Experiments show warming temperatures increased metabolic activity among plants and microbial soil
Scientists found that rising temperatures was increasing both plant and microbial respiration, resulting in the release of carbon in arctic and alpine tundra biomes. Here, arctic tundra flowers in Norway. Photo: iStock
The warming planet may alter the characteristics of tundra environments and could transform them from carbon sinks to carbon sources, a study has warned.
The study, Environmental drivers of increased ecosystem respiration in a warming tundra, revealed that the warming climate may assist ecosystem respiration, which will result in the release of carbon into the atmosphere. Ecosystem respiration is the sum of all respiration occurring by the living organisms in a specific ecosystem.
Rising temperatures change the biogeochemistry of an area, affecting local soil by altering nitrogen levels and pH, the researchers found.
Arctic and alpine tundra ecosystems are known to be large reservoirs of organic carbon.
A group of over 70 scientists from around the world conducted open-top-chamber warming experiments at 28 arctic and alpine tundra sites for 25 years. Open-top chambers simulate global warming by passively increasing air temperatures in field experiments.
The study found that a mean increase of 1.4 degrees Celsius in air temperature, 0.4°C in soil temperature and a 1.6 per cent drop in soil moisture led to a 30 per cent increase in respiration during the growing season.
The increase in activity was due to an increase in both plant and microbial respiration, resulting in the release of carbon.
Moreover, the scientists found that the tundra regions with higher nitrogen limitations and sites that stimulated plant and microbial turnover show more sensitivity to warming through respiration responses.
Regarding the global impact of plant-soil connections, the authors noted that the warming rate in the tundra biome could reach 0.73°C per decade, significantly outpacing the global average rate of 0.19°C per decade.
The researchers indicated that earlier findings about global warming’s impact on biogeochemical conditions have been confirmed. Their data, for the first time, showed that the extent of warming-induced ecosystem respiration is closely tied to the underlying biochemical conditions.
The findings of the latest study are more precise, particularly regarding changes in nitrogen concentrations in the deeper mineral layers of soil.
The scientists noted:
In tundra ecosystems, ecosystem respiration remains enhanced with continued warming at least for 2.5 decades. The ecosystem respiration response to warming shows a nonlinear trend over time between 5 and 15 years of warming, during which the positive respiration response drops in magnitude, after which it rises again.
The nonlinear pattern of ecosystem respiration increase could be the result of underlying microbial and plant processes reacting to warming at different rates.
“For example, ranging from more immediate effects of warming on microbial and plant respiration through accelerated decomposition versus slower effects through changes in biogeochemical and hydrological soil conditions as well as in microbial or vegetation,” the authors observed.
A detailed understanding of the connections between soil nitrogen, carbon, pH, and respiration in response to climate warming can enhance predictions for future warming. This can be achieved by including the tundra carbon cycle in climate models.
The researchers said the results from the experiment could help in generating more accurate global and regional climate models that predict carbon emissions in the future.
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