The Hidden Side of Functional Diversity: Evolution, Ecology and Biogeography of Fine Roots in Woody Plants

Dear Colleagues,

The lack of information around how root traits vary among environments and throughout the history of plant evolution has limited the study of plant evolutionary ecology, ecosystem functioning, and species effects on C cycles. Fine roots, the most distal portions of roots, usually <1 mm in diameter, are the major type of plant tissue that contributes to soil organic matter and are key drivers of mineral weathering and microbial dynamics. Moreover, alterations in root morphology and physiology were likely critical in the surge of leaf photosynthetic capacity during the expansion of angiosperms in the Creataceous era. Despite the overwhelming importance of fine root traits for biogeochemical cycles, basic information about their evolution and ecology is lacking, particularly compared to the remarkable progress in understanding ecology and evolution of leaves and stems.

Tests of hypotheses regarding root trait syndromes have been particularly hampered due to (1) a paucity of systematically collected data and (2) the complexity of root functioning and traits. Contrary to other plant organs, the collection and identification of root systems did not developed as a field of research to this date. Perhaps due to the challenges associated with collection and identification of organs embedded in soil, detailed description of root systems is available only in a small proportion of species, mostly in temperate areas, severely biasing our knowledge toward an ecologically and phylogenetically restricted group. Tropical areas in particular are grossly underrepresented. Moreover, the sensitivity of root biomass to soil heterogeneity may have created the impression that all root traits are inherently plastic and highly similar among species. However, we now know that intraspecific variation is much smaller than interspecific variation in many communities and that relatedness is an important driver of root trait syndromes. Another complication is that root traits are the result of complex evolutionary interactions with soil microbial communities, particularly mycorrhizal fungi. However, few studies have investigated the evolutionary relationship between changes in root traits and the dependency on mycorrhizal partners, particularly in tropical forests.

This Special Issue mainly focuses on describing the drivers of fine root traits in tree species, and how those traits can affect plant fitness and ecosystem services of forests and tree crops in tropical areas. We emphasize on studies that focus on the acquisition portion of the root system and search for potential mechanisms explaining interspecific variation and plasticity across environmental gradients. We welcome the submission of research reports and review papers.

Dr. Oscar J. Valverde-Barrantes
Guest Editor

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• Woody plants
• Belowground ecology
• Fine root functional traits
• Root morphology
• Mycorrhizae
• Plant microbiome
• Plant evolution
• Fungi