The unseen iceberg: plant roots in arctic tundra

Abstract

SummaryPlant roots play a critical role in ecosystem function in arctic tundra, but root dynamics in these ecosystems are poorly understood. To address this knowledge gap, we synthesized available literature on tundra roots, including their distribution, dynamics and contribution to ecosystem carbon and nutrient fluxes, and highlighted key aspects of their representation in terrestrial biosphere models. Across all tundra ecosystems, belowground plant biomass exceeded aboveground biomass, with the exception of polar desert tundra. Roots were shallowly distributed in the thin layer of soil that thaws annually, and were often found in surface organic soil horizons. Root traits – including distribution, chemistry, anatomy and resource partitioning – play an important role in controlling plant species competition, and therefore ecosystem carbon and nutrient fluxes, under changing climatic conditions, but have only been quantified for a small fraction of tundra plants. Further, the annual production and mortality of fine roots are key components of ecosystem processes in tundra, but extant data are sparse. Tundra root traits and dynamics should be the focus of future research efforts. Better representation of the dynamics and characteristics of tundra roots will improve the utility of models for the evaluation of the responses of tundra ecosystems to changing environmental conditions. Contents Summary 34 I. Arctic tundra and plant roots: an introduction 35 II. A comprehensive literature review 35 III. A brief history of fine‐root studies in tundra ecosystems 41 IV. Distribution and dynamics of tundra plant roots: current knowledge and future directions 43 V. Contribution of living plant roots to fluxes of CO2 and CH4 from tundra ecosystems to the atmosphere 49 VI. The role of fine roots in tundra ecosystem nutrient cycling 50 VII. Opportunities for improving the representation of root processes in arctic models 51 VIII. Conclusions and priorities for future research 52 Acknowledgements 53 References 53