Bodenerwärmungs-Experiment Achenkirch

• Antragsteller: Professor Dr. Werner Borken
• Fachliche Zuordnung: Bodenwissenschaften
• Förderung: Förderung von 2018 bis 2022
• Projektkennung: Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 397643203

• Erstellungsjahr: 2023

Zusammenfassung der Projektergebnisse

Temperate forest soils store large amounts of organic carbon and thus are crucial for the global carbon cycle. There is a concern that these soils lose carbon as the global temperature rises, amplifying the increase in the concentration of carbon dioxide (CO2) in the atmosphere. The organic carbon stock of forest soils relies to some extent on the input of carbon by fine root, but long-term studies on the response of fine roots to increasing temperatures are scarce. The main aim of this thesis was to assess the dynamics of fine roots and soil organic carbon (SOC) in response to long-term soil warming in a temperate mountain forest. We took advantage of the long-term soil warming experiment at Achenkirch, Tyrol, Austria, where soil temperature was increased by + 4°C in the warmed plots as compared to control plots since 2005. We combined soil coring on two sampling occasions (2012 and 2019) and DNA extractions on ectomycorrhizal (EcM) root tips (sampled in 2019) to study the effect of warming on fine root biomass, fine root morphology, and EcM fungal community (Study I). Fine root turnover time and carbon input into the soil by fine root litter were studied by combining coring, ingrowth cores and radiocarbon modeling (Study II). Radiocarbon modeling was also used to assess the transit time of SOC, the radiocarbon distribution of SOC, and the carbon released by mineralization of SOC (Study III). Model results were compared with soil CO2 efflux measured over different years to assess the overall response of heterotrophic and autotrophic respiration to warming. Fine root biomass increased by 13% and 17% with soil warming in 2012 and 2019, respectively. Fine root production in ingrowth cores was 128% higher in the warmed plots after one year and 35% higher after two years. In addition, fine root turnover estimated with ingrowth cores increased by 33%, and by 36 – 59% when considering modeled fine root turnover times and fine root biomass from soil coring. Fine root morphology also changed with soil warming on both occasions. Specific root length increased by 17 – 28%, specific root area by 18 – 84%, and root tip density by 28 – 66%. Soil warming did not affect EcM exploration types. However, it shaped the EcM community composition with an increase in the relative abundance of EcM of the genus Cenococcum, Sebacina, and Boletus in the warmed plots. Overall, changes in the fine root system coincided with reduced soil potassium and phosphorus availability in the warmed plots. Mean annual soil CO2 efflux increased by 41%, while no difference between SOC stocks was observed between control and warmed plots. In addition, radiocarbon modeling showed that the mineralization of soil organic carbon accounted for 37 and 29 % of the annual soil CO2 efflux in control and warmed plots, respectively. Together, our findings suggest that climate warming may increase belowground carbon allocation of trees, the input of carbon into the soil by fine root litter, and the absorptive capacity of the fine root system for water and nutrient uptake. Although soil CO2 efflux increased with warming, similar SOC stocks in both treatments suggest that rhizosphere respiration primarily contributes to the increase in soil CO2 efflux by warming in this forest site. Increased root litter input can fully or partly compensate for carbon losses by enhanced SOC mineralization with increasing global warming.

Projektbezogene Publikationen (Auswahl)

• No effect of long-term soil warming on diffusive soil inorganic and organic nitrogen fluxes in a temperate forest soil. Soil Biology and Biochemistry, 158, 108261.
  Heinzle, Jakob; Wanek, Wolfgang; Tian, Ye; Kengdo, Steve Kwatcho; Borken, Werner; Schindlbacher, Andreas & Inselsbacher, Erich
  
• Long‐term soil warming alters fine root dynamics and morphology, and their ectomycorrhizal fungal community in a temperate forest soil. Global Change Biology, 28(10), 3441-3458.
  Kwatcho, Kengdo Steve; Peršoh, Derek; Schindlbacher, Andreas; Heinzle, Jakob; Tian, Ye; Wanek, Wolfgang & Borken, Werner
  
• Does long‐term soil warming affect microbial element limitation? A test by short‐term assays of microbial growth responses to labile C, N and P additions. Global Change Biology, 29(8), 2188-2202.
  Shi, Chupei; Urbina‐Malo, Carolina; Tian, Ye; Heinzle, Jakob; Kwatcho, Kengdo Steve; Inselsbacher, Erich; Borken, Werner; Schindlbacher, Andreas & Wanek, Wolfgang
  
• Increase in carbon input by enhanced fine root turnover in a long-term warmed forest soil. Science of The Total Environment, 855, 158800.
  Kengdo, Steve Kwatcho; Ahrens, Bernhard; Tian, Ye; Heinzle, Jakob; Wanek, Wolfgang; Schindlbacher, Andreas & Borken, Werner
  
• Long-term soil warming decreases microbial phosphorus utilization by increasing abiotic phosphorus sorption and phosphorus losses. Nature Communications, 14(1).
  Tian, Ye; Shi, Chupei; Malo, Carolina Urbina; Kwatcho, Kengdo Steve; Heinzle, Jakob; Inselsbacher, Erich; Ottner, Franz; Borken, Werner; Michel, Kerstin; Schindlbacher, Andreas & Wanek, Wolfgang
  
• Soil CH4 and N2O response diminishes during decadal soil warming in a temperate mountain forest. Agricultural and Forest Meteorology, 329, 109287.
  Heinzle, Jakob; Kitzler, Barbara; Zechmeister-Boltenstern, Sophie; Tian, Ye; Kwatcho, Kengdo Steve; Wanek, Wolfgang; Borken, Werner & Schindlbacher, Andreas