TY - JOUR

T1 - Moderate nitrogen retention in temperate heath ecosystem after elevated CO2, drought and warming through 7 years

AU - Andresen, Louise C.

AU - Ambus, Per

AU - Beier, Claus

AU - Michelsen, Anders

N1 - Publisher Copyright: © 2023 The Authors. European Journal of Soil Science published by John Wiley & Sons Ltd on behalf of British Society of Soil Science.

PY - 2023

Y1 - 2023

N2 - Nitrogen (N) dynamic is one of the main controlling factors of responses to climate change in N-limited terrestrial ecosystems, which rely on nutrient recycling 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 were investigated in a field scale manipulation experiment. A 6-year time-course was assessed by pulse-labelling with the stable N isotope 15N and by sampling after 1 day, 1 year and 6 years. After 6 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 stabilization in soil, with 36% 15N recovery in soil, 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 under 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 control, suggesting unchanged long-term consequences of climate change on retention of pulse added N in this ecosystem.

AB - Nitrogen (N) dynamic is one of the main controlling factors of responses to climate change in N-limited terrestrial ecosystems, which rely on nutrient recycling 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 were investigated in a field scale manipulation experiment. A 6-year time-course was assessed by pulse-labelling with the stable N isotope 15N and by sampling after 1 day, 1 year and 6 years. After 6 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 stabilization in soil, with 36% 15N recovery in soil, 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 under 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 control, suggesting unchanged long-term consequences of climate change on retention of pulse added N in this ecosystem.

KW - N recovery

KW - Calluna vulgaris

KW - climate change

KW - microbial biomass

KW - nitrogen cycling

KW - soil organic matter

U2 - 10.1111/ejss.13397

DO - 10.1111/ejss.13397

M3 - Journal article

AN - SCOPUS:85166008222

VL - 74

JO - Journal of Soil Sciences

JF - Journal of Soil Sciences

SN - 1351-0754

IS - 4

M1 - e13397

ER -