Peatlands, which contain about one third of the global soil carbon stock, are essential carbon sinks. Their net carbon uptake is equivalent to ~1% of human fossil fuel emissions or 3-10% of the current net sink of natural terrestrial ecosystems. However, the carbon sink function could be changed under global changes.

Global temperature is projected to rise by 2-5 ^oC within this century, and nitrogen (N) deposition is predicted to increase two-or three-fold. In addition, vegetation composition is impacted by climate change, nutrient availability, and anthropogenic activities. For instance, burning and grazing increases the growth of graminoids and decreases the growth of shrubs and bryophytes. Whether and how the carbon sink function of peatlands will respond to the interaction of these changes is unclear.

Systems Ecology Group of Wuhan Botanical Garden investigated the net carbon dioxide (CO₂) uptake in a peatland under simulated warming, elevated N deposition, and vegetation composition change.

N addition reduced net CO₂ uptake, suggesting elevated N deposition could weaken the carbon sink function of peatlands. This negative effect of N addition can be mitigated by warming without vegetation composition change. Nevertheless, taking future climate warming and elevated N deposition into account, the carbon sink function of peatlands would be weakened, but not changed under the graminoid-dominant conditions. Furthermore, vegetation composition was found to be more important than warming and N deposition in driving the carbon sink function of peatlands.

Consequently, besides reducing fossil fuel burning and N fertilization, protecting vegetation composition is also essential to conserve peatlands and maintain their carbon sink function.

The research entitled “Vegetation composition regulates the interaction of warming and nitrogen deposition on net carbon dioxide uptake in a boreal peatland” was published in the Functional Ecology.

The impacts of climate warming and N addition on net ecosystem production(NEP), ecosystem respiration(ER), and gross primary production(GPP) in the bog under different vegetation compositions (Image by GONG Yu)