Faculty of Natural Resources Management, Lakehead University, Thunder Bay, ON, Canada.
Glob Chang Biol. 2018 Aug;24(8):3462-3471. doi: 10.1111/gcb.14147. Epub 2018 Apr 17.
Soil respiration (Rs) is the largest terrestrial carbon (C) efflux to the atmosphere and is predicted to increase drastically through global warming. However, the responses of Rs to global warming are complicated by the fact that terrestrial plant growth and the subsequent input of plant litter to soil are also altered by ongoing climate change and human activities. Despite a number of experiments established in various ecosystems around the world, it remains a challenge to predict the magnitude and direction of changes in Rs and its temperature sensitivity (Q ) due to litter alteration. We present a meta-analysis of 100 published studies to examine the responses of Rs and Q to manipulated aboveground and belowground litter alterations. We found that 100% aboveground litter addition (double litter) increased Rs by 26.1% (95% confident intervals, 18.4%-33.7%), whereas 100% aboveground litter removal, root removal and litter + root removal reduced Rs by 22.8% (18.5%-27.1%), 34.1% (27.2%-40.9%) and 43.4% (36.6%-50.2%) respectively. Moreover, the effects of aboveground double litter and litter removal on Rs increased with experimental duration, but not those of root removal. Aboveground litter removal marginally increased Q by 6.2% (0.2%-12.3%) because of the higher temperature sensitivity of stable C substrate than fresh litter. Estimated from the studies that simultaneously tested the responses of Rs to aboveground litter addition and removal and assuming negligible changes in root-derived Rs, "priming effect" on average accounted for 7.3% (0.6%-14.0%) of Rs and increased over time. Across the global variation in terrestrial ecosystems, the effects of aboveground litter removal, root removal, litter + root removal on Rs as well as the positive effect of litter removal on Q increased with water availability. Our meta-analysis indicates that priming effects should be considered in predicting Rs to climate change-induced increases in litterfall. Our analysis also highlights the need to incorporate spatial climate gradient in projecting long-term Rs responses to litter alterations.
土壤呼吸（Rs）是最大的陆地碳（C）向大气的排放通量，预计随着全球变暖将大幅增加。然而，由于陆地植物生长以及由此产生的植物凋落物向土壤的后续输入也受到正在发生的气候变化和人类活动的影响，因此 Rs 对全球变暖的响应变得复杂。尽管在世界各地的各种生态系统中已经进行了许多实验，但由于凋落物的改变，预测 Rs 的幅度和方向及其温度敏感性（Q）仍然是一个挑战。我们对 100 项已发表的研究进行了荟萃分析，以检验 Rs 和 Q 对地上和地下凋落物改变的响应。我们发现，100%地上凋落物添加（双倍凋落物）使 Rs 增加了 26.1%（95%置信区间，18.4%-33.7%），而 100%地上凋落物去除、根系去除和凋落物+根系去除分别使 Rs 减少了 22.8%（18.5%-27.1%）、34.1%（27.2%-40.9%）和 43.4%（36.6%-50.2%）。此外，地上双倍凋落物和凋落物去除对 Rs 的影响随着实验持续时间的增加而增加，但根系去除的影响则没有增加。由于稳定 C 底物的温度敏感性高于新鲜凋落物，地上凋落物去除略微增加了 Q 6.2%（0.2%-12.3%）。从同时测试 Rs 对地上凋落物添加和去除的响应的研究中估计，在平均情况下，“激发效应”占 Rs 的 7.3%（0.6%-14.0%），并且随着时间的推移而增加。在全球陆地生态系统的变化范围内，地上凋落物去除、根系去除、凋落物+根系去除对 Rs 的影响以及凋落物去除对 Q 的正向影响随着水分可用性的增加而增加。我们的荟萃分析表明，在预测气候变化引起的凋落物增加对 Rs 的影响时，应考虑激发效应。我们的分析还强调了在预测长期凋落物变化对 Rs 的响应时，需要纳入空间气候梯度。
