We aimed to clarify the individual and interactive effects of temperature increase during snow-free seasons and snow depth change (increase/decrease) on litter decomposition and microbial community in cool-temperate semi-natural grassland. We conducted a 2-year in situ composite warming experiment comprising temperature increase (ca. 2°C) using infrared heaters during snow-free seasons and manual snow depth manipulation (±50% in snow depth) in Japanese grassland. Changes in litter mass remaining and litter carbon-to-nitrogen ratio (C/N ratio) were assessed by litter bag methods. Microbial biomass and community structure were determined by phospholipid fatty acid analysis. Litter decomposition constant (k) was low in the plots with temperature increase during snow-free seasons (0.56) and with less snow cover (0.57), but combining these two treatments resulted in acceleration of decomposition (k = 0.70); probably, decreased decomposition in the cold climate of early spring resulting from advanced snow melting was compensated for by higher temperature. Differences in mass loss among the treatments were well explained by litter C/N, microbial biomass and microbial community structure. The plots with a high mass loss showed lower litter C/N ratio, larger microbial biomass and different microbial community structure comparing to the plots with low mass loss. Our results showed the complex responses of litter decomposition to summer and winter climate change and combination of less snow cover and summer warming seemed to accelerate the decomposition in cool-temperate semi-natural grassland.

中文翻译：

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温升和积雪变化对冷温带草地凋落物分解和微生物群落的综合影响

我们旨在阐明无雪季节温度升高和积雪深度变化（增加/减少）对冷温带半天然草地凋落物分解和微生物群落的个体和交互影响。我们在日本草原进行了为期 2 年的原位复合变暖实验，包括在无雪季节使用红外线加热器提高温度（约 2°C）和手动操纵雪深（雪深的±50%）。通过垃圾袋方法评估剩余垃圾质量和垃圾碳氮比（C/N 比）的变化。通过磷脂脂肪酸分析确定微生物生物量和群落结构。凋落物分解常数 ( k) 在无雪季节温度升高 (0.56) 和积雪较少 (0.57) 的地块中较低，但结合这两种处理导致分解加速 ( k = 0.70); 可能是由于提前融雪导致早春寒冷气候中分解的减少被较高的温度所补偿。凋落物 C/N、微生物生物量和微生物群落结构很好地解释了处理之间质量损失的差异。与质量损失小的地块相比，质量损失大的地块显示出较低的凋落物 C/N 比、更大的微生物生物量和不同的微生物群落结构。我们的研究结果表明，凋落物分解对夏季和冬季气候变化的复杂响应以及积雪减少和夏季变暖的结合似乎加速了凉温带半天然草地的分解。