umu.sePublications
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Forest edges in boreal landscapes - factors affecting edge influence
Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
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.

Place, publisher, year, edition, pages
2009. , 41 p.
Keyword [en]
aerial photographs, edge contrast, edge density, edge length, fetch size, forest fragmentation, lichen growth, line intersect sampling, pendulous lichen, photo interpretation
Keyword [sv]
skogskant, flygbild, kantlängd, lav
National Category
Ecology
Research subject
Ecological Botany
Identifiers
URN: urn:nbn:se:umu:diva-21664ISBN: 978-91-7264-756-5 (print)OAI: oai:DiVA.org:umu-21664DiVA: diva2:211449
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
List of papers
1. Forest edge quantification by line intersect sampling in aerial photographs
Open this publication in new window or tab >>Forest edge quantification by line intersect sampling in aerial photographs
2006 (English)In: Forest Ecology and Management, ISSN 0378-1127, E-ISSN 1872-7042, Vol. 230, 32-42 p.Article in journal (Refereed) Published
Abstract [en]

There is a need for accurate and efficient methods for quantification and characterisation of forest edges at the landscape level in order to understand and mitigate the effects of forest fragmentation on biodiversity.We present and evaluate a method for collecting detailed data on forest edges in aerial photographs by using line intersect sampling (LIS). A digital photogrammetric system was used to collect data from scanned colour infrared photographs in a managed boreal forest landscape.We focused on high-contrast edges between forest (height ≥10 m) and adjoining open habitat or young, regenerating forest (height ≤5 m). We evaluated the air photo interpretation with respect to accuracy in estimated edge length, edge detection, edge type classification and structural variables recorded in 20 m radius plots, using detailed field data as reference. The estimated length of forest edge in the air photo interpretation (52 ± 8.8 m ha-1; mean ± standard error) was close to that in the field survey (58 ± 9.3 m ha-1). The accuracy in edge type classification (type of open habitat) was high (88% correctly classified). Both tree height and canopy cover showed strong relationships with the field data in the forest, buttree height was underestimated by 2.3 m. Data collection was eight times faster and five times more cost-efficient in aerial photographs than in field sampling. The study shows that line intersect sampling in aerial photographs has large potential as a general tool for collecting detailed information on the quantity and characteristics of high-contrast edges in managed forest ecosystems.

Place, publisher, year, edition, pages
Amsterdam: Elsevier, 2006
Keyword
Canopy cover, Edge influence, Forest fragmentation, Line intersect sampling, Photogrammetry, Tree height
National Category
Ecology
Research subject
Ecological Botany
Identifiers
urn:nbn:se:umu:diva-7415 (URN)10.1016/j.foreco.2006.04.012 (DOI)
Available from: 2008-01-09 Created: 2008-01-09 Last updated: 2017-12-14Bibliographically approved
2. Forest edge density in a gradient of boreal landscapes in Sweden
Open this publication in new window or tab >>Forest edge density in a gradient of boreal landscapes in Sweden
(English)Manuscript (Other academic)
Abstract [en]

The boreal forests in Fennoscandia are strongly fragmented by intensive forestry and other land use resulting in high amount of edge habitat. Detailed data on edge quantity is critical to assess fragmentation effects on biodiversity. We estimated the density of sharp forest edges in 28 landscapes, each 4 km × 4 km, along a 830 km gradient in northern Sweden. Data was collected from colour infrared aerial photographs using line intersect sampling and 20-m radius plots. Forest edge density was 54 ± 4.6 m ha-1 land area (mean ± SE) but variation was high among landscapes (12-102 m ha-1). Natural edges constituted 38% but created edges dominated (36% maintained and 26% regenerating). Thirty percent of edges adjoined narrow (5-19 m) open landscape elements (corridor edges) and seventy percent adjoined more exposed patches (≥20 m, patch edges). We found 34 types of patch edges, with the highest density recorded for edges in mature forest. Edge density increased with proportion of landscape disturbed by forestry and agriculture, and decreased with latitude and altitude, but natural and created edges showed contrasting patterns. The high density of sharp edges and the variability among landscapes implies that edges may have strong and diverse effects on the structure, function and biodiversity of boreal forest ecosystems. This variability must be taken into account when formulating strategies for sustainable forest management.

Keyword
line intersect sampling, aerial photographs, forest fragmentation, edge influence, edge length, edge types
National Category
Ecology
Research subject
Ecological Botany
Identifiers
urn:nbn:se:umu:diva-21660 (URN)
Available from: 2009-04-15 Created: 2009-04-15 Last updated: 2012-02-01
3. Edge, canopy and neighbourhood attributes as predictors of potential edge influence in boreal forests
Open this publication in new window or tab >>Edge, canopy and neighbourhood attributes as predictors of potential edge influence in boreal forests
(English)Manuscript (Other academic)
Abstract [en]

Forest edges play a key role in fragmented ecosystems and may strongly influence biodiversity. Edge influence is complex and site specific due to interactions among several local and regional factors. Data on these factors are crucial to predict potential edge influence. We assessed the variability in edge, canopy and neighbourhood attributes among 1008 sharp forest edges in northern Sweden. The edges represented three edge types: natural (wetland, water), maintained (e.g. roads, agriculture) and regenerating (clearcuts, young forest). Data was collected from 28 landscapes (each 1600 ha) using line intersect sampling and stereo interpretation of colour infrared aerial photographs in a digital photogrammetric system. Due to the topography, natural edges were predominantly oriented towards SW or NE while created edges had a more uniform pattern. Created edges had denser canopies and higher contrast in tree height than natural edges. Regenerating edges had the largest fetch, followed by natural and maintained edges. The regenerating edges thus experience the highest risk of wind damage. The majority of edges in mature productive conifer forest had high contrast and large fetch. Overall, edges showed high variability with respect to potential for microclimatic edge influence. This suggests that biodiversity in boreal forests may have a broad range of responses to edges. Our analysis shows that predictions of edge influence on biodiversity in forest ecosystems can be improved by combining edge, canopy and neighbourhood attributes.

Keyword
aerial photographs, edge contrast, edge orientation, fetch size, forest fragmentation
National Category
Ecology
Research subject
Ecological Botany
Identifiers
urn:nbn:se:umu:diva-21662 (URN)
Available from: 2009-04-15 Created: 2009-04-15 Last updated: 2012-02-01
4. Growth of the old forest lichen Usnea longissima in forest edges
Open this publication in new window or tab >>Growth of the old forest lichen Usnea longissima in forest edges
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
Keyword
chlorophyll concentration, edge influence, edge contrast, lichen growth, pendulous lichen, transplantation experiment
National Category
Ecology
Research subject
Ecological Botany
Identifiers
urn:nbn:se:umu:diva-21663 (URN)10.1017/S0024282909008536 (DOI)
Available from: 2009-04-15 Created: 2009-04-15 Last updated: 2017-12-13Bibliographically approved

Open Access in DiVA

fulltext(541 kB)642 downloads
File information
File name FULLTEXT01.pdfFile size 541 kBChecksum SHA-512
14fcb642db6137d1b3bb4bdbca36379117968275491ba716d54abbb04f7e66903dabca5a65c238fd86e16de78d031a7eccaf72976f95dc60753d7da1f8318dc0
Type fulltextMimetype application/pdf

By organisation
Ecology and Environmental Science
Ecology

Search outside of DiVA

GoogleGoogle Scholar
Total: 642 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

isbn
urn-nbn

Altmetric score

isbn
urn-nbn
Total: 756 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf