TY - JOUR

T1 - Bryophyte species differ widely in their growth and N2-fixation responses to temperature

AU - Rzepczynska, Agnieszka Marta

AU - Michelsen, Anders

AU - Olsen, Maya Anne Nissen

AU - Lett, Signe

N1 - CENPERMOA[2022]

PY - 2022

Y1 - 2022

N2 - Bryophytes are abundant in tundra ecosystems, where they affect carbon and nitrogen cycling through primary production and associations with N-2-fixing bacteria. Bryophyte responses to climate warming are inconclusive, likely because species-specific responses are poorly understood. Here we investigated how warming affects the growth and nitrogenase activity of 10 tundra bryophyte species in two tundra landscapes. Collected bryophyte samples were grown in temperature-controlled growth chambers for 12 weeks at five temperatures from 3 to 18 degrees C. We measured growth, N concentration, delta N-15, and delta C-13 after 3 months and nitrogenase activity after 5 and 12 weeks. Bryophyte growth and associated nitrogenase activity generally increased with temperature, but species differed in their optima. Bryophyte N concentration and delta N-15 indicated that, for some species, increased N-2-fixation could not compensate for growth-induced N limitation. High landscape coverage and large positive warming effects on feather mosses and Sphagnum species highlight their competitive advantages, confirm earlier field observations, and contribute to the mechanistic understanding of differential bryophyte growth in response to warming. We suggest that indirect effects of climate change, such as surface drying and shrub expansion, are likely main threats to slow-growing bryophytes across the Arctic, with consequences for biodiversity and C balance.

AB - Bryophytes are abundant in tundra ecosystems, where they affect carbon and nitrogen cycling through primary production and associations with N-2-fixing bacteria. Bryophyte responses to climate warming are inconclusive, likely because species-specific responses are poorly understood. Here we investigated how warming affects the growth and nitrogenase activity of 10 tundra bryophyte species in two tundra landscapes. Collected bryophyte samples were grown in temperature-controlled growth chambers for 12 weeks at five temperatures from 3 to 18 degrees C. We measured growth, N concentration, delta N-15, and delta C-13 after 3 months and nitrogenase activity after 5 and 12 weeks. Bryophyte growth and associated nitrogenase activity generally increased with temperature, but species differed in their optima. Bryophyte N concentration and delta N-15 indicated that, for some species, increased N-2-fixation could not compensate for growth-induced N limitation. High landscape coverage and large positive warming effects on feather mosses and Sphagnum species highlight their competitive advantages, confirm earlier field observations, and contribute to the mechanistic understanding of differential bryophyte growth in response to warming. We suggest that indirect effects of climate change, such as surface drying and shrub expansion, are likely main threats to slow-growing bryophytes across the Arctic, with consequences for biodiversity and C balance.

KW - acetylene reduction assay

KW - delta C-13

KW - delta N-15

KW - mosses

KW - nitrogen cycling

KW - subarctic tundra ecosystems

KW - CARBON-ISOTOPE DISCRIMINATION

KW - BIOLOGICAL NITROGEN-FIXATION

KW - EXPERIMENTAL WARMING ALTERS

KW - N-15 NATURAL-ABUNDANCE

KW - SUB-ARCTIC BRYOPHYTE

KW - ATMOSPHERIC NITROGEN

KW - COMMUNITY COMPOSITION

KW - LITTER DECOMPOSITION

KW - DINITROGEN FIXATION

KW - SEASONAL-VARIATION

U2 - 10.1139/AS-2021-0053

DO - 10.1139/AS-2021-0053

M3 - Journal article

VL - 8

JO - Arctic Science

JF - Arctic Science

SN - 2368-7460

IS - 4

ER -