氮磷添加对毛竹林土壤有机碳矿化及其激发效应的影响

Effects of Nitrogen and Phosphorus Addition on Organic Carbon Mineralization and Priming Effect in a Moso Bamboo Plantation Soil

养分输入会显著影响土壤有机碳矿化,但毛竹林土壤有机碳激发效应对不同类型养分输入的响应及其机制尚不明确。选用尿素和磷酸二氢钠作为外源养分,通过80 d的培养试验,研究氮素、磷素及两者联合添加对毛竹林土壤有机碳矿化及其激发效应、微生物功能以及土壤理化性质的影响。结果表明,氮素、磷素及两者联合添加均显著提高了土壤原有有机碳矿化CO_(2)累积排放量(增幅分别为91.3%、19.2%和94.9%),产生显著的正激发效应,其中氮素及其与磷素联合添加诱导的正激发效应强度显著大于磷素添加处理。上述三种养分添加处理均显著提高了土壤pH、活性有机碳库(微生物量碳、可溶性有机碳和烷氧碳组分)、碳降解酶(β-葡萄糖苷酶和蔗糖酶)活性以及cbhI和GH48功能基因丰度,但抑制了多酚氧化酶和RubisCO酶活性;此外,土壤无机氮(NH_(4)^(+)-N和NO_(3)^(-))含量在氮和氮磷添加下增加,在磷添加下降低。相关性分析表明,累积激发效应与土壤pH、活性有机碳库、无机氮含量、碳降解酶活性以及cbhI和GH48功能基因丰度呈显著正相关,而与多酚氧化酶和RubisCO酶活性显著负相关。综上所述,氮磷养分添加可能是通过影响土壤pH、活性碳氮含量,并提升微生物的活性和功能,从而显著提高土壤原有有机碳的矿化速率。

【Objective】Nutrients addition to soil have a significant effect on soil organic carbon mineralization.However,the response of soil organic carbon priming effect(PE)to the addition of different nutrients and its mechanism is still not clear.【Method】Urea and sodium dihydrogen phosphate were selected as exogenous nutrients and the effects of nitrogen addition,phosphorus addition and nitrogen combined phosphorus addition on SOC mineralization,PE,microbial function and soil physicochemical properties in a Moso bamboo plantation soil were investigated through an 80-day incubation experiment.【Result】Nitrogen,phosphorus and their interaction significantly increased the cumulative CO2 emissions of native SOC mineralization(by 91.33%,19.18%and 94.88%,respectively),resulting in a cumulative positive PE.The magnitude of positive PE induced by nitrogen and nitrogen combined with phosphorus was greater than that induced by phosphorus alone.The above three nutrient addition treatments all significantly increased soil pH,labile organic carbon pool(microbial biomass carbon,dissolved organic carbon and O-alkyl C),carbon-degrading enzyme(b-glucosidase and invertase)activities and cbhI and GH48 functional gene abundance,but inhibited the activity of polyphenol oxidase and RubisCO enzymes.Also,soil inorganic nitrogen content(NH^(+)_(4)-N and NO^(-)_(3)-N)was enhanced under nitrogen and nitrogen combined phosphorus treatments but reduced under phosphorus treatment.Results of Spearman correlation analysis showed significant positive relationships between cumulative PE and soil pH,labile organic carbon,inorganic nitrogen content,carbon-degrading enzyme activities,cbhI and GH48 functional gene abundances,whereas the activities of polyphenol oxidase and RubisCO enzyme were negatively related to cumulative PE.【Conclusion】The addition of nitrogen and phosphorus nutrients may have enhanced the rate of native SOC mineralization by affecting soil pH,the content of labile carbon and nitrogen,and stimulating the activity and function of microorganisms.