Global ETD Search

1	Lichen decline in areas with increased nitrogen deposition might be explained by parasitic fungi : A survey of parasitic fungi on the lichen Alectoria sarmentosa after 4 years of nitrogen fertilisation Ström, Caspar January 2011 (has links) Nitrogen (N) deposition in Europe has recently increased and is expected to continue to increase in the future. There is a well-documented decline in lichen diversity with higher N availability, although the mechanisms behind this are poorly known. In this study, I tested whether attacks by fungal parasites increase with higher N deposition. This pattern has been found in a number of studies on vascular plants, but it has never been investigated for lichens. I surveyed dark lesions and discolourings caused by fungi on the pollution-sensitive lichen Alectoria sarmentosa, after 4 years of increased N deposition in a whole tree fertilisation experiment in a boreal spruce forest. I found two species of fungi growing on the investigated lichen thalli. One of these species responded positively to increased N deposition. The results show that lichens can suffer from increased parasite attacks under a higher N load. Further studies using multiple lichen species and many years of recording are needed to understand the importance of parasites for the response of whole lichen communities to an increased N load. parasitic fungi lichen diversity Alectoria sarmentosa nitrogen deposition Biology Biologi
2	Ecology of lichens in boreal coniferous forests with reference to spatial and temporal patterns Esseen, Per-Anders January 1983 (has links) The thesis deals with the ecology of lichens in two contrasting types of forest, epiphytic lichens in old Picea abies forest of the fi re-refugia type and epigeic as well as epixylic lichens in a successional sequence of fire- susceptible Pinus sylvestris forests. Results in five separate papers form the basis for a discussion of general patterns of dispersal, succession and life strategies in lichens. The study sites were located in Medelpad and Västerbotten, in the central and northern part of Sweden, respectively. Special attention has been paid to the rare, pendulous, spruce-1ichen Usnea longissima and the coexisting lichen species. U. longissima is largely restricted to north-facing hill slopes covered with old, mesic spruce forest that is characterized by a very long continuity not disturbed by fire. A marked decline in the number of sites with U. longissima was found. The decline was mainly due to the effect of different forestry practices as the species is very sensitive to environmental disturbances. The epiphytic lichen vegetation of six tree species occurring in the spruce forest is described. Clear successional trends with increasing tree size were • obtained for Alectoria sarmentosa, Bryoria fuscescens coll., B. nadvornikiana, Usnea filipendula' and U. subflorida'na, to a lesser extent for Bryoria capii-“" laris while U. longissima had no relationship to tree size or age. TTstudy of the litterfall of macrofragments of epiphytic lichens showed that thallus fragments were dispersed throughout the year with late autumn, winter and early spring as the most critical periods. It is suggested that dispersal through thallus fragmentation is more important in fruticose than in foliose species and that U. longissima has a shorter range of propagule transport than the other species of Alectoria, Bryoria and Usnea studied. The latter proposition was supported through a study of the horizontal patterns of lichen occurrence in the spruce forest. It is shown that the diversity in ground vegetation, after an initial increase, declines with succession in the pine forests. A mechanism of succession in ground vegetation is presented which suggest that variations in habitat heterogeneity, i.e. the diversity of substrates caused by the initial disturbance and the stand development, largely determines diversity changes during succession. Trends of increasing thallus size, increasing size of asexual reproductive propagules and increased competitive ability with succession formed the basis for recognizing three types of strategies in Cladonia» It is concluded that lichens have features that are compatible with the r-K continuum and that they are variously adapted to both the stability of the substrates and that of the forest as a whole. / <p>Diss. (sammanfattning) Umeå : Umeå universitet, 1983, härtill 5 uppsatser</p> / digitalisering@umu Lichens epiphytes Alectoria Bryoria Cladonia Usnea Picea abies Pinus sylvestris dispersal litterfall succession diversity spatial patterns
3	Förekomst och spridning av hänglavar från äldre skogar till unga tidigare avverkade områden i Västerbottens inland Maksimova, Emma January 2023 (has links) The Swedish forestry and the use of clearcutting models has resulted in great losses of older forests in Sweden, resulting in several species being affected negatively. Hair lichens are important organisms that are providing several ecological functions in forest ecosystems and are declining due to being associated with older forests with high continuity. This study investigates the occurrence and dispersal ability of the genus Alectoria, Bryoria and Usnea between older forests and young secondary forests in three different areas in Storuman municipality, Västerbotten county. Bryoria were found on all trees in all forest patches, both in the old and young forest patches, while Alectoria had much lower occurrence in the young secondary forest. Usnea had no observed pattern in occurrence between the different areas. The average length of the lichens, here used as a proxy for lichen biomass, showed a statistical difference in biomass between areas for genera Bryoria and Usnea. The genera Alectoria showed a difference in biomass between areas, distance to closest older forest and the interaction between these two. Therefore, this study suggests that Alectoria is limited in dispersal in these areas. Some of the results could be explained by distribution and dispersal ability of the studied genera. To further evaluate the differences seen in occurrence and biomass between the genera and the different areas more studies are needed. This could provide important information for sustainable forestry that favors lichens and benefits reindeer husbandry. Lichens Dispersal Picea abies Pinus sylvestris Epiphytic Hair lichens Alectoria Bryoria Usnea Ecology Ekologi
4	Manganese as a site factor for epiphytic lichens / Mangan als Standortfaktor für epiphytische Flechten Paul, Alexander 27 April 2005 (has links) No description available. 580 Pflanzen (Botanik) WWH 000 WVR 200 WHA 000 Mathematics and Natural Science Flechtenökologie Hypogymnia physodes Lecanora conizaeoides Bryoria fuscescens Alectoria sarmentosa Lobaria pulmonaria Nephroma helveticum Leptogium saturninum Mangan Schwermetalltoleranz Ultrastruktur Trebouxia Nostoc Röntgenmikroanalyse Chlorophyllfluoreszenz lichen ecology Hypogymnia physodes Lecanora conizaeoides Bryoria fuscescens Alectoria sarmentosa Lobaria pulmonaria Nephroma helveticum Leptogium saturninum manganese heavy metal tolerance ultrastructure Trebouxia Nostoc X-ray microanalysis chlorophyll fluorescence 42.44 42.48 42.51 42.41

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