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Growth of the old forest lichen Usnea longissima in forest edges
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
2009 (English)In: The Lichenologist, ISSN 0024-2829, E-ISSN 1096-1135, Vol. 41, no 6, 663-672 p.Article in journal (Refereed) Published
Abstract [en]

The lichen Usnea longissima was used to examine how distance from forest edge and edge contrast influence growth of pendulous lichens. Thalli of two sizes (12 and 27 cm) were transplanted to the lower canopy of old Picea abies forest at 5, 25 and 100 m distance from cutovers. Sites represented three levels of edge contrast: high (clear-cut), intermediate (3 m tall saplings) and low (6-7 m tall young forest). Lichen growth was assessed as annual length and weight gain. Growth rates of intact thalli were size-dependent, with both growth variables being higher in long than in short thalli. Distance and edge contrast had significant effects on weight gain in long thalli but not in short ones. Weight gain in long thalli was twice as high near the edge (23%) compared to the forest interior (12%). The highest weight gain (31%) occurred at intermediate contrast edges with lower growth at both low (18%) and high contrast edges (20%). Chlorophyll a concentration was highest near the edge and positively correlated with weight gain, so growth was apparently stimulated by both increased photosynthetic capacity and higher light availability near the edge. The lower part of the canopy in forest edges apparently have favourable growth conditions for U. longissima with growth being influenced by vegetation on adjoining cutovers. Therefore growth responses can not explain the previously observed decline of pendulous lichens following edge creation. Our results suggest that vegetation buffers can improve conditions for pendulous lichens near forest edges.

Place, publisher, year, edition, pages
Cambridge University Press , 2009. Vol. 41, no 6, 663-672 p.
Keyword [en]
chlorophyll concentration, edge influence, edge contrast, lichen growth, pendulous lichen, transplantation experiment
National Category
Ecology
Research subject
Ecological Botany
Identifiers
URN: urn:nbn:se:umu:diva-21663DOI: 10.1017/S0024282909008536OAI: oai:DiVA.org:umu-21663DiVA: diva2:211438
Available from: 2009-04-15 Created: 2009-04-15 Last updated: 2017-12-13Bibliographically approved
In thesis
1. Forest edges in boreal landscapes - factors affecting edge influence
Open this publication in new window or tab >>Forest edges in boreal landscapes - factors affecting edge influence
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The boreal forest in Fennoscandia has been subjected to major loss and fragmentation of natural forests due to intensive forestry. This has resulted in that forest edges are now abundant and important landscape features. Edges have documented effects on the structure, function and biodiversity in forests. Edge influence on biodiversity is complex and depends on interactions between many local and regional factors. This thesis focuses on sharp forest edges and their potential to influence biodiversity at the landscape-level. I have developed a method for quantification and characterization of sharp forest edges by interpretation of colour infrared (CIR) aerial photographs in combination with line intersect sampling (LIS) and sample plots. The method was used to estimate density of forest edge in 28 landscapes (each 1600 ha) in northern Sweden, differing in management intensity, landscape composition and geographical location. Forest edges were described in detail using edge, canopy and neighbourhood attributes. By combining these attributes it was possible to classify edges with respect to levels of exposure. A field experiment was conducted to examine the effect of edge contrast on growth of the old forest lichen Usnea longissima. The edge quantification method is accurate and efficient for estimating the length of sharp forest edges on an area basis (edge density, m ha-1) and for collecting detailed attributes of edges and their surroundings. In northern Sweden, the forest edge density is high (54 m ha-1) but varies extensively (12-102 m ha-1) between landscapes. Edge density is strongly correlated with the level of human disturbance and increases towards the southern part of the study area, at lower altitudes were management intensity is highest. Edge orientation, contrast and neighbourhood size shows an immense variation between edges and also varies between edge types. Regenerating edges are generally of higher contrast and face larger neighbourhoods than natural edges. Maintained edges had high contrast but small neighbourhoods. A larger proportion of edges in mature forests are highly exposed to microclimatic edge influence than edges in general. The field experiment revealed that growth of U. longissima was highest near edges where the vegetation on the adjacent area was sheltering, but not shading, the lichen. In the present thesis, I have provided a valuable tool for estimating density of forest edges with potential to yield information on important factors determining edge influence at landscape-level. The large variability in edge density, edge and neighbourhood attributes imply large differences in microclimate anf thus in the potential for ede influence. Management and conservation strategies must incorporate these factors to realistically address edge influence on biota at the landscape-level.

Publisher
41 p.
Keyword
aerial photographs, edge contrast, edge density, edge length, fetch size, forest fragmentation, lichen growth, line intersect sampling, pendulous lichen, photo interpretation, skogskant, flygbild, kantlängd, lav
National Category
Ecology
Research subject
Ecological Botany
Identifiers
urn:nbn:se:umu:diva-21664 (URN)978-91-7264-756-5 (ISBN)
Public defence
2009-05-08, Lilla Hörsalen, KB3A9, KBC, Linneaus v. 6, Umeå, 13:00 (English)
Opponent
Supervisors
Available from: 2009-04-17 Created: 2009-04-15 Last updated: 2009-04-17Bibliographically approved

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