Drivers of legacy soil organic matter decomposition after fire in boreal forests
Drivers of legacy soil organic matter decomposition after fire in boreal forests
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北方森林火灾后遗留土壤有机质分解的驱动因素
DOI：
10.1002/ecs2.4672
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发表时间：
2023
期刊：
影响因子：
2.7
通讯作者：
Mack, Michelle C.
中科院分区：
文献类型：
--
作者：
Izbicki, Brian;Walker, Xanthe J.;Baltzer, Jennifer L.;Day, Nicola J.;Ebert, Christopher;Johnstone, Jill F.;Pegoraro, Elaine;Schuur, Edward A. G.;Turetsky, Merritt R.;Mack, Michelle C.
北方森林含有与大气一样多的碳(C)和大量的有机氮(N)，这种营养物质最有可能限制高纬度生态系统中的植物生产力。在北方生物群中，主要的干扰是野火，它消耗植物生物量和土壤物质，排放温室气体，并影响长期的C和N循环。气候变暖和干燥正在增加野火的严重性和频率，并正在燃烧更多的土壤有机质(SOM)。地表SOM的燃烧暴露出以前在过去的火灾中逃逸的更深、更老的堆积土壤物质层，这里称为遗留SOM。火后SOM分解和养分有效性由这些层决定，但遗留SOM分解的驱动因素尚不清楚。2014年，加拿大西北地区发生了有记录以来最大的火灾年，我们从地块中收集了土壤。我们使用放射性碳测年来测量Δ14C(土壤年龄指数)，土壤提取物来量化N库和微生物生物量，并使用90天的实验室培养来测量元素矿化的潜在速率，并了解遗留的SOM C分解和N有效性的模式和驱动因素。我们发现，大量土壤的C年龄预测了C的分解，在培养过程中，累积起来，年龄较大的土壤(约450.0−‰)产生的碳比较年轻的土壤(~0.0‰)少230%。土壤年龄也预示着C的周转时间，老土壤的周转速度比年轻土壤慢10倍。我们发现呼吸C比土壤C年轻，这表明大多数C进入和离开的速度相对较快，而较老的部分保持稳定的C汇。土壤年龄和其他指标与氮素有效性无关，但微生物量影响氮素有效性，微生物量更多地固定土壤氮库。我们的结果强调了土壤有机质作为稳定的碳汇的重要性，并强调了土壤年龄决定了野火期间土壤碳对大气贡献的速度和幅度。
Boreal forests harbor as much carbon (C) as the atmosphere and significant amounts of organic nitrogen (N), the nutrient most likely to limit plant productivity in high‐latitude ecosystems. In the boreal biome, the primary disturbance is wildfire, which consumes plant biomass and soil material, emits greenhouse gasses, and influences long‐term C and N cycling. Climate warming and drying is increasing wildfire severity and frequency and is combusting more soil organic matter (SOM). Combustion of surface SOM exposes deeper older layers of accumulated soil material that previously escaped combustion during past fires, here termed legacy SOM. Postfire SOM decomposition and nutrient availability are determined by these layers, but the drivers of legacy SOM decomposition are unknown. We collected soils from plots after the largest fire year on record in the Northwest Territories, Canada, in 2014. We used radiocarbon dating to measure Δ14C (soil age index), soil extractions to quantify N pools and microbial biomass, and a 90‐day laboratory incubation to measure the potential rate of element mineralization and understand patterns and drivers of legacy SOM C decomposition and N availability. We discovered that bulk soil C age predicted C decomposition, where cumulatively, older soil (approximately −450.0‰) produced 230% less C during the incubation than younger soil (~0.0‰). Soil age also predicted C turnover times, with old soil turnover 10 times slower than young soil. We found respired C was younger than bulk soil C, indicating most C enters and leaves relatively quickly, while the older portion remains a stable C sink. Soil age and other indices were unrelated to N availability, but microbial biomass influenced N availability, with more microbial biomass immobilizing soil N pools. Our results stress the importance of legacy SOM as a stable C sink and highlight that soil age drives the pace and magnitude of soil C contributions to the atmosphere between wildfires.
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DOI：
10.1080/11956860.2000.11682620
发表时间：
2000
期刊：
Écoscience
影响因子：
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