The state of boreal larch forests near the southern permafrost margin in eastern Eurasia varies considerably, even on a local scale, as a result of anthropogenic disturbances (e.g., clear-cuts and fires) and uneven permafrost distribution. This study aimed to investigate whether various ecosystem conditions affect litter decomposition and organic matter (OM) transformation. Here, we present the results of a field experiment in natural and disturbed larch stands utilising the Tea-Bag Index approach (TBI). We investigated the decomposition in four larch stands in different states (post-fire, clear-cut, permafrost and control). Besides standard TBI indexes, we studied the transformation of OM composition by thermochemolysis–gas chromatography mass spectrometry. Mass loss differed depending on litter quality rather than forest disturbance type or permafrost. No significant differences were found between stabilisation (S) and decomposition constant (k) in disturbed and unaffected forests, whereas soil properties were differently related to decomposition parameters at the study sites. Our results on molecular composition before and after the incubation suggest site-depending, mainly microbial transformation of green tea in various forest conditions. Rooibos did not undergo a considerable microbial transformation. We showed that S and k might not be sensitive to various ecosystem conditions (e.g., disturbances and permafrost). However, the transformation of OM may vary, even on a local scale, having significant implications for carbon sequestration in soil. Our study shows that not a mass loss but a transformation of OM might depend on various conditions of the larch ecosystem at the southern margin of permafrost distribution in eastern Eurasia.

由于人为干扰（例如砍伐和火灾）和不均匀的多年冻土分布，欧亚大陆东部永久冻土边缘南部附近的北方落叶松森林的状况差异很大，即使在局部范围内也是如此。本研究旨在调查各种生态系统条件是否影响凋落物分解和有机物（OM）转化。在这里，我们展示了利用茶袋指数方法 (TBI) 在天然和受干扰的落叶松林中进行的现场实验结果。我们研究了四种落叶松林在不同状态（火灾后、砍伐、永久冻土和控制）下的分解情况。除了标准TBI指标外，我们还通过热化学分解-气相色谱质谱法研究了OM成分的转化。质量损失的不同取决于凋落物质量，而不是森林干扰类型或永久冻土。稳定性 (S) 和分解常数 ( k）在受干扰和未受影响的森林中，而土壤特性与研究地点的分解参数有不同的相关性。我们对孵化前后分子组成的结果表明，绿茶在不同森林条件下的转化取决于地点，主要是微生物转化。路易波士茶并未经历显着的微生物转化。我们表明，S 和k可能对各种生态系统条件（例如干扰和永久冻土）不敏感。然而，即使在局部范围内，有机质的转化也可能有所不同，这对土壤中的碳封存具有重大影响。我们的研究表明，OM 的转变而不是质量损失可能取决于欧亚大陆东部永久冻土分布南缘落叶松生态系统的各种条件。