TY - JOUR

T1 - Cross-scale regulation of seasonal microclimate by vegetation and snow in the Arctic tundra

AU - von Oppen, Jonathan

AU - Assmann, Jakob J.

AU - Bjorkman, Anne D.

AU - Treier, Urs A.

AU - Elberling, Bo

AU - Nabe-Nielsen, Jacob

AU - Normand, Signe

N1 - CENPERMOA[2022]

PY - 2022

Y1 - 2022

N2 - Climate warming is inducing widespread vegetation changes in Arctic tundra ecosystems, with the potential to alter carbon and nutrient dynamics between vegetation and soils. Yet, we lack a detailed understanding of how variation in vegetation and topography influences fine-scale temperatures ("microclimate") that mediate these dynamics, and at what resolution vegetation needs to be sampled to capture these effects. We monitored microclimate at 90 plots across a tundra landscape in western Greenland. Our stratified random study design covered gradients of topography and vegetation, while nested plots (0.8-100 m(2)) enabled comparison across different sampling resolutions. We used Bayesian mixed-effect models to quantify the direct influence of plot-level topography, moisture and vegetation on soil, near-surface and canopy-level temperatures (-6, 2, and 15 cm). During the growing season, colder soils were predicted by shrub cover (-0.24 degrees C per 10% increase), bryophyte cover (-0.35 degrees C per 10% increase), and vegetation height (-0.17 degrees C per 1 cm increase). The same three factors also predicted the magnitude of differences between soil and above-ground temperatures, indicating warmer soils at low cover/height, but colder soils under closed/taller canopies. These findings were consistent across plot sizes, suggesting that spatial predictions of microclimate may be possible at the operational scales of satellite products. During winter, snow cover (+0.75 degrees C per 10 snow-covered days) was the key predictor of soil microclimate. Topography and moisture explained little variation in the measured temperatures. Our results not only underline the close connection of vegetation and snow with microclimate in the Arctic tundra but also point to the need for more studies disentangling their complex interplay across tundra environments and seasons. Future shifts in vegetation cover and height will likely mediate the impact of atmospheric warming on the tundra soil environment, with potential implications for below-ground organisms and ecosystem functioning.

AB - Climate warming is inducing widespread vegetation changes in Arctic tundra ecosystems, with the potential to alter carbon and nutrient dynamics between vegetation and soils. Yet, we lack a detailed understanding of how variation in vegetation and topography influences fine-scale temperatures ("microclimate") that mediate these dynamics, and at what resolution vegetation needs to be sampled to capture these effects. We monitored microclimate at 90 plots across a tundra landscape in western Greenland. Our stratified random study design covered gradients of topography and vegetation, while nested plots (0.8-100 m(2)) enabled comparison across different sampling resolutions. We used Bayesian mixed-effect models to quantify the direct influence of plot-level topography, moisture and vegetation on soil, near-surface and canopy-level temperatures (-6, 2, and 15 cm). During the growing season, colder soils were predicted by shrub cover (-0.24 degrees C per 10% increase), bryophyte cover (-0.35 degrees C per 10% increase), and vegetation height (-0.17 degrees C per 1 cm increase). The same three factors also predicted the magnitude of differences between soil and above-ground temperatures, indicating warmer soils at low cover/height, but colder soils under closed/taller canopies. These findings were consistent across plot sizes, suggesting that spatial predictions of microclimate may be possible at the operational scales of satellite products. During winter, snow cover (+0.75 degrees C per 10 snow-covered days) was the key predictor of soil microclimate. Topography and moisture explained little variation in the measured temperatures. Our results not only underline the close connection of vegetation and snow with microclimate in the Arctic tundra but also point to the need for more studies disentangling their complex interplay across tundra environments and seasons. Future shifts in vegetation cover and height will likely mediate the impact of atmospheric warming on the tundra soil environment, with potential implications for below-ground organisms and ecosystem functioning.

KW - Arctic tundra

KW - microclimate

KW - plant functional types

KW - shrub expansion

KW - snow cover

KW - soil temperature

KW - stratified random sampling

KW - temperature offset

KW - SHRUB EXPANSION

KW - SOIL-TEMPERATURE

KW - PERMAFROST THAW

KW - N-FACTOR

KW - CLIMATE

KW - MOISTURE

KW - ALASKA

KW - VARIABILITY

KW - ECOSYSTEMS

KW - PATTERNS

U2 - 10.1111/gcb.16426

DO - 10.1111/gcb.16426

M3 - Journal article

C2 - 36083034

VL - 28

SP - 7296

EP - 7312

JO - GCB Bioenergy

JF - GCB Bioenergy

SN - 1757-1693

IS - 24

ER -