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Fjällbjörkmätarlarvers påverkan på fjällbjörkskog : en fjärranalysstudie om markvegetationsförhållanden i subalpin miljö

Moon, Melvin LU (2018) In Examensarbete INES NGEK01 20181
Dept of Physical Geography and Ecosystem Science
Abstract
Since the mid-1950s, studies have frequently been conducted on couplings between geometrid
moth outbreaks and mountain birch, though not nearly as much focus has been on connections
between geometrid moth outbreaks and ground cover. Previous studies have shown that major
outbreaks of Epirrita autumnata occur in 9 – 10-year cycles (Karlsson et al., 2004). Sometimes
also the Operophtera brumata are present in outbreaks in Abisko (Bylund, oral comment). Not
until the larvae have finished feeding on the mountain birch, do they move on to the ground
cover (Bylund, oral comment). Historically notorious outbreaks of geometrid moths occurred
1954 – 1955 (the most comprehensive outbreak on record), 1963, 1973 – 1974, 1984, 2003 –
2004 (with... (More)
Since the mid-1950s, studies have frequently been conducted on couplings between geometrid
moth outbreaks and mountain birch, though not nearly as much focus has been on connections
between geometrid moth outbreaks and ground cover. Previous studies have shown that major
outbreaks of Epirrita autumnata occur in 9 – 10-year cycles (Karlsson et al., 2004). Sometimes
also the Operophtera brumata are present in outbreaks in Abisko (Bylund, oral comment). Not
until the larvae have finished feeding on the mountain birch, do they move on to the ground
cover (Bylund, oral comment). Historically notorious outbreaks of geometrid moths occurred
1954 – 1955 (the most comprehensive outbreak on record), 1963, 1973 – 1974, 1984, 2003 –
2004 (with some registered repercussions in 2005) and 2012 – 2014.
The study was aimed at finding methods to describe how geometrid moth larvae affect the
mountain birch forest as an ecosystem. Like many previous studies, the study treated the regions
around Abisko, Vadvetjåkka and Kopparåsen/Katterjåkk (northern Sweden), which all lie in
the subalpine mountain birch belt. In accordance with the Swedish Environmental Protection
Agency (Swe. Naturvårdsverket), mountain birch forests were defined as regions where the
mountain birch constitutes at least 50% of the surface (Naturvårdsverket, 2012). The study
made use of a combination of (i) low-resolution satellite data of vegetation indices (NDVI
provided by MODIS), (ii) photographs (taken from both the air and the ground level) and (iii)
interviews. The interviewed individuals were people which possess highly relevant information
and which together contributed with a wide knowledge of moth outbreaks in the birch forests
around Abisko. The study separated spring season NDVI values from summer (high) season
NDVI values. For the high season, seasonal average NDVI values were calculated for each year
by taking the mean of the four values provided by MODIS for every summer. In contrast to the
treatment of the high season values, the annual spring values were not mean values, but instead
the highest detected value of the spring season (defined as pre-mid-June). The physical regions
were subdivided into two categories – healthy and prosperous forest in 2014 and damaged
forest 2014/2015.
According to the results of the study, there was a set-back in photosynthetic activity in the years
2011, 2012 and 2013. There was a significant (t-test) difference in photosynthetic activity
between the healthy and prosperous forests and the damaged forests. An observation revealed
that the prosperous and the damaged forests also showed differences related to topography
(slope and aspect) and ground vegetation species. Based on the results of the study, three
conclusions can be drawn: 1. Vegetation index from low-resolution satellite data can be used
to investigate vegetation conditions in mountain birch forests. According to the results of this
study, there was a decline in photosynthetic activity over the years of 2011, 2012 and 2013. The
areas with defoliated and non-defoliated trees differ significantly (t-test) with respect to
photosynthetic activity. 2. There may be a connection between ground cover photosynthesis
and insect defoliation in forest ecosystems. Defoliated and non-defoliated forests also appeared
to differ in other aspects, such as topography (gradient and aspect) as well as species
composition in the field layer. The results of this study indicate that these differences could be
used to identify areas that are more prone to be defoliated in the future. To ensure this, however,
a larger study needs to be carried out. 3. Testimonies of those interviewed provide information
about people’s experiences and corroborate the findings of remote sensing. (Less)
Popular Abstract (Swedish)
Syftet med den här studien är att hitta metoder för att kunna beskriva hur mätarlarver påverkar
fjällbjörkskogen som ekosystem. I studien används olika metoder, fjärranalys och statistisk
analys av satellitdata, samt intervjuer med personer som har god lokalkännedom. Genom att
kombinera kvantitativ- och kvalitativmetod har dataanalysens slutsatser kunnat bekräftas.
Det aktuella studieområdet ligger kring Abisko, Vadvetjåkka och Kopparåsen/Katterjåkk, vilka
samtliga ligger i det subalpina björkskogsbältet. I enlighet med Naturvårdsverket (2012) har
fjällbjörkskog i denna studie definierats som områden där fjällbjörk utgör åtminstone 50% av
ytan. I utförandet användes en kombination av (i) lågupplöst satellitdata av vegetationsindex
... (More)
Syftet med den här studien är att hitta metoder för att kunna beskriva hur mätarlarver påverkar
fjällbjörkskogen som ekosystem. I studien används olika metoder, fjärranalys och statistisk
analys av satellitdata, samt intervjuer med personer som har god lokalkännedom. Genom att
kombinera kvantitativ- och kvalitativmetod har dataanalysens slutsatser kunnat bekräftas.
Det aktuella studieområdet ligger kring Abisko, Vadvetjåkka och Kopparåsen/Katterjåkk, vilka
samtliga ligger i det subalpina björkskogsbältet. I enlighet med Naturvårdsverket (2012) har
fjällbjörkskog i denna studie definierats som områden där fjällbjörk utgör åtminstone 50% av
ytan. I utförandet användes en kombination av (i) lågupplöst satellitdata av vegetationsindex
(NDVI) från MODIS, (ii) fotografier (bland annat från luften) samt (iii) intervjuer. Personer
som intervjuats har varit personer som besitter högst relevant information och som tillsammans
bidragit med en bred kunskap om mätarutbrott i björkskogen i områdena kring Abisko. Studien
skiljde på vår- och sommarsäsong (högsäsong). För högsäsongen, beräknades årliga
medelvärden utifrån de av MODIS fyra för varje sommar erhållna NDVI-värden. Till skillnad
från högsäsongsvärdena var vårvärdena inte medelvärden utan varje års högsta givna vårvärde
(före mitten av juni). Områdena delades in i två olika klasser – välmående skog 2014 (A) och
skadad skog 2014/2015 (C).
Utifrån studiens resultat kan tre slutsatser dras.
1. Vegetationsindex från lågupplöst satellitdata kan användas för att undersöka
vegetationsförhållanden i fjällbjörkskog. Enligt resultaten av den här studien var det en nedgång
i fotosyntetisk aktivitet 2011, 2012 och 2013. Områdena angripen och icke angripen skog skiljer
sig signifikant åt (t-test) med avseende på fotosyntetisk aktivitet.
2. Det kan finnas ett samband mellan markvegetationens fotosyntetiska aktivitet och
mätarlarvsangrepp mot fjällbjörkskogen. En intressant iakttagelse uppdagades: Angripen och
icke angripen skog skiljde sig åt även vad gäller andra aspekter, såsom topografi (sluttning och
lutningsgrad), samt undervegetationens artsammansättning. Den här studiens resultat indikerar
att dessa skillnader skulle kunna användas för att identifiera områden som är extra känsliga för
angrepp, både historiskt och i ett framtida perspektiv. För att säkerställa detta behöver dock en
större studie genomföras.
3. Intervjupersonernas berättelser styrker det som framkommit med hjälp av fjärranalysen och
bidrar med beskrivningar av människors upplevelser av fjällbjörkmätarlarvsangrepp. (Less)
Please use this url to cite or link to this publication:
author
Moon, Melvin LU
supervisor
organization
course
NGEK01 20181
year
type
M2 - Bachelor Degree
subject
keywords
Fjärranalys, NDVI, fjällbjörkmätare, Abisko, fjällbjörkskog
publication/series
Examensarbete INES
report number
464
language
Swedish
id
8960313
date added to LUP
2018-10-16 11:20:40
date last changed
2018-10-16 11:20:40
@misc{8960313,
  abstract     = {{Since the mid-1950s, studies have frequently been conducted on couplings between geometrid
moth outbreaks and mountain birch, though not nearly as much focus has been on connections
between geometrid moth outbreaks and ground cover. Previous studies have shown that major
outbreaks of Epirrita autumnata occur in 9 – 10-year cycles (Karlsson et al., 2004). Sometimes
also the Operophtera brumata are present in outbreaks in Abisko (Bylund, oral comment). Not
until the larvae have finished feeding on the mountain birch, do they move on to the ground
cover (Bylund, oral comment). Historically notorious outbreaks of geometrid moths occurred
1954 – 1955 (the most comprehensive outbreak on record), 1963, 1973 – 1974, 1984, 2003 –
2004 (with some registered repercussions in 2005) and 2012 – 2014.
The study was aimed at finding methods to describe how geometrid moth larvae affect the
mountain birch forest as an ecosystem. Like many previous studies, the study treated the regions
around Abisko, Vadvetjåkka and Kopparåsen/Katterjåkk (northern Sweden), which all lie in
the subalpine mountain birch belt. In accordance with the Swedish Environmental Protection
Agency (Swe. Naturvårdsverket), mountain birch forests were defined as regions where the
mountain birch constitutes at least 50% of the surface (Naturvårdsverket, 2012). The study
made use of a combination of (i) low-resolution satellite data of vegetation indices (NDVI
provided by MODIS), (ii) photographs (taken from both the air and the ground level) and (iii)
interviews. The interviewed individuals were people which possess highly relevant information
and which together contributed with a wide knowledge of moth outbreaks in the birch forests
around Abisko. The study separated spring season NDVI values from summer (high) season
NDVI values. For the high season, seasonal average NDVI values were calculated for each year
by taking the mean of the four values provided by MODIS for every summer. In contrast to the
treatment of the high season values, the annual spring values were not mean values, but instead
the highest detected value of the spring season (defined as pre-mid-June). The physical regions
were subdivided into two categories – healthy and prosperous forest in 2014 and damaged
forest 2014/2015.
According to the results of the study, there was a set-back in photosynthetic activity in the years
2011, 2012 and 2013. There was a significant (t-test) difference in photosynthetic activity
between the healthy and prosperous forests and the damaged forests. An observation revealed
that the prosperous and the damaged forests also showed differences related to topography
(slope and aspect) and ground vegetation species. Based on the results of the study, three
conclusions can be drawn: 1. Vegetation index from low-resolution satellite data can be used
to investigate vegetation conditions in mountain birch forests. According to the results of this
study, there was a decline in photosynthetic activity over the years of 2011, 2012 and 2013. The
areas with defoliated and non-defoliated trees differ significantly (t-test) with respect to
photosynthetic activity. 2. There may be a connection between ground cover photosynthesis
and insect defoliation in forest ecosystems. Defoliated and non-defoliated forests also appeared
to differ in other aspects, such as topography (gradient and aspect) as well as species
composition in the field layer. The results of this study indicate that these differences could be
used to identify areas that are more prone to be defoliated in the future. To ensure this, however,
a larger study needs to be carried out. 3. Testimonies of those interviewed provide information
about people’s experiences and corroborate the findings of remote sensing.}},
  author       = {{Moon, Melvin}},
  language     = {{swe}},
  note         = {{Student Paper}},
  series       = {{Examensarbete INES}},
  title        = {{Fjällbjörkmätarlarvers påverkan på fjällbjörkskog : en fjärranalysstudie om markvegetationsförhållanden i subalpin miljö}},
  year         = {{2018}},
}