Investigating the sensitivity of soil heterotrophic respiration to recent snow cover changes in Alaska using a satellite-based permafrost carbon model
Investigating the sensitivity of soil heterotrophic respiration to recent snow cover changes in Alaska using a satellite-based permafrost carbon model
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DOI：
10.5194/bg-17-5861-2020
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发表时间：
2020
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影响因子：
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通讯作者：
Y. Yi;J. Kimball;J. Watts;S. Natali;D. Zona;Junjie Liu;M. Ueyama;Hideki Kobayashi;W. Oechel;C. Miller
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文献类型：
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作者：
Y. Yi;J. Kimball;J. Watts;S. Natali;D. Zona;Junjie Liu;M. Ueyama;Hideki Kobayashi;W. Oechel;C. Miller
土壤异养呼吸对北极-北极碳循环的贡献及其对气候变化的潜在反馈仍然难以量化。我们开发了一个遥感驱动的永久冻土碳模型，在中等尺度（101公里），以调查环境因素如何影响的规模和季节性的土壤异养呼吸在阿拉斯加。永冻层碳模型模拟雪和土壤热动力学，并解释了地表以下3米深处土壤碳的垂直运输和分解。模型输出包括横跨阿拉斯加最近卫星时代（2001 - 2017年）的土壤温度剖面和1公里分辨率的碳通量。与涡度协方差塔测量结果的比较表明，该模型捕捉了碳通量的季节性，在模拟苔原（R> 0.8，均方根误差（RMSE-0.34 g C m − 2 d − 1）和北方森林（R> 0.73; RMSE-0.51 g C m − 2 d − 1）的净生态系统CO2交换（NEE）方面具有良好的准确性。使用两个区域原位数据集的基准评估表明，该模型捕捉雪绝缘对土壤温度和冷季土壤异养呼吸的温度敏感性的复杂影响。在阿拉斯加，我们发现，季节性积雪施加强有力的控制从不同的土壤深度的总土壤异养呼吸的贡献。春季较早的融雪促进了深层土壤变暖，并增强了生长季节后期深层土壤对总土壤异养呼吸的贡献，从而减少了生态系统的净碳吸收。冷季早期土壤异养呼吸与地表冻结后无雪天数密切相关（R =-0.48，p <0.1），即，雪开始相对于地面冻结开始的延迟。最近在阿拉斯加北方的趋势，更早的秋季降雪开始促进更长的零幕期和增强冷季呼吸。相比之下，阿拉斯加西南部显示出强烈的减少无雪的天数后，陆地表面冻结开始，导致早期土壤冻结和冷季土壤异养呼吸大幅减少。我们的研究结果还表明，不可忽视的影响，特别是在10公里尺度的冷季初期，在模式模拟的CO2季节性循环的表面条件的次网格变化。我们的研究结果表明，雪盖影响的季节性的关键作用由哥白尼出版物代表欧洲地球科学联盟。小行星5862 Yi等人：调查土壤异养呼吸对阿拉斯加土壤温度和呼吸的雪盖变化的敏感性，并强调将这些复杂的过程纳入未来的预测中的北极碳循环的挑战。
The contribution of soil heterotrophic respiration to the boreal–Arctic carbon (CO2) cycle and its potential feedback to climate change remains poorly quantified. We developed a remote-sensing-driven permafrost carbon model at intermediate scale (∼ 1 km) to investigate how environmental factors affect the magnitude and seasonality of soil heterotrophic respiration in Alaska. The permafrost carbon model simulates snow and soil thermal dynamics and accounts for vertical soil carbon transport and decomposition at depths up to 3 m below the surface. Model outputs include soil temperature profiles and carbon fluxes at 1 km resolution spanning the recent satellite era (2001–2017) across Alaska. Comparisons with eddy covariance tower measurements show that the model captures the seasonality of carbon fluxes, with favorable accuracy in simulating net ecosystem CO2 exchange (NEE) for both tundra (R > 0.8, root mean square error (RMSE – 0.34 g C m−2 d−1), and boreal forest (R > 0.73; RMSE – 0.51 g C m−2 d−1). Benchmark assessments using two regional in situ data sets indicate that the model captures the complex influence of snow insulation on soil temperature and the temperature sensitivity of coldseason soil heterotrophic respiration. Across Alaska, we find that seasonal snow cover imposes strong controls on the contribution from different soil depths to total soil heterotrophic respiration. Earlier snowmelt in spring promotes deeper soil warming and enhances the contribution of deeper soils to total soil heterotrophic respiration during the later growing season, thereby reducing net ecosystem carbon uptake. Early cold-season soil heterotrophic respiration is closely linked to the number of snow-free days after the land surface freezes (R =−0.48, p < 0.1), i.e., the delay in snow onset relative to surface freeze onset. Recent trends toward earlier autumn snow onset in northern Alaska promote a longer zero-curtain period and enhanced cold-season respiration. In contrast, southwestern Alaska shows a strong reduction in the number of snow-free days after land surface freeze onset, leading to earlier soil freezing and a large reduction in cold-season soil heterotrophic respiration. Our results also show nonnegligible influences of subgrid variability in surface conditions on the model-simulated CO2 seasonal cycle, especially during the early cold season at 10 km scale. Our results demonstrate the critical role of snow cover affecting the seasonality of Published by Copernicus Publications on behalf of the European Geosciences Union. 5862 Y. Yi et al.: Investigating soil heterotrophic respiration sensitivity to snow cover changes in Alaska soil temperature and respiration and highlight the challenges of incorporating these complex processes into future projections of the boreal–Arctic carbon cycle.