Drought susceptibility and recovery of transplanted Quercus rubra seedlings in relation to root system morphology

Abstract

Keywords:gas exchange / northern red oak / root growth / transplant shock / xylem water potential Abstract • Transplant shock, implicated by depressed seedling physiological status associated with moisture stress immediately following planting, limits early plantation establishment. Large root volume (Rv) has potential to alleviate transplant shock because of higher root growth potential and greater access to soil water.• We investigated impacts of drought and transplant Rv on photosynthetic assimilation (A), transpiration (E), stomatal conductance (g s ), predawn leaf xylem water potential (Ψ L ), and growth of northern red oak (Quercus rubra L.) seedlings to explain mechanisms associated with susceptibility to transplant shock. One year-old barerooot seedlings were graded into four Rv categories and either well watered or subjected to drought consisting of low, medium, or high moisture stress by discontinuing irrigation at 22-day intervals for 3 months. Thereafter, all treatments were re-watered to examine recovery.• Transplant shock was signified by reduced A, E, g s , and Ψ L , which generally increased with increasing moisture stress and Rv. Physiological status improved during recovery, though stress was still evident in seedlings exposed to medium or high moisture stress and in larger Rv seedlings. Growth declined with increasing moisture stress but was generally similar among Rv treatments, likely reflecting greater A at the whole plant level and/or reliance upon stored reserves in large Rv seedlings.• The most effective drought avoidance mechanisms were root growth, stomatal regulation, reduced leaf area, and higher growth allocation to roots relative to shoots. Our results suggest that large initial Rv does not enhance drought avoidance during the first season after transplant in northern red oak seedlings. Mots-clés :échanges gazeux / chêne rouge / croissance racinaire / choc de transplantation / potentiel hydrique xylémique Résumé -Sensibilité à la sécheresse et reprise des semis transplantés de Quercus rubra en relation avec la morphologie racinaire.• Le choc de transplantation, lié à l'état physiologique déprimé des plants associé à un stress hydrique, immédiatement après la plantation, limite le début de l'installation des plants. Un important volume racinaire (Rv) a le potentiel d'atténuer le choc de transplantation en raison du fort potentiel de croissance racinaire et d'un meilleur accès à l'eau du sol. Nous avons étudié les impacts de la sécheresse et des transplants Rv sur l'assimilation photosynthé-tique (A), la transpiration (E), la conductance stomatique (g s ), le potentiel hydrique de base (Ψ L ), et la croissance des plants de chêne rouge (Quercus rubra L.) pour expliquer les mécanismes associés à la sensibilité à un choc de transplantation. Des plants de un an à racines nues ont été classés en quatre catégories Rv et soit bien arrosés, ou soumis à une sécheresse, consistant à un faible, moyen ou fort stress hydrique en cessant l'irrigation à 22 jours d'intervalle(27, 49 et 72 après la ...

Amelioration of planting stress by soil amendment with a hydrogel–mycorrhiza mixture for early establishment of beech (Fagus sylvatica L.) seedlings

“…We observed in line with previous studies (Girard et al 1997a;McKay et al 1999;Yu et al 2003;Jacobs et al 2009) that air exposure immediately caused significant water loss of the plants although they were still in the dormant stage with fully closed buds. Bare-rooted beech plants are very sensitive to desiccation (McKay et al 1999).…”

Effects of Visual Grading on Northern Red Oak (Quercus rubra L.) Seedlings Planted in Two Shelterwood Stands on the Cumberland Plateau of Tennessee, USA

“…In particular, the exceptional drought probably caused dieback, inhibited growth, and increased mortality of seedlings from both grades, because average size of trees from both grades was relatively large. Previous studies have found drought negatively impacted larger trees more than smaller trees, but their seedlings sizes were much smaller than in this study [25,56]. Perhaps, the lack of inclusion of cull seedlings in both grades also equalized response to planting shock.…”

“…This finding was surprising given multiple studies that found increased transplant shock for larger seedlings [25,26,28,56]. However, we were approaching significance in survival differences between grades in the shelterwood harvest stand in year 2 (premium grade = 74 percent ± 3.6 versus standard = 64 percent ± 3.9), and in stem dieback in the midstory removal stand across years (premium grade = 23 percent ± 2.2 versus standard 17 percent ± 2.1).…”

“…The drought was classified as abnormally dry to moderately dry from the time of planting for the next 2.5 months, and then worsened to severely dry to exceptionally dry for the following 7.5 months [55]. Seedling size advantages have been shown to dissipate under severe moisture stress due to the inability of larger seedlings to maintain root systems [50,56]. The drought probably caused the heavy mortality and lack of growth for the first three to four years after planting, and perhaps diminished competitive advantages of premium grade seedlings.…”

Water Stress and Afforestation: A Contribution to Ameliorate Forest Seedling Performance During the Establishment

“…The first physiological symptom of transplanting shock is the lowering in predawn water potential. As water potential becomes more negative, other physiological symptoms appear like reduced stomatal conductance, photosynthesis, transpiration and growth (Grossnickle, 1988;Guehl et al, 1989;Jacobs et al, 2009;Sands, 1984). These symptoms were observed by Mena-Petite et al (2005) after transplanting seedlings of Pinus radiata both under drought and under well-watered conditions.…”