Belowground plant traits play important roles in plant diversity loss driven by atmospheric nitrogen (N) deposition. However, the way N enrichment shapes plant microhabitats by patterning belowground traits and finally determines aboveground responses is poorly understood. Here, we investigated the rhizosheath trait of 74 plant species in seven N-addition-simulation experiments across multiple grassland ecosystems in China. We found that rhizosheath formation differed among plant functional groups and contributed to changes in plant community composition induced by N enrichment. Compared with forb species, grass and sedge species exhibited more distinct rhizosheaths; moreover, grasses and sedges expanded their rhizosheaths with increasing N-addition rate which allowed them to colonize belowground habitats. Grasses also shaped a different microenvironment around their roots compared with forbs by affecting the physicochemical, biological and stress-avoiding properties of their rhizosphere soil. Rhizosheaths act as a “biofilm-like shield” by accumulating of protective compounds, carboxylic anions and polysaccharides, determined by both plants and microorganisms. This enhanced the tolerance of grasses and sedges to stresses induced by N enrichment. Conversely, forbs lacked the protective rhizosheaths which renders their roots sensitive to stresses induced by N enrichment, thus contributing to their disappearance under N-enriched conditions. This study uncovers the processes by which belowground facilitation and trait matching affects aboveground responses under conditions of N enrichment, which advances our mechanistic understanding of the contribution of competitive exclusion and environmental tolerance to plant diversity loss caused by N deposition.
This is the peer reviewed version of the following article: Tian, Q., Lu, P., Zhai, X., Zhang, R., Zheng, Y., Wang, H., Nie, B., Bai, W., Niu, S., Shi, P., Yang, Y., Li, K., Yang, D., Stevens, C., Lambers, H., & Zhang, W.-H. (2022). An integrated belowground trait-based understanding of nitrogen-driven plant diversity loss. Global Change Biology, 28, 3651– 3664. doi.org/10.1111/gcb.16147 which has been published in final form at https://onlinelibrary.wiley.com/doi/10.1111/gcb.16147 This article may be used for non-commercial purposes in accordance With Wiley Terms and Conditions for self-archiving.