Soil phosphorus availability alters the correlations between root phosphorus-uptake rates and net photosynthesis of dominant C-3 and C-4 species in a typical temperate grassland of Northern China

Phosphorus (P) fertilization can alleviate a soil P deficiency in grassland ecosystems. Understanding plant functional traits that enhance P uptake can improve grassland management.We measured impacts of P addition on soil chemical and microbial properties, net photosynthetic rate (P-n) and nonstructural carbohydrate concentrations ([NSC]), and root P-uptake rate (PUR), morphology, anatomy, and exudation of two dominant grass species: Leymus chinensis (C-3) and Cleistogenes squarrosa (C-4).For L. chinensis, PUR and P-n showed a nonlinear correlation. Growing more adventitious roots compensated for the decrease in P transport per unit root length, so that it maintained a high PUR. For C. squarrosa, PUR and P-n presented a linear correlation. Increased P-n was associated with modifications in root morphology, which further enhanced its PUR and a greater surplus of photosynthate and significantly stimulated root exudation (proxied by leaf [Mn]), which had a greater impact on rhizosheath micro-environment and microbial PLFAs.Our results present correlations between the PUR and the P-n of L. chinensis and C. squarrosa and reveal that NSC appeared to drive the modifications of root morphology and exudation; they provide more objective basis for more efficient P-input in grasslands to address the urgent problem of P deficiency.

Automated summary

Phosphorus fertilization can alleviate soil P deficiency in grassland ecosystems, and understanding plant functional traits that enhance P uptake can improve grassland management. The study measured the effects of P addition on various factors and found correlations between root P-uptake rate and net photosynthetic rate for different grass species. Nonstructural carbohydrates appeared to drive the modifications of root morphology and exudation. These results provide an objective basis for more efficient P-input in grasslands to address the urgent problem of P deficiency.