Soil characteristics and nitrogen resorption in Stipa krylovii native to northern China

Nitrogen (N) resorption from senescing tissues enables plants to conserve and reuse this important nutrient. As such, it is expected that plant species adapted to infertile soils could have a higher N-resorption efficiency (percentage reduction of nitrogen between green and senescing tissues) and/or higher N-resorption proficiency (absolute reduction of nitrogen in senescing tissues) than those adapted to fertile soils. To test this hypothesis, we investigated the relationships among soil characteristics (total N, nitrate-N, ammonium-N, pH and moisture) and N resorption in Stipa kryloviiRoshev., a species occurred widely in natural grasslands of northern China. N contents in green and senescing tissues were 6.7±0.1 and 3.3±0.1 mg g^–1, respectively. The mean value of N-resorption efficiency was found to be 72.1%. The N-resorption efficiency in S. kryloviiwas independent of soil characteristics. The N-resorption proficiency in S. kryloviiwas dependent on soil nitrate- and ammonium-N, but it was relatively independent of soil total N. The N-resorption proficiency was negatively correlated with soil pH and moisture. There was a positive correlation between N concentration in green tissues and resorption efficiency. However, N-resorption efficiency was not correlated significantly with N concentration in senescing tissues. These results indicate that the intraspecific variation in N resorption of Stipa kryloviiRoshev. is associated with soil regimes and that higher N resorption on N-poor soils is an adaptive strategy for S. kryloviito maximize N use under conditions of limited N supply.