State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China.
Glob Chang Biol. 2014 Aug;20(8):2687-96. doi: 10.1111/gcb.12536. Epub 2014 Apr 25.
Biomass carbon accumulation in forest ecosystems is a widespread phenomenon at both regional and global scales. However, as coupled carbon-climate models predicted, a positive feedback could be triggered if accelerated soil carbon decomposition offsets enhanced vegetation growth under a warming climate. It is thus crucial to reveal whether and how soil carbon stock in forest ecosystems has changed over recent decades. However, large-scale changes in soil carbon stock across forest ecosystems have not yet been carefully examined at both regional and global scales, which have been widely perceived as a big bottleneck in untangling carbon-climate feedback. Using newly developed database and sophisticated data mining approach, here we evaluated temporal changes in topsoil carbon stock across major forest ecosystem in China and analysed potential drivers in soil carbon dynamics over broad geographical scale. Our results indicated that topsoil carbon stock increased significantly within all of five major forest types during the period of 1980s-2000s, with an overall rate of 20.0 g C m(-2) yr(-1) (95% confidence interval, 14.1-25.5). The magnitude of soil carbon accumulation across coniferous forests and coniferous/broadleaved mixed forests exhibited meaningful increases with both mean annual temperature and precipitation. Moreover, soil carbon dynamics across these forest ecosystems were positively associated with clay content, with a larger amount of SOC accumulation occurring in fine-textured soils. In contrast, changes in soil carbon stock across broadleaved forests were insensitive to either climatic or edaphic variables. Overall, these results suggest that soil carbon accumulation does not counteract vegetation carbon sequestration across China's forest ecosystems. The combination of soil carbon accumulation and vegetation carbon sequestration triggers a negative feedback to climate warming, rather than a positive feedback predicted by coupled carbon-climate models.
森林生态系统中的生物量碳积累在区域和全球范围内都是普遍存在的现象。然而，正如耦合碳-气候模型所预测的那样，如果在气候变暖的情况下，加速的土壤碳分解抵消了增强的植被生长，那么可能会引发正反馈。因此，揭示森林生态系统中土壤碳储量是否以及如何在最近几十年发生变化至关重要。然而，森林生态系统中土壤碳储量的大规模变化在区域和全球范围内尚未得到仔细研究，这被广泛认为是解开碳-气候反馈的一个大瓶颈。利用新开发的数据库和复杂的数据挖掘方法，我们在这里评估了中国主要森林生态系统表土碳储量的时间变化，并分析了广阔地理范围内土壤碳动态的潜在驱动因素。我们的结果表明，在 20 世纪 80 年代至 2000 年代期间，所有五种主要森林类型的表土碳储量都显著增加，总体速率为 20.0 g C m(-2) yr(-1)（95%置信区间为 14.1-25.5）。在年均温度和降水的影响下，针叶林和针阔混交林的土壤碳积累幅度表现出明显的增加。此外，这些森林生态系统中的土壤碳动态与粘粒含量呈正相关，在细质地土壤中发生了更大的 SOC 积累。相比之下，阔叶林的土壤碳储量变化对气候或土壤因子均不敏感。总体而言，这些结果表明，在中国的森林生态系统中，土壤碳积累不会抵消植被碳固存。土壤碳积累和植被碳固存的结合对气候变暖产生负反馈，而不是耦合碳-气候模型所预测的正反馈。
