Mycorrhizas play a vital role in ecosystem function, diversity and productivity. However, mycorrhizas in tropical forests are considered to be a neglected area of research in contrast to the well-studied diversity patterns of macro organisms. To this end, soil samples from 0 to 30 cm in depth were collected from six or four elevations in a typical tropical forest of Mt. Jianfeng and Mt. Diaoluo in China. The arbuscular mycorrhizal fungal (AMF) diversity and community composition were explored among different elevations based on high-throughput barcoded sequencing on the Illumina MiSeq platform. Environmental variables of soil characteristics, and elevation on AMF community assembly were analyzed using canonical correspondence analysis. In total, 316 AMF operational taxonomic units (OTUs) were found to belong to four identified and one unclassified order, and Glomus was the most dominant genus in tropical forest. AMF communities or diversity did not clearly reflect local environmental conditions, the spatial distance between mountains and elevation. In total, 68% and 56% of taxa of AMF were observed on multiple elevations in Mt. Jianfeng and Mt. Diaoluo, respectively. Furthermore, 8.9% and 19% of OTUs were exhibited on all elevations in Mt. Jianfeng and Mt. Diaoluo, respectively. The AMF alpha diversity, richness and evenness were similar across the two surveyed tropical mountains. The influence of elevation showed no distinct role on the diversity of AMF taxa. Overall, AMF communities and diversity are abundant in tropical forests and with little influence of elevation in tropical forests of China.

Heavy metal pollution has potential hazards to plant, animal, and human health, and phytoremediation is recognized as a safe and efficient technique for the revegetation of heavy-metal-polluted soil. Macleaya cordata was found in heavily tailing areas with fast growth rates, large biomass, and huge taproots. In our study, the seedlings of M. cordata were exposed to cadmium (Cd), lead (Pb), copper (Cu), and zinc (Zn) in a Hoagland solution. After 20 days, the tolerance index as well as the content and distribution of Cd, Pb, Cu, and Zn in roots, stems, and leaves were determined. The results showed M. cordata had higher tolerance to Pb and Zn than to Cd and Cu under hydroponic culture conditions. Pb and Cu mainly accumulated in the roots, and the translocation efficiency to the shoots was very low, while about three-quarters of Zn concentrations in the plants were accumulated in the shoots; even the Cd content per shoot of M. cordata exceeded some Cd hyperaccumulators. In the present study, the metal ions in the roots or leaves of M. cordata were firstly determined in situ using dithizone staining, and the degree of root-tip staining was consistent with the amountof the total metal content in the roots. The addition of Zn or Cu in the Pb treatment solution increased the Pb content in the stems and leaves of M. cordata, while the addition of Zn or Cu in the Cd treatment solution had the opposite effect. Pb or Cd in the compound treatment decreased the Zn content in all parts of M. cordata. Our results suggest that Pb can be transported above ground via some special pathways in M. cordata. The different absorption and transport mechanisms of M. cordata in relation to Cd, Zn, Cu, and Pb can be important for the plant to be applied for the remediation of compound-polluted soil or water.