Department of Forest Sciences, University of Helsinki, PO Box 27 (Latokartanonkaari 7), Fi-00014, Finland.
Department of Forest Sciences, University of Helsinki, PO Box 27 (Latokartanonkaari 7), Fi-00014, Finland.
J Environ Manage. 2019 Jul 1;241:637-644. doi: 10.1016/j.jenvman.2019.02.130. Epub 2019 Apr 5.
Climate warming in arctic/subarctic ecosystems will result in increased frequency of forest fires, elevated soil temperatures and thawing of permafrost, which have implications for soil organic matter (SOM) decomposition rates, the CO emissions and globally significant soil C stocks in this region. It is still unclear how decomposability and temperature sensitivity of SOM varies in different depths and different stages of succession following forest fire in permafrost regions and studies on long term effects of forest fires in these areas are lacking. To study this question, we took soil samples from 5, 10 and 30 cm depths from forest stands in Northwest Canada, underlain by permafrost, that were burnt by wildfire 3, 25 and over 100 years ago. We measured heterotrophic soil respiration at 1, 7, 13 and 19 °C. Fire had a significant effect on the active layer depth, and it increased the temperature sensitivity (Q) of respiration in the surface (5 cm) and in the deepest soil layer (30 cm) in the 3-year-old area compared to the 25- and more than 100-year-old areas. Also the metabolic quotient (qCO) of soil microbes was increased after fire. Though fires may facilitate the SOM decomposition by increasing active layer depth, they also decreased SOM quality, which may limit the rate of decomposition. After fire all of these changes reverted back to original levels with forest succession.
北极/亚北极生态系统的气候变暖将导致森林火灾发生频率增加、土壤温度升高以及永久冻土融化，这对土壤有机碳（SOM）分解速率、CO 排放以及该地区具有全球重要意义的土壤碳储量都有影响。目前仍不清楚在永久冻土地区森林火灾后的不同深度和演替阶段，SOM 的可分解性和温度敏感性如何变化，而且这些地区的森林火灾长期影响研究也很缺乏。为了研究这个问题，我们从加拿大西北部受永久冻土影响的森林地段中采集了 5、10 和 30 cm 深度的土壤样本，这些森林地段曾在 3、25 年和 100 多年前被野火燃烧过。我们在 1、7、13 和 19°C 下测量了异养土壤呼吸。火灾对活动层深度有显著影响，与 25 年和 100 多年的区域相比，3 年生区域的表层（5 cm）和最深处（30 cm）土壤呼吸的温度敏感性（Q）增加了。火灾后土壤微生物的代谢商（qCO）也增加了。尽管火灾可能通过增加活动层深度来促进 SOM 分解，但它们也降低了 SOM 质量，这可能限制了分解速率。火灾后，随着森林演替，所有这些变化都恢复到原始水平。
