Tree Water Use, Water Use Efficiency, and Carbon Isotope Discrimination in Relation to Growth Potential in Populus deltoides and Hybrids under Field Conditions

Abstract

We explored the relationship between tree growth, water use, and related hydraulic traits in Populus deltoides Bartr. ex Marsh.and hybrid clones, to examine potential trade-offs between growth and water use efficiency. Nine genotypes, six P. deltoides and three hybrid clones, that represented genotypes with high (Group H), intermediate (Group I), and low (Group L) growth performance were selected for study, based on year-two standing stem biomass in a replicated field trial. In year four, tree growth, transpiration (Et), canopy stomatal conductance (Gs), whole-tree hydraulic conductance (Gp), and carbon isotope discrimination (Δ13C) were measured. Tree sap flux was measured continuously using thermal dissipation probes. We hypothesized that Group H genotypes would have increased growth efficiency (GE), increased water use efficiency of production (WUEp, woody biomass growth/Et), lower Δ13C, and greater Gp than slower growing genotypes. Tree GE increased with relative growth rate (RGR), and mean GE in Group H was significantly greater than L, but not I. Tree WUEp ranged between 1.7 and 3.9 kg biomass m3 H2O−1, which increased with RGR. At similar levels of Et, WUEp was significantly greater in Group H (2.45 ± 0.20 kg m−3), compared to I (2.03 ± 0.18 kg m−3) or L (1.72 ± 0.23 kg m−3). Leaf and wood Δ13C scaled positively with stem biomass growth but was not correlated with WUEp. However, at a similar biomass increment, clones in Group H and I had significantly lower leaf Δ13C than Group L. Similarly, Group H clones had a significantly lower wood Δ13C than Group L, supporting our hypothesis of increased WUE in larger trees. Tree physiological and hydraulic traits partially explain differences in WUEp and Δ13C, and suggest that clone selection and management activities that increase tree biomass production will likely increase tree and stand WUE. However, more research is needed to discern the underlying hydraulic mechanisms responsible for the higher WUE exhibited by large trees and distinct clones.

Water Use, Efficiency, and Stomatal Sensitivity in Eastern Cottonwood and Hybrid Poplar Varietals on Contrasting Sites in the Southeastern United States

“…The lower reported WUE of trees in these studies is likely the result of supplemental watering in either greenhouse or irrigated conditions. Additionally, our measured WUE is about double what was found by Maier et al (2019) for eastern cottonwood and hybrid poplars across a range of growth performance in North Carolina, United States. Because Maier et al (2019) included varietals across a range of growth rates, their reported WUE is likely lower than in the varietals tested in our study which were selected in part due to their higher growth rates.…”

Su Stresi Altındaki Bazı Kızılçam Kaynaklarının Tohum Çimlenme Oranı ve Fidelerin Gaz Değişim Performanslarının İncelenmesi

“…The physiological processes, such as photosynthesis and carbon assimilation, are directly linked to the xylem water transportation efficiency for plants [8]. The amount of water used to produce a unit of biomass or fixed carbon unit during photosynthesis is called water use efficiency [9]. It is a key trait that indicates the physiological adaptation of plants to deal with limited water reserves.…”

Accelerating forest tree breeding by integrating genomic selection and greenhouse phenotyping

“…and their hybrids are considered an ideal short-rotation woody crop (SRWC). These species and/or hybrids have multiple applications in the industry, providing reliable wood products, veneer, pulp and paper, excelsior, chemicals, and feedstocks for cellulosic energy and the biofuels industry (Maier et al, 2019). Poplars can also offer important environmental applications such as phytoremediation (Isebrands & Richardson, 2014;Stanton, Neale, & Li, 2010).…”