Fertilization at planting impairs root system development and drought avoidance of Douglas-fir (Pseudotsuga menziesii) seedlings

Abstract

-Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedlings (1 + 1 bareroot) were divided into 8-13 cm 3 and 23-35 cm 3 initial root-volume categories and either not fertilized or fertilized with 60 g Apex ® in the planting hole at a drought-prone clearcut site in the Oregon Coast Range, USA. Regardless of initial root volume, fertilized seedlings consistently reached lower predawn xylem water potential (Ψ xylem ) values than non-fertilized seedlings during summer. Roots did not proliferate relative to fertilizer placement and mean values for lateral-root length, root tips, and root biomass were less for fertilized seedlings in each of four vertical root zones. Poor root system development of fertilized seedlings may have been associated with the rapid release of high fertilizer salt concentrations into the rhizosphere. Root-volume growth was positively correlated with Ψ xylem , emphasizing the importance of new root growth following planting for drought avoidance. Criteria for successful field fertilization must consider the anticipated drought level of the site.seedling / controlled-release fertilizer / root architecture / drought avoidance / Pseudotsuga menziesii Résumé -La fertilisation à la plantation perturbe le développement du système radiculaire et réduit la résistance à la sécheresse des plants de Douglas (Pseudotsuga menziesii). On a utilisé deux catégories de plants à racines nues (1 + 1) de Douglas (Pseudotsuga menziesii (Mirb.) Franco) dont le volume initial des racines était respectivement de 8 à 13 cm 3 et de 23 à 35 cm 3 . Ces plants furent installés dans une station de clairière plutôt sèche, située dans la Chaîne côtière de l'Oregon aux USA, et soumis à deux traitements : pas de fertilisation ou fertilisation avec 60 g d'Apex ® introduits dans le trou de plantation. Quelque soit le volume racinaire initial, les plants fertilisés révèlent, au cours de l'été, des valeurs de potentiel hydrique du xylème en fin de nuit (Ψ xylem ) toujours inférieures à celles obtenues sur plants non fertilisés. Les racines ne se sont pas développées dans les zones en contact avec l'engrais, et les valeurs moyennes de longueur de racines latérales, de nombre de pointes racinaires, et de biomasse racinaire sont inférieures pour les plants fertilisés, dans les quatre plans verticaux. Ce mauvais développement du système racinaire des plants fertilisés peut être associé à la libération rapide d'engrais à forte concentration minérale dans la rhizosphère. La croissance racinaire en volume était corrélée positivement avec le Ψ xylem ce qui permet de souligner l'importance de la croissance des racines après plantation pour limiter les effets de la sécheresse. Les critères à adopter pour réussir une opération de fertilisation de terrain doivent donc prendre en considération l'éventuel degré de sécheresse de la station. plant / engrais à libération contrôlée / architecture racinaire / limitation des effets de sécheresse / Pseudotsuga menziesii

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

“…This suggests that large initial root system size does not confer drought avoidance in bareroot northern red oak seedlings, as was similarly reported for Douglas-fir seedlings (Haase and Rose, 1993;Jacobs et al, 2004a), and that large planting stock should be targeted for sites with relatively higher soil moisture availability. Transplant shock in northern red oak seedlings was implicated by reduced Ψ L , A, E, and growth.…”

“…No differences were found in Ψ L at 95 or 115 d in Douglas-fir seedlings graded into different Rv classes and transplanted into pots (Haase and Rose, 1993). Similarly, Jacobs et al (2004a) reported no significant differences in Ψ L between RvC for Douglas-fir seedlings following field transplant. Contrary to above results, we observed that northern red oak seedlings with larger initial Rv were less able to mitigate effects of drought following transplant, as indicated by lower Ψ L values (Fig.…”

“…It has been argued that large root volume (Rv) of bareroot seedlings at transplanting may act to confer drought avoidance that alleviates transplant shock because of greater root growth potential and access of larger Rv to soil resources (Carlson, 1986;Carlson and Miller, 1990;Haase and Rose, 1993;Jacobs et al, 2004a). However, large Rv is often correlated with large shoots, and the transpirational demand after budbreak coupled with insufficient water uptake may result in higher water deficits (Sands, 1984), which could induce transplant shock detrimental to field performance of seedlings.…”

Linking nursery nutritional status and water availability post-planting under intense summer drought: the case of a South American Mediterranean tree species

“…However, this positive response was not maintained after outplanting and contrasted with other recent studies conducted in Mediterranean conditions that suggested that a high nutrient supply generates early root growth and a positive carbon balance that helps sustain the demand for resources to maintain growth biomass , Cuesta et al 2010, VillarSalvador et al 2012. The low RDM could be attributed to the effects of residual nutrients from the fertilizer contained within the polymer-coated fertilizer, and the root plug, which tends to inhibit the growth ability of roots in the planting hole under low soil water available (Idris et al 2004, Jacobs et al 2004. By contrast, in more temperate and wet environments, CRF promoted root development (Timmer & Teng 2004, Haase et al 2006.…”

“…By contrast, high seedling N loading in the nursery produced a morphological imbalance by increasing shoot biomass over root biomass following planting (Trubat et al 2008, Cortina et al 2013. Under dry conditions, this morphological imbalance increases transpiration rates and reduces stem water potential, root hydraulic conductivity (Hernández et al 2009), and stomatal conductance (Jacobs et al 2004). Low shoot:root ratios could promote a more conservative water use and improve the likelihood of survival after outplanting (Leiva & Fernández-Alés 1998, Lloret et al 1999.…”