The decline in plant biodiversity slows down soil carbon turnover under increasing nitrogen deposition in a temperate steppe

1. Nitrogen (N) deposition not only alters the physiological processes of individual plant, but also leads to worldwide biodiversity loss. However, little is known about how the hierarchical responses from individual physiological processes to plant community structure would have cascading effects on soil carbon (C) cycling.
2. Here, we assessed whether changes in plant chemistry and community composition under increasing N input would affect the turnover rate of litter layer and soil C loss via heterotrophic respiration (Rh) in a temperate grassland.
3. We showed that more than a decade’s N addition significantly decreased plant species richness, litter layer turnover rate and Rh. The 13C-NMR results showed that, for individual species, N addition either increased the abundance of recalcitrant C groups such as Alkyl and Methoxyl, or decreased labile C groups such as Carbohydrate, resulting in decreases in Carbohydrate C to Methoxyl C ratio (CC/MC) for most species. Our data also show...