Aboveground net primary productivity was not limited by phosphorus in a temperate typical steppe in Inner Mongolia

Phosphorus (P) is an essential element for plant growth, however, whether the aboveground net primary productivity (ANPP) of typical steppe was limited by P remains obscure. To detect the effects of P addition on primary productivity and aboveground biomass of different plant functional groups both under ambient and N addition conditions, ANPP and aboveground biomass of grasses and forbs were measured from 2016 to 2020 on a 16-year N and P addition experiment platform in a temperate typical steppe in Inner Mongolia. The soil available N and P concentration were also determined to test the relationship between ANPP and the availability of soil nutrient. We found that P addition under ambient condition had no significant effect on ANPP and the aboveground biomass of grasses and forbs. Whereas, under N addition, P addition significantly increased ANPP and the aboveground biomass of forbs. Furthermore, soil available N and P concentration were increased significantly by N and P addition, respectively. Moreover, there was no significant correlation between ANPP and soil available P concentration, while, ANPP was positively correlated with soil available N concentration. These results suggested that P was not the key factor limiting the primary productivity of the temperate typical steppe in Inner Mongolia. However, under N addition, P addition can promote ANPP and alter the community composition. These findings provide valuable information for the management of the temperate typical steppe.