氮磷添加对荒漠草原植物-凋落物-土壤生态化学计量特征的影响

为明确植物、凋落物和土壤养分含量及化学计量比对土壤中添加多种限制性养分的响应,阐明"植物-凋落物-土壤"连续体化学计量动态及各组分之间的协同作用,以宁夏荒漠草原为研究对象,于2018年开始进行氮（N）、磷（P）养分添加控制试验。试验处理包括对照（CK）、N添加、P添加、NP共同添加4个处理。结果表明：（1） NP共同添加显著增加了荒漠草原植物N和P含量、以及凋落物和土壤P含量,显著降低了荒漠草原植物C：N和C：P、以及土壤和凋落物C：P和N：P。P添加显著增加了荒漠草原植物、凋落物和土壤P含量,显著降低了植物、凋落物、土壤C：P和N：P。N添加分别增加了植物、凋落物N含量和N：P,但对植物N含量影响未达到显著水平。（2） C、N、P含量和N：P大小均表现为植物 > 凋落物 > 土壤,C：N和C：P均表现为凋落物 > 植物。（3） N添加提高了荒漠草原植物对P再吸收效率,降低了荒漠草原植物对N利用效率;P添加提高荒漠草原植物对N再吸收效率,降低荒漠草原对P的利用效率;NP共同添加提高了荒漠草原植物对N和P再吸收效率,降低了荒漠草原植物对N和P利用效率。（4）植物-凋落物-土壤的N、P含量和化学计量比之间显著相关,其中植物N、P、N：P与凋落物和土壤N、P、N：P显著正相关,凋落物P、C：N与植物和土壤C：P、N：P显著负相关。（5）荒漠草原植物和凋落物N较稳定（1/H=0.45和1/H=0.48）,而植物和凋落物P、N：P较敏感（1/H=0.80、0.73和1/H=0.81、0.78）。荒漠草原植物生长受N限制,N添加缓解荒漠草原植物N限制,P添加和NP添加加剧荒漠草原植物N限制,荒漠草原植物通过改变养分利用策略和再吸收利用效率适应土壤中N、P含量的变化。

Effects of nitrogen and phosphorus addition on the ecological stoichiometry of plant-litter-soil in desert grassland

In order to discuss the response of plant, litter, and soil nutrient content and stoichiometric ratio to the addition of multiple restrictive nutrients in the soil, clarify the stoichiometric dynamics of the plant-litter-soil continuum and the synergistic effects between components, Ningxia desert grassland was used as the research object to carry out nitrogen (N) and phosphorus (P) addition experiments. The experimental treatment includes four treatments:control (CK), N addition (10 g/m²/a), P addition (10 g/m²/a), and co-addition of N and P (10 g/m²/a N+10 g/m²/a P). The results showed that:(1) The co-addition of N and P significantly increased the N and P content of plant, litter and soil, while significantly reduced plant C:N and C:P ratio as well as C:P and N:P ratio of soil and litter. P addition significantly increased plant, litter, and soil P content, while significantly reduced C:P and N:P ratio of plant, litter, and soil. The N content and N:P ratio of plant and litter were increased by N addition, but no significant change of plant N content was observed from N addition. (2) The content of C, N, P and N:P ratio showed the order as plant> litter> soil, C:N and C:P ratio showed the order as litter> plant. (3) N addition increased plant phosphorus reabsorption efficiency and reduced plant nitrogen utilization efficiency. P addition increased plant nitrogen reabsorption efficiency and reduced plant phosphorus utilization efficiency. The co-addition of N and P improved the plant nitrogen reabsorption efficiency and phosphorus reabsorption efficiency, and reduced plant nitrogen utilization efficiency and phosphorus utilization efficiency. (4) The N, P content and the stoichiometric ratio of plant, litter and soil were significantly correlated. Among them, N, P, N:P ratio of plant were significantly positively correlated with N, P, N:P ratio of litter and soil. Litter P and C:N ratio were significantly negatively correlated with C:P and N:P ratio of plants and soil. (5) The plant and litter N had strong homeostasis (1/H=0.45 and 0.48), and P and N:P ratio of plant and litter had weak homeostasis (1/H=0.80, 0.73 and 0.81, 0.78) to maintain N balance under N limited in soil. The plant growth was limited by N in desert grassland. The N limitation of desert grassland was alleviated by N addition, while was aggravated by P addition and co-addition of N and P. Desert grassland plant could adapt to the change of soil N and P supply mainly by changing the nutrient utilization strategies and reabsorption efficiency.