Do high-tannin leaves require more roots?
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The well-known deceleration of nitrogen (N) cycling in the soil resulting from addition of large amounts of foliar condensed tannins may require increased fine-root growth in order to meet plant demands for N. We examined correlations between fine-root production, plant genetics, and leaf secondary compounds in Populus angustifolia, P. fremontii, and their hybrids. We measured fine-root (<2mm) production and leaf chemistry along an experimental genetic gradient where leaf litter tannin concentrations are genetically based and exert strong control on net N mineralization in the soil. Fine-root production was highly correlated with leaf tannins and individual tree genetic composition based upon genetic marker estimates, suggesting potential genetic control of compensatory root growth in response to accumulation of foliar secondary compounds in soils. We suggest, based on previous studies in our system and the current study, that genes for tannin production could link foliar chemistry and root growth, which may provide a powerful setting for external feedbacks between above- and belowground processes.
KeywordsFeedback Fine-root growth Genetics and ecosystems Minirhizotron Populus
We thank the Ogden Nature Center and NSF IRCEB and FIBR grants for infrastructure and financial support, respectively. Brett Dickson consulted on use of model selection theory. We also thank Nathan Lojewski, Pam Cox, Piper Townsend, Greg Cox, Jen Schweitzer, Carri LeRoy, Gina Wimp, Julius Cantella, Paul Selmants and the Hart, Lindroth, and Whitham laboratories for field assistance and providing comments on earlier versions of the manuscript. We also thank Drs. Amy Austin, Phyllis Coley, and two anonymous reviewers for providing helpful reviews of this manuscript.
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