In drylands, where soil fertility is typically low, plant litter decomposition provides particularly critical carbon and nitrogen inputs into soil. Although climate change is projected to increase the already large global extent of drylands, it is unknown how warmer temperatures will affect core ecosystem processes, such as plant litter decomposition, in these systems. To address this key unknown, we conducted a litterbag study in a long-term dryland warming experiment in southeastern Utah, USA. Unexpectedly, we did not find an overall effect of warming on leaf litter mass loss over time. Instead, our results indicated both positive and negative effects of warming on mass loss which offset one another. In particular, our findings suggested that a warming-induced degradation of biological soil crusts (soil surface community of mosses, lichens, and/or cyanobacteria that live in drylands worldwide) increased soil-litter mixing, thereby accelerating decomposition. Results also suggested that a warming-induced reduction in litter moisture slowed decomposition. In addition, we found that warming lowered the carbon-to-nitrogen ratio of the decomposing litter. These results showed that warming did not alter the total litter mass-loss rates in this ecosystem, but that decomposition patterns were affected through more nuanced changes to both the biological and physical environment of dryland soils.

在土壤肥力通常较低的干旱地区，植物凋落物分解为土壤提供了特别关键的碳和氮输入。尽管预计气候变化将增加本已很大的全球旱地范围，但尚不清楚温度升高将如何影响这些系统中的核心生态系统过程，例如植物凋落物的分解。为了解决这个关键的未知问题，我们在美国犹他州东南部的一项长期旱地变暖实验中对垃圾袋进行了研究。出乎意料的是，我们并未发现变暖对叶片凋落物质量损失的总体影响。相反，我们的结果表明变暖对质量损失的正反作用相互抵消。特别是，我们的发现表明，气候变暖导致生物土壤结皮（苔藓，地衣，和/或生活在世界各地旱地的蓝细菌）增加了土壤-凋落物的混合，从而加速了分解。结果还表明，变暖导致的垫料水分减少减慢了分解速度。此外，我们发现变暖降低了分解垃圾的碳氮比。这些结果表明，变暖并没有改变该生态系统中凋落物的总质量损失率，但是分解模式受到了旱地土壤生物和物理环境更细微变化的影响。我们发现变暖降低了分解垃圾的碳氮比。这些结果表明，变暖并没有改变该生态系统中凋落物的总失重率，但是分解模式受到了旱地土壤生物和物理环境更细微变化的影响。我们发现变暖降低了分解垃圾的碳氮比。这些结果表明，变暖并没有改变该生态系统中凋落物的总质量损失率，但是分解模式受到了旱地土壤生物和物理环境更细微变化的影响。