## 1 Introduction
On the other hand, the rhizosphere is a hotspot for microbial interactions given that exudates that are released by roots are the main nutrient source for microorganisms as well as a driving force behind their population density and activities [24; 25]. Root exudates can promote heterotrophic growth, which can lead to local competition for inorganic nutrients between roots and microorganisms [24; 26]. Moreover, root-associated microbial communities play a vital role in soil ecosystems, influencing many soil biochemical processes and impacting plant growth and health [27]. Non-rhizosphere soil is either not or only slightly affected by roots and root exudates; thus, this soil zone has a lower level of microbial activity and soil fertility. Nonetheless, non-rhizosphere soil is necessary for the stability of soil aggregates as well as the resistance of soil erosion and nutrient leaching [28]. Although many studies have shown that anthropogenic activities result in changes to the soil microbial structure of both the rhizosphere and non-rhizosphere, few studies have investigated phyllosphere microorganisms in copper tailings dams. Aerial components of living plants, including leaves, stems, buds, flowers, and fruits, provide a habitat for microorganisms, and these habitats are collectively referred to as the phyllosphere [29]. Bacteria are considered to be the dominant microbial inhabitants of the phyllosphere, but archaea, filamentous fungi, and yeasts may also be important inhabitants [29]. It has been shown that bacterial communities in the phyllosphere are able to promote plant growth [30; 31] and increase plant resistance to pathogens [32; 33]. A previous study showed that endophyte infection rates of _Bothriochloa ischaemtum_ and _Festuca rubra_ could be used as indicators of Cd pollution levels, and fungal endophytes that are associated with _Imperata cylindrical_ and _Elymus dahuricus_ developed a certain tolerance to Pb [5]. There have been a few studies to date conducted on the distribution of heavy metals in plants and a comparison of the driving factors between aboveground and subsurface microorganisms in copper tailings dams. Furthermore, a comprehensive comparison between soil microbial communities and the response of physicochemical properties to heavy metal pollution is extremely limited in the literature. In this study, we investigated plant and soil physicochemical properties and their respective microbial abundance and diversity in the no. 536 sub- dams of the Zhongtiao Mountains copper mine, after being subjected to 19 years of remediation. We accomplished this by addressing the following questions: (1) What are the driving factors of the distribution of heavy metals on the aboveground and subsurface _B. ischaemtum_ microbial communities in a copper tailings dam? (2) What is the correlation among plant and soil physicochemical properties, heavy metals, their transfer factors, and soil enzymes? (3) What are the main factors that affect bacterial flora in phyllosphere, rhizosphere, and non-rhizosphere soil microbial communities? The objectives of this study were to understand the potential ecological function of _B. ischaemtum_ as it relates to heavy metal accumulation in a copper tailings dam, and to evaluate the driving factors that affect bacterial community structure and the diversity of _B. ischaemtum_. This study can provide scientific reference for screening dominant combinations of bacterial communities as well as for improving plant-microbial remediation efficiency.