A recent study published in Nature Climate Change has reported mycorrhizae-mediated tradeoff between plant biomass and soil C sequestration in forest ecosystems under N deposition and warming conditions. This research was completed by Prof. ZHU Jiaojun’s research team at the Institute of Applied Ecology, Chinese Academy of Sciences (CAS).

Forest ecosystems store ca. 80% of the carbon (C) in terrestrial ecosystems. Arbuscular mycorrhizal (AM) and ectomycorrhizal (ECM) fungi are the most widespread mycorrhizal types. The type of plant mycorrhizal association is critical for forest C cycling by influencing plant growth, nutrient acquisition, and soil C storage. The C sequestration characteristics of two mycorrhizal types of tree species in forest ecosystem and their response to global change drivers are important issues. ZHU Jiaojun’s team previously researched belowground C accumulation in AM- and ECM-forests in Qingyuan Forest CERN, National Observation and Research Station. The results showed that belowground carbon stocks of AM-dominated forests were 25% higher than those of ECM-dominated forests. However, it is still not clear how do mycorrhizal associations (AM vs ECM) influence C distribution among trees experiencing global changes?

The researchers collected 3050 sets of data on forest biomass, soil C and environmental factors under global changes. A total of 12 forest C-related variables were analyzed and summarized to clarify the impact of global change drivers (N deposition, elevated CO2, and warming) on plant biomass and soil C accumulation in forest ecosystems.

They found that plant biomass increased 17.9%-31.4% under global change drivers whereas soil C stocks varied depending on specific global change drivers in forest ecosystems. Soil C stocks increased 7.8% under elevated CO2 due to increasing root biomass and microbial activity. However, soil C stocks did not significant change under N deposition and warming as a result of soil acidification and priming effect.

Based on above results, the researchers further divide tree species into AM trees and ECM trees because AM or ECM fungi differ in soil nutrient uptake. For example, AM trees tend to grow in soils with relatively low organic/inorganic N ratios whereas ECM trees tend to grow in soils with relatively low inorganic N contents. The different utilization of nutrients in AM and ECM trees may lead to divergent responses to global change drivers.

More notably, the researchers also found that plant biomass and soil C stock increased more under elevated CO2 than under N deposition and warming. Furthermore, soil C stock depended on mycorrhizal associations, decreasing in forests dominated by AM tree species while increasing in forests dominated by ECM tree species under N deposition and warming, implying the mycorrhizal association in forest ecosystems play an important role in regulating soil C stocks under global changes.

In the future study, global forest C models should consider mycorrhizal types when projecting plant-soil C allocation strategies in forest ecosystem responses and feedback to global changes.

This study, entitled “Mycorrhizal type regulates trade-offs between plant and soil carbon in forests” was published online in Nature Climate Change on Nov. 16.

Other contributors include YANG Kai, ZHANG Qian, WANG Qiqi, and GAO Tian from Institute of Applied Ecology, CAS; WANG G. Geoff from Clemson University.

This study was jointly supported by CAS Project for Young Scientists in Basic Research, the National Natural Science Foundation, and the National Key Research and Development Program of China.