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The Influences of Ammonia Oxidizing Archaeal and Bacterial Abundances on Nitrification Responses to Temperature in Topsoil
|Publication Year :||2019|
|Abstract:||在全球氮循環中，土壤硝化作用對溫度的反應具有重要意義，然而不同豐富度之氨氮化族群及硝化抑制劑在此過程中所扮演的角色，至今尚未有研究進行探討。本研究採實驗室規模進行，首先經由20種不同的有機或無機肥沃土壤，調查其中氨氧化古細菌(Ammonia oxidizing archaea, AOA)與氨氧化細菌(Ammonia oxidizing bacteria, AOB)之相對豐富度，對於土壤潛在硝化的溫度反應之影響，其次，從不同的土地覆蓋類型蒐集共16種土壤樣本，並藉助馬可夫鏈蒙地卡羅(Markov Chain Monte Carlo)模擬，以SQRT及MMRT模式評估兩種溫度梯度下所測量的土壤潛在硝化之溫度敏感度參數。研究結果顯示，土壤硝化作用對溫度的反應會受到氨氮化族群的相對豐富度與模式參數預估的敏感度所影響，以不同族群豐富度來說，氨氧化古細菌對氨氧化細菌比例高的土壤，亦會有較高的最適溫度，而兩者比例相近的土壤，其硝化作用的溫度差距不大，此情況表示在定溫下所測量的土壤潛在硝化作用，並無法說明氨氧化族群在之中的實際貢獻；以參數敏感度來說，其中兩個熱力參數特別顯著，為中至高之敏感度，且不論何種溫度範圍皆可在模式中單獨識別，此外，控制最小溫度的參數(Tmin)及潛在硝化曲率(〖〖ΔC〗_ 〗_P^‡)分別在SQRT及MMRT模式下僅有微小之敏感度，建議在土壤硝化作用之溫度敏感度模式選擇上應更加謹慎。
Soil nitrification responses to temperature have significant implications for the global nitrogen cycle. However, no studies have addressed the role of different relative abundance of ammonia oxidizers and nitrification inhibitors on the temperature response of soil nitrification. Here, laboratory-scale experiments were conducted to firstly investigate the effect of the different relative abundance of ammonia-oxidizing archaea (AOA) and bacteria (AOB) on the temperature response of soil nitrification potential (NP), imposed on twenty different organic and inorganic fertilized soils. Furthermore, sixteen soil samples were collected from the different land cover types, and NP response was measured across two different temperature gradients to estimate the sensitivity of SQRT and MMRT model-based estimated parameters with the help of Markov Chain Monte Carlo simulation. Our results showed that nitrification response to temperature influences by both relative abundances of ammonia oxidizers and sensitivity of models estimated parameters. Among the different relative abundance of ammonia oxidizers, the soil with high AOA to AOB ratios showed high optimum temperature, but narrow temperature ranges for nitrification compare to the soil where AOA to AOB ratio was within the same order of magnitude. These results suggest that measuring soil NP at a fixed temperature does not represent the actual contribution of ammonia oxidizers for nitrification. Regarding parameter sensitivity, we found that two thermodynamic parameters stand out as moderately to highly sensitive, and are uniquely identifiable in each model (the parameters a and maximum temperature for SQRT, and the parameters change in enthalpy and change in entropy for MMRT model), regardless of the temperature range. However, parameters that control the minimum temperature and curvature of the NP response curve (Tmin and 〖〖ΔC〗_ 〗_P^‡) were found to have little to no sensitivity to SQRT and MMRT models output, respectively, suggesting a careful selection of complementary model while describing the temperature sensitivity of soil nitrification.
Nitrification inhibition experiment based on cropped and non-cropped soil data showed that the IE of both NIs decreased with NP, and the amount of NI required to achieve an IE of approximately 50% was significantly reduced for soils that exhibited the lowest NP rates, especially for DMPP. However, both NIs significantly reduce the NP across the temperature gradient, suggesting that the difference in temperature is less likely to influences the effectiveness of NIs. These results could help to accurately simulate the temperature response of nitrification in a variety of soils. Moreover, this study’s framework provides meaningful ranges for the model’s sensitivity in the simulation of thermodynamically explain soil nitrification kinetics, which may enhance the accurate interpretation of soil biochemical processes and to improve fertilized soil management.
|Appears in Collections:||生物環境系統工程學系|
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