草原土壤储存有439 Gt有机碳（SOC），在调节区域乃至全球气候变化进程中起着重要作用。然而，全球气候变化背景下，大气氮沉降的“施肥效应”强烈地影响着土壤碳储存。因此，明确高寒草甸SOC组分对氮、磷富集的响应和潜在机制至关重要。
西南民族大学高寒湿地生态保护研究创新团队马文明副研究员课题组依托青藏高原生态保护与畜牧业高科技研究示范基地和四川若尔盖高寒湿地生态系统国家野外科学观测研究站以红原高寒草甸为研究对象进行了长期氮磷添加实验。采取随机区组用尿素(CO(NH2)2)和过磷酸钙(Ca(H2PO4)2·H2O)设计7个施肥梯度，氮肥施尿素(46.65%N)，磷肥施过磷酸钙(16%P2O5)，施肥梯度分别为（0g尿素+0g过磷酸钙）/m2(CK)、（10g尿素）/m2(N10)、（30g尿素）/m2(N30)、（10g过磷酸钙）/m2(P10)、（30g过磷酸钙）/m2(P30)（5g尿素+5g过磷酸钙）/m2(NP10)、（15g尿素+15g过磷酸钙）/m2(NP30)。研究发现，氮和磷添加导致 SOC含量增加19.95%–36.66%；在相同施肥条件下，SOC含量随着施肥梯度的增加而增加，在N30处理下达到最高；N和P添加促进了脂肪族碳和芳香族碳的富集；与其他处理相比，NP30处理下SOC的稳定性最高，而P10处理下SOC的稳定性最低。表明N和P添加促进了不稳定碳的损失和稳定碳的富集，从而提高了SOC的稳定性，促进了高寒草甸SOC的封存。总体而言，氮磷添加改变了高寒草甸土壤有机碳的理化性质以及SOC的官能团组成，进而促进了SOC积累。因此，在退化的生态系统中添加氮和磷可能是改善土壤碳固存的有效措施。
该项研究近期以题为Nitrogen and phosphorus supply controls stability of soil organic carbon in alpine meadow of the Qinghai-Tibetan Plateau发表在生态学领域一区期刊Agriculture Ecosystems & Environment上（IF=6.576）。该研究得到了国家自然科学基金（No. 31600378和U20A2008）、西南民族大学青藏高原研究科技创新团队（2024CXTD10）建设项目、西南民族大学“双一流”建设项目（No. CX2023030）和中央高校优秀学生培养工程项目（2023NYXXS099）等项目资助。
Fig. 2. The effects of N and P addition on soil water content (SWC) and bulk density (BD). Note: Different lowercase letters indicate significant differences between the different nitrogen and phosphorus addition treatment, respectively, at the P < 0.05 level.
Fig. 3. The effects of N and P additions on soil total nutrient content in alpine grassland. Note: Box plots represent the smallest observation, lower quartile, median, upper quartile, and largest observation (n = 6). Different lowercase letters indicate significant differences between the different nitrogen and phosphorus addition treatment, respectively, at the P < 0.05 level.
Fig. 4. The effects of N and P additions on soil available nutrient content in alpine grassland. Note: Box plots represent the smallest observation, lower quartile, median, upper quartile, and largest observation (n = 6). Different lowercase letters indicate significant differences between the different nitrogen and phosphorus addition treatment, respectively, at the P < 0.05 level.
Fig. 5. Effects of nitrogen and phosphorus addition on the relative abundance of soil chemical structure of alpine grassland on QTP. Note: Values are means with 95 % confidence intervals. The p-values indicate the differences among vegetation types. * indicates P < 0.05, ** indicates P < 0.01, ** indicates P < 0.001.
Fig. 6. The effects on SOC stability of N and P addition. Note: Values are means with 95 % confidence intervals. The p-values indicate the differences among vegetation types. * indicates P < 0.05, ** indicates P < 0.01, ** indicates P < 0.001.
Fig. 7. The effects of soil properties on soil carbon chemical structure stability as estimated using the structural equation model. Panel (left), the numbers in blocks are the variance explained by the model (R2), and the numbers on arrows are standardized direct path coefficients. Red and blue arrows indicate positive and negative effects, respectively. The total effects of environmental factors on soil carbon chemical structure stability are presented in Panel (right).