Effects of temperature and land-use change on soil organic matter dynamics in a permafrost-affected ecosystem

• Main Author: Peplau, Tino Andreas
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Hannover : Institutionelles Repositorium der Leibniz Universität Hannover 2023
• Subjects: soil; permafrost; land-use change; warming; climate change; litter decomposition; carbon; Boden; Landnutzungswandel; Erwärmung; Klimawandel; Streuabbau; Kohlenstoff; ddc:500; ddc:550; Yukon; Subarctic
• Online Access: https://www.repo.uni-hannover.de/handle/123456789/13625; https://doi.org/10.15488/13515

Subarctic ecosystems are among the regions on earth that experience the strongest impact by climate change. As a result of global warming, agricultural centers are shifting poleward into previously non-viable regions of subarctic forests. These subarctic ecosystems are among those predicted to be most strongly impacted by rising global temperatures. Additionally, because agriculture north of 60 degrees latitude has been historically limited, there are few studies which systematically examine the effect of converting subarctic forests for cropland or grassland use on soil carbon. The aim of this thesis was to quantify the effects of land-use change from boreal forest to cropland and grassland on the stocks and composition soil organic carbon. Therefore, three studies were conducted in the Canadian Yukon Territory. First, the effect of soil warming on stocks and fractions of the soil organic matter was quantified by using proximity to a geothermal spring in a subarctic ecosystem as a long-term warming experiment. In the second study, 18 sites covering forest soils as well as adjacent agricultural land were sampled to assess differences in soil organic matter. Included were sites with and without permafrost as well as farms of different age, selected to quantify the influence of permafrost and duration of agricultural use on soil carbon dynamics. The aim of the third study was to measure the effect of land-use change on soil temperature and litter decomposition. Tea bags and temperature sensors were buried in the topsoil (10 cm) and in the subsoil (50 cm) at the same sites as used for the second study and retrieved after two years. This work has shown that deforestation for the purpose of agriculture leads to soil warming and therefore to the loss of near-surface permafrost. Consequently, a large loss of soil organic carbon was observed. Furthermore, the results indicated that the loss of soil organic carbon could be minimised if deforestation is restricted to permafrost-free soils and if the deforestation ...