Short-term experimental warming increases soil respiration while alters microbial communities in high-Andean wetlands
image: The vegas’ soil from the highest altitude showed the highest soil organic carbon (SOC) content (A). Warming increased soil respiration rates and this effect was higher in soil from the highest altitude (B). Also, warming affected microbial biomass resulting in a decrease respect to lower temperature treatment (C); however, the biomass-specific soil respiration rates were higher in warming treatment (D). These results evidence that, in the short-term, warming stimulates resource allocation to respiration rather than microbial growth, which could be related to a reduction in the carbon use efficiency by microorganisms, with the consequence of soil C losses.
Credit: M. Fernanda Chiappero , María V. Vaieretti , Norma Gallardo , Andrea E. Izquierdo
High-Andean wetlands of the Argentinean Puna region, called vegas by local inhabitants, although covering less than 1% of this arid mountain region, are important ecosystems as they support biodiversity and provide to local people with fresh water and food for their livestock. Vegas are also critical for soil carbon sequestration. Because of the waterlogging conditions and low temperatures they can store large amounts of soil carbon. These carbon reservoirs could be very sensitive to raising temperature, which can increase microbial decomposition increasing the release of CO2 from the soil. However, the magnitude of CO2 emissions could depend on the altitude at which the vegas are located.
In this experimental study, the authors, incubated soils form vegas located at different altitudes (from 3793 to 4206 m a.s.l.) at 10 °C and 25 °C for 68 days and measured the soil respiration rates and its temperature sensitivity (Q10). Also, the researchers measured biomass and composition and enzymatic activity of soil microbial communities. The researchers’ finding appeared April 11, 2024 in Soil Ecology Letters.
The researchers found that soils of vegas released threefold more CO2 when they were incubated at 25 °C compared to the incubation at 10 °C. In addition, soil from the highest altitude (4206 m a.s.l.), containing twice more stored carbon than soil from vegas located at lower altitudes, also presented the highest respiration rate at warming treatment. Despite having these differential responses, the Q10 did not differ between vegas, the authors say: “These results suggest that raising temperatures over the Puna region, in the short-term, could increase CO2 emissions from wetlands located at similar altitudes that studied here, which also could present a similar sensitivity to warming”.
Soil microbial communities were also affected by warming. Soils incubated at 25 °C showed lower microbial biomass, however, they were more active as they showed more respiration rate and enzymatic activity expressed per unit biomass. These results suggested that in the short-term warming could alter the metabolism of microorganisms, particularly carbon use efficiency, with microbial communities deriving more carbon resources to catabolic activities than biomass accrual.
This study represented a first step in disentangling the effects of raising temperatures in soil carbon processes linked to microorganisms of vegas. The findings indicated that warming could affect the carbon balance of these important high-Andean ecosystems, reducing the capacity of storing carbon in their soils.