Global meta‐analysis reveals different patterns of root tip adjustments by angiosperm and gymnosperm trees in response to environmental gradients

Aim Rising air temperature and changing precipitation patterns already strongly influence forest ecosystems, yet large-scale patterns of belowground root trait variation and their underlying drivers are poorly understood. Here, we investigated general patterns of root tip adjustments within fine-root systems and the potential ecological implications of these patterns. Location Global. Methods We synthesize key fine-root traits related to resource acquisition and determined their responses along climate and edaphic gradients. We specifically identified patterns of root tip abundance (number of root tips per dry biomass of fine roots <= 2 mm in diameter), and root tip density (number of root tips per soil volume) among angiosperm and gymnosperm trees to climate, edaphic gradients and stand properties. Results We found that angiosperm trees, which were more common in warmer, sometimes drier climates with more fertile soil, formed more root tips (higher root tip abundance, root tip density and higher slope of root tip density vs. fine-root biomass) than gymnosperm trees, which lived in cooler, wetter climates with poor soil. Angiosperm and gymnosperm trees exhibited opposing trends in response to gradients in climate as gymnosperm trees tended to decrease root tip abundance and root tip density but alternatively increase mycorrhizal mycelial biomass with increasing MAT/MAP (ratio of mean annual temperature to mean annual precipitation), while angiosperm trees tended to increase root tip abundance and root tip density with increasing MAT/MAP. However, the individual trends of root tip abundance and root tip density for angiosperm and gymnosperm trees to MAT or MAP were more similar and often non-significant. Main conclusions These results suggest disparate carbon or biomass adjustment strategies within gymnosperm and angiosperm tree fine-root systems along climate gradients. Differences in angiosperm and gymnosperm tree adjustments in their fine-root systems to changing environments have implications for how these plant groups are likely to perform in different environments and how their responses to future climate change should be modelled.