Variability in root production, phenology, and turnover rate among 12 temperate tree species

Authors

  • M. Luke McCormack,

    1. Intercollege Graduate Degree Program in Ecology, Pennsylvania State University, University Park, Pennsylvania 16801 USA
    2. Key Laboratory of Ecosystem Network Observation and Modeling, Synthesis Research Center of Chinese Ecosystem Research Network, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, 22A Datun Road, Chaoyang District, Beijing 100101 China
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  • Thomas S. Adams,

    1. Intercollege Graduate Degree Program in Ecology, Pennsylvania State University, University Park, Pennsylvania 16801 USA
    2. Department of Ecosystem Science and Management, Pennsylvania State University, University Park, Pennsylvania 16801 USA
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  • Erica A. H. Smithwick,

    1. Intercollege Graduate Degree Program in Ecology, Pennsylvania State University, University Park, Pennsylvania 16801 USA
    2. Department of Geography, Pennsylvania State University, University Park, Pennsylvania 16801 USA
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  • David M. Eissenstat

    Corresponding author
    1. Intercollege Graduate Degree Program in Ecology, Pennsylvania State University, University Park, Pennsylvania 16801 USA
    2. Department of Ecosystem Science and Management, Pennsylvania State University, University Park, Pennsylvania 16801 USA
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  • Corresponding Editor: R. W. Ruess.

Abstract

The timing of fine root production and turnover strongly influences both the seasonal potential for soil resource acquisition among competing root systems and the plant fluxes of root carbon into soil pools. However, basic patterns and variability in the rates and timing or fine root production and turnover are generally unknown among perennial plants species. We address this shortfall using a heuristic model relating root phenology to turnover together with three years of minirhizotron observations of root dynamics in 12 temperate tree species grown in a common garden. We specifically investigated how the amount and the timing of root production differ among species and how they impact estimates of fine root turnover. Across the 12 species, there was wide variation in the timing of root production with some species producing a single root flush in early summer and others producing roots either more uniformly over the growing season or in multiple pulses. Additionally, the pattern and timing of root production appeared to be consistent across years for some species but varied in others. Root turnover rate was related to total root production (P < 0.001) as species with greater root production typically had faster root turnover rates. We also found that, within species, annual root production varied up to a threefold increase between years, which led to large interannual differences in turnover rate. Results from the heuristic model indicated that shifting the pattern or timing of root production can impact estimates of root turnover rates for root populations with life spans less than one year while estimates of root turnover rate for longer lived roots were unaffected by changes in root phenology. Overall, we suggest that more detailed observations of root phenology and production will improve fidelity of root turnover estimates. Future efforts should link patterns of root phenology and production with whole-plant life history traits and variation in annual and seasonal climate.

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