Clear-cutting means forest removal (stems only) and is the most common type of forest harvesting but undoubtedly has a negative impact on the C budget in soils. This work aimed to describe responses of soil organic matter (SOM) in the mixed coniferous forest following the removal of trees under temperate climate conditions in lowland and mountain regions in southwestern Poland. Investigated soils are described as Brunic Arenosols derived from sand with an average content of total organic carbon (TOC) in the Oa-horizons of 244 g·kg⁻¹ in the lowland and Dystric Cambisols derived from gneiss; the average content of TOC in the Oa-horizons in the mountain regions was 309 g.kg^-1. Analyzed soils were very acidic in the both regions (pH 2.7–3.5 in the topsoil). In the experiment, two replicated soil profiles were located on each site, both taken after clear-cutting and without any harvesting. Humic fraction was isolated from Oa- and A-horizons; differences between investigated objects were checked with a significance p < 0.05, (n = 16). Using the instrumental analysis, like electron paramagnetic resonance (EPR), proton nuclear magnetic resonance (¹H NMR), and Fourier transformed infrared (FTIR) spectroscopy applied to isolated humic fractions, it has been found that clear-cutting alters C cycling and accelerates decomposition in the forest floor, leading to loss of humic fractions in the investigated soils. In the mountain forests, the more labile, low-molecular-weight fulvic fraction decreased as the effect of harvesting practice by 30% in Oa-horizon and by 54% in A-horizon. The analysis of stable radicals by EPR showed a decrease in radical concentration observed for humic acids (HA) from mountain clear-cut areas compared to the undisturbed forest. Results presented in this article have proved there is less aliphatic character of HA molecules from the lowlands, compared to the mountain forest as the effect of clear-cutting. Changes in plant cover observed as a consequence of deforestation lead to the decrease in concentration of humic fractions with different solubility properties.

中文翻译：

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腐殖质分数作为土壤有机质对波兰西南部山区和低地条件清除的响应指标

砍伐意味着森林砍伐（仅限茎），是最常见的森林采伐类型，但无疑会对土壤中的碳预算产生负面影响。这项工作旨在描述在波兰西南部低地和山区温带气候条件下砍伐树木后混合针叶林土壤有机质 (SOM) 的响应。调查的土壤被描述为来自沙子的布鲁尼克阿里诺索尔，在低地的 Oa 地平线中总有机碳 (TOC) 的平均含量为 244 g·kg ^-1和来自片麻岩的 Dystric Cambisols；山区OA水平TOC平均含量为309 g.kg ^-1. 分析的土壤在这两个地区都非常酸性（表土中的 pH 值为 2.7-3.5）。在实验中，在每个地点定位了两个重复的土壤剖面，都是在清除后拍摄的，没有任何收获。腐殖质部分从 Oa 和 A 层中分离出来；检查被调查对象之间的差异，显着性p <  0.05 ( n  = 16)。使用仪器分析，如电子顺磁共振（EPR）、质子核磁共振（¹H NMR) 和傅里叶变换红外 (FTIR) 光谱应用于分离的腐殖质部分，已经发现清除改变 C 循环并加速森林地面的分解，导致所研究土壤中腐殖质部分的损失。在山地森林中，随着采伐实践的影响，更不稳定的低分子量黄腐成分在 Oa 水平下降了 30%，在 A 水平下降了 54%。通过 EPR 对稳定自由基的分析表明，与未受干扰的森林相比，从山区空旷地区观察到的腐植酸 (HA) 的自由基浓度降低。本文提出的结果证明，与山林相比，低地 HA 分子的脂肪族特征较少，因为砍伐的效果。