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Environmental effects on soil microbial nitrogen use efficiency are controlled by allocation of organic nitrogen to microbial growth and regulate gross N mineralization.
Soil Biology and Biochemistry ( IF 9.7 ) Pub Date : 2019-05-23 , DOI: 10.1016/j.soilbio.2019.05.019
Shasha Zhang 1 , Qing Zheng 1 , Lisa Noll 1 , Yuntao Hu 1, 2 , Wolfgang Wanek 1
Affiliation  

Microbial nitrogen use efficiency (NUE) is the efficiency by which microbes allocate organic N acquired to biomass formation relative to the N in excess of microbial demand released through N mineralization. Microbial NUE thus is critical to estimate the capacity of soil microbes to retain N in soils and thereby affects inorganic N availability to plants and ecosystem N losses. However, how soil temperature and soil moisture/O2 affect microbial NUE to date is not clear. Therefore, two independent incubation experiments were conducted with soils from three land uses (cropland, grassland and forest) on two bedrocks (silicate and limestone). Soils were exposed to 5, 15 and 25 °C overnight at 60% water holding capacity (WHC) or acclimated to 30 and 60% WHC at 21% O2 and to 90% WHC at 1% O2 over one week at 20 °C. Microbial NUE was measured as microbial growth over microbial organic N uptake (the sum of growth N demand and gross N mineralization). Microbial NUE responded positively to temperature increases with Q10 values ranging from 1.30 ± 0.11 to 2.48 ± 0.67. This was due to exponentially increasing microbial growth rates with incubation temperature while gross N mineralization rates were relatively insensitive to temperature increases (Q10 values 0.66 ± 0.30 to 1.63 ± 0.15). Under oxic conditions (21% O2), microbial NUE as well as gross N mineralization were not stimulated by the increase in soil moisture from 30 to 60% WHC. Under suboxic conditions (90% WHC and 1% O2), microbial NUE markedly declined as microbial growth rates were strongly negatively affected due to increasing microbial energy limitation. In contrast, gross N mineralization rates increased strongly as organic N uptake became in excess of microbial growth N demand. Therefore, in the moisture/O2 experiment microbial NUE was mainly regulated by the shift in O2 status (to suboxic conditions) and less affected by increasing water availability per se. These temperature and moisture/O2 effects on microbial organic N metabolism were consistent across the soils differing in bedrock and land use. Overall it has been demonstrated that microbial NUE was controlled by microbial growth, and that NUE controlled gross N mineralization as an overflow metabolism when energy (C) became limiting or N in excess in soils. This study thereby greatly contributes to the understanding of short-term environmental responses of microbial community N metabolism and the regulation of microbial organic-inorganic N transformations in soils.



中文翻译:

环境对土壤微生物氮利用效率的影响是通过有机氮向微生物生长的分配和调节总氮矿化来控制的。

微生物氮利用效率(NUE)是微生物将获得的有机氮分配给生物质形成的效率,相对于通过氮矿化释放的超过微生物需求的氮。因此,微生物 NUE 对于估计土壤微生物在土壤中保留氮的能力至关重要,从而影响植物的无机氮可用性和生态系统氮损失。然而,迄今为止,土壤温度和土壤湿度/O 2如何影响微生物NUE尚不清楚。因此,利用来自三种土地利用(农田、草地和森林)的土壤在两种基岩(硅酸盐和石灰岩)上进行了两次独立的孵化实验。将土壤在 60% 持水能力 (WHC) 下暴露于 5、15 和 25 °C 过夜,或在 20 ° 下适应 30 和 60% WHC、21% O 2 和 90% WHC、1 % O 2一周。 C。微生物 NUE 被测量为微生物生长量与微生物有机氮吸收量(生长氮需求量与总氮矿化量之和)。微生物 NUE 对温度升高有积极反应,Q 10值范围为 1.30 ± 0.11 至 2.48 ± 0.67。这是由于微生物生长速率随培养温度呈指数增加,而总氮矿化速率对温度升高相对不敏感(Q 10值 0.66 ± 0.30 至 1.63 ± 0.15)。在含氧条件下(21% O 2),土壤湿度从 30% WHC 增加到 60% WHC 不会刺激微生物 NUE 以及总氮矿化。在低氧条件下(90% WHC 和 1% O 2),微生物 NUE 显着下降,因为微生物能量限制增加,微生物生长速率受到强烈负面影响。相比之下,随着有机氮的吸收超过微生物生长的氮需求,总氮矿化率大幅增加。因此,在水分/O 2实验中,微生物NUE主要受O 2状态转变(至低氧条件)的调节,而受水本身可用性增加的影响较小。这些温度和湿度/O 2对微生物有机氮代谢的影响在不同基岩和土地利用的土壤中是一致的。总体而言,已证明微生物 NUE 受微生物生长控制,并且当能量 (C) 受到限制或土壤中 N 过量时,NUE 作为溢出代谢控制总 N 矿化。因此,这项研究极大地有助于理解微生物群落氮代谢的短期环境响应以及土壤中微生物有机-无机氮转化的调节。

更新日期:2019-05-23
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