Moderate nitrogen retention in temperate heath ecosystem after elevated CO2, drought and warming through 7years

• Nitrogen (N) dynamic is one of the main controlling factors of responses to climate change in N-limited terrestrial ecosystems, which rely on nutrient re-cycling and retention. In this study we investigate the N partitioning in ecosystem compartments of a grassland heath, and the impact of multiple climate change factors on long-term N retention after 15N pulse labelling. The impacts of elevated carbon dioxide (eCO2), warming and drought and the treatments in combination on ecosystem N retention was investigated in a field scale manipulation experiment. A six-year time-course was assessed by pulse-labelling with the stable N isotope 15N and by sampling after 1 day, 1 year and 6years. After the six years we observed that the total ecosystem retained 42 % of the amended 15N across treatments (recovery of the amended 15N in the pool). The fate of the applied 15N was mainly stabilisation in soil, with 36 % recovery, while the plant compartment and microbial biomass each retained only 1-2 % of the added 15N. This suggests a moderate retention of N, for all treatments, as compared to similar long-term studies of forest ecosystems. A decreased ammonium and vegetation N pool combined with higher 15N retention in the soil at eCO2 treatments suggests that eCO2 promoted processes that immobilize N in soil, while warming counteracted this when combined with eCO2. Drought treatments contrastingly increased the vegetation N pool. We conclude that as the organic soil layer has the main capacity for N storage in a temperate heathland-grassland, it is important for buffering nutrient availability and maintaining a resilient ecosystem. However, the full treatment combination of drought, warming and eCO2 did not differ in 15N recovery from the controls, suggesting unchanged long-term consequences of climate change on retention of pulse added N in this ecosystem.

Ämnesord

NATURVETENSKAP  -- Geovetenskap och miljövetenskap -- Annan geovetenskap och miljövetenskap (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences -- Other Earth and Related Environmental Sciences (hsv//eng)

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