Similar below‐ground carbon cycling dynamics but contrasting modes of nitrogen cycling between arbuscular mycorrhizal and ectomycorrhizal forests

• DOI: 10.1111/nph.14206
• Publication Date: 2016-09-28T10:09:43Z
• Authors: Guigang Lin; M. Luke McCormack; Chengen Ma; Dali Guo
• Keywords: 0106 biological sciences; Geography; Nitrogen; Forests; Nitrogen Cycle; 15. Life on land; 01 natural sciences; Carbon; Carbon Cycle; Plant Leaves; Mycorrhizae; Biomass

Summary

Compared with ectomycorrhizal (ECM) forests, arbuscular mycorrhizal (AM) forests are hypothesized to have higher carbon (C) cycling rates and a more open nitrogen (N) cycle. To test this hypothesis, we synthesized 645 observations, including 22 variables related to below‐ground C and N dynamics from 100 sites, where AM and ECM forests co‐occurred at the same site. Leaf litter quality was lower in ECM than in AM trees, leading to greater forest floor C stocks in ECM forests. By contrast, AM forests had significantly higher mineral soil C concentrations, and this result was strongly mediated by plant traits and climate. No significant differences were found between AM and ECM forests in C fluxes and labile C concentrations. Furthermore, inorganic N concentrations, net N mineralization and nitrification rates were all higher in AM than in ECM forests, indicating ‘mineral’ N economy in AM but ‘organic’ N economy in ECM trees. AM and ECM forests show systematic differences in mineral vs organic N cycling, and thus mycorrhizal type may be useful in predicting how different tree species respond to multiple environmental change factors. By contrast, mycorrhizal type alone cannot reliably predict below‐ground C dynamics without considering plant traits and climate.