Nutrient reabsorption efficiency of three tree species in Beijing plain afforestation and its C∶N∶P stoichiometry

Elucidating variability in nutrient resorption and carbon (C), nitrogen (N) and phosphorus (P) stoichiometry is important for holistically understanding plant approaches to nutrient adaption. However, the patterns of these phenomena in afforested regions of the Beijing Plain have been ignored. Herein, we assessed patterns of leaf and litter C, N, and P stoichiometry and nutrient resorption in Robinia pseudoacacia L., Ailanthus altissima (Mill.) Swingle, and Salix matsudana Koidz. forests in afforested areas in Beijing, China. We found that the plantation growth of R. pseudoacacia and S. matsudana was mainly limited by P nutrients. Both the N and P in the fresh leaves of R. pseudoacacia were significantly higher than those in the fresh leaves of S. matsudana and A. altissima, indicating that the N resorption efficiency (NRE) of R. pseudoacacia was higher. However, the P resorption efficiency (PRE) was significantly correlated with the leaf P nutrients in the R. pseudoacacia and A. altissima forests. Except for the significant correlation between the N content of fresh leaves and the AN content in soil, there were no significant correlations between the leaf C, N and P contents and the contents of these nutrients in the soil. These results suggested that of the factors studied, leaf P stoichiometry and PRE were more responsive indicators of the afforestation area on the Beijing Plain. Together, our data indicated that P deficiency is an important factor for the forests on the Beijing Plain and that the ability of afforested areas to adapt to barren land through nutrient resorption is gradually weakened and the N and P nutrient preservation ability is reduced over time. We thus clarified the nutrient resorption and leaf P and N patterns for the three forests studied. The findings have important implications for the application of P fertilizer, which must be conducted in a timely fashion to ensure that nutrient addition meets the nutritional needs of the plants.