Relative growth rates of two epiphytic lichens, Lobaria pulmonaria and Hypogymnia occidentalis, transplanted within and outside of Populus dripzones

Abstract

Overstory Populus has been shown to facilitate establishment by cyano-and cephalolichens on conifer branches within its dripzone; though the mechanisms behind this "dripzone effect" have yet to be elucidated. Here we test the following hypotheses that throughfall from Populus: (i) elevates bark pH; (ii) increases relative growth rate in cephalolichens; and (iii) stimulates their growth through phosphorus (P) fertilization. In southern British Columbia we transplanted the cephalolichen Lobaria pulmonaria (L.) Hoffm. (promoted by dripzones) and the acidophytic chlorolichen Hypogymnia occidentalis L.H. Pike for 14 months to 26 pairs of similar-sized Picea glauca × engelmannii situated within and outside of Populus dripzones. Half of our transplants were fertilized with P. Bark pH was significantly higher on spruce branches within than outside dripzones. Relative growth rate in L. pulmonaria increased with bark pH and was slightly higher within dripzones than outside, consistent with a facilitating effect of Populus on the Lobarion community. By contrast, the addition of P decreased relative thallus area growth in L. pulmonaria and increased relative thallus area growth in H. occidentalis; though a stronger influence on growth could be attributed to variation in canopy cover and tree height. We conclude that cephalolichens in our study area are unlikely to be facilitated by P leached from Populus.Résumé : On a déjà démontré que les peupliers dominant facilitent l'établissement des cyano-et céphalolichens sur les branches des conifères via leur eau de lessivage; cependant, le mécanisme de cet effet de lessivage reste à expliquer. Les auteurs ont cherché à vérifier les hypothèses voulant que les eaux de lessivage des peupliers : (i) relèvent le pH de l'écorce; (ii) augmentent le taux de croissance relative (TCR) chez les céphalolichens; et (iii) stimulent leur croissance via une fertilisation phosphatée. Dans le sud de la Colombie Britannique, les auteurs ont transplanté le céphalolichen Lobaria pulmonaria (L.) Hoffm. (favorisé par les eaux de lessivage) et le chlorolichen acidophile Hypogymnia occidentalis L.H. Pike pendant 14 mois, sur 26 paires de Picea glauca × engelmannii de même dimension situées à l'intérieur ou à l'extérieur de zones de lessivage venant de peupliers. Ils ont fertilisé la moitié des transplants avec du P. Le pH de l'écorce s'est avéré significativement plus élevé chez les branches d'épinette sous l'influence du lessivage que celles situées à l'extérieur. Le TCR du L. pulmonaria a augmenté avec le pH de l'écorce et était légèrement plus grand dans la zone de lessivage qu'à l'extérieur, congrument avec une assistance du peuplier sur la communauté du Lobaria. Au contraire, l'addition de P a déprimé la surface relative de croissance du thalle (CRsT) chez le L. pulmonaria et a augmenté la CRsT chez le H. occidentalis; bien que l'on puisse attribuer une plus forte influence sur la croissance à une variation de la couverture de la canopée et de la hauteur des arbres. Les auteurs concluent que, dans le ...

High-Throughput Sequencing in Studies of Lichen Population Biology

“…relative annual growth rate). Studies of lichen growth based on transplanted lichens are numerous, with firmly established methods (Antoine and McCune 2004;Gauslaa and Goward 2012;Gauslaa et al 2009;Hallingbäck 1990;Larsson et al 2012;McCune et al 1996;Walser and Scheidegger 2002). A crucial factor for understanding lichen growth (and fitness) is being able to separate the effects of acclimation of thalli to specific local environmental conditions from the effect of the genetic background.…”

Tree species shape the elemental composition in the lichen Hypogymnia physodes transplanted to pairs of spruce and beech trunks

“…Thereby, they are sensitive biomonitors of airborne pollutants and natural element availability (Nimis et al 2002). In this context it is welldocumented that lichen-dominated epiphytic communities are shaped by the elemental composition of the host tree bark (Gauslaa 1995(Gauslaa , 1985 and/or phorophyte-specific canopy leachates (Campbell et al 2013;Gauslaa and Goward 2012). For example, spruce branches beneath the dripzone of aspen support a rich cyanolichen flora (Goward and Arsenault 2000) with a high N-fixation capacity, enriching the forests in which they grow with N through litter formation and leaching from a major epiphytic biomass component (Antoine 2004).…”

Lichens in the inland rainforest: Climate biomonitoring and population structure of Lobaria pulmonaria (L.) Hoffm.

“…Although growing conditions for lichen communities differ considerably between conifers and deciduous trees, due to differences in factors such as light availability (Coxson and Stevenson, 2007b), water availability (Gauslaa et al 2009), and bark pH (Goward and Arsenault, 2000a;Gauslaa and Goward, 2012), both can develop high cyanolichen loading within ITR stands. Sample trees were located in the same drainages described in Chapter 1, east o f Prince George in the upper Fraser watershed (Fig 2.).…”

“…Similar protocols were followed in selecting sample branches from both species: sample trees were identified at a distance by their abundance of cyanolichens, primarily Lobaria pulmonaria. Trees with abundant cyanolichens were not selected if they were found within the drip-zone o f a western redcedar {Thuja plicata) or a cottonwood {Populus balsamifera) tree, where additional influences of throughflow leachate may influence lichen growth (Goward and Arsenault, 2000a;Gauslaa and Goward, 2012). Trees were all selected within topographically similar primary and secondary creek drainages, with similar elevation, aspect, and levels of light exposure.…”

“…Specific thallus mass (STM) is a measure o f lobe thickness in weight per unit area which varies greatly among Lobaria pulmonaria thalli by season, age, and in different light and humidity environments (Larsson and Gauslaa, 2011;Gauslaa and Goward, 2012;Larsson et al 2012). Active photosynthesis causes STM to increase through the CO2 assimilation by photobionts (Larsson and Gauslaa,201 l).Decreased turgor pressure for fungal hyphae occurring under 60 % humidity can also cause increases in STM by impeding fungal expansion (Larsson and Gauslaa, 2011).…”