An integrated belowground trait‐based understanding of nitrogen‐driven plant diversity loss

Abstract

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 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 the accumulation 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 affect aboveground responses under conditions of N enrichment, which advances our

Root exudates enhanced rhizobacteria complexity and microbial carbon metabolism of toxic plants

“…Some autotoxins, including phenolics, omilactone B, artemisinin, phenolic acids, and cyclic hydroxamic acids ( Ni et al., 2012 ), inhibit or delay the germination and growth of conspecific plants ( Miller, 1996 ). Owing to overlapping and interference mechanisms, roots provide a specific micro-habitat for the proliferation of specific soil microorganisms, with new interactions developing among colonizing microbes in densely colonized rhizospheres ( Petermann and Buzhdygan, 2021 ; Tian et al., 2022 ).…”

The potential bias of nitrogen deposition effects on primary productivity and biodiversity

“…In general, increased soil acidification can drive plant species loss directly or indirectly. Soil acidification is directly harmful to plant growth (Bobbink et al, 2010;Yadav et al, 2020) and the tolerance of plant species to soil acidification is different (Tian et al, 2022), resulting in the loss of species richness increasing with increases in soil acidification. Moreover, soil acidification usually increases the mobilization of soil metal ions such as aluminum (Al 3+ ) and manganese (Mn 2+ ) (Bobbink et al, 1998(Bobbink et al, , 2010Tian et al, 2016;Tian & Niu, 2015), which would indirectly contribute to N-induced species loss through metal toxicity.…”

Global change re‐structures alpine plant communities through interacting abiotic and biotic effects

“…One functional strategy that provided insight outside of the abundance-based framework was the positive response of graminoids (grasses + sedges) to N addition. D. cespitosa growth responded positively to N addition (Figure 2), which is common for grasses due to belowground rhizosheath traits that allow for better N absorption while buffering against N-induced stressors (Tian et al, 2021(Tian et al, , 2022. Although not modelled individually, a subdominant sedge (Carex scopulorum) also increased in cover over time in both SNW and NW plots, in contrast to the other two subdominant species (forbs) which declined in these treatments (Figure S2).…”