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

Abstract

Aims 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.Methods Root production was observed using minirhizotrons and related to leaf phenology across six temperate tree species with different wood anatomy in a common garden. Results 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. Conclusions 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.

Root phenology unresponsive to earlier snowmelt despite advanced above‐ground phenology in two subarctic plant communities

“…Our results thus support mounting evidence that significant amounts of root growth can occur outside of the photosynthetically active period (see also McCormack et al . ; Blume‐Werry et al . ; Sloan, Fletcher & Phoenix ), urging a decoupling of those processes in terrestrial biosphere models.…”

“…For example, warmer temperatures early in the season can induce earlier root growth in arctic tundra (Sullivan & Welker ) and temperate trees (McCormack et al . ). Whether and how root phenology responds to earlier snowmelt, a key factor in high altitude and latitude systems, remains unknown.…”

“…Assessing changes in root phenology in response to various climate change factors is thus important to enable terrestrial biosphere models to correctly model future ecosystem processes (Smithwick et al 2014;Iversen et al 2015;Warren et al 2015). For example, warmer temperatures early in the season can induce earlier root growth in arctic tundra (Sullivan & Welker 2005) and temperate trees (McCormack et al 2014b). Whether and how root phenology responds to earlier snowmelt, a key factor in high altitude and latitude systems, remains unknown.…”

Estimating the onset of spring from a complex phenology database: trade-offs across geographic scales

“…Taken collectively, data derived from these vast networks of observers can help address phenological research questions on broad spatial and temporal scales as well as at site to regional scales that are of particular importance to natural resource managers and decision-makers . In fact, numerous recent studies have used datasets from these programs to examine short and long-term phenological responses and to validate phenological model predictions at large spatial scales (Jeong et al 2011;Hurlbert and Liang 2012;Courter et al 2013;Jeong et al 2013;Chapman et al 2014;Euskirchen et al 2014;McCormack et al 2014). These data also provide valuable baseline data for future studies to investigate shifts and patterns in phenology relative to ongoing climate change.…”

A physiological model for predicting dynamics of tree stem‐wood non‐structural carbohydrates

“…The mechanisms of primary growth and leaf growth in this model are the same as the CASSIA model: the predicted NSC consumptions are determined by the daily growth rate and the length of thermal time. Although we lacked observations on fine root growth, we simply assumed that this growth scaled in proportion to the leaf growth due to previous studies, which showed that the two growth rates are linked (McCormack, Gaines, Pastore, & Eissenstat, ; Nadelhoffer & Raich, ). We may have to redefine the root growth sub‐module when more detailed measurements can be obtained.…”