Early season root production in relation to leaf production among six diverse temperate tree species

Leaf and root phenology play important roles controlling plant productivity and ecosystem function, yet, few studies link patterns of leaf and root phenology across woody species. Trees with diffuse-porous wood anatomy tend to leaf-out before ring-porous species and we expected that increases in transpiration with spring leaf-out would be coupled with initiation of root production to support uptake of soil resources. Therefore, we hypothesized that the timing of root production would follow patterns of leaf production and wood anatomy. Root production was observed using minirhizotrons and related to leaf phenology across six temperate tree species with different wood anatomy in a common garden. As expected, leaves of diffuse-porous species emerged before ring-porous, followed by tracheid species. Root production peaked before bud break in five of the six species and before maximum leaf area index in all species, but did not follow expected patterns with leaf production. Our observations did not indicate tight linkages between root and leaf phenology but do highlight the potential for very early season root production and greater variation in the phenology of roots than leaves. Future work should identify the environmental factors and species traits that best explain variation in root phenology.