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Breaking the Ice – Consequences of northwards extending agriculture for soil organic matter cycling under a changing climate

破冰 â 气候变化下农业向北延伸对土壤有机质循环的影响

基本信息

批准号：
401106790
负责人：
Dr. Christopher Poeplau
金额：
--
依托单位：
Institut für Agrarklimaschutz
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2018
资助国家：
德国
起止时间：
2017-12-31 至 2021-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/401106790?language=en
关键词：
Breaking Ice Consequences northwards extending

项目摘要

Soils store the largest terrestrial carbon (C) pool and a multiple of the atmospheric C pool. The highest soil organic C (SOC) stocks are found in high northern latitudes, where soils are mostly uncultivated and discontinuously or continuously frozen. At the same time, the strongest temperature increase is also expected in northern latitudes, making this region a global hot spot for climate carbon-cycle feedbacks. Thawing of permafrost will evidently lead to losses in SOC and thereby increase atmospheric CO2. However, global warming will also have another indirect, but strong influence on the carbon cycle of northern circumpolar permafrost soils: human interventions. With increasing area of land that can be cultivated as well as improved living conditions in the North, extensive land use changes will occur and started to occur, which are acknowledged to change a wide range of biotic and abiotic soil properties. The land use changes may thereby amplify soil warming effects. Without quantifying these changes and associated consequences for processes affecting SOC cycling, the impact of human interventions on climate-carbon cycle feedbacks cannot be predicted. To calibrate models that can reliably predict SOC stock changes under a changing climate with associated land use changes, the following aspects will be addressed in the project: Direct biotic and abiotic responses of permafrost soils to cultivation as compared to non-permafrost soils, long-term SOC stock and quality development of agricultural soils (boreal forests converted to cropland and grassland) and potential changes in microbial carbon use efficiency and its temperature sensitivity due to land use change. The latter is critical to understand how cultivated soils will respond to climate change as compared to uncultivated soils with regard to carbon cycling. To quantify carbon use efficiencies, a novel 18O-labeling approach will be applied. The Yukon, the north-westernmost province of Canada, was identified as the perfect research area. Due to the ‘goldrush’, it has an agricultural history of more than a century, even in areas where soils under natural vegetation are still influenced by shallow permafrost. Land use change effects can thus be studied in a chronosequential approach. In relative small distance, permafrost depth varies greatly, enabling to study land-use change effects also along a thermosequence. The fact that agriculture occurs mainly on river sediments constrains confounding factors. Most often, farmers conduct small-scale mixed farming, thus conversion from forest to cropland and grassland can be studied at the same time. The approached farmers have been very open and cooperative, resulting in a large and balanced number of sites that can be sampled, all of which being easily accessible. Results of the project will enable a new view on soil C cycling in the C-rich Northern regions with double pressure: permafrost thawing and deforestation.

土壤储存着最大的陆地碳(C)库和大气碳库的数倍。土壤有机碳（SOC）储量最高的地区是北纬高纬度地区，那里的土壤大多是未开垦的，并且是不连续或连续冻结的。与此同时，北纬地区的气温上升幅度最大，使该地区成为全球气候碳循环反馈的热点地区。永久冻土的融化将明显导致有机碳的损失，从而增加大气中的二氧化碳。然而，全球变暖还将对北部环极永久冻土的碳循环产生另一种间接但强烈的影响：人类干预。随着北方可耕种土地面积的增加以及生活条件的改善，广泛的土地利用变化将发生并开始发生，这被认为会改变广泛的生物和非生物土壤性质。因此，土地利用的变化可能会放大土壤变暖效应。如果不量化这些变化和影响有机碳循环过程的相关后果，就无法预测人类干预对气候-碳循环反馈的影响。为了校准能够在气候变化和相关土地利用变化下可靠预测碳储量变化的模型，该项目将解决以下方面的问题：与非永久冻土相比，多年冻土土壤对耕作的直接生物和非生物响应、农业土壤（北方森林转化为农田和草地）长期有机碳储量和质量发展，以及土地利用变化对微生物碳利用效率及其温度敏感性的潜在变化。后者对于理解与未开垦土壤相比，耕作土壤在碳循环方面如何对气候变化作出反应至关重要。为了量化碳利用效率，将采用一种新颖的180标签方法。加拿大最西北的育空地区被认为是完美的研究区域。由于“淘金热”，它有一个多世纪的农业历史，即使在自然植被下的土壤仍然受到浅层永久冻土影响的地区也是如此。因此，可以用时间顺序的方法研究土地利用变化的影响。在相对较短的距离内，永久冻土深度变化很大，从而能够沿着热序研究土地利用变化的影响。农业主要发生在河流沉积物上的事实限制了混杂因素。大多数情况下，农民进行小规模混合耕作，因此可以同时研究从森林到农田和草地的转变。接触到的农民都非常开放和合作，导致大量和平衡的地点可以采样，所有这些都很容易到达。该项目的结果将使人们对具有双重压力（永久冻土融化和森林砍伐）的富含碳的北方地区的土壤碳循环有新的认识。