Long-term nitrogen deposition increases heathland carbon sequestration.

Area of Science:

• Ecology
• Environmental Science
• Biogeochemistry

Background:

• Industrial Revolution led to increased reactive nitrogen (N) deposition, negatively impacting ecosystems by reducing species richness and increasing N leaching.
• Nitrogen acts as a fertilizer, potentially increasing primary productivity and ecosystem carbon (C) storage.

Purpose of the Study:

• To investigate the effects of experimental N addition on C and N pools in an upland heath ecosystem over 10 years.
• To quantify N-driven C sequestration rates and identify factors influencing them.

Main Methods:

• Experimental N addition to an upland heath over a decade.
• Measurement of plant and soil C and N pools.
• Analysis of C sequestration rates in different N treatment levels.

Main Results:

• Significant increases in plant and soil C and N pools were observed.
• N-driven C sequestration rates ranged from 13-138 kg C kg^-1, higher than in forests or lowland heaths, primarily due to litter layer accumulation.
• C sequestration was highest at lower N addition rates (10, 20, 40 kg N ha^-1 yr^-1 above ambient), with saturation at the highest rate.

Conclusions:

• Upland heath ecosystems can sequester significant amounts of C in response to N deposition, particularly in litter and organic soil layers.
• Managing Calluna vulgaris canopy to maximize its building phase is crucial for sustained C sequestration.
• While N deposition increases C storage (0.77 Mt CO2e/annum in UK heathlands), policy must prioritize reducing N emissions due to adverse effects on biodiversity and species composition.