Tundra Root Responses to Environmental Change - A Meta-Analysis

Arctic tundra ecosystems are experiencing rapid climatic change, including accelerated warming, altered soil moisture regimes, and widespread permafrost thaw, with potentially strong feedbacks to high-latitude carbon and nutrient cycling. In these ecosystems, a disproportionately large proportion of plant biomass is allocated belowground, making roots as a key player in plant-soil interactions and ecosystem processes in Arctic tundra. Therefore, it is necessary to understand how tundra roots respond to environmental changes and their implications of terrestrial climate-cycle feedback. However, despite their importance, tundra root responses to environmental change remain poorly studied, and existing experimental evidence vary across study sites, conditions and focuses.

In this study, we integrated experimental evidence of root response to environmental changes from 34 studies across the pan-Arctic region, using a comprehensive framework that combines component network meta-analysis, meta-regression, and non-linear models. Across the studies, we collected 14 root traits and investigated their responses to 6 different types of treatments and 8 environmental moderators, respectively.

Warming treatments generally showed modest and insignificant effects on most root traits. However, meta-regression analyses revealed pronounced temperature-driven shifts toward thinner yet longer-lived roots, effects that are frequently obscured by concurrent soil drying in warming experiments. Nutrient addition triggered the strongest belowground responses, where we found an unexpectedly key role of phosphorus and co-limitation of multiple elements. Significant differences in root responses among plant functional types and mycorrhizal strategies further indicate species-specific belowground adaptation pathways. Temporal analyses indicate that environmental changes produce gradual but cumulative effects on root morphology, whereas root chemical traits tend to stabilize following an initial rapid response. Across soil temperature, moisture, nutrient inputs, and active layer depth, we identified widespread non-linear and threshold-dependent responses that were not captured by conventional linear regression approaches.

In summary, our study demonstrates that tundra belowground responses are driven by interacting climatic, hydrological, and nutrient factors, and are further shaped by species-specific strategies and temporal dynamics. We highlight the need to incorporate non-monotonic root responses, multi-element nutrient constraints, species-specific strategies, and temporal patterns into Arctic ecosystem models to improve predictions of climate-carbon feedbacks.