Interactive effects of phosphorus and light availability on early growth of maritime pine seedlings

Abstract

-We examined the response of early growth of maritime pine seedlings to combined levels of light and phosphorus. Seedlings were grown under three levels of phosphorous availability, i.e., two relative addition rates (RAR = 2 and 4 g P (100 g -1 )P d -1 ) and a free-access to P, crossed with two light levels (photosynthetic photon flux densities of 150 and 450 µmol m -2 s -1 , respectively). Relative growth rate (RGR) and relative uptake rate of phosphorus (RUR) were computed, as well as the amount of light absorbed per seedling. We found that phosphorus and light acted as limiting factors with a complex interaction. Under low light and at the lowest P level, P and light were co-limiting, i.e., growth was enhanced only when P and light were increased together. Light was the limiting factor for growth under low light conditions at all other levels of P availability. P was the limiting factor at a RAR of 2% under high light. Enhancing P from 4% to free access did not significantly improve growth under high light. RUR was controlled systematically by P availability at 2 and 4% RAR. RGR values were close to RUR values except under free access to P. Therefore, growth-independent accumulation of P was observed under high P conditions. The differences in biomass production among P treatments were explained primarily by the reduced amount of radiation intercepted by the seedlings as a consequence of their reduced leaf area. No effect of P treatments were observed on the calculated radiation-use efficiency (RUE), which was found to be larger under low light. This confirms that pine seedlings adjust to moderate phosphorus deficiency mainly by changing their morphology (leaf area, dry-mass partitioning) while biochemical and photochemical limitations of photosynthesis play only a very secondary role.phosphorus nutrition / shade / growth / Pinus pinaster Aït.Résumé -Interaction des effets de la disponibilité en phosphore et en lumière sur la croissance de jeunes plants de pin maritime. La croissance de jeunes plants de pin maritime a été suivie en chambre de culture à deux niveaux d'éclairement et trois de disponibilité en phosphore. Deux taux d'addition relatifs en P (RAR = 2 et 4 g P (100 g -1 P j -1 ) et un libre accès au P ont été appliqués en combinaison avec deux niveaux d'éclairement (150 et 450 µmol m -2 s -1 ). Le taux de croissance relatif (RGR) et le taux d'absorption relatif de P (RUR) ont été calculés. La surface foliaire, la quantité de rayonnement absorbé et l'efficience d'utilisation du rayonnement (RUE) ont aussi été estimés. Les disponibilités en phosphore et en lumière ont limité la croissance suivant un schéma d'interaction complexe. Au plus faible niveau d'éclairement et d'ajout en phosphore, les deux facteurs étaient co-limitants et la croissance n'était augmentée que lorsque les deux facteurs augmentaient simultanément. La lumière était le facteur limitant pour les traitements sous faible éclairement à tous les autres niveaux de disponibilité en P. Le phosphore était limitant pour des RAR de 2...

Tree nutrition of Norway spruce as modified by liming and experimental acidification at the Höglwald site, Germany, from 1982 to 2004

“…Even though the stands at the Höglwald site exhibited years with "low" nutrient concentrations for some elements according to [43], they showed regularly high yearly increments [19]. We also observed a very high heterogeneity within the same treatments (see also [7,35]). Often small scale site effects, genetic differences, or weather conditions are suggested as reasons for the observed variations [13,42].…”

Influence de la méthode de fertilisation sur la mycorhization contrôlée de deux espèces de Pins méditerranéens

“…Complexes environmental variables can be interconnected with seedling nutrient requirements, as demonstrated for P. pinaster and its demand of phosphorous being dependent on light availability [10]. The fertilisation methods (SF and SRF) at the dosage used were adequate for obtaining good morphological standards of seedling quality for both pine species.…”

Field effect of P fertilization on N2 fixation rate of Ulex europaeus

“…P fertilization, used in maritime pine forests due to its positive effect on pine growth [7,24], may increase these natural inputs in two different ways: (i) by increasing the abundance and biomass of N 2 -fixing shrubs [3]; and (ii) by increasing the N 2 fixation rate [1]. This second point has been mostly developed in laboratory studies that suggest a P effect on N 2 fixation rate.…”

“…Pines C130: Circumference at 130 cm height. Significant differences are as given by a t-test with a 5% error threshold, and confirm the P effect on pine growth [7,24] …”