In agroecosystems, fungi not only attract attention as crop pathogens, but also play crucial roles in nutrient cycling as decomposers and arbuscular mycorrhizal mutualists. Consequently soil fungi strongly influence agroecosystem function, and are conspicuously influenced by agricultural practices. We examined the effects of four compost rates (0, 11.25, 22.5, and 45 Mg ha −1 ) on soil fungal community compositions and network patterns in soybean at seedling, flowering, and mature stage in a field experiment in black soil of Northeast China. Miseq sequencing was used to characterize the soil fungal community. Our results revealed that soil fungal richness was unaffected by compost addition, while soil fungal community composition was significantly influenced by compost addition across the growing season. Among the combined “top 20” fungal OTUs, 15 OTUs positively responded to compost addition, while 10 negatively responded. The abundance of predicted pathotroph was greatly decreased by the 45 Mg ha −1 compost addition. Network analysis indicated that the fungal networks in compost amended soils were more complex and harbored more positive links than the control. Fungal network harbored more positive links among saprotroph-saprotroph and saprotroph-symbiotroph in moderate level of compost amended soils than other networks. In conclusion, this study revealed that compost addition impacted positively both the soil fungal communities and network patterns within a single growing season. Thus, compost addition could be a good practice to enhance the soil fungal community and function and ultimately soil health and quality.

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The criterion for judging the successful revegetation largely focuses on the aboveground indicators, whereas the information for soil ecosystem during the revegetation is often ignored. To better understand the effects of the revegetation on the development of the soil ecosystem near Shaoguan Pb/Zn Smelter, Guangdong Province of Southern China, we compared the difference of the microbial and physico-chemical parameters between the four revegetated sites and two control sites (bare ground and native forest area). The soil organic C, total N, total P, NH 4 -N, NO 3 -N, available P, WHC and porosity significantly increased and bulk density decreased in the four revegetated sites compared with those in bare ground, indicating the processive effects of the revegetation on the reestablishment of the soil nutrient pools. The heavy metal contents were higher in the four revegetated sites than in the bare ground, thus the revegetation resulted in the accumulation of heavy metals released from smelter in surface soil. The soil microbial composition and activities, except that the oligotrophic bacterial number decreased over revegetation time, significantly increased in the revegetated sites compared with those in the bare ground, and predominantly correlated with soil organic C, total N, NH 4 -N, NO 3 -N and WHC. The soil oligotrophic bacteria was negatively related to all individual heavy metal contents, thus was the most sensitive indicator in reflecting heavy metal stress, while other microbial parameters, despite not showing negative relationships to the individual heavy metal contents, were sensitive to the potential availability of Pb and Cu (ratio of available to total heavy metal contents), but less sensitive to those of Zn and Cd. Both the principal component analysis (PCA) and the discriminant analysis (DA) resulted from microbial and physico-chemical datasets not only revealed the shifts of the soil physico-chemical and microbial patterns from the unrevegetated to non-polluted conditions, but also implied the possible loss of effects of revegetation on soil remediation in the sites revegetated for four (RIV) and five (RV) years, respectively.

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