Do genetically-specific tree canopy environments feed back to affect genetically specific leaf decomposition rates?
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In forest ecosystems, trees may have genetically distinct patterns in leaf decomposition. Trees also can have genetically distinct canopy environments which modify temperature, moisture, and microbial communities on the forest floor. The interaction between these factors may result in underexplored interactions between microenvironment and leaf decomposition at the genotype level.
We compare litter decomposition rates for distinct genotypes of Fremont cottonwood (Populus fremontii) grown in a common garden environment under three different riparian conditions: 1) under a 16-tree stand of the same genotype, 2) under a 16-tree stand of another genotype, and 3) under a 16-tree stand of 16 different genotypes. Genotypes differed in canopy size and phenology.
While genotype exerted a strong effect on decomposition, this effect was most pronounced when litter was decomposed under a self-similar (“home”) canopy. The strongest driver of decomposition rates across all factors (including litter quality and environmental factors) was spring (leaf-out) and fall (leaf-drop) phenology, but responses were variable by genotype.
The influence of genetics on litter decomposition, canopy environment, and tree phenology provides justification for the inclusion of stand-level traits like canopy cover into models of decomposition and complicates the results of studies that rely on litter quality traits alone.
KeywordsDecomposition environment Genes-to-ecosystems Intraspecific variation Home-field advantage Phenology
We would like to thank The Evergreen State College (Evergreen) for sabbatical funding for DGF, G. Garnett of the U.S. Bureau of Reclamation, and Cibola National Wildlife Refuge staff. We would like to thank T. Whitham, A. Keith, J. Schweitzer, J. Bailey, S. Ferrier, R. Bangert, K. Kennedy, C. Dirks, and G. Wimp. The common garden was supported by NSF DEB-0425908 and NSF DEB-0816675. Undergraduates in the 2014 class, “Advanced Field and Laboratory Biology in Southwest Ecosystems” at Evergreen contributed to data collection.
CJL and DGF conceived, designed, and executed this study and wrote the manuscript together. CJL led decomposition experiment study design, analysis, interpretation, and writing. DGF aided in study design, data collection, statistical analysis, and writing.
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