Department of Biology Sciences, Institute of Environment Sciences, University of Quebec, Montreal, QC, Canada H3C 3P8.
Proc Natl Acad Sci U S A. 2012 Feb 14;109(7):2423-7. doi: 10.1073/pnas.1111576109. Epub 2012 Jan 30.
The boreal forests, identified as a critical "tipping element" of the Earth's climate system, play a critical role in the global carbon budget. Recent findings have suggested that terrestrial carbon sinks in northern high-latitude regions are weakening, but there has been little observational evidence to support the idea of a reduction of carbon sinks in northern terrestrial ecosystems. Here, we estimated changes in the biomass carbon sink of natural stands throughout Canada's boreal forests using data from long-term forest permanent sampling plots. We found that in recent decades, the rate of biomass change decreased significantly in western Canada (Alberta, Saskatchewan, and Manitoba), but there was no significant trend for eastern Canada (Ontario and Quebec). Our results revealed that recent climate change, and especially drought-induced water stress, is the dominant cause of the observed reduction in the biomass carbon sink, suggesting that western Canada's boreal forests may become net carbon sources if the climate change-induced droughts continue to intensify.
北方森林被认为是地球气候系统的一个关键“ tipping element”，在全球碳预算中起着至关重要的作用。最近的研究结果表明，高纬度地区陆地碳汇正在减弱，但几乎没有观测证据支持北方陆地生态系统碳汇减少的观点。在这里，我们利用加拿大北方森林长期森林固定采样点的数据，估算了整个加拿大北方森林天然林分的生物量碳汇变化。我们发现，近几十年来，加拿大西部（艾伯塔省、萨斯喀彻温省和马尼托巴省）的生物量变化率显著下降，但加拿大东部（安大略省和魁北克省）则没有明显的趋势。我们的研究结果表明，最近的气候变化，特别是干旱引起的水分胁迫，是观察到的生物量碳汇减少的主要原因，这表明如果气候变化引起的干旱继续加剧，加拿大西部的北方森林可能会成为净碳源。
