Rapid microbial uptake and mineralization of amino acids and peptides along a grassland productivity gradient
Rapid microbial uptake and mineralization of amino acids and peptides along a grassland productivity gradient
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DOI：
10.1016/j.soilbio.2014.01.026
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发表时间：
2014-05
影响因子：
9.7
通讯作者：
Anna Wilkinson;P. Hill;J. Farrar;Davey L. Jones;R. Bardgett
中科院分区：
文献类型：
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作者：
Anna Wilkinson;P. Hill;J. Farrar;Davey L. Jones;R. Bardgett
氨基酸和寡肽氮 (N) 仅构成草原土壤中总溶解氮库的一小部分，但这些氮库对植物生产力的重要性最终取决于这些库的周转速度。通过土壤溶液的溶解有机物 (DOM) 的通量通常通过呼吸测量来估计，但该方法未能考虑微生物底物获取和矿化之间的任何延迟。在这里，我们将 14 C 标记的丙氨酸和三丙氨酸 (10 μM) 添加到从天然草地生产力梯度收集的 4 个土壤中，然后测量土壤溶液中的底物消耗以及随后 1-60 分钟矿化产生的 14 CO2 的产生。微生物从土壤溶液中去除 14 C 的速度非常快（添加的底物在一分钟内耗尽高达 96%），与丙氨酸和三丙氨酸快速周转导致的 14 CO 2 释放之间存在相当大的延迟。这表明仅通过矿化测量就大大高估了该草原生产力梯度中土壤溶液中氨基酸和肽的寿命。在生产力较低、微生物生物量水平较低、氮受限的草原土壤中，微生物对底物的吸收和矿化率下降，这表明植物吸收有机氮的有效性可能受到土壤微生物活动的控制。我们估计，生产力最高的草原土壤中的氨基酸和肽库可能以每分钟高达 20 次的速度周转，这意味着通过土壤的氮通量非常可观。
Amino acid and oligopeptide-nitrogen (N) forms only a minor component of the total dissolved N pool in grassland soils, yet the importance of these N-pools for plant productivity will ultimately depend on the rate at which these pools turnover. Fluxes of dissolved organic matter (DOM) through the soil solution are frequently estimated from measurements of respiration, but this method fails to consider any delay between microbial substrate acquisition and mineralization. Here, we added14C-labelled alanine and tri-alanine (10 μM) to 4 soils collected from a natural grassland productivity gradient and then measured substrate depletion from the soil solution and the subsequent production of14CO2resulting from mineralization at 1–60 min. There was a considerable delay between microbial14C removal from the soil solution, which occurred extremely rapidly (up to 96% of added substrate depleted within a minute), and14CO2evolution resulting from the fast turnover of the alanine and tri-alanine. This indicates that amino acid and peptide longevity in the soil solution of the soils in this grassland productivity gradient has been greatly overestimated from measurements of mineralization alone. Rates of substrate uptake and mineralization by microbes declined in less productive, N-limited grassland soils with lower levels of microbial biomass, suggesting that the availability of organic N for plant uptake is likely to be controlled by soil microbial activity. We estimate that amino acid and peptide pools occurring in the most productive grassland soils may turnover at a rate of up to 20 times a minute, representing a very considerable flux of N through the soil.