Soil microbial populations in deep floodplain soils are adapted to infrequent but regular carbon substrate addition
Soil microbial populations in deep floodplain soils are adapted to infrequent but regular carbon substrate addition
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DOI：
10.1016/j.soilbio.2018.04.001
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发表时间：
2018-07
影响因子：
9.7
通讯作者：
E. Cressey;J. Dungait;D. Jones;A. Nicholas;T. Quine
中科院分区：
文献类型：
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作者：
E. Cressey;J. Dungait;D. Jones;A. Nicholas;T. Quine
洪泛区土壤是陆地-海洋水生连续体的重要纽带。了解这些土壤（可能深达数米）中的微生物活动是我们了解洪泛区在碳 (C) 循环中的作用的关键组成部分。我们在英国西南部卡尔姆河附近的长期牧场下的两个洪泛区采样了 3m 深的矿质土壤剖面。土壤化学（C、氮（N）、磷（P）、土壤微生物量（SMB）、水分含量）和土壤溶液（pH、溶解有机碳（DOC）和氮、硝酸盐、铵、水可提取磷）在 3m 深度内以 6 个增量进行分析：0.0–0.2、0.2–0.7、1.0–1.5、1.5–2.0、2.0–2.5 和将2.5–3.0m.14C-葡萄糖添加到土壤中，并在29天的培养过程中测量14CO2的演变。根据土壤性质和 14 C-葡萄糖矿化，出现了三个深度组，从初始 k1 矿化速率常数 2 小时（表土 0.0-0.2 m）、4 小时（下土 0.2-0.7 m）和 11 小时（深层土 1.0-3.0 m）推断出不同的周转时间。然而，当通过 SMB 标准化时，k1rate 常数在所有深度上没有显着差异。深层底土需要 2 小时才能达到最大 14CO2 产量，而表土和底土 (0.2-0.7m) 会立即达到最大矿化率。 SMB随着深度的增加而减少，但仅占地表种群的一半，SMB-C占总C的比例从表土中的1%增加到深层土（>1.0m）中的15%。相对较大的SMB浓度和14 C-葡萄糖的快速矿化表明，洪泛区深层土壤层中的DOC周转受到生物可利用C的获取的限制，而不是微生物群体的大小。
Floodplain soils provide an important link in the land-ocean aquatic continuum. Understanding microbial activity in these soils, which can be many metres deep, is a key component in our understanding of the role of floodplains in the carbon (C) cycle. We sampled the mineral soil profile to 3 m depth from two floodplain sites under long-term pasture adjacent to the river Culm in SW England, UK. Soil chemistry (C, nitrogen (N), phosphorus (P), soil microbial biomass (SMB), moisture content) and soil solution (pH, dissolved organic C (DOC) and N, nitrate, ammonium, water extractable P) were analysed over the 3 m depth in 6 increments: 0.0–0.2, 0.2–0.7, 1.0–1.5, 1.5–2.0, 2.0–2.5, and 2.5–3.0 m.14C-glucose was added to the soil and the evolution of14CO2measured during a 29 d incubation. From soil properties and14C-glucose mineralisation, three depth groups emerged, with distinct turnover times extrapolated from initialk1mineralisation rate constants of 2 h (topsoil 0.0–0.2 m), 4 h (subsoil 0.2–0.7 m), and 11 h (deep subsoil 1.0–3.0 m). However, when normalised by SMB,k1rate constants had no significant differences across all depths. Deep subsoil had a 2 h lag to reach maximal14CO2production whereas the topsoil and subsoil (0.2–0.7 m) achieved maximum mineralisation rates immediately. SMB decreased with depth, but only to half of the surface population, with the proportion of SMB-C to total C increasing from 1% in topsoil to 15% in deep subsoil (>1.0 m). The relatively large SMB concentration and rapid mineralisation of14C-glucose suggests that DOC turnover in deep soil horizons in floodplains is limited by access to biologically available C and not the size of the microbial population.