Short-term effects of soil warming and nitrogen addition on the N:P stoichiometry of Cunninghamia lanceolata in subtropical regions

Increasing temperature and nitrogen (N) deposition are major drivers of global change that will influence plant-soil systems. We aimed to understand how plant stoichiometry and nutrient limiting types could change with continued warming and N inputs in subtropical regions. In 2014, the experiments were established in 30 mini-plots (2 x 2 m) with the following treatments: control, high N addition, low N addition, warming, warming + high N addition, and warming + low N addition. We sampled the leaf and root of Cunninghamia lanceolata and soils to assess their elemental and stoichiometric variables and delta N-15 under all six conditions. Both experimental warming and N fertilization consistently induced an increase in fine-root N, P, and N:P. The N:P ratio of the mature green-leaf and soil was 7.24-11.63 and 4.79-6.56, respectively. On average, C. lanceolata showed higher proportional P resorption, but lower N resorption. The delta N-15 enrichment factor significantly increased in the warming and N addition treatments. N addition decrease leaf N content, and increased the plant growth, which was due to the effect of the N dilution of C. lanceolata. In subtropical regions, N-limitation affects the growth of C. lanceolata, and the concurrent increase in warming and N fertilization should help relieve N-limiting conditions.