1.Between-species variation in nutrient resorption is one of the mechanisms explaining the positive relationship between biodiversity and primary productivity. Yet, the role of within-species variations in nutrient resorption in mediating the relationship between biodiversity and productivity remains unclear. 2.We examined how within-species nutrient resorption, and ultimately productivity, respond to changes in species richness by using four traits related to nitrogen and phosphorus use in four dominant species from different plant functional groups in a biodiversity removal experiment in the temperate steppe. 3.Nitrogen and phosphorus concentrations in both green and senesced leaves in all species significantly decreased with increasing plant species richness, suggesting that plants used those limiting nutrients more efficiently with increasing biodiversity. Plants in higher-diversity communities resorbed more nutrients during senescence, which may facilitate reproduction and vegetative regrowth in the next year. 4.Synthesis. Our results highlight the importance of considering within-species variation in nutrient resorption as an important underlying mechanism explaining the positive effects of biodiversity on primary productivity and ecosystem carbon accumulation.