Populus and its hybrids are attractive bioenergy crops and the southeastern United States has broad ability to supply bioenergy markets with woody biomass. Breeding and hybridization have led to superior eastern cottonwood (Populus deltoides W. Bartram ex Marshall) and hybrid poplars adapted to a wide variety of site types not suited for agricultural production. In order to maximize productivity and minimize inputs, genotypes need to efficiently use available site resources and tolerate environmental stresses. In addition, we need to determine plasticity of traits and their coordination across sites to select traits that will broadly characterize genotypes. Therefore, our study objectives were to determine which leaf traits were correlated with growth and if they exhibited significant plasticity across sites as well as determine how traits were coordinated within and across sites and Populus taxa. We measured trees across two growing seasons planted at two sites in northeastern Mississippi, USA. Genotypes included eastern cottonwoods as well as F1 crosses of eastern cottonwood and P. maximowiczii (Henry), P. nigra (L.) and P. trichocarpa (Torr. & Gray). We found that net assimilation rates, leaf nitrogen concentration and carbon isotope ratios were negatively correlated with growth across taxa. Tree size and growth, leaf isotope composition (d13C and d15N), as well as LMA exhibited the least plasticity across sites, while physiological gas exchange parameters and leaf nitrogen concentration exhibited the highest plasticity. Broadly, leaf carbon isotope ratios were correlated with intrinsic water use efficiency across sites and taxa while leaf nitrogen isotope ratios exhibited contrasting relationships with leaf nitrogen concentration across sites. Overall, these results allow us to refine selections of productive genotypes based on useful traits including carbon isotope ratios that exhibit low plasticity across sites and were correlated with growth to provide next generation, bioenergy fuels.
College of Forest Resources
Department of Forestry
short rotation woody crops; cottonwood; bioenergy feedstocks; genotype x environment interactions; gas exchange; isotopes
"Leaf-level physiological strategies related to productivity and plasticity of Populus in the southeastern US" (2023). Forest & Wildlife Research Center Publications and Scholarship. 13.