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 ¹⁴C-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.

蛋白质代表了土壤中有机物的主要输入，并且是微生物的碳（C）和氮（N）的重要来源。因此，确定哪种土壤特性影响土壤中蛋白质的矿化作用是理解和模拟土壤碳氮循环的关键。但是，人们对不同土壤性质对蛋白质矿化的影响，尤其是土壤性质之间的相互作用的了解很少。我们调查了表层土壤和下层土壤的特性如何影响沿草地海拔（catena）序列（包含土壤类型和初级生产力的梯度）的蛋白质矿化作用。我们设计了示意图来测试可能影响土壤中蛋白质矿化的关键营养因素（例如pH值，微生物生物量，无机和有机氮的利用率，酶活性和吸附）。¹⁴两个月内土壤中C标记的可溶性植物衍生的蛋白质和氨基酸。相关分析用于确定蛋白质矿化速率与土壤特性之间的关联。与预期相反，我们发现蛋白质矿化速度几乎与氨基酸更新速度一样快。我们将这种快速的蛋白质更新归因于此处使用的蛋白质水平低，其可溶性，微生物群落中高度的功能冗余以及微生物酶对其生态位的适应性。与其他关键的土壤氮过程（例如硝化，反硝化）不同，蛋白酶的活性不受一小部分因素的调节，而是受到多种相互作用因素的影响，这些因素的重要性取决于海拔高度和土壤深度[例如 地上净初级生产力（NPP），土壤pH，硝酸盐，阳离子交换容量（CEC），C：N比]。根据我们的结果，我们假设土壤氮循环和铵离子产生的差异与蛋白质供应的速率有关，而不是蛋白酶活性和蛋白质更新的限制。本身。