Non-growing season plant nutrient uptake controls Arctic tundra vegetation composition under future climate

Journal Article · Mon Jul 12 00:00:00 EDT 2021 · Environmental Research Letters

DOI:https://doi.org/10.1088/1748-9326/ac0e63· OSTI ID:1835415

Riley, William J.; Mekonnen, Zelalem A.; Tang, Jinyun; Zhu, Qing; Bouskill, Nicholas J.; Grant, Robert F.

Abstract

Plant growth and distribution in high-latitude tundra ecosystems is strongly limited by nutrient availability and is critical for quantifying centennial-scale carbon-climate interactions. However, land model representations of plant–nutrient interactions are uncertain, leading to poor comparisons with high-latitude observations. Although it has been recognized for decades in the observational community that plants continue to acquire nutrients well past when aboveground activity has ceased, most large-scale land models ignore this process. Here we address the role tundra plant nutrient acquisition during the non-growing season (NGS) has on centennial-scale vegetation growth and dynamics, with a focus on shrub expansion. We apply a well-tested mechanistic model of coupled plant, microbial, hydrological, and thermal dynamics that explicitly represents nutrient acquisition based on plant and microbial traits, thereby allowing a prognostic assessment of NGS nutrient uptake. We first show that the model accurately represents observed seasonality of NGS plant nutrient uptake in a northern Alaskan tundra site. Applying the model across the North America tundra indicates that NGS nutrient uptake is consistent with observations and ranges between ∼5% and 50% of annual uptake, with large spatial variability and dependence on plant functional type. We show that NGS plant nutrient acquisition strongly enhances modeled 21 ^st century tundra shrub growth and expansion rates. Our results suggest that without NGS nutrient uptake, total shrub aboveground dominance would be ∼50% lower, limited primarily by their inability to grow tall enough to maximize their inherent capacity for light competition. Evergreen shrubs would be more strongly affected because of their relatively lower capacity for nutrient remobilization and acquisition compared to deciduous shrubs. Our results highlight the importance of NGS plant and soil processes on high-latitude biogeochemistry and vegetation dynamics and motivate new observations and model structures to represent these dynamics.

• Research Organization: Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: USDOE; USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
• Grant/Contract Number: AC02-05CH11231
• OSTI ID: 1835415
• Alternate ID(s): OSTI ID: 1813398; OSTI ID: 23136427
• Journal Information: Environmental Research Letters, Journal Name: Environmental Research Letters Journal Issue: 7 Vol. 16; ISSN 1748-9326
• Publisher: IOP Publishing
• Country of Publication: United Kingdom
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
carbon cycle
climate
shrub expansion
shrubification
tundra