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Mapping moth induced birch forest damage in northern Sweden, with MODIS satellite data

Morin, Kristian LU (2013) In Student thesis series INES NGEM01 20122
Dept of Physical Geography and Ecosystem Science
Abstract
Large synchronous outbreaks of herbivory geometrids is regularly occurring at 9-10 years intervals when they reach peak densities in the Fennoscandian birch forest, in the northern part of Scandinavia (Tenow 1972, Bylund 1995). Climate change is likely to increase the frequency, intensity and extent of the outbreak due to increasing temperatures in the area (Callaghan 2010, Heliasz et al. 2011, Wolf et al. 2008). The consequence is a detrimental effect to the birch forest since the forest might not have enough time to recover between outbreaks, which will potentially decrease the proliferation and distribution of birch forest (Tenow et al. 2001, 2003, Karlsson et al 2004). This will have an ecological cost by making the forest inhabitable... (More)
Large synchronous outbreaks of herbivory geometrids is regularly occurring at 9-10 years intervals when they reach peak densities in the Fennoscandian birch forest, in the northern part of Scandinavia (Tenow 1972, Bylund 1995). Climate change is likely to increase the frequency, intensity and extent of the outbreak due to increasing temperatures in the area (Callaghan 2010, Heliasz et al. 2011, Wolf et al. 2008). The consequence is a detrimental effect to the birch forest since the forest might not have enough time to recover between outbreaks, which will potentially decrease the proliferation and distribution of birch forest (Tenow et al. 2001, 2003, Karlsson et al 2004). This will have an ecological cost by making the forest inhabitable and non-resourceful for the animals and people that depend on it (Helle 2001). However, the effects on the Birch forest are not well known, therefore it is important to continue studying the distribution of forest damage, to gain a better understanding of its dynamics and the underlying spatio-temporal factors controlling the synchronous outbreaks.

The most current year of infestation in the study area of the surroundings of lake Torneträsk in northern Sweden was 2012. To map the distribution and dynamics of the geometrids of the birch forest, time series data of MODIS 16-day NDVI composites were analyzed. To facilitate the analysis, a tree cover map with high resolution was created based on Lidar data. The Lidar based forest cover map was created to mask the forest. The topographical distribution of infested forest at four altitudinal intervals with 100 meter equidistance in between was also studied.

A method was developed in this study to separate infested from non-infested forest with a threshold value based on z-score, which was successful at showing the distribution of the geometrid outbreak in 2012. The size of the infested area was 80km², equal to 54.3% of the forest in the area. If the forest classified as “likely infested” would have been included, the ratio of infested forest would increase to 64.4%. This is a significant proportion of the forest that will certainly affect the forest in future years. The topographical distribution of the infestation over the study area was relatively evenly distributed, without displaying any range of altitude that was more prone to infestation. (Less)
Abstract (Swedish)
Stora synkrona utbrott av björkmätare förekommer vart 9-10 år i de norra delarna av Skandinavien i den Fenoskandiska björkskogen. Björkmätaren konsumerar bladen och kan orsaka stora skador under ett toppår. Man misstänker att klimatförändringarna kommer att öka utbrottens omfattning och intensitet på grund av ökad temperatur i området. Konsekvenserna kan bli förödande för björkskogen, eftersom tiden mellan utbrotten riskerar att bli för korta för skogen att återhämta sig. Det kan resultera i att träden dör och skogen försvinner i de värst drabbade områdena. Om skogen minskar eller försvinner kan det få ekologiska konsekvenser för de djur som är beroende av den och människor som utnyttjar dess resurser.
Hur skogen kommer att påverkas vet... (More)
Stora synkrona utbrott av björkmätare förekommer vart 9-10 år i de norra delarna av Skandinavien i den Fenoskandiska björkskogen. Björkmätaren konsumerar bladen och kan orsaka stora skador under ett toppår. Man misstänker att klimatförändringarna kommer att öka utbrottens omfattning och intensitet på grund av ökad temperatur i området. Konsekvenserna kan bli förödande för björkskogen, eftersom tiden mellan utbrotten riskerar att bli för korta för skogen att återhämta sig. Det kan resultera i att träden dör och skogen försvinner i de värst drabbade områdena. Om skogen minskar eller försvinner kan det få ekologiska konsekvenser för de djur som är beroende av den och människor som utnyttjar dess resurser.
Hur skogen kommer att påverkas vet man inte säkert, därför är det viktigt att studera utbredningen av skogsskador och på så sätt få bättre kunskap om de underliggande faktorerna som kontrollerar utbrottens dynamik.

Ett utbrott inträffade sommaren 2012 i studieområdet vilket var indelat i 2 olika stora överlappande område; Ett större som täcker området runt sjön Torneträsk i norra Sverige och ett mindre som täcker den västra delen av sjön runt Abisko. För att kartlägga omfattningen av björmatarutbrottet användes tidsserier av MODIS 16-dagars NDVI kompositer som analyserades men en utvecklad förändrings analys för projektet. Som en del i analysen skapades en högupplöst skogsutbredningskarta med Lidar data. Den topografiska utbredningen av utbrotten studerades också genom att dela in området i fyra höjdintervall med 100 meters ekvidistans mellan intervallen.

För att identifiera skadade område utvecklades en metod baserat på standardiserade z-värde och definierade gränsvärde för klassificeringen av skogen. Det angripna området i Torneträsk var 251 km² stort, motsvarande 32% av skogen. I studieområdet i Abisko var utbrottet 80km2 stort, vilket motsvarar 54.3% av skogen i studieområdet. Om skogen klassad som ”troligen angripen” inkluderas i beräkningen, skulle den del av skogen som var angripen ökas ytterligare. Det är en signifikant andel skog som med stor sannolikhet kommer att påverka skogen i flera år. Den topografiska utbredningen av utbrottet i studieområdet var relativt jämnt fördelat, inget höjdintervall visade sig vara extra känsligt för att bli angripen. (Less)
Please use this url to cite or link to this publication:
author
Morin, Kristian LU
supervisor
organization
course
NGEM01 20122
year
type
H2 - Master's Degree (Two Years)
subject
keywords
physical geography, topography, TIMESAT, Epirrita autumnata, geometrids, time series, MODIS, remote sensing, geography, birch forest
publication/series
Student thesis series INES
report number
267
language
English
id
3512920
date added to LUP
2013-02-21 14:34:44
date last changed
2013-02-27 13:06:02
@misc{3512920,
  abstract     = {Large synchronous outbreaks of herbivory geometrids is regularly occurring at 9-10 years intervals when they reach peak densities in the Fennoscandian birch forest, in the northern part of Scandinavia (Tenow 1972, Bylund 1995). Climate change is likely to increase the frequency, intensity and extent of the outbreak due to increasing temperatures in the area (Callaghan 2010, Heliasz et al. 2011, Wolf et al. 2008). The consequence is a detrimental effect to the birch forest since the forest might not have enough time to recover between outbreaks, which will potentially decrease the proliferation and distribution of birch forest (Tenow et al. 2001, 2003, Karlsson et al 2004). This will have an ecological cost by making the forest inhabitable and non-resourceful for the animals and people that depend on it (Helle 2001). However, the effects on the Birch forest are not well known, therefore it is important to continue studying the distribution of forest damage, to gain a better understanding of its dynamics and the underlying spatio-temporal factors controlling the synchronous outbreaks. 

The most current year of infestation in the study area of the surroundings of lake Torneträsk in northern Sweden was 2012. To map the distribution and dynamics of the geometrids of the birch forest, time series data of MODIS 16-day NDVI composites were analyzed. To facilitate the analysis, a tree cover map with high resolution was created based on Lidar data. The Lidar based forest cover map was created to mask the forest. The topographical distribution of infested forest at four altitudinal intervals with 100 meter equidistance in between was also studied.

A method was developed in this study to separate infested from non-infested forest with a threshold value based on z-score, which was successful at showing the distribution of the geometrid outbreak in 2012. The size of the infested area was 80km², equal to 54.3% of the forest in the area. If the forest classified as “likely infested” would have been included, the ratio of infested forest would increase to 64.4%. This is a significant proportion of the forest that will certainly affect the forest in future years. The topographical distribution of the infestation over the study area was relatively evenly distributed, without displaying any range of altitude that was more prone to infestation.},
  author       = {Morin, Kristian},
  keyword      = {physical geography,topography,TIMESAT,Epirrita autumnata,geometrids,time series,MODIS,remote sensing,geography,birch forest},
  language     = {eng},
  note         = {Student Paper},
  series       = {Student thesis series INES},
  title        = {Mapping moth induced birch forest damage in northern Sweden, with MODIS satellite data},
  year         = {2013},
}