In a groundbreaking study published in Nature Climate Change, Professor Zhu Jiaojun and his team from the Institute of Applied Ecology of the Chinese Academy of Sciences (CAS) have unveiled a mycorrhizae-mediated trade-off between plant biomass and soil carbon sequestration in forest ecosystems experiencing nitrogen deposition and warming conditions.
Forests, responsible for storing approximately 80% of terrestrial carbon, play a pivotal role in global carbon cycling. The study focused on arbuscular mycorrhizal (AM) and ectomycorrhizal (ECM) fungi, the predominant types of mycorrhizal fungi, whose associations with plant roots significantly influence plant growth, nutrient acquisition, and soil carbon storage.
The research builds upon previous investigations by Zhu’s team, which demonstrated that AM-dominated forests exhibited 25% higher below-ground carbon stocks compared to ECM-dominated forests in the Qingyuan Forest CERN, National Observation and Research Station. However, understanding how mycorrhizal associations impact carbon distribution among trees under global change remained a key knowledge gap.
To address this, the researchers collected an extensive dataset comprising 3,050 observations on forest biomass, soil carbon, and environmental factors under global change conditions. Analyzing a total of 12 forest carbon-related variables, the team sought to elucidate the influence of global change drivers—specifically nitrogen deposition, elevated CO2 levels, and warming—on plant biomass and soil carbon accumulation in forest ecosystems.
The findings indicated a noteworthy 17.9%–31.4% increase in plant biomass under the influence of global change drivers. Conversely, soil carbon stocks exhibited variations based on specific global change drivers. Elevated CO2 led to a 7.8% increase in soil carbon stocks attributed to heightened root biomass and microbial activity. However, nitrogen deposition and warming did not significantly alter soil carbon stocks, attributed to soil acidification and the priming effect.
Delving deeper into the study, the researchers categorized tree species into AM and ECM trees, recognizing the distinct soil nutrient uptake patterns associated with each mycorrhizal type. AM trees, thriving in soils with lower organic/inorganic nitrogen ratios, exhibited different responses compared to ECM trees, which preferred soils with lower inorganic nitrogen contents. The divergence in nutrient utilization among AM and ECM trees showcased varied responses to global change drivers.
Remarkably, the study highlighted that plant biomass and soil carbon stocks experienced more significant increases under elevated CO2 levels compared to nitrogen deposition and warming. Moreover, soil carbon stocks were influenced by mycorrhizal associations, decreasing in AM-dominated forests but increasing in ECM-dominated forests under nitrogen deposition and warming. This underscores the pivotal role of mycorrhizal associations in regulating soil carbon stocks in the face of global change.
The implications of this research extend to future global forest carbon models, urging a consideration of mycorrhizal species in projecting plant-soil carbon allocation strategies. Understanding the intricate interplay between mycorrhizal associations and global change drivers is essential for accurate predictions of forest ecosystem responses and feedback to a changing climate.