EGU22-4539
https://doi.org/10.5194/egusphere-egu22-4539
EGU General Assembly 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Effects of soil warming on in situ fine root exudation rates in a temperate forest soil

Jakob Heinzle1, Xiaofei Liu2, Ye Tian2, Steve Kwatcho-Kengdo3, Werner Borken3, Erich Inselsbacher4, Wolfgang Wanek2, and Andreas Schindlbacher1
Jakob Heinzle et al.
  • 1Department of Forest Ecology and Soils, Federal Research and Training Centre for Forests, Natural Hazards and Landscape - BFW, Seckendorff-Gudent Weg 8, 1131 Vienna, Austria
  • 2Division of Terrestrial Ecosystem Research, Department of Microbiology and Ecosystem Science, Center of Microbiology and Environmental Systems Science, University of Vienna, Djerassiplatz 1, 1030 Vienna, Austria
  • 3Department of Soil Ecology, University of Bayreuth, Dr.-Hans-Frisch-Straße 1-3, 95448, Bayreuth, Germany
  • 4Institute of Soil Research, Department of Forest- and Soil Sciences, University of Natural Resources and Life Sciences – BOKU, Peter-Jordan-Strasse 82, 1190 Vienna, Austria

Trees invest up to one third of the carbon (C) fixed by photosynthesis into belowground allocation, including fine root exudation into the rhizosphere. Rising soil temperatures in a warmer world could modify the allocation of labile C below ground, thereby affecting biogeochemical cycling in forest soils. Up to date our understanding of how fine root exudation of labile carbon compounds responds to warming is yet emerging and in-situ analyses under warming conditions are scarce, especially in mature forests. Using a C-free cuvette incubation method, we investigated in situ rates of root exudation from fine roots in a mature spruce forest across three seasons after 14 and 15 years of warming in the Achenkirch soil warming (+4°C) experiment. In addition, we run a complementary short-term experiment on root exudation, during which we increased soil temperatures on warmed plots stepwise up to a difference of 12°C between treatments within a few days. We found no effect of long-term soil warming on in situ root exudation rates (n = 120 roots sampled). Mean exudation rates per biomass were 16.23 ± 4.03 and 17.94 ± 2.94 µg g-1 h-1 on control and warmed plots respectively, with highest rates found in the late growing season in both treatments. Exudation rates were positively related to the specific root length and were negatively related to soil moisture, but unrelated to soil inorganic N availability and in situ soil temperature. However, the short-term temperature manipulation resulted in an exponential increase of estimated root exudation rates with soil temperature. Our results therefore indicate that fine root exudation from mature trees in the studied ecosystem is inherently controlled by soil temperature, but an interplay with other parameters such as nutrient availability, root morphology and/or soil moisture are the dominant controlling mechanisms across the seasons in the long run. Our observations further indicate that the long-term soil warming by 4°C caused only a subtle increase in root exudation per fine root surface area or per fine root biomass.

How to cite: Heinzle, J., Liu, X., Tian, Y., Kwatcho-Kengdo, S., Borken, W., Inselsbacher, E., Wanek, W., and Schindlbacher, A.: Effects of soil warming on in situ fine root exudation rates in a temperate forest soil, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4539, https://doi.org/10.5194/egusphere-egu22-4539, 2022.