Changes in plant cover and soil characteristics induced by grazing may affect litter quality and nitrogen (N) release under varying abiotic conditions. Our study was focused on the importance of litter chemistry as a main driver of inorganic N (ammonium‐N: NH4+‐N and nitrate‐N: NO3−‐N) release to soil. Both inorganic N forms are important components for N availability to plants and soil processes, and the long‐term conservation of soil‐N fertility. We analyzed the effect of secondary compounds and the C/N ratio in litter under varying soil water, and UV exposure on soil inorganic N (NH4+‐N and NO3−‐N) in Patagonian Monte degraded soils. We hypothesized that secondary compounds and C/N ratio in litter are main drivers of soil inorganic N under varying abiotic conditions. We conducted a microcosm experiment (13 months) using intact upper soil blocks from denuded soil areas. Surface soils were added with shrub (SL), and mixed grass and shrub (GSL) litter with high versus low secondary metabolites concentration and low vs. high C/N ratio, respectively. Microcosms were maintained under ambient and reduced UV exposure, and high and low soil water. We used microcosms without litter as controls. Monthly, we assessed NH4+‐N and NO3−‐N concentrations in upper and sub‐superficial soils. Litter chemistry interacting with abiotic factors did not significantly influence soil NH4+‐N at any soil depth while litter chemistry was a main driver of NO3−‐N in upper soil. SL enhanced NO3−‐N in upper soil compared with GSL independently of abiotic factors. In upper soils without litter and in those with GSL, the highest NO3−‐N concentration occurred mostly under high soil water and exposition to UV. We concluded that litter chemistry was a main driver of soil N fertility in disturbed rangelands. Shrub litter may enhance N fertility (NO3−‐N) in degraded soils.

中文翻译：

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凋落物化学是干旱巴塔哥尼亚山受干扰土壤中无机氮的主要驱动因素


放牧引起的植物覆盖和土壤特性的变化可能会影响不同非生物条件下的凋落物质量和氮 （N） 释放。我们的研究重点是凋落物化学作为无机 N （铵-N：NH4+-N 和硝酸盐-N：NO3--N）释放到土壤中的主要驱动因素的重要性。两种无机氮形式都是植物和土壤过程氮可用性以及长期保持土壤氮肥力的重要组成部分。我们分析了不同土壤水下凋落物中次生化合物和 C/N 比的影响，以及紫外线暴露对巴塔哥尼亚蒙特降解土壤土壤无机 N （NH4+-N 和 NO3--N） 的影响。我们假设凋落物中的次生化合物和 C/N 比是不同非生物条件下土壤无机氮的主要驱动因素。我们进行了一项微观实验（13 个月），使用来自裸露土壤区域的完整上层土壤块。表层土壤中添加了灌木 （SL） 和草和灌木混合 （GSL） 凋落物，分别具有高与低次生代谢物浓度以及低与高 C/N 比。在环境和减少的紫外线照射以及高低土壤水的情况下保持微观世界。我们使用没有垃圾的微观世界作为对照。每月，我们评估上层和表层土壤中的 NH4+--N 和 NO3---N 浓度。凋落物化学与非生物因子的相互作用在任何土壤深度都不会显着影响土壤 NH4+-N，而凋落物化学是上层土壤 NO3--N 的主要驱动因素。与 GSL 相比，SL 增强了上层土壤中的 NO3−‐N，与非生物因素无关。在没有凋落物的上层土壤和有 GSL 的土壤中，最高的 NO3−-N 浓度主要发生在土壤水分充足和暴露于紫外线下。 我们得出结论，凋落物化学是受干扰牧场土壤氮肥力的主要驱动因素。灌木凋落物可以提高退化土壤中的氮肥力 （NO3−‐N）。