Research Starter Grant: Potential Loss of Old Soil Carbon in Response to Permafrost Melting

自冰期以来，由于土壤有机质受到低温和冻土的气候保护而不被分解，在高纬度生态系统中积累了大量的土壤C。据观察，在过去的25年里，高纬度地区的气温有所上升，随着土壤解冻，这些“老”储存的土壤C可能容易分解。能够对气候变化产生正反馈的持续和显著的碳向大气的转移必须来自储存的土壤C，它构成了这些生态系统中土壤库的大部分。因此，了解碳呼吸的来源对于预测碳循环对气候变化的响应至关重要。本研究利用土壤有机质（SOM）和土壤呼吸的放射性碳和稳定同位素测量来表征土壤解冻后释放的土壤C的来源。从图利克湖长期生态研究站的酸性和非酸性tussock冻土带站点收集的有机和矿物土壤岩心将进行研究，以确定北极土壤在永久冻土融化时释放旧碳的潜力。这一信息对于预测全球变化导致的高纬度生态系统向大气的碳损失至关重要。

Large pools of soil C have accumulated in high latitude ecosystems since glaciation as soil organic matter was climatically protected from decomposition by low temperatures and frozen soil. Air temperatures have been observed to increase at high latitudes over the last 25 years, and this "old" stored soil C may be susceptible to decomposition as soils thaw. Sustained and significant transfers of C to the atmosphere that could cause a positive feedback to climate change must come from stored soil C, which forms the bulk of the soil pool in these ecosystems. Therefore, understanding the sources of carbon respiration is critical to predicting the response of C cycling to climate change. The proposed research uses radiocarbon and stable isotope measurements of soil organic matter (SOM) and soil respiration to characterize the sources of soil C released following soil thaw. Organic and mineral soil cores collected from acidic and non-acidic tussock tundra sites at the Toolik Lake Long Term Ecological Research station will be studied to determine the potential of arctic soils to release old C as permafrost melts. This information is critical for predicting C loss from high latitude ecosystems to the atmosphere as a result of global change.