Background Most species of the Russulaceae are ectomycorrhizal (ECM) fungi, which are widely distributed in different types of forest ecology and drive important ecological and economic functions. Little is known about the composition variation of the Russulaceae fungal community aboveground and in the root and soil during the growing season (June–October) from a Quercus mongolica forest. In this study, we investigated the changes in the composition of the Russulaceae during the growing season of this type of forest in Wudalianchi City, China. Methods To achieve this, the Sanger sequencing method was used to identify the Russulaceae aboveground, and the high-throughput sequencing method was used to analyze the species composition of the Russulaceae in the root and soil. Moreover, we used the Pearson correlation analysis, the redundancy analysis and the multivariate linear regression analysis to analyze which factors significantly affected the composition and distribution of the Russulaceae fungal community. Results A total of 56 species of Russulaceae were detected in the Q. mongolica forest, which included 48 species of Russula, seven species of Lactarius, and one species of Lactifluus. Russula was the dominant group. During the growing season, the sporocarps of Russula appeared earlier than those of Lactarius. The number of species aboveground exhibited a decrease after the increase and were significantly affected by the average monthly air temperature (r = −0.822, p = 0.045), average monthly relative humidity (r = −0.826, p = 0.043), monthly rainfall (r = 0.850, p = 0.032), soil moisture (r = 0.841, p = 0.036) and soil organic matter (r = 0.911, p = 0.012). In the roots and soils under the Q. mongolica forest, the number of species did not show an apparent trend. The number of species from the roots was the largest in September and the lowest in August, while those from the soils were the largest in October and the lowest in June. Both were significantly affected by the average monthly air temperature (r2 = 0.6083, p = 0.040) and monthly rainfall (r2 = 0.6354, p = 0.039). Moreover, the relative abundance of Russula and Lactarius in the roots and soils showed a linear correlation with the relative abundance of the other fungal genera.

We used a space-for-time substitution as an alternative to investigate the variation in rootfungal communities from four Korean pine forest lands with different ages. An analysis of the communityin the root revealed that the fungal community composition differed, and it was affected bya combination of host age, climate factors and soil factors which including the soil fungi and soilphysical and chemical properties. We assembled 464,490 seq uences into 2,066 fungal operationaltaxonomic units (OTUs), of these, 1,955 OTUs were classified as 5 phyla, 20 classes, 69 orders, 131families, 330 genera. More than 75% root fungi overlap with the fungi of the habit soil. The fungalcommunities both from the root and soil bulk showed the highest species diversity in the >150 yearsold forest compared with 50–100 years old forests and five years old seedlings. With advancingforest age, in the root there were not only the unique dominant genera, but showed uniqueness bothin the totally fungal community and functional fungi community succession took place in thesesample plots. In 5 years old land, the relative abundance of pathotrophic fungi and symbiotrophicfungi were higher than saprotrophic fungi, in the mature forests, pathotrophic fungi and symbiotrophicfungi showed stabilized and a little lower than saprotrophic fungi in richness. These changesin the fungal community, respectively, were influenced significantly by pH, rainfall, and themean air temperature (P < 0.05). This study findings focused on the dynamics of changes within thetaxonomy of the root fungal community as a response to the age of the host tree (Korean pine), maybe used for forest management and as the reference for evaluation the stability of forest ecosystem.

Russula rubiginosus sp. nov. (Subsect. Maculatinae) associated with Quercus mongolica is described and illustrated based on phylogenetic analyses of internal transcribed spacer (ITS) ribosomal DNA sequences and morphological evidence. This species is characterized by the rusty spots on the pileus and stipe, an acrid taste, a yellow spore print, smaller basidiospores, and abundant cystidia in pileipellis and stipitipellis. Furthermore, the morphological characteristics were described in detail and compared with R. globispora and R. subrubescens.

Russula quercina sp. nov. (sect. Polychromidia, subsect. Integroidinae) from a Quercus mongolica forest in Northeast China is described. This new species is recognized by its coral pink and glabrous pileus, slightly yellowish context, yellow basidiospore print, and abundant cystidia in stipitipellis and pileipellis. The morphological characteristics are illustrated in detail and are compared with morphologically similar species, R. integriformis, and R. laeta. Russula quercina identification is supported by molecular phylogenetic analyses based on the internal transcribed spacer regions (ITS) in the ribosomal DNA.