title: Temperature sensitivity and enzymatic mechanisms of soil organic matter decomposition along an altitudinal gradient on Mount Kilimanjaro.
abstract: Short-term acceleration of soil organic matter decomposition by increasing temperature conflicts with the thermal adaptation observed in long-term studies. Here we used the altitudinal gradient on Mt. Kilimanjaro to demonstrate the mechanisms of thermal adaptation of extra- and intracellular enzymes that hydrolyze cellulose, chitin and phytate and oxidize monomers ((14)C-glucose) in warm- and cold-climate soils. We revealed that no response of decomposition rate to temperature occurs because of a cancelling effect consisting in an increase in half-saturation constants (Km), which counteracts the increase in maximal reaction rates (Vmax with temperature). We used the parameters of enzyme kinetics to predict thresholds of substrate concentration (Scrit) below which decomposition rates will be insensitive to global warming. Increasing values of Scrit, and hence stronger canceling effects with increasing altitude on Mt. Kilimanjaro, explained the thermal adaptation of polymer decomposition. The reduction of the temperature sensitivity of Vmax along the altitudinal gradient contributed to thermal adaptation of both polymer and monomer degradation. Extrapolating the altitudinal gradient to the large-scale latitudinal gradient, these results show that the soils of cold climates with stronger and more frequent temperature variation are less sensitive to global warming than soils adapted to high temperatures.
authors.affiliation: Dept. of Soil Science of Temperate Ecosystems, University of Göttingen, 37077 Göttingen, Germany.|Institute of Physicochemical and Biological Problems in Soil Science, Russian Academy of Sciences, 142290 Pushchino, Russia.|Department of Agricultural Soil Science, University of Göttingen, 37077 Göttingen, Germany.
authors.forename: Еvgenia
authors.initials: Е
authors.lastname: Blagodatskaya
authors.affiliation: Institute of Physicochemical and Biological Problems in Soil Science, Russian Academy of Sciences, 142290 Pushchino, Russia.|Institute of Plant Production and Agroecology in the Tropics and Subtropics, University of Hohenheim, 70593 Stuttgart, Germany.
authors.forename: Sergey
authors.initials: S
authors.lastname: Blagodatsky
authors.affiliation: Forensic Science Centre of the Ministry of Internal Affairs of the Russian Federation, 125130 Moscow Russia.
authors.forename: Nikita
authors.initials: N
authors.lastname: Khomyakov
authors.affiliation: Institute of General and Inorganic Chemistry, 100170 Tashkent, Uzbekistan.
authors.forename: Olga
authors.initials: O
authors.lastname: Myachina
authors.affiliation: Dept. of Soil Science of Temperate Ecosystems, University of Göttingen, 37077 Göttingen, Germany.|Department of Agricultural Soil Science, University of Göttingen, 37077 Göttingen, Germany.
authors.forename: Yakov
authors.initials: Y
authors.lastname: Kuzyakov
mesh_terms: D000531:Altitude; D002244:Carbon / Q000737:chemistry; D057486:Carbon Cycle; D012987:Soil / Q000737:chemistry*; D013696:Temperature
chemical_list: D012987:Soil; D002244:Carbon