草原土壤儲存有439 Gt有機(jī)碳（SOC），在調(diào)節(jié)區(qū)域乃至全球氣候變化進(jìn)程中起著重要作用。然而，全球氣候變化背景下，大氣氮沉降的“施肥效應(yīng)”強(qiáng)烈地影響著土壤碳儲存。因此，明確高寒草甸SOC組分對氮、磷富集的響應(yīng)和潛在機(jī)制至關(guān)重要。

西南民族大學(xué)高寒濕地生態(tài)保護(hù)研究創(chuàng)新團(tuán)隊(duì)馬文明副研究員課題組依托青藏高原生態(tài)保護(hù)與畜牧業(yè)高科技研究示范基地和四川若爾蓋高寒濕地生態(tài)系統(tǒng)國家野外科學(xué)觀測研究站以紅原高寒草甸為研究對象進(jìn)行了長期氮磷添加實(shí)驗(yàn)。采取隨機(jī)區(qū)組用尿素(CO(NH₂)₂)和過磷酸鈣(Ca(H₂PO₄)₂·H₂O)設(shè)計(jì)7個施肥梯度，氮肥施尿素(46.65%N)，磷肥施過磷酸鈣(16%P₂O₅)，施肥梯度分別為（0g尿素+0g過磷酸鈣）/m²(CK)、（10g尿素）/m²(N10)、（30g尿素）/m²(N30)、（10g過磷酸鈣）/m²(P10)、（30g過磷酸鈣）/m²(P30)（5g尿素+5g過磷酸鈣）/m²(NP10)、（15g尿素+15g過磷酸鈣）/m²(NP30)。研究發(fā)現(xiàn)，氮和磷添加導(dǎo)致 SOC含量增加19.95%–36.66%；在相同施肥條件下，SOC含量隨著施肥梯度的增加而增加，在N30處理下達(dá)到最高；N和P添加促進(jìn)了脂肪族碳和芳香族碳的富集；與其他處理相比，NP30處理下SOC的穩(wěn)定性最高，而P10處理下SOC的穩(wěn)定性最低。表明N和P添加促進(jìn)了不穩(wěn)定碳的損失和穩(wěn)定碳的富集，從而提高了SOC的穩(wěn)定性，促進(jìn)了高寒草甸SOC的封存。總體而言，氮磷添加改變了高寒草甸土壤有機(jī)碳的理化性質(zhì)以及SOC的官能團(tuán)組成，進(jìn)而促進(jìn)了SOC積累。因此，在退化的生態(tài)系統(tǒng)中添加氮和磷可能是改善土壤碳固存的有效措施。

該項(xiàng)研究近期以題為Nitrogen and phosphorus supply controls stability of soil organic carbon in alpine meadow of the Qinghai-Tibetan Plateau發(fā)表在生態(tài)學(xué)領(lǐng)域一區(qū)期刊Agriculture Ecosystems & Environment上（IF=6.576）。該研究得到了國家自然科學(xué)基金（No. 31600378和U20A2008）、西南民族大學(xué)青藏高原研究科技創(chuàng)新團(tuán)隊(duì)（2024CXTD10）建設(shè)項(xiàng)目、西南民族大學(xué)“雙一流”建設(shè)項(xiàng)目（No. CX2023030）和中央高校優(yōu)秀學(xué)生培養(yǎng)工程項(xiàng)目（2023NYXXS099）等項(xiàng)目資助。

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).

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