Is soluble protein mineralisation and protease activity in soil regulated by supply or demand?
Is soluble protein mineralisation and protease activity in soil regulated by supply or demand?
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DOI：
10.1016/j.soilbio.2020.108007
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发表时间：
2020-11-01
影响因子：
9.7
通讯作者：
Jones, Davey L.
中科院分区：
文献类型：
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作者：
Greenfield, Lucy M.;Hill, Paul W.;Jones, Davey L.
蛋白质是土壤有机质的主要输入，也是微生物碳（C）和氮（N）的重要来源。因此，确定哪些土壤性质影响土壤中的蛋白质矿化是理解和模拟土壤C和N循环的关键。然而，不同土壤性质对蛋白质矿化的影响，特别是土壤性质之间的相互作用，知之甚少。我们调查了表土和底土的性质如何影响蛋白质矿化沿着草原海拔（catena）序列，包含梯度的土壤类型和初级生产力。我们设计了一个示意图来测试可能影响土壤中蛋白质矿化的关键土壤因素（例如pH值，微生物生物量，无机和有机氮的可用性，酶活性和吸附）。然后，我们测量了两个月内土壤中C-14标记的可溶性植物源蛋白和氨基酸的矿化率。相关分析被用来确定蛋白质矿化率和土壤性质之间的关联。与预期相反，我们发现蛋白质矿化速率几乎与氨基酸周转一样快。我们将这种快速的蛋白质周转归因于这里使用的蛋白质的低水平、其可溶性、微生物群落中高度的功能冗余和微生物酶对其生态位的适应。与其他关键的土壤氮素过程（如硝化、反硝化）不同，蛋白酶活性不受小范围因素的调控，而是受到广泛的相互作用因素的影响，这些因素的重要性取决于海拔和土壤深度[如地上净初级生产力（NPP）、土壤pH、硝酸盐、阳离子交换量（CEC）、C：N比]。根据我们的研究结果，我们假设，土壤氮循环和铵的产生的差异更相关的蛋白质供应的速度，而不是限制蛋白酶活性和蛋白质周转本身。
Protein represents a major input of organic matter to soil and is an important source of carbon (C) and nitrogen (N) for microorganisms. Therefore, determining which soil properties influence protein mineralisation in soil is key to understanding and modelling soil C and N cycling. However, the effect of different soil properties on protein mineralisation, and especially the interactions between soil properties, are poorly understood. We investigated how topsoil and subsoil properties affect protein mineralisation along a grassland altitudinal (catena) sequence that contained a gradient in soil type and primary productivity. We devised a schematic diagram to test the key edaphic factors that may influence protein mineralisation in soil (e.g. pH, microbial biomass, inorganic and organic N availability, enzyme activity and sorption). We then measured the mineralisation rate of C-14-labelled soluble plant-derived protein and amino acids in soil over a two-month period. Correlation analysis was used to determine the associations between rates of protein mineralisation and soil properties. Contrary to expectation, we found that protein mineralisation rate was nearly as fast as for amino acid turnover. We ascribe this rapid protein turnover to the low levels of protein used here, its soluble nature, a high degree of functional redundancy in the microbial community and microbial enzyme adaptation to their ecological niche. Unlike other key soil N processes (e.g. nitrification, denitrification), protease activity was not regulated by a small range of factors, but rather appeared to be affected by a wide range of interacting factors whose importance was dependent on altitude and soil depth [e.g. above-ground net primary productivity (NPP), soil pH, nitrate, cation exchange capacity (CEC), C:N ratio]. Based on our results, we hypothesise that differences in soil N cycling and the generation of ammonium are more related to the rate of protein supply rather than limitations in protease activity and protein turnover per se.