The Loess Plateau region of northwestern China has unique geological and dry/semi-dry climate characteristics. However, knowledge about ectomycorrhizal fungal (EMF) communities in the Loess Plateau is limited. In this study, we investigated EMF communities in Populus simonii and Pinus tabuliformis patches within the forest-steppe zone, in pine forests within the forest zone, and the transitional zone between them. We revealed high species richness (115 operational taxonomic units [OTUs]) of indigenous EMF resources at the Loess Plateau, of which Tomentella (35 OTUs), Inocybe (16), Sebacina (16), and Geopora (7) were the most OTU-rich lineages. EMF richness within the forest-steppe zone and the transitional zone was limited, while the natural pine forest maintained diverse EMF communities in the forest zone. The changes of EMF community richness and composition along arid eco-zones were highlighted for the complex factors including precipitation, soil factors, host, DBH, and altitude. Indicator analysis revealed that some EMF showed clear host preference and some taxa, i.e., genera Geopora and Inocybe, were dominant in drought and alkaline-saline conditions attributed to their environmental preference. This study revealed that EMF communities were quite limited in the forest-steppe zone, while the forest region contained diverse EMF communities in the Loess Plateau.

Alpine treeline ecotones represent ecosystems that are vulnerable to climate change. We investigated the ectomycorrhizal (ECM) community, which has potential to stabilize alpine ecosystems. ECM communities associated with Larix chinensis were studied in four zones along a natural ecotone from a mixed forest stand over pure forest stands, the timberline, and eventually, the treeline (3050-3450 m) in Tabai Mountain, China. Sixty operational taxonomic units (OTUs) of ECM fungi were identified by sequencing the rDNA internal transcribed spacer of ECM tips. The richness of ECM species increased with elevation. The soil C/N ratio was the most important factor explaining ECM species richness. The treeline zone harbored some unique ECM fungi whereas no unique genera were observed in the timberline and pure forest zone. Elevation and topography were equally important factors influencing ECM communities in the alpine region. We suggest that a higher diversity of the ECM fungal community associated with L. chinensis in the treeline zone could result from niche differentiation.

Ensuring ecological sustainability in fragile ecosystems has always been a top priority in China. Under the ‘Grain for Green’ Program (GGP), Caragana korshinskii Kom plantations are valued for their important use in soil and water conservation efforts on the Loess Plateau. This study was to estimate biomass increment and carbon accumulation in five different age classes [young age (YO), middle age (MI), pre‐mature (PR), mature (MA) and post‐mature (PO)], as well as the distribution of carbon stock among the various biomass components and soil depths. The results showed afforestation with C. korshinskii resulted in a significant increase in plant biomass and carbon stock, and soil organic carbon stocks. The total ecosystem carbon stock showed a notable carbon sink increase rate of 1.33 Mg ha−1 yr−1 from the YO to the MA stage, and then slightly decreased. The total biomass carbon of the understory plants represented only a relatively small fraction in the ecosystem, accounting for 2.4%–8.7% (median 3.8%). The proportion of ligneous components (roots, stems and branches) of C. korshinskii was increased following stand development. Our study suggested that C. korshinskii plantations should be harvested and revegetated following the MA stage (~35 years). Continuation of the GGP on the Loess Plateau, together with maturation of C. korshinskii trees over the next few years, will increase carbon sequestration in the medium term. Copyright © 2016 John Wiley & Sons, Ltd.

Quercus liaotungensis is a major tree species in deciduous broad-leaved forests in northern China. In this study, we investigated ectomycorrhizal (ECM) communities associated with Q. liaotungensis from five typical habitats across northern China. We used internal transcribed spacer-polymerase chain reaction and DNA sequencing to identify ECM fungi, and we detected 220 operational taxonomic units. In general, at the regional scale, the dominant ECM lineages were /tomentella-thelephora, /cenococcum, /russula-lactarius, and /inocybe. Analysis of variance demonstrated significant differences in alpha diversity among these ECM communities, and the ECM fungal richness was positively correlated with elevation and soil organic matter. Analysis of similarity and a nonmetric multidimensional scaling analysis revealed that there were significant differences in community composition, and the geographical distance was correlated with the ECM fungal communities. Among the environmental factors we studied, soil parameters and climate factors were the primary direct driving factors of the ECM fungal communities. Our study primarily advances our understanding of environmental factors affecting ECM fungal communities at regional scale.

Chinese jujube (Ziziphus jujuba) is an important fruit tree in China, and soil salinity is the main constraint affecting jujube production. It is unclear how arbuscular mycorrhizal (AM) symbiosis supports jujube adaptation to salt stress. Herein, we performed comparative physiological, ion flux, fatty acid (FA) metabolomic, and transcriptomic analyses to examine the mechanism of AM jujube responding to salt stress. AM seedlings showed better performance during salt stress. AM symbiosis altered phytohormonal levels: IAA and ABA contents were significantly increased in AM roots and reduced by salt stress. Mycorrhizal colonization enhanced root H+ efflux and K+ influx, while inducing expression of plasma membrane-type ATPase 7 (ZjAHA7) and high-affinity K+ transporter 2 (ZjHAK2) in roots. High K+/Na+ homeostasis was maintained throughout salt exposure. FA content was elevated in AM leaves as well as roots, especially for palmitic acid, oleic acid, trans oleic acid, and linoleic acid, and similar effects were also observed in AM poplar (P. alba × P. glandulosa cv. 84K) and Medicago truncatula, indicating AM symbiosis elevating FA levels could be a conserved physiological effect. Gene co-expression network analyses uncovered a core gene set including 267 genes in roots associated with AM symbiosis and conserved transcriptional responses, e.g., FA metabolism, phytohormone signal transduction, SNARE interaction in vesicular transport, and biotin metabolism. In contrast to widely up-regulated genes related to FA metabolism in AM roots, limited genes were affected in leaves. We propose a model of AM symbiosis-linked reprogramming of FA metabolism and provide a comprehensive insight into AM symbiosis with a woody species adaptation to salt stress.