Abstract：
Although the effects of human-enhanced atmospheric nitrogen (N) deposition are well documented, the response of dryland soils to N deposition remains unclear owing to the divergence in hydrological outputs and soil heterogeneity. We selected a typical desert steppe in western China to simulate the effects of long-term N deposition by applying 0 (CK), 3.5, 7, and 14 g N m-2 yr-1 for 12 consecutive years. We found that, compared with the CK plots, the total N content of the upper (0-10 cm) and lower (10-20 cm) soil layers in fertilized plots increased by 8.3-14.6 % and 2.4-8.2 %, respectively. Correspondingly, the available, NH4+-, and NO3--N contents in the upper soil significantly increased by 25.5-68.3 %. However, in the lower soil, available and NO3--N contents were significantly lower than those in the CK plots, and their variation trend was opposite to that of NH4+-N, implying N turnover and leaching. As a result, the upper and lower soil pH in fertilized plots significantly decreased by 0.36-0.53 and 0.31-0.37 units; however, their CaCO3 content significantly increased by 9.8-22.8 % and 7.2-30.3 %, respectively. The total phosphorus (P) content in the upper and lower soil layers in fertilized plots significantly increased and decreased by 3.6-51.3 % and 16.7-62.5 %, respectively, however, both significantly decreased along the N fertilization gradient. Furthermore, the upper and lower soil organic carbon (SOC) content in the fertilized plots significantly increased by 57.7-78.1 % and 19.2-27.4 %, respectively. Pearson\'s correlation analysis revealed that available soil P was significantly negatively correlated with plant shoot Mn content (a proxy for rhizosphere carboxylates), whereas dissolved OC, SOC, and CaCO3 were significantly positively correlated, suggesting that Ca cycling is involved in P cycling and SOC sequestration. Our study suggests that long-term N input exacerbates P limitation in desert steppes, however, enhances SOC sequestration.
摘要：
尽管人类增加的大气氮（N）沉积的影响是有据可查的，由于水文产出和土壤异质性的差异，旱地土壤对氮沉积的响应尚不清楚。我们选择了中国西部典型的荒漠草原，通过应用0（CK）模拟长期N沉积的影响，连续12年为3.5、7和14gNm-2yr-1。我们发现,与CK地块相比，施肥地块上部(0-10厘米)和下部(10-20厘米)土层的总氮含量分别增加8.3-14.6%和2.4-8.2%,分别。相应地,可用的，NH4+-,上层土壤NO3--N含量显着增加了25.5-68.3％。然而,在较低的土壤中，有效和NO3--N含量明显低于CK地块，它们的变化趋势与NH4+-N相反，意味着N周转和浸出。因此,施肥地块的上下土壤pH值显着降低了0.36-0.53和0.31-0.37个单位；但是，它们的CaCO3含量显著增加了9.8-22.8%和7.2-30.3%，分别。施肥地块上、下土层全磷(P)含量显著升高和降低3.6-51.3%和16.7-62.5%,分别,然而,两者均沿N施肥梯度显着降低。此外，施肥地块的上部和下部土壤有机碳（SOC）含量显着增加了57.7-78.1％和19.2-27.4％，分别。Pearson的相关分析表明，有效土壤P与植物芽Mn含量（根际羧酸盐的代表）显着负相关，而溶解的OC，SOC,与CaCO3呈显著正相关,表明钙循环参与磷循环和SOC封存。我们的研究表明，长期的氮输入会加剧沙漠草原的磷限制，然而,增强SOC封存。
