polluted environment of the tailings dam investigated. Nectriaceae, belonging to Ascomycota, has a parasitic and saprophytic behavior pattern and it generally grows in animals and monocotyledons that tend to decline or die or be taken over by other fungal species. At the same time, Nectriaceae also plays a certain role in maintaining the balance of native ecosystems, which functions changed with the environment and host genotypes [35]. In our study, Nectriaceae was only found in _B. ischaemiaum_. This was due to the fact that _B. ischaemiaum_, with its particular growth and development stages, was more suitable for Nectriaceae survival under the environmental sampling conditions of this study. Meruliaceae are widely distributed throughout the world and mostly subsist on rotten wood and litter. The sampling site of this study was in Yuanqu County, Shanxi Province, China, where relatively high temperatures are common. During sample collection, _E. dahuricus_ had entered the seed maturation stage and a few leaves had begun to wither. This type of habitat is suitable for Meruliaceae. Therefore, it had become a special fungal family in _E. dahuricus_. In China, _C. epigejos_ is a perennial herb and is widely distributed. It contains ergotines, alkaloids, sterols and fatty oils. Sporormiaceae are distributed within a variety of plants and produce secondary metabolites, such as polyketones, terpen and steroids [36]. In our study, however, the phyllosphere Sporormiaceae community in _C. epigejos_ could produce special secondary metabolites and are therefore unique grass fungi. Thus, it was in accordance with [PERSON] et al.