Abstract
The genetic and physiological quality of seedlings is a critical component for longleaf pine (Pinus palustris Mill.) restoration, because planting genetic material that is adapted to environmental stress is required for long-term restoration success. Planting trees that exhibit high water-use efficiency (WUE) is a practice that could maximize this species’ survival and growth in a changing climate. Our study evaluates genetic variation in WUE and growth, as well as WUE-growth relationships, a key step to determine potential for breeding and planting trees with high WUE. We measured carbon isotope discrimination (∆)—a proxy for WUE—in 106 longleaf pine increment cores extracted from trees belonging to nine full-sib families. Tree diameter and total tree height were also measured at ages 7, 17, 30 and 40 years. Each increment core was divided into segments corresponding to ages 7–17, 18–30 and 31–40, representing early, intermediate and mature growth of the trees. We identified significant genetic variation in DBH and WUE among families that merit further exploration for identifying trees that can potentially withstand drought stress. Mean family growth rates were not associated with mean family values for carbon isotope discrimination. Family variation in both diameter growth and WUE but no relationship between family values for these traits, suggests it is possible to improve longleaf pines in both diameter growth and WUE through appropriate breeding.
Highlights
Longleaf pine (Pinus palustris Mill.) once dominated the coastal plains of the southeastern UnitedStates, covering 25 million hectares but its area has been reduced to less than 3% of its range prior to European colonization of North America [1]
Means for diameter at breast height (DBH) and tree height at ages 7, 17, 30, 40 years showed nonlinear growth trends meansoccurring for DBH at and height ages 7, 17, 30, 2, 40respectively)
This study found significant variation among the families studied for growth in tree diameter as well as in water-use efficiency, as estimated by ∆ in mature longleaf pine
Summary
Longleaf pine (Pinus palustris Mill.) once dominated the coastal plains of the southeastern UnitedStates, covering 25 million hectares but its area has been reduced to less than 3% of its range prior to European colonization of North America [1]. Extensive efforts to restore longleaf pine ecosystems have been initiated across its native range, which extends from southeastern Virginia to eastern Texas, as approximately 53,000 hectares of longleaf pine were established in 2017 alone [2]. Despite high levels of longleaf pine plantation establishment, there is limited knowledge regarding the genetic make-up and subsequent physiological characteristics of the seedlings of this species being planted across the southeastern US. One potential strategy to adapt forests to future climates is to plant genotypes that use less water for biomass production and can better cope with a decrease in water availability [6]. Longleaf pine trees with good growth and moderate water loss, that is, high water-use efficiency (WUE), would potentially be better adapted to future climates
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