Arbuscular Mycorrhizal Community in Roots and Nitrogen Uptake Patterns of Understory Trees Beneath Ectomycorrhizal and Non-ectomycorrhizal Overstory Trees

Chikae Tatsumi; Fujio Hyodo; Takeshi Taniguchi; Weiyu Shi; Keisuke Koba; Keitaro Fukushima; Sheng Du; Norikazu Yamanaka; Pamela Templer; Ryunosuke Tateno

doi:10.3389/fpls.2020.583585

Arbuscular Mycorrhizal Community in Roots and Nitrogen Uptake Patterns of Understory Trees Beneath Ectomycorrhizal and Non-ectomycorrhizal Overstory Trees

Front Plant Sci. 2021 Jan 14:11:583585. doi: 10.3389/fpls.2020.583585. eCollection 2020.

Authors

Chikae Tatsumi^{1

2

3}, Fujio Hyodo⁴, Takeshi Taniguchi⁵, Weiyu Shi⁶, Keisuke Koba⁷, Keitaro Fukushima⁷, Sheng Du⁸, Norikazu Yamanaka⁵, Pamela Templer³, Ryunosuke Tateno⁹

Affiliations

¹ Research Faculty of Agriculture, Hokkaido University, Sapporo, Japan.
² Graduate School of Agriculture, Kyoto University, Kyoto, Japan.
³ Department of Biology, Boston University, Boston, MA, United States.
⁴ Research Core for Interdisciplinary Sciences, Okayama University, Okayama, Japan.
⁵ Arid Land Research Center, Tottori University, Tottori, Japan.
⁶ School of Geographical Sciences, Southwest University, Chongqing, China.
⁷ Center for Ecological Research, Kyoto University, Shiga, Japan.
⁸ State Key Laboratory of Soil Erosion and Dryland Farming on Loess Plateau, Institute of Soil and Water Conservation, Chinese Academy of Sciences, Beijing, China.
⁹ Field Science Education and Research Center, Kyoto University, Kyoto, Japan.

Abstract

Nitrogen (N) is an essential plant nutrient, and plants can take up N from several sources, including via mycorrhizal fungal associations. The N uptake patterns of understory plants may vary beneath different types of overstory trees, especially through the difference in their type of mycorrhizal association (arbuscular mycorrhizal, AM; or ectomycorrhizal, ECM), because soil mycorrhizal community and N availability differ beneath AM (non-ECM) and ECM overstory trees (e.g., relatively low nitrate content beneath ECM overstory trees). To test this hypothesis, we examined six co-existing AM-symbiotic understory tree species common beneath both AM-symbiotic black locust (non-ECM) and ECM-symbiotic oak trees of dryland forests in China. We measured AM fungal community composition of roots and natural abundance stable isotopic composition of N (δ¹⁵N) in plant leaves, roots, and soils. The root mycorrhizal community composition of understory trees did not significantly differ between beneath non-ECM and ECM overstory trees, although some OTUs more frequently appeared beneath non-ECM trees. Understory trees beneath non-ECM overstory trees had similar δ¹⁵N values in leaves and soil nitrate, suggesting that they took up most of their nitrogen as nitrate. Beneath ECM overstory trees, understory trees had consistently lower leaf than root δ¹⁵N, suggesting they depended on mycorrhizal fungi for N acquisition since mycorrhizal fungi transfer isotopically light N to host plants. Additionally, leaf N concentrations in the understory trees were lower beneath ECM than the non-ECM overstory trees. Our results show that, without large differences in root mycorrhizal community, the N uptake patterns of understory trees vary between beneath different overstory trees.

Keywords: 15N natural abundance; arbuscular mycorrhizal fungi; dryland; ectomycorrhizal fungi (ECM fungi); mycorrhizal dependence; nitrate.