Cyanolichens ( Lobaria hallii , Lobaria retigera , Lobaria scrobiculata , Pseudocyphellaria anomala ) and cephalodial ( Lobaria pulmonaria ) and noncephalodial ( Platismatia glauca ) chlorolichens were sampled in dry open, mesic open, and mesic closed forests in central British Columbia. Specific thallus mass (STM), water-holding capacity (WHC), percent water content at saturation, and thickness of upper cortex, photobiont layer, and medulla plus lower cortex were measured. Whereas STM did not differ much between cyanolichens (9.8 ± 0.1 mg dry mass·cm–2) and chlorolichens (8.0 ± 0.1 mg dry mass·cm–2), cyanolichens had a WHC (20.3 ± 0.2 mg H2O·cm–2) that was nearly twice that of the chlorolichens (10.8 ± 0.2 mg H2O·cm–2). STM and WHC increased with light exposure at the studied sites, presumably as an acclimation to higher evaporation demands. Within species, WHC was strongly coupled to STM and increased substantially faster with STM in cyanolichens, compensating their inability to use humid air to restore photosynthesis. The photobiont layer was two times thicker in cyanolichens, whereas the thickest layer (the hydrophobic medulla) did not differ between cyanolichens and chlorolichens. Most interspecific variation (88.3%) in WHC could be accounted for in a multiple regression model where STM and photobiont to total thickness ratio were the most important independent variables. Photobionts thus play significant roles in the water economy of lichens.

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 ...

All specimens of three foliose lichens (Lobaria pulmonaria (L.) Hoffm., n = 725; Lobaria scrobiculata (Scop.) DC., n = 6613; Pseudocyphellaria crocata (L.) Vain., n = 1237) and two pendulous lichens (Alectoria sarmentosa (Ach.) Ach., n = 441; Ramalina thrausta (Ach.) Nyl., n = 990) were collected from 160 random Picea abies (L.) H. Karst. branches (2–15 m above the ground) in three spruce-dominated boreal rainforests in Norway. Maximum diameter (foliose lichens), length (pendulous lichens), and reproductive structures were quantified in each thallus. The effects of measured tree and branch variables on abundance and reproduction were tested by generalized linear mixed models with binomial errors (binomial GLMM) and zero-altered (over-dispersed) Poisson generalized linear mixed models (ZAPGLMM). Lobaria pulmonaria, P. crocata, and R. thrausta occurred predominantly in the lower canopy, whereas the remaining species were also common at higher levels. The portions of thalli producing soredia and (or) isidia were 60%, 22%, and 14% for P. crocata, L. scrobiculata, and L. pulmonaria, respectively. Isidiate and (or) sorediate L. pulmonaria thalli occurred mainly on low, dead branches, whereas sorediate L. scrobiculata and P. crocata occurred at all heights. The occurrence of small P. crocata, <5 mm, decreased by branch height and small L. scrobiculata, <5 mm, increased with branch length and decreased with tree age. Upper branches supported a significant part of the total populations of studied lichens and are, thus, important when evaluating epiphyte conservation status.